text: // Copyright (c) 2004-2010 Sergey Lyubka
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  
  #if defined(_WIN32)
  #define _CRT_SECURE_NO_WARNINGS // Disable deprecation warning in VS2005
  #else
  #define _XOPEN_SOURCE 600 // For flockfile() on Linux
  #define _LARGEFILE_SOURCE // Enable 64-bit file offsets
  #define __STDC_FORMAT_MACROS // <inttypes.h> wants this for C++
  #endif
  
  #if defined(__SYMBIAN32__)
  #define NO_SSL // SSL is not supported
  #define NO_CGI // CGI is not supported
  #define PATH_MAX FILENAME_MAX
  #endif // __SYMBIAN32__
  
  #ifndef _WIN32_WCE // Some ANSI #includes are not available on Windows CE
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <errno.h>
  #include <signal.h>
  #include <fcntl.h>
  #endif // !_WIN32_WCE
  
  #include <time.h>
  #include <stdlib.h>
  #include <stdarg.h>
  #include <assert.h>
  #include <string.h>
  #include <ctype.h>
  #include <limits.h>
  #include <stddef.h>
  #include <stdio.h>
  
  #if defined(_WIN32) && !defined(__SYMBIAN32__) // Windows specific
  #define _WIN32_WINNT 0x0400 // To make it link in VS2005
  #include <windows.h>
  
  #ifndef PATH_MAX
  #define PATH_MAX MAX_PATH
  #endif
  
  #ifndef _WIN32_WCE
  #include <process.h>
  #include <direct.h>
  #include <io.h>
  #else // _WIN32_WCE
  #include <winsock2.h>
  #define NO_CGI // WinCE has no pipes
  
  typedef long off_t;
  #define BUFSIZ  4096
  
  #define errno   GetLastError()
  #define strerror(x)  _ultoa(x, (char *) _alloca(sizeof(x) *3 ), 10)
  #endif // _WIN32_WCE
  
  #define MAKEUQUAD(lo, hi) ((uint64_t)(((uint32_t)(lo)) | \
        ((uint64_t)((uint32_t)(hi))) << 32))
  #define RATE_DIFF 10000000 // 100 nsecs
  #define EPOCH_DIFF MAKEUQUAD(0xd53e8000, 0x019db1de)
  #define SYS2UNIX_TIME(lo, hi) \
    (time_t) ((MAKEUQUAD((lo), (hi)) - EPOCH_DIFF) / RATE_DIFF)
  
  // Visual Studio 6 does not know __func__ or __FUNCTION__
  // The rest of MS compilers use __FUNCTION__, not C99 __func__
  // Also use _strtoui64 on modern M$ compilers
  #if defined(_MSC_VER) && _MSC_VER < 1300
  #define STRX(x) #x
  #define STR(x) STRX(x)
  #define __func__ "line " STR(__LINE__)
  #define strtoull(x, y, z) strtoul(x, y, z)
  #define strtoll(x, y, z) strtol(x, y, z)
  #else
  #define __func__  __FUNCTION__
  #define strtoull(x, y, z) _strtoui64(x, y, z)
  #define strtoll(x, y, z) _strtoi64(x, y, z)
  #endif // _MSC_VER
  
  #define ERRNO   GetLastError()
  #define NO_SOCKLEN_T
  #define SSL_LIB   "ssleay32.dll"
  #define CRYPTO_LIB  "libeay32.dll"
  #define DIRSEP '\\'
  #define IS_DIRSEP_CHAR(c) ((c) == '/' || (c) == '\\')
  #define O_NONBLOCK  0
  #if !defined(EWOULDBLOCK)
  #define EWOULDBLOCK  WSAEWOULDBLOCK
  #endif // !EWOULDBLOCK
  #define _POSIX_
  #define INT64_FMT  "I64d"
  
  #define WINCDECL __cdecl
  #define SHUT_WR 1
  #define snprintf _snprintf
  #define vsnprintf _vsnprintf
  #define sleep(x) Sleep((x) * 1000)
  
  #define pipe(x) _pipe(x, BUFSIZ, _O_BINARY)
  #define popen(x, y) _popen(x, y)
  #define pclose(x) _pclose(x)
  #define close(x) _close(x)
  #define dlsym(x,y) GetProcAddress((HINSTANCE) (x), (y))
  #define RTLD_LAZY  0
  #define fseeko(x, y, z) fseek((x), (y), (z))
  #define fdopen(x, y) _fdopen((x), (y))
  #define write(x, y, z) _write((x), (y), (unsigned) z)
  #define read(x, y, z) _read((x), (y), (unsigned) z)
  #define flockfile(x) (void) 0
  #define funlockfile(x) (void) 0
  
  #if !defined(fileno)
  #define fileno(x) _fileno(x)
  #endif // !fileno MINGW #defines fileno
  
  typedef HANDLE pthread_mutex_t;
  typedef struct {HANDLE signal, broadcast;} pthread_cond_t;
  typedef DWORD pthread_t;
  #define pid_t HANDLE // MINGW typedefs pid_t to int. Using #define here.
  
  struct timespec {
    long tv_nsec;
    long tv_sec;
  };
  
  static int pthread_mutex_lock(pthread_mutex_t *);
  static int pthread_mutex_unlock(pthread_mutex_t *);
  static FILE *mg_fopen(const char *path, const char *mode);
  
  #if defined(HAVE_STDINT)
  #include <stdint.h>
  #else
  typedef unsigned int  uint32_t;
  typedef unsigned short  uint16_t;
  typedef unsigned __int64 uint64_t;
  typedef __int64   int64_t;
  #define INT64_MAX  9223372036854775807
  #endif // HAVE_STDINT
  
  // POSIX dirent interface
  struct dirent {
    char d_name[PATH_MAX];
  };
  
  typedef struct DIR {
    HANDLE   handle;
    WIN32_FIND_DATAW info;
    struct dirent  result;
  } DIR;
  
  #else    // UNIX  specific
  #include <sys/wait.h>
  #include <sys/socket.h>
  #include <sys/select.h>
  #include <netinet/in.h>
  #include <arpa/inet.h>
  #include <sys/time.h>
  #include <stdint.h>
  #include <inttypes.h>
  #include <netdb.h>
  
  #include <pwd.h>
  #include <unistd.h>
  #include <dirent.h>
  #if !defined(NO_SSL_DL) && !defined(NO_SSL)
  #include <dlfcn.h>
  #endif
  #include <pthread.h>
  #if defined(__MACH__)
  #define SSL_LIB   "libssl.dylib"
  #define CRYPTO_LIB  "libcrypto.dylib"
  #else
  #if !defined(SSL_LIB)
  #define SSL_LIB   "libssl.so"
  #endif
  #if !defined(CRYPTO_LIB)
  #define CRYPTO_LIB  "libcrypto.so"
  #endif
  #endif
  #define DIRSEP   '/'
  #define IS_DIRSEP_CHAR(c) ((c) == '/')
  #ifndef O_BINARY
  #define O_BINARY  0
  #endif // O_BINARY
  #define closesocket(a) close(a)
  #define mg_fopen(x, y) fopen(x, y)
  #define mg_mkdir(x, y) mkdir(x, y)
  #define mg_remove(x) remove(x)
  #define mg_rename(x, y) rename(x, y)
  #define ERRNO errno
  #define INVALID_SOCKET (-1)
  #define INT64_FMT PRId64
  typedef int SOCKET;
  #define WINCDECL
  
  #endif // End of Windows and UNIX specific includes
  
  #include "mongoose.h"
  
  #define MONGOOSE_VERSION "3.0"
  #define PASSWORDS_FILE_NAME ".htpasswd"
  #define CGI_ENVIRONMENT_SIZE 4096
  #define MAX_CGI_ENVIR_VARS 64
  #define ARRAY_SIZE(array) (sizeof(array) / sizeof(array[0]))
  
  #if defined(DEBUG)
  #define DEBUG_TRACE(x) do { \
    flockfile(stdout); \
    printf("*** %lu.%p.%s.%d: ", \
           (unsigned long) time(NULL), (void *) pthread_self(), \
           __func__, __LINE__); \
    printf x; \
    putchar('\n'); \
    fflush(stdout); \
    funlockfile(stdout); \
  } while (0)
  #else
  #define DEBUG_TRACE(x)
  #endif // DEBUG
  
  // Darwin prior to 7.0 and Win32 do not have socklen_t
  #ifdef NO_SOCKLEN_T
  typedef int socklen_t;
  #endif // NO_SOCKLEN_T
  
  typedef void * (*mg_thread_func_t)(void *);
  
  static const char *http_500_error = "Internal Server Error";
  
  // Snatched from OpenSSL includes. I put the prototypes here to be independent
  // from the OpenSSL source installation. Having this, mongoose + SSL can be
  // built on any system with binary SSL libraries installed.
  typedef struct ssl_st SSL;
  typedef struct ssl_method_st SSL_METHOD;
  typedef struct ssl_ctx_st SSL_CTX;
  
  #define SSL_ERROR_WANT_READ 2
  #define SSL_ERROR_WANT_WRITE 3
  #define SSL_FILETYPE_PEM 1
  #define CRYPTO_LOCK  1
  
  #if defined(NO_SSL_DL)
  extern void SSL_free(SSL *);
  extern int SSL_accept(SSL *);
  extern int SSL_connect(SSL *);
  extern int SSL_read(SSL *, void *, int);
  extern int SSL_write(SSL *, const void *, int);
  extern int SSL_get_error(const SSL *, int);
  extern int SSL_set_fd(SSL *, int);
  extern SSL *SSL_new(SSL_CTX *);
  extern SSL_CTX *SSL_CTX_new(SSL_METHOD *);
  extern SSL_METHOD *SSLv23_server_method(void);
  extern int SSL_library_init(void);
  extern void SSL_load_error_strings(void);
  extern int SSL_CTX_use_PrivateKey_file(SSL_CTX *, const char *, int);
  extern int SSL_CTX_use_certificate_file(SSL_CTX *, const char *, int);
  extern int SSL_CTX_use_certificate_chain_file(SSL_CTX *, const char *);
  extern void SSL_CTX_set_default_passwd_cb(SSL_CTX *, mg_callback_t);
  extern void SSL_CTX_free(SSL_CTX *);
  extern unsigned long ERR_get_error(void);
  extern char *ERR_error_string(unsigned long, char *);
  extern int CRYPTO_num_locks(void);
  extern void CRYPTO_set_locking_callback(void (*)(int, int, const char *, int));
  extern void CRYPTO_set_id_callback(unsigned long (*)(void));
  #else
  // Dynamically loaded SSL functionality
  struct ssl_func {
    const char *name;   // SSL function name
    void  (*ptr)(void); // Function pointer
  };
  
  #define SSL_free (* (void (*)(SSL *)) ssl_sw[0].ptr)
  #define SSL_accept (* (int (*)(SSL *)) ssl_sw[1].ptr)
  #define SSL_connect (* (int (*)(SSL *)) ssl_sw[2].ptr)
  #define SSL_read (* (int (*)(SSL *, void *, int)) ssl_sw[3].ptr)
  #define SSL_write (* (int (*)(SSL *, const void *,int)) ssl_sw[4].ptr)
  #define SSL_get_error (* (int (*)(SSL *, int)) ssl_sw[5].ptr)
  #define SSL_set_fd (* (int (*)(SSL *, SOCKET)) ssl_sw[6].ptr)
  #define SSL_new (* (SSL * (*)(SSL_CTX *)) ssl_sw[7].ptr)
  #define SSL_CTX_new (* (SSL_CTX * (*)(SSL_METHOD *)) ssl_sw[8].ptr)
  #define SSLv23_server_method (* (SSL_METHOD * (*)(void)) ssl_sw[9].ptr)
  #define SSL_library_init (* (int (*)(void)) ssl_sw[10].ptr)
  #define SSL_CTX_use_PrivateKey_file (* (int (*)(SSL_CTX *, \
          const char *, int)) ssl_sw[11].ptr)
  #define SSL_CTX_use_certificate_file (* (int (*)(SSL_CTX *, \
          const char *, int)) ssl_sw[12].ptr)
  #define SSL_CTX_set_default_passwd_cb \
    (* (void (*)(SSL_CTX *, mg_callback_t)) ssl_sw[13].ptr)
  #define SSL_CTX_free (* (void (*)(SSL_CTX *)) ssl_sw[14].ptr)
  #define SSL_load_error_strings (* (void (*)(void)) ssl_sw[15].ptr)
  #define SSL_CTX_use_certificate_chain_file \
    (* (int (*)(SSL_CTX *, const char *)) ssl_sw[16].ptr)
  
  #define CRYPTO_num_locks (* (int (*)(void)) crypto_sw[0].ptr)
  #define CRYPTO_set_locking_callback \
    (* (void (*)(void (*)(int, int, const char *, int))) crypto_sw[1].ptr)
  #define CRYPTO_set_id_callback \
    (* (void (*)(unsigned long (*)(void))) crypto_sw[2].ptr)
  #define ERR_get_error (* (unsigned long (*)(void)) crypto_sw[3].ptr)
  #define ERR_error_string (* (char * (*)(unsigned long,char *)) crypto_sw[4].ptr)
  
  // set_ssl_option() function updates this array.
  // It loads SSL library dynamically and changes NULLs to the actual addresses
  // of respective functions. The macros above (like SSL_connect()) are really
  // just calling these functions indirectly via the pointer.
  static struct ssl_func ssl_sw[] = {
    {"SSL_free",   NULL},
    {"SSL_accept",   NULL},
    {"SSL_connect",   NULL},
    {"SSL_read",   NULL},
    {"SSL_write",   NULL},
    {"SSL_get_error",  NULL},
    {"SSL_set_fd",   NULL},
    {"SSL_new",   NULL},
    {"SSL_CTX_new",   NULL},
    {"SSLv23_server_method", NULL},
    {"SSL_library_init",  NULL},
    {"SSL_CTX_use_PrivateKey_file", NULL},
    {"SSL_CTX_use_certificate_file",NULL},
    {"SSL_CTX_set_default_passwd_cb",NULL},
    {"SSL_CTX_free",  NULL},
    {"SSL_load_error_strings", NULL},
    {"SSL_CTX_use_certificate_chain_file", NULL},
    {NULL,    NULL}
  };
  
  // Similar array as ssl_sw. These functions could be located in different lib.
  static struct ssl_func crypto_sw[] = {
    {"CRYPTO_num_locks",  NULL},
    {"CRYPTO_set_locking_callback", NULL},
    {"CRYPTO_set_id_callback", NULL},
    {"ERR_get_error",  NULL},
    {"ERR_error_string", NULL},
    {NULL,    NULL}
  };
  #endif // NO_SSL_DL
  
  static const char *month_names[] = {
    "Jan", "Feb", "Mar", "Apr", "May", "Jun",
    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  };
  
  // Unified socket address. For IPv6 support, add IPv6 address structure
  // in the union u.
  struct usa {
    socklen_t len;
    union {
      struct sockaddr sa;
      struct sockaddr_in sin;
    } u;
  };
  
  // Describes a string (chunk of memory).
  struct vec {
    const char *ptr;
    size_t len;
  };
  
  // Structure used by mg_stat() function. Uses 64 bit file length.
  struct mgstat {
    int is_directory;  // Directory marker
    int64_t size;      // File size
    time_t mtime;      // Modification time
  };
  
  // Describes listening socket, or socket which was accept()-ed by the master
  // thread and queued for future handling by the worker thread.
  struct socket {
    struct socket *next;  // Linkage
    SOCKET sock;          // Listening socket
    struct usa lsa;       // Local socket address
    struct usa rsa;       // Remote socket address
    int is_ssl;           // Is socket SSL-ed
    int is_proxy;
  };
  
  enum {
    CGI_EXTENSIONS, CGI_ENVIRONMENT, PUT_DELETE_PASSWORDS_FILE, CGI_INTERPRETER,
    PROTECT_URI, AUTHENTICATION_DOMAIN, SSI_EXTENSIONS, ACCESS_LOG_FILE,
    SSL_CHAIN_FILE, ENABLE_DIRECTORY_LISTING, ERROR_LOG_FILE,
    GLOBAL_PASSWORDS_FILE, INDEX_FILES,
    ENABLE_KEEP_ALIVE, ACCESS_CONTROL_LIST, MAX_REQUEST_SIZE,
    EXTRA_MIME_TYPES, LISTENING_PORTS,
    DOCUMENT_ROOT, SSL_CERTIFICATE, NUM_THREADS, RUN_AS_USER,
    NUM_OPTIONS
  };
  
  static const char *config_options[] = {
    "C", "cgi_extensions", ".cgi,.pl,.php",
    "E", "cgi_environment", NULL,
    "G", "put_delete_passwords_file", NULL,
    "I", "cgi_interpreter", NULL,
    "P", "protect_uri", NULL,
    "R", "authentication_domain", "mydomain.com",
    "S", "ssi_extensions", ".shtml,.shtm",
    "a", "access_log_file", NULL,
    "c", "ssl_chain_file", NULL,
    "d", "enable_directory_listing", "yes",
    "e", "error_log_file", NULL,
    "g", "global_passwords_file", NULL,
    "i", "index_files", "index.html,index.htm,index.cgi",
    "k", "enable_keep_alive", "no",
    "l", "access_control_list", NULL,
    "M", "max_request_size", "16384",
    "m", "extra_mime_types", NULL,
    "p", "listening_ports", "8080",
    "r", "document_root",  ".",
    "s", "ssl_certificate", NULL,
    "t", "num_threads", "10",
    "u", "run_as_user", NULL,
    NULL
  };
  #define ENTRIES_PER_CONFIG_OPTION 3
  
  struct mg_context {
    volatile int stop_flag;       // Should we stop event loop
    SSL_CTX *ssl_ctx;             // SSL context
    char *config[NUM_OPTIONS];    // Mongoose configuration parameters
    mg_callback_t user_callback;  // User-defined callback function
    void *user_data;              // User-defined data
  
    struct socket *listening_sockets;
  
    volatile int num_threads;  // Number of threads
    pthread_mutex_t mutex;     // Protects (max|num)_threads
    pthread_cond_t  cond;      // Condvar for tracking workers terminations
  
    struct socket queue[20];   // Accepted sockets
    volatile int sq_head;      // Head of the socket queue
    volatile int sq_tail;      // Tail of the socket queue
    pthread_cond_t sq_full;    // Singaled when socket is produced
    pthread_cond_t sq_empty;   // Signaled when socket is consumed
  };
  
  struct mg_connection {
    struct mg_connection *peer; // Remote target in proxy mode
    struct mg_request_info request_info;
    struct mg_context *ctx;
    SSL *ssl;                   // SSL descriptor
    struct socket client;       // Connected client
    time_t birth_time;          // Time connection was accepted
    int64_t num_bytes_sent;     // Total bytes sent to client
    int64_t content_len;        // Content-Length header value
    int64_t consumed_content;   // How many bytes of content is already read
    char *buf;                  // Buffer for received data
    int buf_size;               // Buffer size
    int request_len;            // Size of the request + headers in a buffer
    int data_len;               // Total size of data in a buffer
  };
  
  const char **mg_get_valid_option_names(void) {
    return config_options;
  }
  
  static void *call_user(struct mg_connection *conn, enum mg_event event) {
    conn->request_info.user_data = conn->ctx->user_data;
    return conn->ctx->user_callback == NULL ? NULL :
      conn->ctx->user_callback(event, conn, &conn->request_info);
  }
  
  static int get_option_index(const char *name) {
    int i;
  
    for (i = 0; config_options[i] != NULL; i += ENTRIES_PER_CONFIG_OPTION) {
      if (strcmp(config_options[i], name) == 0 ||
          strcmp(config_options[i + 1], name) == 0) {
        return i / ENTRIES_PER_CONFIG_OPTION;
      }
    }
    return -1;
  }
  
  const char *mg_get_option(const struct mg_context *ctx, const char *name) {
    int i;
    if ((i = get_option_index(name)) == -1) {
      return NULL;
    } else if (ctx->config[i] == NULL) {
      return "";
    } else {
      return ctx->config[i];
    }
  }
  
  // Print error message to the opened error log stream.
  static void cry(struct mg_connection *conn, const char *fmt, ...) {
    char buf[BUFSIZ];
    va_list ap;
    FILE *fp;
    time_t timestamp;
  
    va_start(ap, fmt);
    (void) vsnprintf(buf, sizeof(buf), fmt, ap);
    va_end(ap);
  
    // Do not lock when getting the callback value, here and below.
    // I suppose this is fine, since function cannot disappear in the
    // same way string option can.
    conn->request_info.log_message = buf;
    if (call_user(conn, MG_EVENT_LOG) == NULL) {
      fp = conn->ctx->config[ERROR_LOG_FILE] == NULL ? NULL :
        mg_fopen(conn->ctx->config[ERROR_LOG_FILE], "a+");
  
      if (fp != NULL) {
        flockfile(fp);
        timestamp = time(NULL);
  
        (void) fprintf(fp,
            "[%010lu] [error] [client %s] ",
            (unsigned long) timestamp,
            inet_ntoa(conn->client.rsa.u.sin.sin_addr));
  
        if (conn->request_info.request_method != NULL) {
          (void) fprintf(fp, "%s %s: ",
              conn->request_info.request_method,
              conn->request_info.uri);
        }
  
        (void) fprintf(fp, "%s", buf);
        fputc('\n', fp);
        funlockfile(fp);
        if (fp != stderr) {
          fclose(fp);
        }
      }
    }
    conn->request_info.log_message = NULL;
  }
  
  // Return OpenSSL error message
  static const char *ssl_error(void) {
    unsigned long err;
    err = ERR_get_error();
    return err == 0 ? "" : ERR_error_string(err, NULL);
  }
  
  // Return fake connection structure. Used for logging, if connection
  // is not applicable at the moment of logging.
  static struct mg_connection *fc(struct mg_context *ctx) {
    static struct mg_connection fake_connection;
    fake_connection.ctx = ctx;
    return &fake_connection;
  }
  
  const char *mg_version(void) {
    return MONGOOSE_VERSION;
  }
  
  static void mg_strlcpy(register char *dst, register const char *src, size_t n) {
    for (; *src != '\0' && n > 1; n--) {
      *dst++ = *src++;
    }
    *dst = '\0';
  }
  
  static int lowercase(const char *s) {
    return tolower(* (const unsigned char *) s);
  }
  
  static int mg_strncasecmp(const char *s1, const char *s2, size_t len) {
    int diff = 0;
  
    if (len > 0)
      do {
        diff = lowercase(s1++) - lowercase(s2++);
      } while (diff == 0 && s1[-1] != '\0' && --len > 0);
  
    return diff;
  }
  
  static int mg_strcasecmp(const char *s1, const char *s2) {
    int diff;
  
    do {
      diff = lowercase(s1++) - lowercase(s2++);
    } while (diff == 0 && s1[-1] != '\0');
  
    return diff;
  }
  
  static char * mg_strndup(const char *ptr, size_t len) {
    char *p;
  
    if ((p = (char *) malloc(len + 1)) != NULL) {
      mg_strlcpy(p, ptr, len + 1);
    }
  
    return p;
  }
  
  static char * mg_strdup(const char *str) {
    return mg_strndup(str, strlen(str));
  }
  
  // Like snprintf(), but never returns negative value, or the value
  // that is larger than a supplied buffer.
  // Thanks to Adam Zeldis to pointing snprintf()-caused vulnerability
  // in his audit report.
  static int mg_vsnprintf(struct mg_connection *conn, char *buf, size_t buflen,
                          const char *fmt, va_list ap) {
    int n;
  
    if (buflen == 0)
      return 0;
  
    n = vsnprintf(buf, buflen, fmt, ap);
  
    if (n < 0) {
      cry(conn, "vsnprintf error");
      n = 0;
    } else if (n >= (int) buflen) {
      cry(conn, "truncating vsnprintf buffer: [%.*s]",
          n > 200 ? 200 : n, buf);
      n = (int) buflen - 1;
    }
    buf[n] = '\0';
  
    return n;
  }
  
  static int mg_snprintf(struct mg_connection *conn, char *buf, size_t buflen,
                         const char *fmt, ...) {
    va_list ap;
    int n;
  
    va_start(ap, fmt);
    n = mg_vsnprintf(conn, buf, buflen, fmt, ap);
    va_end(ap);
  
    return n;
  }
  
  // Skip the characters until one of the delimiters characters found.
  // 0-terminate resulting word. Skip the delimiter and following whitespaces if any.
  // Advance pointer to buffer to the next word. Return found 0-terminated word.
  // Delimiters can be quoted with quotechar.
  static char *skip_quoted(char **buf, const char *delimiters, const char *whitespace, char quotechar) {
    char *p, *begin_word, *end_word, *end_whitespace;
  
    begin_word = *buf;
    end_word = begin_word + strcspn(begin_word, delimiters);
  
    /* Check for quotechar */
    if (end_word > begin_word) {
      p = end_word - 1;
      while (*p == quotechar) {
        /* If there is anything beyond end_word, copy it */
        if (*end_word == '\0') {
          *p = '\0';
          break;
        } else {
          size_t end_off = strcspn(end_word + 1, delimiters);
          memmove (p, end_word, end_off + 1);
          p += end_off; /* p must correspond to end_word - 1 */
          end_word += end_off + 1;
        }
      }
      for (p++; p < end_word; p++) {
        *p = '\0';
      }
    }
  
    if (*end_word == '\0') {
      *buf = end_word;
    } else {
      end_whitespace = end_word + 1 + strspn(end_word + 1, whitespace);
  
      for (p = end_word; p < end_whitespace; p++) {
        *p = '\0';
      }
  
      *buf = end_whitespace;
    }
  
    return begin_word;
  }
  
  // Simplified version of skip_quoted without quote char
  // and whitespace == delimiters
  static char *skip(char **buf, const char *delimiters) {
    return skip_quoted(buf, delimiters, delimiters, 0);
  }
  
  
  // Return HTTP header value, or NULL if not found.
  static const char *get_header(const struct mg_request_info *ri,
                                const char *name) {
    int i;
  
    for (i = 0; i < ri->num_headers; i++)
      if (!mg_strcasecmp(name, ri->http_headers[i].name))
        return ri->http_headers[i].value;
  
    return NULL;
  }
  
  const char *mg_get_header(const struct mg_connection *conn, const char *name) {
    return get_header(&conn->request_info, name);
  }
  
  // A helper function for traversing comma separated list of values.
  // It returns a list pointer shifted to the next value, of NULL if the end
  // of the list found.
  // Value is stored in val vector. If value has form "x=y", then eq_val
  // vector is initialized to point to the "y" part, and val vector length
  // is adjusted to point only to "x".
  static const char *next_option(const char *list, struct vec *val,
                                 struct vec *eq_val) {
    if (list == NULL || *list == '\0') {
      /* End of the list */
      list = NULL;
    } else {
      val->ptr = list;
      if ((list = strchr(val->ptr, ',')) != NULL) {
        /* Comma found. Store length and shift the list ptr */
        val->len = list - val->ptr;
        list++;
      } else {
        /* This value is the last one */
        list = val->ptr + strlen(val->ptr);
        val->len = list - val->ptr;
      }
  
      if (eq_val != NULL) {
        /*
         * Value has form "x=y", adjust pointers and lengths
         * so that val points to "x", and eq_val points to "y".
         */
        eq_val->len = 0;
        eq_val->ptr = (const char *) memchr(val->ptr, '=', val->len);
        if (eq_val->ptr != NULL) {
          eq_val->ptr++;  /* Skip over '=' character */
          eq_val->len = val->ptr + val->len - eq_val->ptr;
          val->len = (eq_val->ptr - val->ptr) - 1;
        }
      }
    }
  
    return list;
  }
  
  #if !defined(NO_CGI)
  static int match_extension(const char *path, const char *ext_list) {
    struct vec ext_vec;
    size_t path_len;
  
    path_len = strlen(path);
  
    while ((ext_list = next_option(ext_list, &ext_vec, NULL)) != NULL)
      if (ext_vec.len < path_len &&
          mg_strncasecmp(path + path_len - ext_vec.len,
            ext_vec.ptr, ext_vec.len) == 0)
        return 1;
  
    return 0;
  }
  #endif // !NO_CGI
  
  // HTTP 1.1 assumes keep alive if "Connection:" header is not set
  // This function must tolerate situations when connection info is not
  // set up, for example if request parsing failed.
  static int should_keep_alive(const struct mg_connection *conn) {
    const char *http_version = conn->request_info.http_version;
    const char *header = mg_get_header(conn, "Connection");
    return (header == NULL && http_version && !strcmp(http_version, "1.1")) ||
        (header != NULL && !mg_strcasecmp(header, "keep-alive"));
  }
  
  static const char *suggest_connection_header(const struct mg_connection *conn) {
    return should_keep_alive(conn) ? "keep-alive" : "close";
  }
  
  static void send_http_error(struct mg_connection *conn, int status,
                              const char *reason, const char *fmt, ...) {
    char buf[BUFSIZ];
    va_list ap;
    int len;
  
    conn->request_info.status_code = status;
  
    if (call_user(conn, MG_HTTP_ERROR) == NULL) {
      buf[0] = '\0';
      len = 0;
  
      /* Errors 1xx, 204 and 304 MUST NOT send a body */
      if (status > 199 && status != 204 && status != 304) {
        len = mg_snprintf(conn, buf, sizeof(buf), "Error %d: %s", status, reason);
        cry(conn, "%s", buf);
        buf[len++] = '\n';
  
        va_start(ap, fmt);
        len += mg_vsnprintf(conn, buf + len, sizeof(buf) - len, fmt, ap);
        va_end(ap);
      }
      DEBUG_TRACE(("[%s]", buf));
  
      mg_printf(conn, "HTTP/1.1 %d %s\r\n"
                "Content-Type: text/plain\r\n"
                "Content-Length: %d\r\n"
                "Connection: %s\r\n\r\n", status, reason, len,
                suggest_connection_header(conn));
      conn->num_bytes_sent += mg_printf(conn, "%s", buf);
    }
  }
  
  #if defined(_WIN32) && !defined(__SYMBIAN32__)
  static int pthread_mutex_init(pthread_mutex_t *mutex, void *unused) {
    unused = NULL;
    *mutex = CreateMutex(NULL, FALSE, NULL);
    return *mutex == NULL ? -1 : 0;
  }
  
  static int pthread_mutex_destroy(pthread_mutex_t *mutex) {
    return CloseHandle(*mutex) == 0 ? -1 : 0;
  }
  
  static int pthread_mutex_lock(pthread_mutex_t *mutex) {
    return WaitForSingleObject(*mutex, INFINITE) == WAIT_OBJECT_0? 0 : -1;
  }
  
  static int pthread_mutex_unlock(pthread_mutex_t *mutex) {
    return ReleaseMutex(*mutex) == 0 ? -1 : 0;
  }
  
  static int pthread_cond_init(pthread_cond_t *cv, const void *unused) {
    unused = NULL;
    cv->signal = CreateEvent(NULL, FALSE, FALSE, NULL);
    cv->broadcast = CreateEvent(NULL, TRUE, FALSE, NULL);
    return cv->signal != NULL && cv->broadcast != NULL ? 0 : -1;
  }
  
  static int pthread_cond_wait(pthread_cond_t *cv, pthread_mutex_t *mutex) {
    HANDLE handles[] = {cv->signal, cv->broadcast};
    ReleaseMutex(*mutex);
    WaitForMultipleObjects(2, handles, FALSE, INFINITE);
    return WaitForSingleObject(*mutex, INFINITE) == WAIT_OBJECT_0? 0 : -1;
  }
  
  static int pthread_cond_signal(pthread_cond_t *cv) {
    return SetEvent(cv->signal) == 0 ? -1 : 0;
  }
  
  static int pthread_cond_broadcast(pthread_cond_t *cv) {
    // Implementation with PulseEvent() has race condition, see
    // http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
    return PulseEvent(cv->broadcast) == 0 ? -1 : 0;
  }
  
  static int pthread_cond_destroy(pthread_cond_t *cv) {
    return CloseHandle(cv->signal) && CloseHandle(cv->broadcast) ? 0 : -1;
  }
  
  static pthread_t pthread_self(void) {
    return GetCurrentThreadId();
  }
  
  // For Windows, change all slashes to backslashes in path names.
  static void change_slashes_to_backslashes(char *path) {
    int i;
  
    for (i = 0; path[i] != '\0'; i++) {
      if (path[i] == '/')
        path[i] = '\\';
      // i > 0 check is to preserve UNC paths, like \\server\file.txt
      if (path[i] == '\\' && i > 0)
        while (path[i + 1] == '\\' || path[i + 1] == '/')
          (void) memmove(path + i + 1,
              path + i + 2, strlen(path + i + 1));
    }
  }
  
  // Encode 'path' which is assumed UTF-8 string, into UNICODE string.
  // wbuf and wbuf_len is a target buffer and its length.
  static void to_unicode(const char *path, wchar_t *wbuf, size_t wbuf_len) {
    char buf[PATH_MAX], *p;
  
    mg_strlcpy(buf, path, sizeof(buf));
    change_slashes_to_backslashes(buf);
  
    // Point p to the end of the file name
    p = buf + strlen(buf) - 1;
  
    // Trim trailing backslash character
    while (p > buf && *p == '\\' && p[-1] != ':') {
      *p-- = '\0';
    }
  
     // Protect from CGI code disclosure.
     // This is very nasty hole. Windows happily opens files with
     // some garbage in the end of file name. So fopen("a.cgi    ", "r")
     // actually opens "a.cgi", and does not return an error!
    if (*p == 0x20 ||               // No space at the end
        (*p == 0x2e && p > buf) ||  // No '.' but allow '.' as full path
        *p == 0x2b ||               // No '+'
        (*p & ~0x7f)) {             // And generally no non-ascii chars
      (void) fprintf(stderr, "Rejecting suspicious path: [%s]", buf);
      buf[0] = '\0';
    }
  
    (void) MultiByteToWideChar(CP_UTF8, 0, buf, -1, wbuf, (int) wbuf_len);
  }
  
  #if defined(_WIN32_WCE)
  static time_t time(time_t *ptime) {
    time_t t;
    SYSTEMTIME st;
    FILETIME ft;
  
    GetSystemTime(&st);
    SystemTimeToFileTime(&st, &ft);
    t = SYS2UNIX_TIME(ft.dwLowDateTime, ft.dwHighDateTime);
  
    if (ptime != NULL) {
      *ptime = t;
    }
  
    return t;
  }
  
  static time_t mktime(struct tm *ptm) {
    SYSTEMTIME st;
    FILETIME ft, lft;
  
    st.wYear = ptm->tm_year + 1900;
    st.wMonth = ptm->tm_mon + 1;
    st.wDay = ptm->tm_mday;
    st.wHour = ptm->tm_hour;
    st.wMinute = ptm->tm_min;
    st.wSecond = ptm->tm_sec;
    st.wMilliseconds = 0;
  
    SystemTimeToFileTime(&st, &ft);
    LocalFileTimeToFileTime(&ft, &lft);
    return (time_t) ((MAKEUQUAD(lft.dwLowDateTime, lft.dwHighDateTime) -
                      EPOCH_DIFF) / RATE_DIFF);
  }
  
  static struct tm *localtime(const time_t *ptime, struct tm *ptm) {
    int64_t t = ((int64_t) *ptime) * RATE_DIFF + EPOCH_DIFF;
    FILETIME ft, lft;
    SYSTEMTIME st;
    TIME_ZONE_INFORMATION tzinfo;
  
    if (ptm == NULL) {
      return NULL;
    }
  
    * (int64_t *) &ft = t;
    FileTimeToLocalFileTime(&ft, &lft);
    FileTimeToSystemTime(&lft, &st);
    ptm->tm_year = st.wYear - 1900;
    ptm->tm_mon = st.wMonth - 1;
    ptm->tm_wday = st.wDayOfWeek;
    ptm->tm_mday = st.wDay;
    ptm->tm_hour = st.wHour;
    ptm->tm_min = st.wMinute;
    ptm->tm_sec = st.wSecond;
    ptm->tm_yday = 0; // hope nobody uses this
    ptm->tm_isdst =
      GetTimeZoneInformation(&tzinfo) == TIME_ZONE_ID_DAYLIGHT ? 1 : 0;
  
    return ptm;
  }
  
  static size_t strftime(char *dst, size_t dst_size, const char *fmt,
                         const struct tm *tm) {
    (void) snprintf(dst, dst_size, "implement strftime() for WinCE");
    return 0;
  }
  #endif
  
  static int mg_rename(const char* oldname, const char* newname) {
    wchar_t woldbuf[PATH_MAX];
    wchar_t wnewbuf[PATH_MAX];
  
    to_unicode(oldname, woldbuf, ARRAY_SIZE(woldbuf));
    to_unicode(newname, wnewbuf, ARRAY_SIZE(wnewbuf));
  
    return MoveFileW(woldbuf, wnewbuf) ? 0 : -1;
  }
  
  
  static FILE *mg_fopen(const char *path, const char *mode) {
    wchar_t wbuf[PATH_MAX], wmode[20];
  
    to_unicode(path, wbuf, ARRAY_SIZE(wbuf));
    MultiByteToWideChar(CP_UTF8, 0, mode, -1, wmode, ARRAY_SIZE(wmode));
  
    return _wfopen(wbuf, wmode);
  }
  
  static int mg_stat(const char *path, struct mgstat *stp) {
    int ok = -1; // Error
    wchar_t wbuf[PATH_MAX];
    WIN32_FILE_ATTRIBUTE_DATA info;
  
    to_unicode(path, wbuf, ARRAY_SIZE(wbuf));
  
    if (GetFileAttributesExW(wbuf, GetFileExInfoStandard, &info) != 0) {
      stp->size = MAKEUQUAD(info.nFileSizeLow, info.nFileSizeHigh);
      stp->mtime = SYS2UNIX_TIME(info.ftLastWriteTime.dwLowDateTime,
                                 info.ftLastWriteTime.dwHighDateTime);
      stp->is_directory =
        info.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY;
      ok = 0;  // Success
    }
  
    return ok;
  }
  
  static int mg_remove(const char *path) {
    wchar_t wbuf[PATH_MAX];
    to_unicode(path, wbuf, ARRAY_SIZE(wbuf));
    return DeleteFileW(wbuf) ? 0 : -1;
  }
  
  static int mg_mkdir(const char *path, int mode) {
    char buf[PATH_MAX];
    wchar_t wbuf[PATH_MAX];
  
    mode = 0; // Unused
    mg_strlcpy(buf, path, sizeof(buf));
    change_slashes_to_backslashes(buf);
  
    (void) MultiByteToWideChar(CP_UTF8, 0, buf, -1, wbuf, sizeof(wbuf));
  
    return CreateDirectoryW(wbuf, NULL) ? 0 : -1;
  }
  
  // Implementation of POSIX opendir/closedir/readdir for Windows.
  static DIR * opendir(const char *name) {
    DIR *dir = NULL;
    wchar_t wpath[PATH_MAX];
    DWORD attrs;
  
    if (name == NULL) {
      SetLastError(ERROR_BAD_ARGUMENTS);
    } else if ((dir = (DIR *) malloc(sizeof(*dir))) == NULL) {
      SetLastError(ERROR_NOT_ENOUGH_MEMORY);
    } else {
      to_unicode(name, wpath, ARRAY_SIZE(wpath));
      attrs = GetFileAttributesW(wpath);
      if (attrs != 0xFFFFFFFF &&
          ((attrs & FILE_ATTRIBUTE_DIRECTORY) == FILE_ATTRIBUTE_DIRECTORY)) {
        (void) wcscat(wpath, L"\\*");
        dir->handle = FindFirstFileW(wpath, &dir->info);
        dir->result.d_name[0] = '\0';
      } else {
        free(dir);
        dir = NULL;
      }
    }
  
    return dir;
  }
  
  static int closedir(DIR *dir) {
    int result = 0;
  
    if (dir != NULL) {
      if (dir->handle != INVALID_HANDLE_VALUE)
        result = FindClose(dir->handle) ? 0 : -1;
  
      free(dir);
    } else {
      result = -1;
      SetLastError(ERROR_BAD_ARGUMENTS);
    }
  
    return result;
  }
  
  struct dirent * readdir(DIR *dir) {
    struct dirent *result = 0;
  
    if (dir) {
      if (dir->handle != INVALID_HANDLE_VALUE) {
        result = &dir->result;
        (void) WideCharToMultiByte(CP_UTF8, 0,
            dir->info.cFileName, -1, result->d_name,
            sizeof(result->d_name), NULL, NULL);
  
        if (!FindNextFileW(dir->handle, &dir->info)) {
          (void) FindClose(dir->handle);
          dir->handle = INVALID_HANDLE_VALUE;
        }
  
      } else {
        SetLastError(ERROR_FILE_NOT_FOUND);
      }
    } else {
      SetLastError(ERROR_BAD_ARGUMENTS);
    }
  
    return result;
  }
  
  #define set_close_on_exec(fd) // No FD_CLOEXEC on Windows
  
  static int start_thread(struct mg_context *ctx, mg_thread_func_t func,
                          void *param) {
    HANDLE hThread;
    ctx = NULL; // Unused
  
    hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE) func, param, 0,
                           NULL);
    if (hThread != NULL) {
      (void) CloseHandle(hThread);
    }
  
    return hThread == NULL ? -1 : 0;
  }
  
  static HANDLE dlopen(const char *dll_name, int flags) {
    wchar_t wbuf[PATH_MAX];
    flags = 0; // Unused
    to_unicode(dll_name, wbuf, ARRAY_SIZE(wbuf));
    return LoadLibraryW(wbuf);
  }
  
  #if !defined(NO_CGI)
  #define SIGKILL 0
  static int kill(pid_t pid, int sig_num) {
    (void) TerminateProcess(pid, sig_num);
    (void) CloseHandle(pid);
    return 0;
  }
  
  static pid_t spawn_process(struct mg_connection *conn, const char *prog,
                             char *envblk, char *envp[], int fd_stdin,
                             int fd_stdout, const char *dir) {
    HANDLE me;
    char *p, *interp, cmdline[PATH_MAX], buf[PATH_MAX];
    FILE *fp;
    STARTUPINFOA si;
    PROCESS_INFORMATION pi;
  
    envp = NULL; // Unused
  
    (void) memset(&si, 0, sizeof(si));
    (void) memset(&pi, 0, sizeof(pi));
  
    // TODO(lsm): redirect CGI errors to the error log file
    si.cb  = sizeof(si);
    si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
    si.wShowWindow = SW_HIDE;
  
    me = GetCurrentProcess();
    (void) DuplicateHandle(me, (HANDLE) _get_osfhandle(fd_stdin), me,
        &si.hStdInput, 0, TRUE, DUPLICATE_SAME_ACCESS);
    (void) DuplicateHandle(me, (HANDLE) _get_osfhandle(fd_stdout), me,
        &si.hStdOutput, 0, TRUE, DUPLICATE_SAME_ACCESS);
  
    // If CGI file is a script, try to read the interpreter line
    interp = conn->ctx->config[CGI_INTERPRETER];
    if (interp == NULL) {
      buf[2] = '\0';
      if ((fp = fopen(cmdline, "r")) != NULL) {
        (void) fgets(buf, sizeof(buf), fp);
        if (buf[0] != '#' || buf[1] != '!') {
          // First line does not start with "#!". Do not set interpreter.
          buf[2] = '\0';
        } else {
          // Trim whitespaces in interpreter name
          for (p = &buf[strlen(buf) - 1]; p > buf && isspace(*p); p--) {
            *p = '\0';
          }
        }
        (void) fclose(fp);
      }
      interp = buf + 2;
    }
  
    (void) mg_snprintf(conn, cmdline, sizeof(cmdline), "%s%s%s%c%s",
                       interp, interp[0] == '\0' ? "" : " ", dir, DIRSEP, prog);
  
    DEBUG_TRACE(("Running [%s]", cmdline));
    if (CreateProcessA(NULL, cmdline, NULL, NULL, TRUE,
          CREATE_NEW_PROCESS_GROUP, envblk, dir, &si, &pi) == 0) {
      cry(conn, "%s: CreateProcess(%s): %d",
          __func__, cmdline, ERRNO);
      pi.hProcess = (pid_t) -1;
    } else {
      (void) close(fd_stdin);
      (void) close(fd_stdout);
    }
  
    (void) CloseHandle(si.hStdOutput);
    (void) CloseHandle(si.hStdInput);
    (void) CloseHandle(pi.hThread);
  
    return (pid_t) pi.hProcess;
  }
  #endif /* !NO_CGI */
  
  static int set_non_blocking_mode(SOCKET sock) {
    unsigned long on = 1;
    return ioctlsocket(sock, FIONBIO, &on);
  }
  
  #else
  static int mg_stat(const char *path, struct mgstat *stp) {
    struct stat st;
    int ok;
  
    if (stat(path, &st) == 0) {
      ok = 0;
      stp->size = st.st_size;
      stp->mtime = st.st_mtime;
      stp->is_directory = S_ISDIR(st.st_mode);
    } else {
      ok = -1;
    }
  
    return ok;
  }
  
  static void set_close_on_exec(int fd) {
    (void) fcntl(fd, F_SETFD, FD_CLOEXEC);
  }
  
  static int start_thread(struct mg_context *ctx, mg_thread_func_t func,
                          void *param) {
    pthread_t thread_id;
    pthread_attr_t attr;
    int retval;
  
    (void) pthread_attr_init(&attr);
    (void) pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
    // TODO(lsm): figure out why mongoose dies on Linux if next line is enabled
    // (void) pthread_attr_setstacksize(&attr, sizeof(struct mg_connection) * 5);
  
    if ((retval = pthread_create(&thread_id, &attr, func, param)) != 0) {
      cry(fc(ctx), "%s: %s", __func__, strerror(retval));
    }
  
    return retval;
  }
  
  #ifndef NO_CGI
  static pid_t spawn_process(struct mg_connection *conn, const char *prog,
                             char *envblk, char *envp[], int fd_stdin,
                             int fd_stdout, const char *dir) {
    pid_t pid;
    const char *interp;
  
    envblk = NULL; // Unused
  
    if ((pid = fork()) == -1) {
      // Parent
      send_http_error(conn, 500, http_500_error, "fork(): %s", strerror(ERRNO));
    } else if (pid == 0) {
      // Child
      if (chdir(dir) != 0) {
        cry(conn, "%s: chdir(%s): %s", __func__, dir, strerror(ERRNO));
      } else if (dup2(fd_stdin, 0) == -1) {
        cry(conn, "%s: dup2(%d, 0): %s", __func__, fd_stdin, strerror(ERRNO));
      } else if (dup2(fd_stdout, 1) == -1) {
        cry(conn, "%s: dup2(%d, 1): %s", __func__, fd_stdout, strerror(ERRNO));
      } else {
        (void) dup2(fd_stdout, 2);
        (void) close(fd_stdin);
        (void) close(fd_stdout);
  
        // Execute CGI program. No need to lock: new process
        interp = conn->ctx->config[CGI_INTERPRETER];
        if (interp == NULL) {
          (void) execle(prog, prog, NULL, envp);
          cry(conn, "%s: execle(%s): %s", __func__, prog, strerror(ERRNO));
        } else {
          (void) execle(interp, interp, prog, NULL, envp);
          cry(conn, "%s: execle(%s %s): %s", __func__, interp, prog,
              strerror(ERRNO));
        }
      }
      exit(EXIT_FAILURE);
    } else {
      // Parent. Close stdio descriptors
      (void) close(fd_stdin);
      (void) close(fd_stdout);
    }
  
    return pid;
  }
  #endif // !NO_CGI
  
  static int set_non_blocking_mode(SOCKET sock) {
    int flags;
  
    flags = fcntl(sock, F_GETFL, 0);
    (void) fcntl(sock, F_SETFL, flags | O_NONBLOCK);
  
    return 0;
  }
  #endif // _WIN32
  
  // Write data to the IO channel - opened file descriptor, socket or SSL
  // descriptor. Return number of bytes written.
  static int64_t push(FILE *fp, SOCKET sock, SSL *ssl, const char *buf,
                      int64_t len) {
    int64_t sent;
    int n, k;
  
    sent = 0;
    while (sent < len) {
  
      /* How many bytes we send in this iteration */
      k = len - sent > INT_MAX ? INT_MAX : (int) (len - sent);
  
      if (ssl != NULL) {
        n = SSL_write(ssl, buf + sent, k);
      } else if (fp != NULL) {
        n = fwrite(buf + sent, 1, (size_t)k, fp);
        if (ferror(fp))
          n = -1;
      } else {
        n = send(sock, buf + sent, (size_t)k, 0);
      }
  
      if (n < 0)
        break;
  
      sent += n;
    }
  
    return sent;
  }
  
  // Read from IO channel - opened file descriptor, socket, or SSL descriptor.
  // Return number of bytes read.
  static int pull(FILE *fp, SOCKET sock, SSL *ssl, char *buf, int len) {
    int nread;
  
    if (ssl != NULL) {
      nread = SSL_read(ssl, buf, len);
    } else if (fp != NULL) {
      // Use read() instead of fread(), because if we're reading from the CGI
      // pipe, fread() may block until IO buffer is filled up. We cannot afford
      // to block and must pass all read bytes immediately to the client.
      nread = read(fileno(fp), buf, (size_t) len);
      if (ferror(fp))
        nread = -1;
    } else {
      nread = recv(sock, buf, (size_t) len, 0);
    }
  
    return nread;
  }
  
  int mg_read(struct mg_connection *conn, void *buf, size_t len) {
    int n, buffered_len, nread;
    const char *buffered;
  
    assert((conn->content_len == -1 && conn->consumed_content == 0) ||
           conn->consumed_content <= conn->content_len);
    DEBUG_TRACE(("%p %zu %lld %lld", buf, len,
                 conn->content_len, conn->consumed_content));
    nread = 0;
    if (conn->consumed_content < conn->content_len) {
  
      // Adjust number of bytes to read.
      int64_t to_read = conn->content_len - conn->consumed_content;
      if (to_read < (int64_t) len) {
        len = (int) to_read;
      }
  
      // How many bytes of data we have buffered in the request buffer?
      buffered = conn->buf + conn->request_len + conn->consumed_content;
      buffered_len = conn->data_len - conn->request_len;
      assert(buffered_len >= 0);
  
      // Return buffered data back if we haven't done that yet.
      if (conn->consumed_content < (int64_t) buffered_len) {
        buffered_len -= (int) conn->consumed_content;
        if (len < (size_t) buffered_len) {
          buffered_len = len;
        }
        memcpy(buf, buffered, (size_t)buffered_len);
        len -= buffered_len;
        buf = (char *) buf + buffered_len;
        conn->consumed_content += buffered_len;
        nread = buffered_len;
      }
  
      // We have returned all buffered data. Read new data from the remote socket.
      while (len > 0) {
        n = pull(NULL, conn->client.sock, conn->ssl, (char *) buf, (int) len);
        if (n <= 0) {
          break;
        }
        buf = (char *) buf + n;
        conn->consumed_content += n;
        nread += n;
        len -= n;
      }
    }
    return nread;
  }
  
  int mg_write(struct mg_connection *conn, const void *buf, size_t len) {
    return (int) push(NULL, conn->client.sock, conn->ssl,
        (const char *) buf, (int64_t) len);
  }
  
  int mg_printf(struct mg_connection *conn, const char *fmt, ...) {
    char buf[BUFSIZ];
    int len;
    va_list ap;
  
    va_start(ap, fmt);
    len = mg_vsnprintf(conn, buf, sizeof(buf), fmt, ap);
    va_end(ap);
  
    return mg_write(conn, buf, (size_t)len);
  }
  
  // URL-decode input buffer into destination buffer.
  // 0-terminate the destination buffer. Return the length of decoded data.
  // form-url-encoded data differs from URI encoding in a way that it
  // uses '+' as character for space, see RFC 1866 section 8.2.1
  // http://ftp.ics.uci.edu/pub/ietf/html/rfc1866.txt
  static size_t url_decode(const char *src, size_t src_len, char *dst,
                           size_t dst_len, int is_form_url_encoded) {
    size_t i, j;
    int a, b;
  #define HEXTOI(x) (isdigit(x) ? x - '0' : x - 'W')
  
    for (i = j = 0; i < src_len && j < dst_len - 1; i++, j++) {
      if (src[i] == '%' &&
          isxdigit(* (const unsigned char *) (src + i + 1)) &&
          isxdigit(* (const unsigned char *) (src + i + 2))) {
        a = tolower(* (const unsigned char *) (src + i + 1));
        b = tolower(* (const unsigned char *) (src + i + 2));
        dst[j] = (char) ((HEXTOI(a) << 4) | HEXTOI(b));
        i += 2;
      } else if (is_form_url_encoded && src[i] == '+') {
        dst[j] = ' ';
      } else {
        dst[j] = src[i];
      }
    }
  
    dst[j] = '\0'; /* Null-terminate the destination */
  
    return j;
  }
  
  // Scan given buffer and fetch the value of the given variable.
  // It can be specified in query string, or in the POST data.
  // Return NULL if the variable not found, or allocated 0-terminated value.
  // It is caller's responsibility to free the returned value.
  int mg_get_var(const char *buf, size_t buf_len, const char *name,
                 char *dst, size_t dst_len) {
    const char *p, *e, *s;
    size_t name_len, len;
  
    name_len = strlen(name);
    e = buf + buf_len;
    len = -1;
    dst[0] = '\0';
  
    // buf is "var1=val1&var2=val2...". Find variable first
    for (p = buf; p != NULL && p + name_len < e; p++) {
      if ((p == buf || p[-1] == '&') && p[name_len] == '=' &&
          !mg_strncasecmp(name, p, name_len)) {
  
        // Point p to variable value
        p += name_len + 1;
  
        // Point s to the end of the value
        s = (const char *) memchr(p, '&', (size_t)(e - p));
        if (s == NULL) {
          s = e;
        }
        assert(s >= p);
  
        // Decode variable into destination buffer
        if ((size_t) (s - p) < dst_len) {
          len = url_decode(p, (size_t)(s - p), dst, dst_len, 1);
        }
        break;
      }
    }
  
    return len;
  }
  
  int mg_get_cookie(const struct mg_connection *conn, const char *cookie_name,
                    char *dst, size_t dst_size) {
    const char *s, *p, *end;
    int name_len, len = -1;
  
    dst[0] = '\0';
    if ((s = mg_get_header(conn, "Cookie")) == NULL) {
      return 0;
    }
  
    name_len = strlen(cookie_name);
    end = s + strlen(s);
  
    for (; (s = strstr(s, cookie_name)) != NULL; s += name_len)
      if (s[name_len] == '=') {
        s += name_len + 1;
        if ((p = strchr(s, ' ')) == NULL)
          p = end;
        if (p[-1] == ';')
          p--;
        if (*s == '"' && p[-1] == '"' && p > s + 1) {
          s++;
          p--;
        }
        if ((size_t) (p - s) < dst_size) {
          len = (p - s) + 1;
          mg_strlcpy(dst, s, (size_t)len);
        }
        break;
      }
  
    return len;
  }
  
  // Mongoose allows to specify multiple directories to serve,
  // like /var/www,/~bob=/home/bob. That means that root directory depends on URI.
  // This function returns root dir for given URI.
  static int get_document_root(const struct mg_connection *conn,
                               struct vec *document_root) {
    const char *root, *uri;
    int len_of_matched_uri;
    struct vec uri_vec, path_vec;
  
    uri = conn->request_info.uri;
    len_of_matched_uri = 0;
    root = next_option(conn->ctx->config[DOCUMENT_ROOT], document_root, NULL);
  
    while ((root = next_option(root, &uri_vec, &path_vec)) != NULL) {
      if (memcmp(uri, uri_vec.ptr, uri_vec.len) == 0) {
        *document_root = path_vec;
        len_of_matched_uri = uri_vec.len;
        break;
      }
    }
  
    return len_of_matched_uri;
  }
  
  static void convert_uri_to_file_name(struct mg_connection *conn,
                                       const char *uri, char *buf,
                                       size_t buf_len) {
    struct vec vec;
    int match_len;
  
    match_len = get_document_root(conn, &vec);
    mg_snprintf(conn, buf, buf_len, "%.*s%s", vec.len, vec.ptr, uri + match_len);
  
  #if defined(_WIN32) && !defined(__SYMBIAN32__)
    change_slashes_to_backslashes(buf);
  #endif /* _WIN32 */
  
    DEBUG_TRACE(("[%s] -> [%s], [%.*s]", uri, buf, (int) vec.len, vec.ptr));
  }
  
  static int sslize(struct mg_connection *conn, int (*func)(SSL *)) {
    return (conn->ssl = SSL_new(conn->ctx->ssl_ctx)) != NULL &&
      SSL_set_fd(conn->ssl, conn->client.sock) == 1 &&
      func(conn->ssl) == 1;
  }
  
  static struct mg_connection *mg_connect(struct mg_connection *conn,
                                   const char *host, int port, int use_ssl) {
    struct mg_connection *newconn = NULL;
    struct sockaddr_in sin;
    struct hostent *he;
    int sock;
  
    if (conn->ctx->ssl_ctx == NULL && use_ssl) {
      cry(conn, "%s: SSL is not initialized", __func__);
    } else if ((he = gethostbyname(host)) == NULL) {
      cry(conn, "%s: gethostbyname(%s): %s", __func__, host, strerror(ERRNO));
    } else if ((sock = socket(PF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) {
      cry(conn, "%s: socket: %s", __func__, strerror(ERRNO));
    } else {
      sin.sin_family = AF_INET;
      sin.sin_port = htons((uint16_t) port);
      sin.sin_addr = * (struct in_addr *) he->h_addr_list[0];
      if (connect(sock, (struct sockaddr *) &sin, sizeof(sin)) != 0) {
        cry(conn, "%s: connect(%s:%d): %s", __func__, host, port,
            strerror(ERRNO));
        closesocket(sock);
      } else if ((newconn = (struct mg_connection *)
                  calloc(1, sizeof(*newconn))) == NULL) {
        cry(conn, "%s: calloc: %s", __func__, strerror(ERRNO));
        closesocket(sock);
      } else {
        newconn->client.sock = sock;
        newconn->client.rsa.u.sin = sin;
        if (use_ssl) {
          sslize(newconn, SSL_connect);
        }
      }
    }
  
    return newconn;
  }
  
  // Check whether full request is buffered. Return:
  //   -1  if request is malformed
  //    0  if request is not yet fully buffered
  //   >0  actual request length, including last \r\n\r\n
  static int get_request_len(const char *buf, int buflen) {
    const char *s, *e;
    int len = 0;
  
    DEBUG_TRACE(("buf: %p, len: %d", buf, buflen));
    for (s = buf, e = s + buflen - 1; len <= 0 && s < e; s++)
      // Control characters are not allowed but >=128 is.
      if (!isprint(* (const unsigned char *) s) && *s != '\r' &&
          *s != '\n' && * (const unsigned char *) s < 128) {
        len = -1;
      } else if (s[0] == '\n' && s[1] == '\n') {
        len = (int) (s - buf) + 2;
      } else if (s[0] == '\n' && &s[1] < e &&
          s[1] == '\r' && s[2] == '\n') {
        len = (int) (s - buf) + 3;
      }
  
    return len;
  }
  
  // Convert month to the month number. Return -1 on error, or month number
  static int month_number_to_month_name(const char *s) {
    size_t i;
  
    for (i = 0; i < ARRAY_SIZE(month_names); i++)
      if (!strcmp(s, month_names[i]))
        return (int) i;
  
    return -1;
  }
  
  // Parse date-time string, and return the corresponding time_t value
  static time_t parse_date_string(const char *s) {
    time_t current_time;
    struct tm tm, *tmp;
    char mon[32];
    int sec, min, hour, mday, month, year;
  
    (void) memset(&tm, 0, sizeof(tm));
    sec = min = hour = mday = month = year = 0;
  
    if (((sscanf(s, "%d/%3s/%d %d:%d:%d",
              &mday, mon, &year, &hour, &min, &sec) == 6) ||
          (sscanf(s, "%d %3s %d %d:%d:%d",
                  &mday, mon, &year, &hour, &min, &sec) == 6) ||
          (sscanf(s, "%*3s, %d %3s %d %d:%d:%d",
                  &mday, mon, &year, &hour, &min, &sec) == 6) ||
          (sscanf(s, "%d-%3s-%d %d:%d:%d",
                  &mday, mon, &year, &hour, &min, &sec) == 6)) &&
        (month = month_number_to_month_name(mon)) != -1) {
      tm.tm_mday = mday;
      tm.tm_mon = month;
      tm.tm_year = year;
      tm.tm_hour = hour;
      tm.tm_min = min;
      tm.tm_sec = sec;
    }
  
    if (tm.tm_year > 1900) {
      tm.tm_year -= 1900;
    } else if (tm.tm_year < 70) {
      tm.tm_year += 100;
    }
  
    // Set Daylight Saving Time field
    current_time = time(NULL);
    tmp = localtime(&current_time);
    tm.tm_isdst = tmp->tm_isdst;
  
    return mktime(&tm);
  }
  
  // Protect against directory disclosure attack by removing '..',
  // excessive '/' and '\' characters
  static void remove_double_dots_and_double_slashes(char *s) {
    char *p = s;
  
    while (*s != '\0') {
      *p++ = *s++;
      if (s[-1] == '/' || s[-1] == '\\') {
        // Skip all following slashes and backslashes
        while (*s == '/' || *s == '\\') {
          s++;
        }
  
        // Skip all double-dots
        while (*s == '.' && s[1] == '.') {
          s += 2;
        }
      }
    }
    *p = '\0';
  }
  
  static const struct {
    const char *extension;
    size_t ext_len;
    const char *mime_type;
    size_t mime_type_len;
  } builtin_mime_types[] = {
    {".html", 5, "text/html",   9},
    {".htm", 4, "text/html",   9},
    {".shtm", 5, "text/html",   9},
    {".shtml", 6, "text/html",   9},
    {".css", 4, "text/css",   8},
    {".js",  3, "application/x-javascript", 24},
    {".ico", 4, "image/x-icon",   12},
    {".gif", 4, "image/gif",   9},
    {".jpg", 4, "image/jpeg",   10},
    {".jpeg", 5, "image/jpeg",   10},
    {".png", 4, "image/png",   9},
    {".svg", 4, "image/svg+xml",  13},
    {".torrent", 8, "application/x-bittorrent", 24},
    {".wav", 4, "audio/x-wav",   11},
    {".mp3", 4, "audio/x-mp3",   11},
    {".mid", 4, "audio/mid",   9},
    {".m3u", 4, "audio/x-mpegurl",  15},
    {".ram", 4, "audio/x-pn-realaudio",  20},
    {".xml", 4, "text/xml",   8},
    {".xslt", 5, "application/xml",  15},
    {".ra",  3, "audio/x-pn-realaudio",  20},
    {".doc", 4, "application/msword",  19},
    {".exe", 4, "application/octet-stream", 24},
    {".zip", 4, "application/x-zip-compressed", 28},
    {".xls", 4, "application/excel",  17},
    {".tgz", 4, "application/x-tar-gz",  20},
    {".tar", 4, "application/x-tar",  17},
    {".gz",  3, "application/x-gunzip",  20},
    {".arj", 4, "application/x-arj-compressed", 28},
    {".rar", 4, "application/x-arj-compressed", 28},
    {".rtf", 4, "application/rtf",  15},
    {".pdf", 4, "application/pdf",  15},
    {".swf", 4, "application/x-shockwave-flash",29},
    {".mpg", 4, "video/mpeg",   10},
    {".mpeg", 5, "video/mpeg",   10},
    {".asf", 4, "video/x-ms-asf",  14},
    {".avi", 4, "video/x-msvideo",  15},
    {".bmp", 4, "image/bmp",   9},
    {NULL,  0, NULL,    0}
  };
  
  // Look at the "path" extension and figure what mime type it has.
  // Store mime type in the vector.
  static void get_mime_type(struct mg_context *ctx, const char *path,
                            struct vec *vec) {
    struct vec ext_vec, mime_vec;
    const char *list, *ext;
    size_t i, path_len;
  
    path_len = strlen(path);
  
    // Scan user-defined mime types first, in case user wants to
    // override default mime types.
    list = ctx->config[EXTRA_MIME_TYPES];
    while ((list = next_option(list, &ext_vec, &mime_vec)) != NULL) {
      // ext now points to the path suffix
      ext = path + path_len - ext_vec.len;
      if (mg_strncasecmp(ext, ext_vec.ptr, ext_vec.len) == 0) {
        *vec = mime_vec;
        return;
      }
    }
  
    // Now scan built-in mime types
    for (i = 0; builtin_mime_types[i].extension != NULL; i++) {
      ext = path + (path_len - builtin_mime_types[i].ext_len);
      if (path_len > builtin_mime_types[i].ext_len &&
          mg_strcasecmp(ext, builtin_mime_types[i].extension) == 0) {
        vec->ptr = builtin_mime_types[i].mime_type;
        vec->len = builtin_mime_types[i].mime_type_len;
        return;
      }
    }
  
    // Nothing found. Fall back to "text/plain"
    vec->ptr = "text/plain";
    vec->len = 10;
  }
  
  #ifndef HAVE_MD5
  typedef struct MD5Context {
    uint32_t buf[4];
    uint32_t bits[2];
    unsigned char in[64];
  } MD5_CTX;
  
  #if defined(__BYTE_ORDER) && (__BYTE_ORDER == 1234)
  #define byteReverse(buf, len) // Do nothing
  #else
  static void byteReverse(unsigned char *buf, unsigned longs) {
    uint32_t t;
    do {
      t = (uint32_t) ((unsigned) buf[3] << 8 | buf[2]) << 16 |
        ((unsigned) buf[1] << 8 | buf[0]);
      *(uint32_t *) buf = t;
      buf += 4;
    } while (--longs);
  }
  #endif
  
  #define F1(x, y, z) (z ^ (x & (y ^ z)))
  #define F2(x, y, z) F1(z, x, y)
  #define F3(x, y, z) (x ^ y ^ z)
  #define F4(x, y, z) (y ^ (x | ~z))
  
  #define MD5STEP(f, w, x, y, z, data, s) \
    ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )
  
  // Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
  // initialization constants.
  static void MD5Init(MD5_CTX *ctx) {
    ctx->buf[0] = 0x67452301;
    ctx->buf[1] = 0xefcdab89;
    ctx->buf[2] = 0x98badcfe;
    ctx->buf[3] = 0x10325476;
  
    ctx->bits[0] = 0;
    ctx->bits[1] = 0;
  }
  
  static void MD5Transform(uint32_t buf[4], uint32_t const in[16]) {
    register uint32_t a, b, c, d;
  
    a = buf[0];
    b = buf[1];
    c = buf[2];
    d = buf[3];
  
    MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
    MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
    MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
    MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
    MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
    MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
    MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
    MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
    MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
    MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
    MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
    MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
    MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
    MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
    MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
    MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);
  
    MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
    MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
    MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
    MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
    MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
    MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
    MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
    MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
    MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
    MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
    MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
    MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
    MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
    MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
    MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
    MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);
  
    MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
    MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
    MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
    MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
    MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
    MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
    MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
    MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
    MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
    MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
    MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
    MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
    MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
    MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
    MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
    MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);
  
    MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
    MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
    MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
    MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
    MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
    MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
    MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
    MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
    MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
    MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
    MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
    MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
    MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
    MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
    MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
    MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);
  
    buf[0] += a;
    buf[1] += b;
    buf[2] += c;
    buf[3] += d;
  }
  
  static void MD5Update(MD5_CTX *ctx, unsigned char const *buf, unsigned len) {
    uint32_t t;
  
    t = ctx->bits[0];
    if ((ctx->bits[0] = t + ((uint32_t) len << 3)) < t)
      ctx->bits[1]++;
    ctx->bits[1] += len >> 29;
  
    t = (t >> 3) & 0x3f;
  
    if (t) {
      unsigned char *p = (unsigned char *) ctx->in + t;
  
      t = 64 - t;
      if (len < t) {
        memcpy(p, buf, len);
        return;
      }
      memcpy(p, buf, t);
      byteReverse(ctx->in, 16);
      MD5Transform(ctx->buf, (uint32_t *) ctx->in);
      buf += t;
      len -= t;
    }
  
    while (len >= 64) {
      memcpy(ctx->in, buf, 64);
      byteReverse(ctx->in, 16);
      MD5Transform(ctx->buf, (uint32_t *) ctx->in);
      buf += 64;
      len -= 64;
    }
  
    memcpy(ctx->in, buf, len);
  }
  
  static void MD5Final(unsigned char digest[16], MD5_CTX *ctx) {
    unsigned count;
    unsigned char *p;
  
    count = (ctx->bits[0] >> 3) & 0x3F;
  
    p = ctx->in + count;
    *p++ = 0x80;
    count = 64 - 1 - count;
    if (count < 8) {
      memset(p, 0, count);
      byteReverse(ctx->in, 16);
      MD5Transform(ctx->buf, (uint32_t *) ctx->in);
      memset(ctx->in, 0, 56);
    } else {
      memset(p, 0, count - 8);
    }
    byteReverse(ctx->in, 14);
  
    ((uint32_t *) ctx->in)[14] = ctx->bits[0];
    ((uint32_t *) ctx->in)[15] = ctx->bits[1];
  
    MD5Transform(ctx->buf, (uint32_t *) ctx->in);
    byteReverse((unsigned char *) ctx->buf, 4);
    memcpy(digest, ctx->buf, 16);
    memset((char *) ctx, 0, sizeof(*ctx));
  }
  #endif // !HAVE_MD5
  
  // Stringify binary data. Output buffer must be twice as big as input,
  // because each byte takes 2 bytes in string representation
  static void bin2str(char *to, const unsigned char *p, size_t len) {
    static const char *hex = "0123456789abcdef";
  
    for (; len--; p++) {
      *to++ = hex[p[0] >> 4];
      *to++ = hex[p[0] & 0x0f];
    }
    *to = '\0';
  }
  
  // Return stringified MD5 hash for list of vectors. Buffer must be 33 bytes.
  void mg_md5(char *buf, ...) {
    unsigned char hash[16];
    const char *p;
    va_list ap;
    MD5_CTX ctx;
  
    MD5Init(&ctx);
  
    va_start(ap, buf);
    while ((p = va_arg(ap, const char *)) != NULL) {
      MD5Update(&ctx, (const unsigned char *) p, (unsigned) strlen(p));
    }
    va_end(ap);
  
    MD5Final(hash, &ctx);
    bin2str(buf, hash, sizeof(hash));
  }
  
  // Check the user's password, return 1 if OK
  static int check_password(const char *method, const char *ha1, const char *uri,
                            const char *nonce, const char *nc, const char *cnonce,
                            const char *qop, const char *response) {
    char ha2[32 + 1], expected_response[32 + 1];
  
    // Some of the parameters may be NULL
    if (method == NULL || nonce == NULL || nc == NULL || cnonce == NULL ||
        qop == NULL || response == NULL) {
      return 0;
    }
  
    // NOTE(lsm): due to a bug in MSIE, we do not compare the URI
    // TODO(lsm): check for authentication timeout
    if (// strcmp(dig->uri, c->ouri) != 0 ||
        strlen(response) != 32
        // || now - strtoul(dig->nonce, NULL, 10) > 3600
        ) {
      return 0;
    }
  
    mg_md5(ha2, method, ":", uri, NULL);
    mg_md5(expected_response, ha1, ":", nonce, ":", nc,
        ":", cnonce, ":", qop, ":", ha2, NULL);
  
    return mg_strcasecmp(response, expected_response) == 0;
  }
  
  // Use the global passwords file, if specified by auth_gpass option,
  // or search for .htpasswd in the requested directory.
  static FILE *open_auth_file(struct mg_connection *conn, const char *path) {
    struct mg_context *ctx = conn->ctx;
    char name[PATH_MAX];
    const char *p, *e;
    struct mgstat st;
    FILE *fp;
  
    if (ctx->config[GLOBAL_PASSWORDS_FILE] != NULL) {
      // Use global passwords file
      fp =  mg_fopen(ctx->config[GLOBAL_PASSWORDS_FILE], "r");
      if (fp == NULL)
        cry(fc(ctx), "fopen(%s): %s",
            ctx->config[GLOBAL_PASSWORDS_FILE], strerror(ERRNO));
    } else if (!mg_stat(path, &st) && st.is_directory) {
      (void) mg_snprintf(conn, name, sizeof(name), "%s%c%s",
          path, DIRSEP, PASSWORDS_FILE_NAME);
      fp = mg_fopen(name, "r");
    } else {
       // Try to find .htpasswd in requested directory.
      for (p = path, e = p + strlen(p) - 1; e > p; e--)
        if (IS_DIRSEP_CHAR(*e))
          break;
      (void) mg_snprintf(conn, name, sizeof(name), "%.*s%c%s",
          (int) (e - p), p, DIRSEP, PASSWORDS_FILE_NAME);
      fp = mg_fopen(name, "r");
    }
  
    return fp;
  }
  
  // Parsed Authorization header
  struct ah {
    char *user, *uri, *cnonce, *response, *qop, *nc, *nonce;
  };
  
  static int parse_auth_header(struct mg_connection *conn, char *buf,
                               size_t buf_size, struct ah *ah) {
    char *name, *value, *s;
    const char *auth_header;
  
    if ((auth_header = mg_get_header(conn, "Authorization")) == NULL ||
        mg_strncasecmp(auth_header, "Digest ", 7) != 0) {
      return 0;
    }
  
    // Make modifiable copy of the auth header
    (void) mg_strlcpy(buf, auth_header + 7, buf_size);
  
    s = buf;
    (void) memset(ah, 0, sizeof(*ah));
  
    // Parse authorization header
    for (;;) {
      // Gobble initial spaces
      while (isspace(* (unsigned char *) s)) {
        s++;
      }
      name = skip_quoted(&s, "=", " ", 0);
      /* Value is either quote-delimited, or ends at first comma or space. */
      if (s[0] == '\"') {
        s++;
        value = skip_quoted(&s, "\"", " ", '\\');
        if (s[0] == ',') {
          s++;
        }
      } else {
        value = skip_quoted(&s, ", ", " ", 0);  // IE uses commas, FF uses spaces
      }
      if (*name == '\0') {
        break;
      }
  
      if (!strcmp(name, "username")) {
        ah->user = value;
      } else if (!strcmp(name, "cnonce")) {
        ah->cnonce = value;
      } else if (!strcmp(name, "response")) {
        ah->response = value;
      } else if (!strcmp(name, "uri")) {
        ah->uri = value;
      } else if (!strcmp(name, "qop")) {
        ah->qop = value;
      } else if (!strcmp(name, "nc")) {
        ah->nc = value;
      } else if (!strcmp(name, "nonce")) {
        ah->nonce = value;
      }
    }
  
    // CGI needs it as REMOTE_USER
    if (ah->user != NULL) {
      conn->request_info.remote_user = mg_strdup(ah->user);
    } else {
      return 0;
    }
  
    return 1;
  }
  
  // Authorize against the opened passwords file. Return 1 if authorized.
  static int authorize(struct mg_connection *conn, FILE *fp) {
    struct ah ah;
    char line[256], f_user[256], ha1[256], f_domain[256], buf[BUFSIZ];
  
    if (!parse_auth_header(conn, buf, sizeof(buf), &ah)) {
      return 0;
    }
  
    // Loop over passwords file
    while (fgets(line, sizeof(line), fp) != NULL) {
      if (sscanf(line, "%[^:]:%[^:]:%s", f_user, f_domain, ha1) != 3) {
        continue;
      }
  
      if (!strcmp(ah.user, f_user) &&
          !strcmp(conn->ctx->config[AUTHENTICATION_DOMAIN], f_domain))
        return check_password(
              conn->request_info.request_method,
              ha1, ah.uri, ah.nonce, ah.nc, ah.cnonce, ah.qop,
              ah.response);
    }
  
    return 0;
  }
  
  // Return 1 if request is authorised, 0 otherwise.
  static int check_authorization(struct mg_connection *conn, const char *path) {
    FILE *fp;
    char fname[PATH_MAX];
    struct vec uri_vec, filename_vec;
    const char *list;
    int authorized;
  
    fp = NULL;
    authorized = 1;
  
    list = conn->ctx->config[PROTECT_URI];
    while ((list = next_option(list, &uri_vec, &filename_vec)) != NULL) {
      if (!memcmp(conn->request_info.uri, uri_vec.ptr, uri_vec.len)) {
        (void) mg_snprintf(conn, fname, sizeof(fname), "%.*s",
            filename_vec.len, filename_vec.ptr);
        if ((fp = mg_fopen(fname, "r")) == NULL) {
          cry(conn, "%s: cannot open %s: %s", __func__, fname, strerror(errno));
        }
        break;
      }
    }
  
    if (fp == NULL) {
      fp = open_auth_file(conn, path);
    }
  
    if (fp != NULL) {
      authorized = authorize(conn, fp);
      (void) fclose(fp);
    }
  
    return authorized;
  }
  
  static void send_authorization_request(struct mg_connection *conn) {
    conn->request_info.status_code = 401;
    (void) mg_printf(conn,
        "HTTP/1.1 401 Unauthorized\r\n"
        "WWW-Authenticate: Digest qop=\"auth\", "
        "realm=\"%s\", nonce=\"%lu\"\r\n\r\n",
        conn->ctx->config[AUTHENTICATION_DOMAIN],
        (unsigned long) time(NULL));
  }
  
  static int is_authorized_for_put(struct mg_connection *conn) {
    FILE *fp;
    int ret = 0;
  
    fp = conn->ctx->config[PUT_DELETE_PASSWORDS_FILE] == NULL ? NULL :
      mg_fopen(conn->ctx->config[PUT_DELETE_PASSWORDS_FILE], "r");
  
    if (fp != NULL) {
      ret = authorize(conn, fp);
      (void) fclose(fp);
    }
  
    return ret;
  }
  
  int mg_modify_passwords_file(const char *fname, const char *domain,
                               const char *user, const char *pass) {
    int found;
    char line[512], u[512], d[512], ha1[33], tmp[PATH_MAX];
    FILE *fp, *fp2;
  
    found = 0;
    fp = fp2 = NULL;
  
    // Regard empty password as no password - remove user record.
    if (pass[0] == '\0') {
      pass = NULL;
    }
  
    (void) snprintf(tmp, sizeof(tmp), "%s.tmp", fname);
  
    // Create the file if does not exist
    if ((fp = mg_fopen(fname, "a+")) != NULL) {
      (void) fclose(fp);
    }
  
    // Open the given file and temporary file
    if ((fp = mg_fopen(fname, "r")) == NULL) {
      return 0;
    } else if ((fp2 = mg_fopen(tmp, "w+")) == NULL) {
      fclose(fp);
      return 0;
    }
  
    // Copy the stuff to temporary file
    while (fgets(line, sizeof(line), fp) != NULL) {
      if (sscanf(line, "%[^:]:%[^:]:%*s", u, d) != 2) {
        continue;
      }
  
      if (!strcmp(u, user) && !strcmp(d, domain)) {
        found++;
        if (pass != NULL) {
          mg_md5(ha1, user, ":", domain, ":", pass, NULL);
          fprintf(fp2, "%s:%s:%s\n", user, domain, ha1);
        }
      } else {
        (void) fprintf(fp2, "%s", line);
      }
    }
  
    // If new user, just add it
    if (!found && pass != NULL) {
      mg_md5(ha1, user, ":", domain, ":", pass, NULL);
      (void) fprintf(fp2, "%s:%s:%s\n", user, domain, ha1);
    }
  
    // Close files
    (void) fclose(fp);
    (void) fclose(fp2);
  
    // Put the temp file in place of real file
    (void) mg_remove(fname);
    (void) mg_rename(tmp, fname);
  
    return 1;
  }
  
  struct de {
    struct mg_connection *conn;
    char *file_name;
    struct mgstat st;
  };
  
  static void url_encode(const char *src, char *dst, size_t dst_len) {
    static const char *dont_escape = "._-$,;~()";
    static const char *hex = "0123456789abcdef";
    const char *end = dst + dst_len - 1;
  
    for (; *src != '\0' && dst < end; src++, dst++) {
      if (isalnum(*(const unsigned char *) src) ||
          strchr(dont_escape, * (const unsigned char *) src) != NULL) {
        *dst = *src;
      } else if (dst + 2 < end) {
        dst[0] = '%';
        dst[1] = hex[(* (const unsigned char *) src) >> 4];
        dst[2] = hex[(* (const unsigned char *) src) & 0xf];
        dst += 2;
      }
    }
  
    *dst = '\0';
  }
  
  static void print_dir_entry(struct de *de) {
    char size[64], mod[64], href[PATH_MAX];
  
    if (de->st.is_directory) {
      (void) mg_snprintf(de->conn, size, sizeof(size), "%s", "[DIRECTORY]");
    } else {
       // We use (signed) cast below because MSVC 6 compiler cannot
       // convert unsigned __int64 to double. Sigh.
      if (de->st.size < 1024) {
        (void) mg_snprintf(de->conn, size, sizeof(size),
            "%lu", (unsigned long) de->st.size);
      } else if (de->st.size < 1024 * 1024) {
        (void) mg_snprintf(de->conn, size, sizeof(size),
            "%.1fk", (double) de->st.size / 1024.0);
      } else if (de->st.size < 1024 * 1024 * 1024) {
        (void) mg_snprintf(de->conn, size, sizeof(size),
            "%.1fM", (double) de->st.size / 1048576);
      } else {
        (void) mg_snprintf(de->conn, size, sizeof(size),
            "%.1fG", (double) de->st.size / 1073741824);
      }
    }
    (void) strftime(mod, sizeof(mod), "%d-%b-%Y %H:%M", localtime(&de->st.mtime));
    url_encode(de->file_name, href, sizeof(href));
    de->conn->num_bytes_sent += mg_printf(de->conn,
        "<tr><td><a href=\"%s%s%s\">%s%s</a></td>"
        "<td>&nbsp;%s</td><td>&nbsp;&nbsp;%s</td></tr>\n",
        de->conn->request_info.uri, href, de->st.is_directory ? "/" : "",
        de->file_name, de->st.is_directory ? "/" : "", mod, size);
  }
  
  // This function is called from send_directory() and used for
  // sorting directory entries by size, or name, or modification time.
  // On windows, __cdecl specification is needed in case if project is built
  // with __stdcall convention. qsort always requires __cdels callback.
  static int WINCDECL compare_dir_entries(const void *p1, const void *p2) {
    const struct de *a = (const struct de *) p1, *b = (const struct de *) p2;
    const char *query_string = a->conn->request_info.query_string;
    int cmp_result = 0;
  
    if (query_string == NULL) {
      query_string = "na";
    }
  
    if (a->st.is_directory && !b->st.is_directory) {
      return -1;  // Always put directories on top
    } else if (!a->st.is_directory && b->st.is_directory) {
      return 1;   // Always put directories on top
    } else if (*query_string == 'n') {
      cmp_result = strcmp(a->file_name, b->file_name);
    } else if (*query_string == 's') {
      cmp_result = a->st.size == b->st.size ? 0 :
        a->st.size > b->st.size ? 1 : -1;
    } else if (*query_string == 'd') {
      cmp_result = a->st.mtime == b->st.mtime ? 0 :
        a->st.mtime > b->st.mtime ? 1 : -1;
    }
  
    return query_string[1] == 'd' ? -cmp_result : cmp_result;
  }
  
  static void handle_directory_request(struct mg_connection *conn,
                                       const char *dir) {
    struct dirent *dp;
    DIR *dirp;
    struct de *entries = NULL;
    char path[PATH_MAX];
    int i, sort_direction, num_entries = 0, arr_size = 128;
  
    if ((dirp = opendir(dir)) == NULL) {
      send_http_error(conn, 500, "Cannot open directory",
          "Error: opendir(%s): %s", path, strerror(ERRNO));
      return;
    }
  
    (void) mg_printf(conn, "%s",
        "HTTP/1.1 200 OK\r\n"
        "Connection: close\r\n"
        "Content-Type: text/html; charset=utf-8\r\n\r\n");
  
    sort_direction = conn->request_info.query_string != NULL &&
      conn->request_info.query_string[1] == 'd' ? 'a' : 'd';
  
    while ((dp = readdir(dirp)) != NULL) {
  
      // Do not show current dir and passwords file
      if (!strcmp(dp->d_name, ".") ||
          !strcmp(dp->d_name, "..") ||
          !strcmp(dp->d_name, PASSWORDS_FILE_NAME))
        continue;
  
      if (entries == NULL || num_entries >= arr_size) {
        arr_size *= 2;
        entries = (struct de *) realloc(entries,
            arr_size * sizeof(entries[0]));
      }
  
      if (entries == NULL) {
        closedir(dirp);
        send_http_error(conn, 500, "Cannot open directory",
            "%s", "Error: cannot allocate memory");
        return;
      }
  
      mg_snprintf(conn, path, sizeof(path), "%s%c%s", dir, DIRSEP, dp->d_name);
  
      // If we don't memset stat structure to zero, mtime will have
      // garbage and strftime() will segfault later on in
      // print_dir_entry(). memset is required only if mg_stat()
      // fails. For more details, see
      // http://code.google.com/p/mongoose/issues/detail?id=79
      if (mg_stat(path, &entries[num_entries].st) != 0) {
        memset(&entries[num_entries].st, 0, sizeof(entries[num_entries].st));
      }
  
      entries[num_entries].conn = conn;
      entries[num_entries].file_name = mg_strdup(dp->d_name);
      num_entries++;
    }
    (void) closedir(dirp);
  
    conn->num_bytes_sent += mg_printf(conn,
        "<html><head><title>Index of %s</title>"
        "<style>th {text-align: left;}</style></head>"
        "<body><h1>Index of %s</h1><pre><table cellpadding=\"0\">"
        "<tr><th><a href=\"?n%c\">Name</a></th>"
        "<th><a href=\"?d%c\">Modified</a></th>"
        "<th><a href=\"?s%c\">Size</a></th></tr>"
        "<tr><td colspan=\"3\"><hr></td></tr>",
        conn->request_info.uri, conn->request_info.uri,
        sort_direction, sort_direction, sort_direction);
  
    // Print first entry - link to a parent directory
    conn->num_bytes_sent += mg_printf(conn,
        "<tr><td><a href=\"%s%s\">%s</a></td>"
        "<td>&nbsp;%s</td><td>&nbsp;&nbsp;%s</td></tr>\n",
        conn->request_info.uri, "..", "Parent directory", "-", "-");
  
    // Sort and print directory entries
    qsort(entries, (size_t)num_entries, sizeof(entries[0]), compare_dir_entries);
    for (i = 0; i < num_entries; i++) {
      print_dir_entry(&entries[i]);
      free(entries[i].file_name);
    }
    free(entries);
  
    conn->num_bytes_sent += mg_printf(conn, "%s", "</table></body></html>");
    conn->request_info.status_code = 200;
  }
  
  // Send len bytes from the opened file to the client.
  static void send_file_data(struct mg_connection *conn, FILE *fp, int64_t len) {
    char buf[BUFSIZ];
    int to_read, num_read, num_written;
  
    while (len > 0) {
      // Calculate how much to read from the file in the buffer
      to_read = sizeof(buf);
      if ((int64_t) to_read > len)
        to_read = (int) len;
  
      // Read from file, exit the loop on error
      if ((num_read = fread(buf, 1, (size_t)to_read, fp)) == 0)
        break;
  
      // Send read bytes to the client, exit the loop on error
      if ((num_written = mg_write(conn, buf, (size_t)num_read)) != num_read)
        break;
  
      // Both read and were successful, adjust counters
      conn->num_bytes_sent += num_written;
      len -= num_written;
    }
  }
  
  static int parse_range_header(const char *header, int64_t *a, int64_t *b) {
    return sscanf(header, "bytes=%" INT64_FMT "-%" INT64_FMT, a, b);
  }
  
  static void handle_file_request(struct mg_connection *conn, const char *path,
                                  struct mgstat *stp) {
    char date[64], lm[64], etag[64], range[64];
    const char *fmt = "%a, %d %b %Y %H:%M:%S %Z", *msg = "OK", *hdr;
    time_t curtime = time(NULL);
    int64_t cl, r1, r2;
    struct vec mime_vec;
    FILE *fp;
    int n;
  
    get_mime_type(conn->ctx, path, &mime_vec);
    cl = stp->size;
    conn->request_info.status_code = 200;
    range[0] = '\0';
  
    if ((fp = mg_fopen(path, "rb")) == NULL) {
      send_http_error(conn, 500, http_500_error,
          "fopen(%s): %s", path, strerror(ERRNO));
      return;
    }
    set_close_on_exec(fileno(fp));
  
    // If Range: header specified, act accordingly
    r1 = r2 = 0;
    hdr = mg_get_header(conn, "Range");
    if (hdr != NULL && (n = parse_range_header(hdr, &r1, &r2)) > 0) {
      conn->request_info.status_code = 206;
      (void) fseeko(fp, (off_t) r1, SEEK_SET);
      cl = n == 2 ? r2 - r1 + 1: cl - r1;
      (void) mg_snprintf(conn, range, sizeof(range),
          "Content-Range: bytes "
          "%" INT64_FMT "-%"
          INT64_FMT "/%" INT64_FMT "\r\n",
          r1, r1 + cl - 1, stp->size);
      msg = "Partial Content";
    }
  
    // Prepare Etag, Date, Last-Modified headers
    (void) strftime(date, sizeof(date), fmt, localtime(&curtime));
    (void) strftime(lm, sizeof(lm), fmt, localtime(&stp->mtime));
    (void) mg_snprintf(conn, etag, sizeof(etag), "%lx.%lx",
        (unsigned long) stp->mtime, (unsigned long) stp->size);
  
    (void) mg_printf(conn,
        "HTTP/1.1 %d %s\r\n"
        "Date: %s\r\n"
        "Last-Modified: %s\r\n"
        "Etag: \"%s\"\r\n"
        "Content-Type: %.*s\r\n"
        "Content-Length: %" INT64_FMT "\r\n"
        "Connection: %s\r\n"
        "Accept-Ranges: bytes\r\n"
        "%s\r\n",
        conn->request_info.status_code, msg, date, lm, etag,
        mime_vec.len, mime_vec.ptr, cl, suggest_connection_header(conn), range);
  
    if (strcmp(conn->request_info.request_method, "HEAD") != 0) {
      send_file_data(conn, fp, cl);
    }
    (void) fclose(fp);
  }
  
  // Parse HTTP headers from the given buffer, advance buffer to the point
  // where parsing stopped.
  static void parse_http_headers(char **buf, struct mg_request_info *ri) {
    int i;
  
    for (i = 0; i < (int) ARRAY_SIZE(ri->http_headers); i++) {
      ri->http_headers[i].name = skip_quoted(buf, ":", " ", 0);
      ri->http_headers[i].value = skip(buf, "\r\n");
      if (ri->http_headers[i].name[0] == '\0')
        break;
      ri->num_headers = i + 1;
    }
  }
  
  static int is_valid_http_method(const char *method) {
    return !strcmp(method, "GET") || !strcmp(method, "POST") ||
      !strcmp(method, "HEAD") || !strcmp(method, "CONNECT") ||
      !strcmp(method, "PUT") || !strcmp(method, "DELETE");
  }
  
  // Parse HTTP request, fill in mg_request_info structure.
  static int parse_http_request(char *buf, struct mg_request_info *ri) {
    int status = 0;
  
    // RFC says that all initial whitespaces should be ingored
    while (*buf != '\0' && isspace(* (unsigned char *) buf)) {
      buf++;
    }
  
    ri->request_method = skip(&buf, " ");
    ri->uri = skip(&buf, " ");
    ri->http_version = skip(&buf, "\r\n");
  
    if (is_valid_http_method(ri->request_method) &&
        strncmp(ri->http_version, "HTTP/", 5) == 0) {
      ri->http_version += 5;   /* Skip "HTTP/" */
      parse_http_headers(&buf, ri);
      status = 1;
    }
  
    return status;
  }
  
  // Keep reading the input (either opened file descriptor fd, or socket sock,
  // or SSL descriptor ssl) into buffer buf, until \r\n\r\n appears in the
  // buffer (which marks the end of HTTP request). Buffer buf may already
  // have some data. The length of the data is stored in nread.
  // Upon every read operation, increase nread by the number of bytes read.
  static int read_request(FILE *fp, SOCKET sock, SSL *ssl, char *buf, int bufsiz,
                          int *nread) {
    int n, request_len;
  
    request_len = 0;
    while (*nread < bufsiz && request_len == 0) {
      n = pull(fp, sock, ssl, buf + *nread, bufsiz - *nread);
      if (n <= 0) {
        break;
      } else {
        *nread += n;
        request_len = get_request_len(buf, *nread);
      }
    }
  
    return request_len;
  }
  
  // For given directory path, substitute it to valid index file.
  // Return 0 if index file has been found, -1 if not found.
  // If the file is found, it's stats is returned in stp.
  static int substitute_index_file(struct mg_connection *conn, char *path,
                                   size_t path_len, struct mgstat *stp) {
    const char *list = conn->ctx->config[INDEX_FILES];
    struct mgstat st;
    struct vec filename_vec;
    size_t n = strlen(path);
    int found = 0;
  
    // The 'path' given to us points to the directory. Remove all trailing
    // directory separator characters from the end of the path, and
    // then append single directory separator character.
    while (n > 0 && IS_DIRSEP_CHAR(path[n - 1])) {
      n--;
    }
    path[n] = DIRSEP;
  
    // Traverse index files list. For each entry, append it to the given
    // path and see if the file exists. If it exists, break the loop
    while ((list = next_option(list, &filename_vec, NULL)) != NULL) {
  
      // Ignore too long entries that may overflow path buffer
      if (filename_vec.len > path_len - n)
        continue;
  
      // Prepare full path to the index file
      (void) mg_strlcpy(path + n + 1, filename_vec.ptr, filename_vec.len + 1);
  
      // Does it exist?
      if (mg_stat(path, &st) == 0) {
        // Yes it does, break the loop
        *stp = st;
        found = 1;
        break;
      }
    }
  
    // If no index file exists, restore directory path
    if (!found) {
      path[n] = '\0';
    }
  
    return found;
  }
  
  // Return True if we should reply 304 Not Modified.
  static int is_not_modified(const struct mg_connection *conn,
                             const struct mgstat *stp) {
    const char *ims = mg_get_header(conn, "If-Modified-Since");
    return ims != NULL && stp->mtime <= parse_date_string(ims);
  }
  
  static int forward_body_data(struct mg_connection *conn, FILE *fp,
                               SOCKET sock, SSL *ssl) {
    const char *expect, *buffered;
    char buf[BUFSIZ];
    int to_read, nread, buffered_len, success = 0;
  
    expect = mg_get_header(conn, "Expect");
    assert(fp != NULL);
  
    if (conn->content_len == -1) {
      send_http_error(conn, 411, "Length Required", "");
    } else if (expect != NULL && mg_strcasecmp(expect, "100-continue")) {
      send_http_error(conn, 417, "Expectation Failed", "");
    } else {
      if (expect != NULL) {
        (void) mg_printf(conn, "%s", "HTTP/1.1 100 Continue\r\n\r\n");
      }
  
      buffered = conn->buf + conn->request_len;
      buffered_len = conn->data_len - conn->request_len;
      assert(buffered_len >= 0);
      assert(conn->consumed_content == 0);
  
      if (buffered_len > 0) {
        if ((int64_t) buffered_len > conn->content_len) {
          buffered_len = (int) conn->content_len;
        }
        push(fp, sock, ssl, buffered, (int64_t) buffered_len);
        conn->consumed_content += buffered_len;
      }
  
      while (conn->consumed_content < conn->content_len) {
        to_read = sizeof(buf);
        if ((int64_t) to_read > conn->content_len - conn->consumed_content) {
          to_read = (int) (conn->content_len - conn->consumed_content);
        }
        nread = pull(NULL, conn->client.sock, conn->ssl, buf, to_read);
        if (nread <= 0 || push(fp, sock, ssl, buf, nread) != nread) {
          break;
        }
        conn->consumed_content += nread;
      }
  
      if (conn->consumed_content == conn->content_len) {
        success = 1;
      }
  
      // Each error code path in this function must send an error
      if (!success) {
        send_http_error(conn, 577, http_500_error, "");
      }
    }
  
    return success;
  }
  
  #if !defined(NO_CGI)
  // This structure helps to create an environment for the spawned CGI program.
  // Environment is an array of "VARIABLE=VALUE\0" ASCIIZ strings,
  // last element must be NULL.
  // However, on Windows there is a requirement that all these VARIABLE=VALUE\0
  // strings must reside in a contiguous buffer. The end of the buffer is
  // marked by two '\0' characters.
  // We satisfy both worlds: we create an envp array (which is vars), all
  // entries are actually pointers inside buf.
  struct cgi_env_block {
    struct mg_connection *conn;
    char buf[CGI_ENVIRONMENT_SIZE]; // Environment buffer
    int len; // Space taken
    char *vars[MAX_CGI_ENVIR_VARS]; // char **envp
    int nvars; // Number of variables
  };
  
  // Append VARIABLE=VALUE\0 string to the buffer, and add a respective
  // pointer into the vars array.
  static char *addenv(struct cgi_env_block *block, const char *fmt, ...) {
    int n, space;
    char *added;
    va_list ap;
  
    // Calculate how much space is left in the buffer
    space = sizeof(block->buf) - block->len - 2;
    assert(space >= 0);
  
    // Make a pointer to the free space int the buffer
    added = block->buf + block->len;
  
    // Copy VARIABLE=VALUE\0 string into the free space
    va_start(ap, fmt);
    n = mg_vsnprintf(block->conn, added, (size_t) space, fmt, ap);
    va_end(ap);
  
    // Make sure we do not overflow buffer and the envp array
    if (n > 0 && n < space &&
        block->nvars < (int) ARRAY_SIZE(block->vars) - 2) {
      // Append a pointer to the added string into the envp array
      block->vars[block->nvars++] = block->buf + block->len;
      // Bump up used length counter. Include \0 terminator
      block->len += n + 1;
    }
  
    return added;
  }
  
  static void prepare_cgi_environment(struct mg_connection *conn,
                                      const char *prog,
                                      struct cgi_env_block *blk) {
    const char *s, *slash;
    struct vec var_vec, root;
    char *p;
    int  i;
  
    blk->len = blk->nvars = 0;
    blk->conn = conn;
  
    get_document_root(conn, &root);
  
    addenv(blk, "SERVER_NAME=%s", conn->ctx->config[AUTHENTICATION_DOMAIN]);
    addenv(blk, "SERVER_ROOT=%.*s", root.len, root.ptr);
    addenv(blk, "DOCUMENT_ROOT=%.*s", root.len, root.ptr);
  
    // Prepare the environment block
    addenv(blk, "%s", "GATEWAY_INTERFACE=CGI/1.1");
    addenv(blk, "%s", "SERVER_PROTOCOL=HTTP/1.1");
    addenv(blk, "%s", "REDIRECT_STATUS=200"); // For PHP
    addenv(blk, "SERVER_PORT=%d", ntohs(conn->client.lsa.u.sin.sin_port));
    addenv(blk, "REQUEST_METHOD=%s", conn->request_info.request_method);
    addenv(blk, "REMOTE_ADDR=%s",
        inet_ntoa(conn->client.rsa.u.sin.sin_addr));
    addenv(blk, "REMOTE_PORT=%d", conn->request_info.remote_port);
    addenv(blk, "REQUEST_URI=%s", conn->request_info.uri);
  
    // SCRIPT_NAME
    assert(conn->request_info.uri[0] == '/');
    slash = strrchr(conn->request_info.uri, '/');
    if ((s = strrchr(prog, '/')) == NULL)
      s = prog;
    addenv(blk, "SCRIPT_NAME=%.*s%s", slash - conn->request_info.uri,
           conn->request_info.uri, s);
  
    addenv(blk, "SCRIPT_FILENAME=%s", prog);
    addenv(blk, "PATH_TRANSLATED=%s", prog);
    addenv(blk, "HTTPS=%s", conn->ssl == NULL ? "off" : "on");
  
    if ((s = mg_get_header(conn, "Content-Type")) != NULL)
      addenv(blk, "CONTENT_TYPE=%s", s);
  
    if (conn->request_info.query_string != NULL)
      addenv(blk, "QUERY_STRING=%s", conn->request_info.query_string);
  
    if ((s = mg_get_header(conn, "Content-Length")) != NULL)
      addenv(blk, "CONTENT_LENGTH=%s", s);
  
    if ((s = getenv("PATH")) != NULL)
      addenv(blk, "PATH=%s", s);
  
  #if defined(_WIN32)
    if ((s = getenv("COMSPEC")) != NULL)
      addenv(blk, "COMSPEC=%s", s);
    if ((s = getenv("SYSTEMROOT")) != NULL)
      addenv(blk, "SYSTEMROOT=%s", s);
  #else
    if ((s = getenv("LD_LIBRARY_PATH")) != NULL)
      addenv(blk, "LD_LIBRARY_PATH=%s", s);
  #endif /* _WIN32 */
  
    if ((s = getenv("PERLLIB")) != NULL)
      addenv(blk, "PERLLIB=%s", s);
  
    if (conn->request_info.remote_user != NULL) {
      addenv(blk, "REMOTE_USER=%s", conn->request_info.remote_user);
      addenv(blk, "%s", "AUTH_TYPE=Digest");
    }
  
    // Add all headers as HTTP_* variables
    for (i = 0; i < conn->request_info.num_headers; i++) {
      p = addenv(blk, "HTTP_%s=%s",
          conn->request_info.http_headers[i].name,
          conn->request_info.http_headers[i].value);
  
      // Convert variable name into uppercase, and change - to _
      for (; *p != '=' && *p != '\0'; p++) {
        if (*p == '-')
          *p = '_';
        *p = (char) toupper(* (unsigned char *) p);
      }
    }
  
    // Add user-specified variables
    s = conn->ctx->config[CGI_ENVIRONMENT];
    while ((s = next_option(s, &var_vec, NULL)) != NULL) {
      addenv(blk, "%.*s", var_vec.len, var_vec.ptr);
    }
  
    blk->vars[blk->nvars++] = NULL;
    blk->buf[blk->len++] = '\0';
  
    assert(blk->nvars < (int) ARRAY_SIZE(blk->vars));
    assert(blk->len > 0);
    assert(blk->len < (int) sizeof(blk->buf));
  }
  
  static void handle_cgi_request(struct mg_connection *conn, const char *prog) {
    int headers_len, data_len, i, fd_stdin[2], fd_stdout[2];
    const char *status;
    char buf[BUFSIZ], *pbuf, dir[PATH_MAX], *p;
    struct mg_request_info ri;
    struct cgi_env_block blk;
    FILE *in, *out;
    pid_t pid;
  
    prepare_cgi_environment(conn, prog, &blk);
  
    // CGI must be executed in its own directory. 'dir' must point to the
    // directory containing executable program, 'p' must point to the
    // executable program name relative to 'dir'.
    (void) mg_snprintf(conn, dir, sizeof(dir), "%s", prog);
    if ((p = strrchr(dir, DIRSEP)) != NULL) {
      *p++ = '\0';
    } else {
      dir[0] = '.', dir[1] = '\0';
      p = (char *) prog;
    }
  
    pid = (pid_t) -1;
    fd_stdin[0] = fd_stdin[1] = fd_stdout[0] = fd_stdout[1] = -1;
    in = out = NULL;
  
    if (pipe(fd_stdin) != 0 || pipe(fd_stdout) != 0) {
      send_http_error(conn, 500, http_500_error,
          "Cannot create CGI pipe: %s", strerror(ERRNO));
      goto done;
    } else if ((pid = spawn_process(conn, p, blk.buf, blk.vars,
            fd_stdin[0], fd_stdout[1], dir)) == (pid_t) -1) {
      goto done;
    } else if ((in = fdopen(fd_stdin[1], "wb")) == NULL ||
        (out = fdopen(fd_stdout[0], "rb")) == NULL) {
      send_http_error(conn, 500, http_500_error,
          "fopen: %s", strerror(ERRNO));
      goto done;
    }
  
    setbuf(in, NULL);
    setbuf(out, NULL);
  
    // spawn_process() must close those!
    // If we don't mark them as closed, close() attempt before
    // return from this function throws an exception on Windows.
    // Windows does not like when closed descriptor is closed again.
    fd_stdin[0] = fd_stdout[1] = -1;
  
    // Send POST data to the CGI process if needed
    if (!strcmp(conn->request_info.request_method, "POST") &&
        !forward_body_data(conn, in, INVALID_SOCKET, NULL)) {
      goto done;
    }
  
    // Now read CGI reply into a buffer. We need to set correct
    // status code, thus we need to see all HTTP headers first.
    // Do not send anything back to client, until we buffer in all
    // HTTP headers.
    data_len = 0;
    headers_len = read_request(out, INVALID_SOCKET, NULL,
        buf, sizeof(buf), &data_len);
    if (headers_len <= 0) {
      send_http_error(conn, 500, http_500_error,
                      "CGI program sent malformed HTTP headers: [%.*s]",
                      data_len, buf);
      goto done;
    }
    pbuf = buf;
    buf[headers_len - 1] = '\0';
    parse_http_headers(&pbuf, &ri);
  
    // Make up and send the status line
    status = get_header(&ri, "Status");
    conn->request_info.status_code = status == NULL ? 200 : atoi(status);
    (void) mg_printf(conn, "HTTP/1.1 %d OK\r\n", conn->request_info.status_code);
  
    // Send headers
    for (i = 0; i < ri.num_headers; i++) {
      mg_printf(conn, "%s: %s\r\n",
                ri.http_headers[i].name, ri.http_headers[i].value);
    }
    (void) mg_write(conn, "\r\n", 2);
  
    // Send chunk of data that may be read after the headers
    conn->num_bytes_sent += mg_write(conn, buf + headers_len,
                                     (size_t)(data_len - headers_len));
  
    // Read the rest of CGI output and send to the client
    send_file_data(conn, out, INT64_MAX);
  
  done:
    if (pid != (pid_t) -1) {
      kill(pid, SIGKILL);
  #if !defined(_WIN32)
      do {} while (waitpid(-1, &i, WNOHANG) > 0);
  #endif
    }
    if (fd_stdin[0] != -1) {
      (void) close(fd_stdin[0]);
    }
    if (fd_stdout[1] != -1) {
      (void) close(fd_stdout[1]);
    }
  
    if (in != NULL) {
      (void) fclose(in);
    } else if (fd_stdin[1] != -1) {
      (void) close(fd_stdin[1]);
    }
  
    if (out != NULL) {
      (void) fclose(out);
    } else if (fd_stdout[0] != -1) {
      (void) close(fd_stdout[0]);
    }
  }
  #endif // !NO_CGI
  
  // For a given PUT path, create all intermediate subdirectories
  // for given path. Return 0 if the path itself is a directory,
  // or -1 on error, 1 if OK.
  static int put_dir(const char *path) {
    char buf[PATH_MAX];
    const char *s, *p;
    struct mgstat st;
    size_t len;
  
    for (s = p = path + 2; (p = strchr(s, '/')) != NULL; s = ++p) {
      len = p - path;
      assert(len < sizeof(buf));
      (void) memcpy(buf, path, len);
      buf[len] = '\0';
  
      // Try to create intermediate directory
      if (mg_stat(buf, &st) == -1 && mg_mkdir(buf, 0755) != 0) {
        return -1;
      }
  
      // Is path itself a directory?
      if (p[1] == '\0') {
        return 0;
      }
    }
  
    return 1;
  }
  
  static void put_file(struct mg_connection *conn, const char *path) {
    struct mgstat st;
    const char *range;
    int64_t r1, r2;
    FILE *fp;
    int rc;
  
    conn->request_info.status_code = mg_stat(path, &st) == 0 ? 200 : 201;
  
    if ((rc = put_dir(path)) == 0) {
      mg_printf(conn, "HTTP/1.1 %d OK\r\n\r\n", conn->request_info.status_code);
    } else if (rc == -1) {
      send_http_error(conn, 500, http_500_error,
          "put_dir(%s): %s", path, strerror(ERRNO));
    } else if ((fp = mg_fopen(path, "wb+")) == NULL) {
      send_http_error(conn, 500, http_500_error,
          "fopen(%s): %s", path, strerror(ERRNO));
    } else {
      set_close_on_exec(fileno(fp));
      range = mg_get_header(conn, "Content-Range");
      r1 = r2 = 0;
      if (range != NULL && parse_range_header(range, &r1, &r2) > 0) {
        conn->request_info.status_code = 206;
        // TODO(lsm): handle seek error
        (void) fseeko(fp, (off_t) r1, SEEK_SET);
      }
      if (forward_body_data(conn, fp, INVALID_SOCKET, NULL))
        (void) mg_printf(conn, "HTTP/1.1 %d OK\r\n\r\n",
            conn->request_info.status_code);
      (void) fclose(fp);
    }
  }
  
  static void send_ssi_file(struct mg_connection *, const char *, FILE *, int);
  
  static void do_ssi_include(struct mg_connection *conn, const char *ssi,
                             char *tag, int include_level) {
    char file_name[BUFSIZ], path[PATH_MAX], *p;
    struct vec root;
    int is_ssi;
    FILE *fp;
  
    get_document_root(conn, &root);
  
    // sscanf() is safe here, since send_ssi_file() also uses buffer
    // of size BUFSIZ to get the tag. So strlen(tag) is always < BUFSIZ.
    if (sscanf(tag, " virtual=\"%[^\"]\"", file_name) == 1) {
      // File name is relative to the webserver root
      (void) mg_snprintf(conn, path, sizeof(path), "%.*s%c%s",
          root.len, root.ptr, DIRSEP, file_name);
    } else if (sscanf(tag, " file=\"%[^\"]\"", file_name) == 1) {
      // File name is relative to the webserver working directory
      // or it is absolute system path
      (void) mg_snprintf(conn, path, sizeof(path), "%s", file_name);
    } else if (sscanf(tag, " \"%[^\"]\"", file_name) == 1) {
      // File name is relative to the currect document
      (void) mg_snprintf(conn, path, sizeof(path), "%s", ssi);
      if ((p = strrchr(path, DIRSEP)) != NULL) {
        p[1] = '\0';
      }
      (void) mg_snprintf(conn, path + strlen(path),
          sizeof(path) - strlen(path), "%s", file_name);
    } else {
      cry(conn, "Bad SSI #include: [%s]", tag);
      return;
    }
  
    if ((fp = mg_fopen(path, "rb")) == NULL) {
      cry(conn, "Cannot open SSI #include: [%s]: fopen(%s): %s",
          tag, path, strerror(ERRNO));
    } else {
      set_close_on_exec(fileno(fp));
      is_ssi = match_extension(path, conn->ctx->config[SSI_EXTENSIONS]);
      if (is_ssi) {
        send_ssi_file(conn, path, fp, include_level + 1);
      } else {
        send_file_data(conn, fp, INT64_MAX);
      }
      (void) fclose(fp);
    }
  }
  
  #if !defined(NO_POPEN)
  static void do_ssi_exec(struct mg_connection *conn, char *tag) {
    char cmd[BUFSIZ];
    FILE *fp;
  
    if (sscanf(tag, " \"%[^\"]\"", cmd) != 1) {
      cry(conn, "Bad SSI #exec: [%s]", tag);
    } else if ((fp = popen(cmd, "r")) == NULL) {
      cry(conn, "Cannot SSI #exec: [%s]: %s", cmd, strerror(ERRNO));
    } else {
      send_file_data(conn, fp, INT64_MAX);
      (void) pclose(fp);
    }
  }
  #endif // !NO_POPEN
  
  static void send_ssi_file(struct mg_connection *conn, const char *path,
                            FILE *fp, int include_level) {
    char buf[BUFSIZ];
    int ch, len, in_ssi_tag;
  
    if (include_level > 10) {
      cry(conn, "SSI #include level is too deep (%s)", path);
      return;
    }
  
    in_ssi_tag = 0;
    len = 0;
  
    while ((ch = fgetc(fp)) != EOF) {
      if (in_ssi_tag && ch == '>') {
        in_ssi_tag = 0;
        buf[len++] = (char) ch;
        buf[len] = '\0';
        assert(len <= (int) sizeof(buf));
        if (len < 6 || memcmp(buf, "<!--#", 5) != 0) {
          // Not an SSI tag, pass it
          (void) mg_write(conn, buf, (size_t)len);
        } else {
          if (!memcmp(buf + 5, "include", 7)) {
            do_ssi_include(conn, path, buf + 12, include_level);
  #if !defined(NO_POPEN)
          } else if (!memcmp(buf + 5, "exec", 4)) {
            do_ssi_exec(conn, buf + 9);
  #endif // !NO_POPEN
          } else {
            cry(conn, "%s: unknown SSI " "command: \"%s\"", path, buf);
          }
        }
        len = 0;
      } else if (in_ssi_tag) {
        if (len == 5 && memcmp(buf, "<!--#", 5) != 0) {
          // Not an SSI tag
          in_ssi_tag = 0;
        } else if (len == (int) sizeof(buf) - 2) {
          cry(conn, "%s: SSI tag is too large", path);
          len = 0;
        }
        buf[len++] = ch & 0xff;
      } else if (ch == '<') {
        in_ssi_tag = 1;
        if (len > 0) {
          (void) mg_write(conn, buf, (size_t)len);
        }
        len = 0;
        buf[len++] = ch & 0xff;
      } else {
        buf[len++] = ch & 0xff;
        if (len == (int) sizeof(buf)) {
          (void) mg_write(conn, buf, (size_t)len);
          len = 0;
        }
      }
    }
  
    // Send the rest of buffered data
    if (len > 0) {
      (void) mg_write(conn, buf, (size_t)len);
    }
  }
  
  static void handle_ssi_file_request(struct mg_connection *conn,
                                      const char *path) {
    FILE *fp;
  
    if ((fp = mg_fopen(path, "rb")) == NULL) {
      send_http_error(conn, 500, http_500_error, "fopen(%s): %s", path,
                      strerror(ERRNO));
    } else {
      set_close_on_exec(fileno(fp));
      mg_printf(conn, "HTTP/1.1 200 OK\r\n"
                "Content-Type: text/html\r\nConnection: %s\r\n\r\n",
                suggest_connection_header(conn));
      send_ssi_file(conn, path, fp, 0);
      (void) fclose(fp);
    }
  }
  
  // This is the heart of the Mongoose's logic.
  // This function is called when the request is read, parsed and validated,
  // and Mongoose must decide what action to take: serve a file, or
  // a directory, or call embedded function, etcetera.
  static void handle_request(struct mg_connection *conn) {
    struct mg_request_info *ri = &conn->request_info;
    char path[PATH_MAX];
    int uri_len;
    struct mgstat st;
  
    if ((conn->request_info.query_string = strchr(ri->uri, '?')) != NULL) {
      * conn->request_info.query_string++ = '\0';
    }
    uri_len = strlen(ri->uri);
    (void) url_decode(ri->uri, (size_t)uri_len, ri->uri, (size_t)(uri_len + 1), 0);
    remove_double_dots_and_double_slashes(ri->uri);
    convert_uri_to_file_name(conn, ri->uri, path, sizeof(path));
  
    DEBUG_TRACE(("%s", ri->uri));
    if (!check_authorization(conn, path)) {
      send_authorization_request(conn);
    } else if (call_user(conn, MG_NEW_REQUEST) != NULL) {
      // Do nothing, callback has served the request
    } else if (strstr(path, PASSWORDS_FILE_NAME)) {
      // Do not allow to view passwords files
      send_http_error(conn, 403, "Forbidden", "Access Forbidden");
    } else if (conn->ctx->config[DOCUMENT_ROOT] == NULL) {
      send_http_error(conn, 404, "Not Found", "Not Found");
    } else if ((!strcmp(ri->request_method, "PUT") ||
          !strcmp(ri->request_method, "DELETE")) &&
        (conn->ctx->config[PUT_DELETE_PASSWORDS_FILE] == NULL ||
         !is_authorized_for_put(conn))) {
      send_authorization_request(conn);
    } else if (!strcmp(ri->request_method, "PUT")) {
      put_file(conn, path);
    } else if (!strcmp(ri->request_method, "DELETE")) {
      if (mg_remove(path) == 0) {
        send_http_error(conn, 200, "OK", "");
      } else {
        send_http_error(conn, 500, http_500_error, "remove(%s): %s", path,
                        strerror(ERRNO));
      }
    } else if (mg_stat(path, &st) != 0) {
      send_http_error(conn, 404, "Not Found", "%s", "File not found");
    } else if (st.is_directory && ri->uri[uri_len - 1] != '/') {
      (void) mg_printf(conn,
          "HTTP/1.1 301 Moved Permanently\r\n"
          "Location: %s/\r\n\r\n", ri->uri);
    } else if (st.is_directory &&
               !substitute_index_file(conn, path, sizeof(path), &st)) {
      if (!mg_strcasecmp(conn->ctx->config[ENABLE_DIRECTORY_LISTING], "yes")) {
        handle_directory_request(conn, path);
      } else {
        send_http_error(conn, 403, "Directory Listing Denied",
            "Directory listing denied");
      }
    } else if (match_extension(path, conn->ctx->config[CGI_EXTENSIONS])) {
      if (strcmp(ri->request_method, "POST") &&
          strcmp(ri->request_method, "GET")) {
        send_http_error(conn, 501, "Not Implemented",
            "Method %s is not implemented", ri->request_method);
      } else {
        handle_cgi_request(conn, path);
      }
    } else if (match_extension(path, conn->ctx->config[SSI_EXTENSIONS])) {
      handle_ssi_file_request(conn, path);
    } else if (is_not_modified(conn, &st)) {
      send_http_error(conn, 304, "Not Modified", "");
    } else {
      handle_file_request(conn, path, &st);
    }
  }
  
  static void close_all_listening_sockets(struct mg_context *ctx) {
    struct socket *sp, *tmp;
    for (sp = ctx->listening_sockets; sp != NULL; sp = tmp) {
      tmp = sp->next;
      (void) closesocket(sp->sock);
      free(sp);
    }
  }
  
  // Valid listening port specification is: [ip_address:]port[s|p]
  // Examples: 80, 443s, 127.0.0.1:3128p, 1.2.3.4:8080sp
  static int parse_port_string(const struct vec *vec, struct socket *so) {
    struct usa *usa = &so->lsa;
    int a, b, c, d, port, len;
  
    // MacOS needs that. If we do not zero it, subsequent bind() will fail.
    memset(so, 0, sizeof(*so));
  
    if (sscanf(vec->ptr, "%d.%d.%d.%d:%d%n", &a, &b, &c, &d, &port, &len) == 5) {
      // IP address to bind to is specified
      usa->u.sin.sin_addr.s_addr = htonl((a << 24) | (b << 16) | (c << 8) | d);
    } else if (sscanf(vec->ptr, "%d%n", &port, &len) == 1) {
      // Only port number is specified. Bind to all addresses
      usa->u.sin.sin_addr.s_addr = htonl(INADDR_ANY);
    } else {
      return 0;
    }
    assert(len > 0 && len <= (int) vec->len);
  
    if (strchr("sp,", vec->ptr[len]) == NULL) {
      return 0;
    }
  
    so->is_ssl = vec->ptr[len] == 's';
    so->is_proxy = vec->ptr[len] == 'p';
    usa->len = sizeof(usa->u.sin);
    usa->u.sin.sin_family = AF_INET;
    usa->u.sin.sin_port = htons((uint16_t) port);
  
    return 1;
  }
  
  static int set_ports_option(struct mg_context *ctx) {
    const char *list = ctx->config[LISTENING_PORTS];
    int reuseaddr = 1, success = 1;
    SOCKET sock;
    struct vec vec;
    struct socket so, *listener;
  
    while (success && (list = next_option(list, &vec, NULL)) != NULL) {
      if (!parse_port_string(&vec, &so)) {
        cry(fc(ctx), "%s: %.*s: invalid port spec. Expecting list of: %s",
            __func__, vec.len, vec.ptr, "[IP_ADDRESS:]PORT[s|p]");
        success = 0;
      } else if (so.is_ssl && ctx->ssl_ctx == NULL) {
        cry(fc(ctx), "Cannot add SSL socket, is -ssl_cert option set?");
        success = 0;
      } else if ((sock = socket(PF_INET, SOCK_STREAM, 6)) == INVALID_SOCKET ||
  #if !defined(_WIN32)
                 // On Windows, SO_REUSEADDR is recommended only for
                 // broadcast UDP sockets
                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &reuseaddr,
                            sizeof(reuseaddr)) != 0 ||
  #endif // !_WIN32
                 bind(sock, &so.lsa.u.sa, so.lsa.len) != 0 ||
                 listen(sock, 20) != 0) {
        closesocket(sock);
        cry(fc(ctx), "%s: cannot bind to %.*s: %s", __func__,
            vec.len, vec.ptr, strerror(ERRNO));
        success = 0;
      } else if ((listener = (struct socket *)
                  calloc(1, sizeof(*listener))) == NULL) {
        closesocket(sock);
        cry(fc(ctx), "%s: %s", __func__, strerror(ERRNO));
        success = 0;
      } else {
        *listener = so;
        listener->sock = sock;
        set_close_on_exec(listener->sock);
        listener->next = ctx->listening_sockets;
        ctx->listening_sockets = listener;
      }
    }
  
    if (!success) {
      close_all_listening_sockets(ctx);
    }
  
    return success;
  }
  
  static void log_header(const struct mg_connection *conn, const char *header,
                         FILE *fp) {
    const char *header_value;
  
    if ((header_value = mg_get_header(conn, header)) == NULL) {
      (void) fprintf(fp, "%s", " -");
    } else {
      (void) fprintf(fp, " \"%s\"", header_value);
    }
  }
  
  static void log_access(const struct mg_connection *conn) {
    const struct mg_request_info *ri;
    FILE *fp;
    char date[64];
  
    fp = conn->ctx->config[ACCESS_LOG_FILE] == NULL ?  NULL :
      mg_fopen(conn->ctx->config[ACCESS_LOG_FILE], "a+");
  
    if (fp == NULL)
      return;
  
    (void) strftime(date, sizeof(date), "%d/%b/%Y:%H:%M:%S %z",
        localtime(&conn->birth_time));
  
    ri = &conn->request_info;
  
    flockfile(fp);
  
    (void) fprintf(fp,
        "%s - %s [%s] \"%s %s HTTP/%s\" %d %" INT64_FMT,
        inet_ntoa(conn->client.rsa.u.sin.sin_addr),
        ri->remote_user == NULL ? "-" : ri->remote_user,
        date,
        ri->request_method ? ri->request_method : "-",
        ri->uri ? ri->uri : "-",
        ri->http_version,
        conn->request_info.status_code, conn->num_bytes_sent);
    log_header(conn, "Referer", fp);
    log_header(conn, "User-Agent", fp);
    (void) fputc('\n', fp);
    (void) fflush(fp);
  
    funlockfile(fp);
    (void) fclose(fp);
  }
  
  static int isbyte(int n) {
    return n >= 0 && n <= 255;
  }
  
  // Verify given socket address against the ACL.
  // Return -1 if ACL is malformed, 0 if address is disallowed, 1 if allowed.
  static int check_acl(struct mg_context *ctx, const struct usa *usa) {
    int a, b, c, d, n, mask, allowed;
    char flag;
    uint32_t acl_subnet, acl_mask, remote_ip;
    struct vec vec;
    const char *list = ctx->config[ACCESS_CONTROL_LIST];
  
    if (list == NULL) {
      return 1;
    }
  
    (void) memcpy(&remote_ip, &usa->u.sin.sin_addr, sizeof(remote_ip));
  
    // If any ACL is set, deny by default
    allowed = '-';
  
    while ((list = next_option(list, &vec, NULL)) != NULL) {
      mask = 32;
  
      if (sscanf(vec.ptr, "%c%d.%d.%d.%d%n", &flag, &a, &b, &c, &d, &n) != 5) {
        cry(fc(ctx), "%s: subnet must be [+|-]x.x.x.x[/x]", __func__);
        return -1;
      } else if (flag != '+' && flag != '-') {
        cry(fc(ctx), "%s: flag must be + or -: [%s]", __func__, vec.ptr);
        return -1;
      } else if (!isbyte(a)||!isbyte(b)||!isbyte(c)||!isbyte(d)) {
        cry(fc(ctx), "%s: bad ip address: [%s]", __func__, vec.ptr);
        return -1;
      } else if (sscanf(vec.ptr + n, "/%d", &mask) == 0) {
        // Do nothing, no mask specified
      } else if (mask < 0 || mask > 32) {
        cry(fc(ctx), "%s: bad subnet mask: %d [%s]", __func__, n, vec.ptr);
        return -1;
      }
  
      acl_subnet = (a << 24) | (b << 16) | (c << 8) | d;
      acl_mask = mask ? 0xffffffffU << (32 - mask) : 0;
  
      if (acl_subnet == (ntohl(remote_ip) & acl_mask)) {
        allowed = flag;
      }
    }
  
    return allowed == '+';
  }
  
  static void add_to_set(SOCKET fd, fd_set *set, int *max_fd) {
    FD_SET(fd, set);
    if (fd > (SOCKET) *max_fd) {
      *max_fd = (int) fd;
    }
  }
  
  #if !defined(_WIN32)
  static int set_uid_option(struct mg_context *ctx) {
    struct passwd *pw;
    const char *uid = ctx->config[RUN_AS_USER];
    int success = 0;
  
    if (uid == NULL) {
      success = 1;
    } else {
      if ((pw = getpwnam(uid)) == NULL) {
        cry(fc(ctx), "%s: unknown user [%s]", __func__, uid);
      } else if (setgid(pw->pw_gid) == -1) {
        cry(fc(ctx), "%s: setgid(%s): %s", __func__, uid, strerror(errno));
      } else if (setuid(pw->pw_uid) == -1) {
        cry(fc(ctx), "%s: setuid(%s): %s", __func__, uid, strerror(errno));
      } else {
        success = 1;
      }
    }
  
    return success;
  }
  #endif // !_WIN32
  
  #if !defined(NO_SSL)
  static pthread_mutex_t *ssl_mutexes;
  
  static void ssl_locking_callback(int mode, int mutex_num, const char *file,
                                   int line) {
    line = 0;    // Unused
    file = NULL; // Unused
  
    if (mode & CRYPTO_LOCK) {
      (void) pthread_mutex_lock(&ssl_mutexes[mutex_num]);
    } else {
      (void) pthread_mutex_unlock(&ssl_mutexes[mutex_num]);
    }
  }
  
  static unsigned long ssl_id_callback(void) {
    return (unsigned long) pthread_self();
  }
  
  #if !defined(NO_SSL_DL)
  static int load_dll(struct mg_context *ctx, const char *dll_name,
                      struct ssl_func *sw) {
    union {void *p; void (*fp)(void);} u;
    void  *dll_handle;
    struct ssl_func *fp;
  
    if ((dll_handle = dlopen(dll_name, RTLD_LAZY)) == NULL) {
      cry(fc(ctx), "%s: cannot load %s", __func__, dll_name);
      return 0;
    }
  
    for (fp = sw; fp->name != NULL; fp++) {
  #ifdef _WIN32
      // GetProcAddress() returns pointer to function
      u.fp = (void (*)(void)) dlsym(dll_handle, fp->name);
  #else
      // dlsym() on UNIX returns void *. ISO C forbids casts of data pointers to
      // function pointers. We need to use a union to make a cast.
      u.p = dlsym(dll_handle, fp->name);
  #endif /* _WIN32 */
      if (u.fp == NULL) {
        cry(fc(ctx), "%s: %s: cannot find %s", __func__, dll_name, fp->name);
        return 0;
      } else {
        fp->ptr = u.fp;
      }
    }
  
    return 1;
  }
  #endif // NO_SSL_DL
  
  // Dynamically load SSL library. Set up ctx->ssl_ctx pointer.
  static int set_ssl_option(struct mg_context *ctx) {
    struct mg_request_info request_info;
    SSL_CTX *CTX;
    int i, size;
    const char *pem = ctx->config[SSL_CERTIFICATE];
    const char *chain = ctx->config[SSL_CHAIN_FILE];
  
    if (pem == NULL) {
      return 1;
    }
  
  #if !defined(NO_SSL_DL)
    if (!load_dll(ctx, SSL_LIB, ssl_sw) ||
        !load_dll(ctx, CRYPTO_LIB, crypto_sw)) {
      return 0;
    }
  #endif // NO_SSL_DL
  
    // Initialize SSL crap
    SSL_library_init();
    SSL_load_error_strings();
  
    if ((CTX = SSL_CTX_new(SSLv23_server_method())) == NULL) {
      cry(fc(ctx), "SSL_CTX_new error: %s", ssl_error());
    } else if (ctx->user_callback != NULL) {
      memset(&request_info, 0, sizeof(request_info));
      request_info.user_data = ctx->user_data;
      ctx->user_callback(MG_INIT_SSL, (struct mg_connection *) CTX,
                         &request_info);
    }
  
    if (CTX != NULL && SSL_CTX_use_certificate_file(CTX, pem,
          SSL_FILETYPE_PEM) == 0) {
      cry(fc(ctx), "%s: cannot open %s: %s", __func__, pem, ssl_error());
      return 0;
    } else if (CTX != NULL && SSL_CTX_use_PrivateKey_file(CTX, pem,
          SSL_FILETYPE_PEM) == 0) {
      cry(fc(ctx), "%s: cannot open %s: %s", NULL, pem, ssl_error());
      return 0;
    }
  
    if (CTX != NULL && chain != NULL &&
        SSL_CTX_use_certificate_chain_file(CTX, chain) == 0) {
      cry(fc(ctx), "%s: cannot open %s: %s", NULL, chain, ssl_error());
      return 0;
    }
  
    // Initialize locking callbacks, needed for thread safety.
    // http://www.openssl.org/support/faq.html#PROG1
    size = sizeof(pthread_mutex_t) * CRYPTO_num_locks();
    if ((ssl_mutexes = (pthread_mutex_t *) malloc((size_t)size)) == NULL) {
      cry(fc(ctx), "%s: cannot allocate mutexes: %s", __func__, ssl_error());
      return 0;
    }
  
    for (i = 0; i < CRYPTO_num_locks(); i++) {
      pthread_mutex_init(&ssl_mutexes[i], NULL);
    }
  
    CRYPTO_set_locking_callback(&ssl_locking_callback);
    CRYPTO_set_id_callback(&ssl_id_callback);
  
    // Done with everything. Save the context.
    ctx->ssl_ctx = CTX;
  
    return 1;
  }
  #endif // !NO_SSL
  
  static int set_gpass_option(struct mg_context *ctx) {
    struct mgstat mgstat;
    const char *path = ctx->config[GLOBAL_PASSWORDS_FILE];
    return path == NULL || mg_stat(path, &mgstat) == 0;
  }
  
  static int set_acl_option(struct mg_context *ctx) {
    struct usa fake;
    return check_acl(ctx, &fake) != -1;
  }
  
  static void reset_per_request_attributes(struct mg_connection *conn) {
    struct mg_request_info *ri = &conn->request_info;
  
    // Reset request info attributes. DO NOT TOUCH is_ssl, remote_ip, remote_port
    if (ri->remote_user != NULL) {
      free((void *) ri->remote_user);
    }
    ri->remote_user = ri->request_method = ri->uri = ri->http_version = NULL;
    ri->num_headers = 0;
    ri->status_code = -1;
  
    conn->num_bytes_sent = conn->consumed_content = 0;
    conn->content_len = -1;
    conn->request_len = conn->data_len = 0;
  }
  
  static void close_socket_gracefully(SOCKET sock) {
    char buf[BUFSIZ];
    int n;
  
    // Send FIN to the client
    (void) shutdown(sock, SHUT_WR);
    set_non_blocking_mode(sock);
  
    // Read and discard pending data. If we do not do that and close the
    // socket, the data in the send buffer may be discarded. This
    // behaviour is seen on Windows, when client keeps sending data
    // when server decide to close the connection; then when client
    // does recv() it gets no data back.
    do {
      n = pull(NULL, sock, NULL, buf, sizeof(buf));
    } while (n > 0);
  
    // Now we know that our FIN is ACK-ed, safe to close
    (void) closesocket(sock);
  }
  
  static void close_connection(struct mg_connection *conn) {
    if (conn->ssl) {
      SSL_free(conn->ssl);
      conn->ssl = NULL;
    }
  
    if (conn->client.sock != INVALID_SOCKET) {
      close_socket_gracefully(conn->client.sock);
    }
  }
  
  static void discard_current_request_from_buffer(struct mg_connection *conn) {
    char *buffered;
    int buffered_len, body_len;
  
    buffered = conn->buf + conn->request_len;
    buffered_len = conn->data_len - conn->request_len;
    assert(buffered_len >= 0);
  
    if (conn->content_len == -1) {
      body_len = 0;
    } else if (conn->content_len < (int64_t) buffered_len) {
      body_len = (int) conn->content_len;
    } else {
      body_len = buffered_len;
    }
  
    conn->data_len -= conn->request_len + body_len;
    memmove(conn->buf, conn->buf + conn->request_len + body_len,
            (size_t) conn->data_len);
  }
  
  static int parse_url(const char *url, char *host, int *port) {
    int len;
  
    if (sscanf(url, "%*[htps]://%1024[^:]:%d%n", host, port, &len) == 2 ||
        sscanf(url, "%1024[^:]:%d%n", host, port, &len) == 2) {
    } else if (sscanf(url, "%*[htps]://%1024[^/]%n", host, &len) == 1) {
      *port = 80;
    } else {
      sscanf(url, "%1024[^/]%n", host, &len);
      *port = 80;
    }
    DEBUG_TRACE(("Host:%s, port:%d", host, *port));
  
    return len;
  }
  
  static void handle_proxy_request(struct mg_connection *conn) {
    struct mg_request_info *ri = &conn->request_info;
    char host[1025], buf[BUFSIZ];
    int port, is_ssl, len, i, n;
  
    DEBUG_TRACE(("URL: %s", ri->uri));
    if (conn->request_info.uri[0] == '/' ||
        (ri->uri == NULL || (len = parse_url(ri->uri, host, &port))) == 0) {
      return;
    }
  
    if (conn->peer == NULL) {
      is_ssl = !strcmp(ri->request_method, "CONNECT");
      if ((conn->peer = mg_connect(conn, host, port, is_ssl)) == NULL) {
        return;
      }
      conn->peer->client.is_ssl = is_ssl;
    }
    
    // Forward client's request to the target
    mg_printf(conn->peer, "%s %s HTTP/%s\r\n", ri->request_method, ri->uri + len,
              ri->http_version);
  
    // And also all headers. TODO(lsm): anonymize!
    for (i = 0; i < ri->num_headers; i++) {
      mg_printf(conn->peer, "%s: %s\r\n", ri->http_headers[i].name,
                ri->http_headers[i].value);
    }
    // End of headers, final newline
    mg_write(conn->peer, "\r\n", 2);
  
    // Read and forward body data if any
    if (!strcmp(ri->request_method, "POST")) {
      forward_body_data(conn, NULL, conn->peer->client.sock, conn->peer->ssl);
    }
  
    // Read data from the target and forward it to the client
    while ((n = pull(NULL, conn->peer->client.sock, conn->peer->ssl,
                     buf, sizeof(buf))) > 0) {
      if (mg_write(conn, buf, (size_t)n) != n) {
        break;
      }
    }
  
    if (!conn->peer->client.is_ssl) {
      close_connection(conn->peer);
      free(conn->peer);
      conn->peer = NULL;
    }
  }
  
  static int is_valid_uri(const char *uri) {
    // Conform to http://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html#sec5.1.2
    // URI can be an asterisk (*) or should start with slash.
    return (uri[0] == '/' || (uri[0] == '*' && uri[1] == '\0'));
  }
  
  static void process_new_connection(struct mg_connection *conn) {
    struct mg_request_info *ri = &conn->request_info;
    int keep_alive_enabled;
    const char *cl;
  
    keep_alive_enabled = !strcmp(conn->ctx->config[ENABLE_KEEP_ALIVE], "yes");
  
    do {
      reset_per_request_attributes(conn);
  
      // If next request is not pipelined, read it in
      if ((conn->request_len = get_request_len(conn->buf, conn->data_len)) == 0) {
        conn->request_len = read_request(NULL, conn->client.sock, conn->ssl,
            conn->buf, conn->buf_size, &conn->data_len);
      }
      assert(conn->data_len >= conn->request_len);
      if (conn->request_len == 0 && conn->data_len == conn->buf_size) {
        send_http_error(conn, 413, "Request Too Large", "");
        return;
      } if (conn->request_len <= 0) {
        return;  // Remote end closed the connection
      }
  
      // Nul-terminate the request cause parse_http_request() uses sscanf
      conn->buf[conn->request_len - 1] = '\0';
      if (!parse_http_request(conn->buf, ri) ||
          (!conn->client.is_proxy && !is_valid_uri(ri->uri))) {
        // Do not put garbage in the access log, just send it back to the client
        send_http_error(conn, 400, "Bad Request",
            "Cannot parse HTTP request: [%.*s]", conn->data_len, conn->buf);
      } else if (strcmp(ri->http_version, "1.0") &&
                 strcmp(ri->http_version, "1.1")) {
        // Request seems valid, but HTTP version is strange
        send_http_error(conn, 505, "HTTP version not supported", "");
        log_access(conn);
      } else {
        // Request is valid, handle it
        cl = get_header(ri, "Content-Length");
        conn->content_len = cl == NULL ? -1 : strtoll(cl, NULL, 10);
        conn->birth_time = time(NULL);
        if (conn->client.is_proxy) {
          handle_proxy_request(conn);
        } else {
          handle_request(conn);
        }
        log_access(conn);
        discard_current_request_from_buffer(conn);
      }
      // conn->peer is not NULL only for SSL-ed proxy connections
    } while (conn->peer || (keep_alive_enabled && should_keep_alive(conn)));
  }
  
  // Worker threads take accepted socket from the queue
  static int consume_socket(struct mg_context *ctx, struct socket *sp) {
    (void) pthread_mutex_lock(&ctx->mutex);
    DEBUG_TRACE(("going idle"));
  
    // If the queue is empty, wait. We're idle at this point.
    while (ctx->sq_head == ctx->sq_tail && ctx->stop_flag == 0) {
      pthread_cond_wait(&ctx->sq_full, &ctx->mutex);
    }
    // Master thread could wake us up without putting a socket.
    // If this happens, it is time to exit.
    if (ctx->stop_flag) {
      (void) pthread_mutex_unlock(&ctx->mutex);
      return 0;
    }
    assert(ctx->sq_head > ctx->sq_tail);
  
    // Copy socket from the queue and increment tail
    *sp = ctx->queue[ctx->sq_tail % ARRAY_SIZE(ctx->queue)];
    ctx->sq_tail++;
    DEBUG_TRACE(("grabbed socket %d, going busy", sp->sock));
  
    // Wrap pointers if needed
    while (ctx->sq_tail > (int) ARRAY_SIZE(ctx->queue)) {
      ctx->sq_tail -= ARRAY_SIZE(ctx->queue);
      ctx->sq_head -= ARRAY_SIZE(ctx->queue);
    }
  
    (void) pthread_cond_signal(&ctx->sq_empty);
    (void) pthread_mutex_unlock(&ctx->mutex);
  
    return 1;
  }
  
  static void worker_thread(struct mg_context *ctx) {
    struct mg_connection *conn;
    int buf_size = atoi(ctx->config[MAX_REQUEST_SIZE]);
  
    conn = (struct mg_connection *) calloc(1, sizeof(*conn) + buf_size);
    conn->buf_size = buf_size;
    conn->buf = (char *) (conn + 1);
    assert(conn != NULL);
  
    while (ctx->stop_flag == 0 && consume_socket(ctx, &conn->client)) {
      conn->birth_time = time(NULL);
      conn->ctx = ctx;
  
      // Fill in IP, port info early so even if SSL setup below fails,
      // error handler would have the corresponding info.
      // Thanks to Johannes Winkelmann for the patch.
      conn->request_info.remote_port = ntohs(conn->client.rsa.u.sin.sin_port);
      memcpy(&conn->request_info.remote_ip,
             &conn->client.rsa.u.sin.sin_addr.s_addr, 4);
      conn->request_info.remote_ip = ntohl(conn->request_info.remote_ip);
      conn->request_info.is_ssl = conn->client.is_ssl;
  
      if (!conn->client.is_ssl ||
          (conn->client.is_ssl && sslize(conn, SSL_accept))) {
        process_new_connection(conn);
      }
  
      close_connection(conn);
    }
    free(conn);
  
    // Signal master that we're done with connection and exiting
    (void) pthread_mutex_lock(&ctx->mutex);
    ctx->num_threads--;
    (void) pthread_cond_signal(&ctx->cond);
    assert(ctx->num_threads >= 0);
    (void) pthread_mutex_unlock(&ctx->mutex);
  
    DEBUG_TRACE(("exiting"));
  }
  
  // Master thread adds accepted socket to a queue
  static void produce_socket(struct mg_context *ctx, const struct socket *sp) {
    (void) pthread_mutex_lock(&ctx->mutex);
  
    // If the queue is full, wait
    while (ctx->sq_head - ctx->sq_tail >= (int) ARRAY_SIZE(ctx->queue)) {
      (void) pthread_cond_wait(&ctx->sq_empty, &ctx->mutex);
    }
    assert(ctx->sq_head - ctx->sq_tail < (int) ARRAY_SIZE(ctx->queue));
  
    // Copy socket to the queue and increment head
    ctx->queue[ctx->sq_head % ARRAY_SIZE(ctx->queue)] = *sp;
    ctx->sq_head++;
    DEBUG_TRACE(("queued socket %d", sp->sock));
  
    (void) pthread_cond_signal(&ctx->sq_full);
    (void) pthread_mutex_unlock(&ctx->mutex);
  }
  
  static void accept_new_connection(const struct socket *listener,
                                    struct mg_context *ctx) {
    struct socket accepted;
    int allowed;
  
    accepted.rsa.len = sizeof(accepted.rsa.u.sin);
    accepted.lsa = listener->lsa;
    accepted.sock = accept(listener->sock, &accepted.rsa.u.sa, &accepted.rsa.len);
    if (accepted.sock != INVALID_SOCKET) {
      allowed = check_acl(ctx, &accepted.rsa);
      if (allowed) {
        // Put accepted socket structure into the queue
        DEBUG_TRACE(("accepted socket %d", accepted.sock));
        accepted.is_ssl = listener->is_ssl;
        accepted.is_proxy = listener->is_proxy;
        produce_socket(ctx, &accepted);
      } else {
        cry(fc(ctx), "%s: %s is not allowed to connect",
            __func__, inet_ntoa(accepted.rsa.u.sin.sin_addr));
        (void) closesocket(accepted.sock);
      }
    }
  }
  
  static void master_thread(struct mg_context *ctx) {
    fd_set read_set;
    struct timeval tv;
    struct socket *sp;
    int max_fd;
  
    while (ctx->stop_flag == 0) {
      FD_ZERO(&read_set);
      max_fd = -1;
  
      // Add listening sockets to the read set
      for (sp = ctx->listening_sockets; sp != NULL; sp = sp->next) {
        add_to_set(sp->sock, &read_set, &max_fd);
      }
  
      tv.tv_sec = 0;
      tv.tv_usec = 200 * 1000;
  
      if (select(max_fd + 1, &read_set, NULL, NULL, &tv) < 0) {
  #ifdef _WIN32
        // On windows, if read_set and write_set are empty,
        // select() returns "Invalid parameter" error
        // (at least on my Windows XP Pro). So in this case, we sleep here.
        sleep(1);
  #endif // _WIN32
      } else {
        for (sp = ctx->listening_sockets; sp != NULL; sp = sp->next) {
          if (FD_ISSET(sp->sock, &read_set)) {
            accept_new_connection(sp, ctx);
          }
        }
      }
    }
    DEBUG_TRACE(("stopping workers"));
  
    // Stop signal received: somebody called mg_stop. Quit.
    close_all_listening_sockets(ctx);
  
    // Wakeup workers that are waiting for connections to handle.
    pthread_cond_broadcast(&ctx->sq_full);
  
    // Wait until all threads finish
    (void) pthread_mutex_lock(&ctx->mutex);
    while (ctx->num_threads > 0) {
      (void) pthread_cond_wait(&ctx->cond, &ctx->mutex);
    }
    (void) pthread_mutex_unlock(&ctx->mutex);
  
    // All threads exited, no sync is needed. Destroy mutex and condvars
    (void) pthread_mutex_destroy(&ctx->mutex);
    (void) pthread_cond_destroy(&ctx->cond);
    (void) pthread_cond_destroy(&ctx->sq_empty);
    (void) pthread_cond_destroy(&ctx->sq_full);
  
    // Signal mg_stop() that we're done
    ctx->stop_flag = 2;
  
    DEBUG_TRACE(("exiting"));
  }
  
  static void free_context(struct mg_context *ctx) {
    int i;
  
    // Deallocate config parameters
    for (i = 0; i < NUM_OPTIONS; i++) {
      if (ctx->config[i] != NULL)
        free(ctx->config[i]);
    }
  
    // Deallocate SSL context
    if (ctx->ssl_ctx != NULL) {
      SSL_CTX_free(ctx->ssl_ctx);
    }
  #ifndef NO_SSL
    if (ssl_mutexes != NULL) {
      free(ssl_mutexes);
    }
  #endif // !NO_SSL
  
    // Deallocate context itself
    free(ctx);
  }
  
  void mg_stop(struct mg_context *ctx) {
    ctx->stop_flag = 1;
  
    // Wait until mg_fini() stops
    while (ctx->stop_flag != 2) {
      (void) sleep(0);
    }
    free_context(ctx);
  
  #if defined(_WIN32) && !defined(__SYMBIAN32__)
    (void) WSACleanup();
  #endif // _WIN32
  }
  
  struct mg_context *mg_start(mg_callback_t user_callback, void *user_data,
                              const char **options) {
    struct mg_context *ctx;
    const char *name, *value, *default_value;
    int i;
  
  #if defined(_WIN32) && !defined(__SYMBIAN32__)
    WSADATA data;
    WSAStartup(MAKEWORD(2,2), &data);
  #endif // _WIN32
  
    // Allocate context and initialize reasonable general case defaults.
    // TODO(lsm): do proper error handling here.
    ctx = (struct mg_context *) calloc(1, sizeof(*ctx));
    ctx->user_callback = user_callback;
    ctx->user_data = user_data;
  
    while (options && (name = *options++) != NULL) {
      if ((i = get_option_index(name)) == -1) {
        cry(fc(ctx), "Invalid option: %s", name);
        free_context(ctx);
        return NULL;
      } else if ((value = *options++) == NULL) {
        cry(fc(ctx), "%s: option value cannot be NULL", name);
        free_context(ctx);
        return NULL;
      }
      ctx->config[i] = mg_strdup(value);
      DEBUG_TRACE(("[%s] -> [%s]", name, value));
    }
  
    // Set default value if needed
    for (i = 0; config_options[i * ENTRIES_PER_CONFIG_OPTION] != NULL; i++) {
      default_value = config_options[i * ENTRIES_PER_CONFIG_OPTION + 2];
      if (ctx->config[i] == NULL && default_value != NULL) {
        ctx->config[i] = mg_strdup(default_value);
        DEBUG_TRACE(("Setting default: [%s] -> [%s]",
                     config_options[i * ENTRIES_PER_CONFIG_OPTION + 1],
                     default_value));
      }
    }
  
    // NOTE(lsm): order is important here. SSL certificates must
    // be initialized before listening ports. UID must be set last.
    if (!set_gpass_option(ctx) ||
  #if !defined(NO_SSL)
        !set_ssl_option(ctx) ||
  #endif
        !set_ports_option(ctx) ||
  #if !defined(_WIN32)
        !set_uid_option(ctx) ||
  #endif
        !set_acl_option(ctx)) {
      free_context(ctx);
      return NULL;
    }
  
  #if !defined(_WIN32) && !defined(__SYMBIAN32__)
    // Ignore SIGPIPE signal, so if browser cancels the request, it
    // won't kill the whole process.
    (void) signal(SIGPIPE, SIG_IGN);
  #endif // !_WIN32
  
    (void) pthread_mutex_init(&ctx->mutex, NULL);
    (void) pthread_cond_init(&ctx->cond, NULL);
    (void) pthread_cond_init(&ctx->sq_empty, NULL);
    (void) pthread_cond_init(&ctx->sq_full, NULL);
  
    // Start master (listening) thread
    start_thread(ctx, (mg_thread_func_t) master_thread, ctx);
  
    // Start worker threads
    for (i = 0; i < atoi(ctx->config[NUM_THREADS]); i++) {
      if (start_thread(ctx, (mg_thread_func_t) worker_thread, ctx) != 0) {
        cry(fc(ctx), "Cannot start worker thread: %d", ERRNO);
      } else {
        ctx->num_threads++;
      }
    }
  
    return ctx;
  }
  