text: /*
   * Copyright (c) 2001-2003 Swedish Institute of Computer Science.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without modification,
   * are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice,
   *    this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   * 3. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
   * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
   * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
   * OF SUCH DAMAGE.
   *
   * This file is part of the lwIP TCP/IP stack.
   *
   * Author: Adam Dunkels <adam@sics.se>
   *         Simon Goldschmidt
   *
   */
  
  /* This httpd supports for a
   * rudimentary server-side-include facility which will replace tags of the form
   * <!--#tag--> in any file whose extension is .shtml, .shtm or .ssi with
   * strings provided by an include handler whose pointer is provided to the
   * module via function http_set_ssi_handler().
   * Additionally, a simple common
   * gateway interface (CGI) handling mechanism has been added to allow clients
   * to hook functions to particular request URIs.
   *
   * To enable SSI support, define label LWIP_HTTPD_SSI in lwipopts.h.
   * To enable CGI support, define label LWIP_HTTPD_CGI in lwipopts.h.
   *
   * By default, the server assumes that HTTP headers are already present in
   * each file stored in the file system.  By defining LWIP_HTTPD_DYNAMIC_HEADERS in
   * lwipopts.h, this behavior can be changed such that the server inserts the
   * headers automatically based on the extension of the file being served.  If
   * this mode is used, be careful to ensure that the file system image used
   * does not already contain the header information.
   *
   * File system images without headers can be created using the makefsfile
   * tool with the -h command line option.
   *
   *
   * Notes about valid SSI tags
   * --------------------------
   *
   * The following assumptions are made about tags used in SSI markers:
   *
   * 1. No tag may contain '-' or whitespace characters within the tag name.
   * 2. Whitespace is allowed between the tag leadin "<!--#" and the start of
   *    the tag name and between the tag name and the leadout string "-->".
   * 3. The maximum tag name length is LWIP_HTTPD_MAX_TAG_NAME_LEN, currently 8 characters.
   *
   * Notes on CGI usage
   * ------------------
   *
   * The simple CGI support offered here works with GET method requests only
   * and can handle up to 16 parameters encoded into the URI. The handler
   * function may not write directly to the HTTP output but must return a
   * filename that the HTTP server will send to the browser as a response to
   * the incoming CGI request.
   *
   *
   *
   * The list of supported file types is quite short, so if makefsdata complains
   * about an unknown extension, make sure to add it (and its doctype) to
   * the 'g_psHTTPHeaders' list.
   */
  #include "httpd.h"
  #include "lwip/debug.h"
  #include "lwip/stats.h"
  #include "httpd_structs.h"
  #include "lwip/tcp.h"
  #include "fs.h"
  
  #include <string.h>
  #include <stdlib.h>
  
  #if LWIP_TCP
  
  #ifndef HTTPD_DEBUG
  #define HTTPD_DEBUG         LWIP_DBG_OFF
  #endif
  
  /** Set this to 1 and add the next line to lwippools.h to use a memp pool
   * for allocating struct http_state instead of the heap:
   *
   * LWIP_MEMPOOL(HTTPD_STATE, 20, 100, "HTTPD_STATE")
   */
  #ifndef HTTPD_USE_MEM_POOL
  #define HTTPD_USE_MEM_POOL  0
  #endif
  
  /** The server port for HTTPD to use */
  #ifndef HTTPD_SERVER_PORT
  #define HTTPD_SERVER_PORT                   80
  #endif
  
  /** Maximum retries before the connection is aborted/closed.
   * - number of times pcb->poll is called -> default is 4*500ms = 2s;
   * - reset when pcb->sent is called
   */
  #ifndef HTTPD_MAX_RETRIES
  #define HTTPD_MAX_RETRIES                   4
  #endif
  
  /** The poll delay is X*500ms */
  #ifndef HTTPD_POLL_INTERVAL
  #define HTTPD_POLL_INTERVAL                 4
  #endif
  
  /** Priority for tcp pcbs created by HTTPD (very low by default).
   *  Lower priorities get killed first when running out of memroy.
   */
  #ifndef HTTPD_TCP_PRIO
  #define HTTPD_TCP_PRIO                      TCP_PRIO_MIN
  #endif
  
  /** Set this to 1 to enabled timing each file sent */
  #ifndef LWIP_HTTPD_TIMING
  #define LWIP_HTTPD_TIMING                   0
  #endif
  #ifndef HTTPD_DEBUG_TIMING
  #define HTTPD_DEBUG_TIMING                  LWIP_DBG_OFF
  #endif
  
  /** Set this to 1 on platforms where strnstr is not available */
  #ifndef LWIP_HTTPD_STRNSTR_PRIVATE
  #define LWIP_HTTPD_STRNSTR_PRIVATE          1
  #endif
  
  /** Set this to one to show error pages when parsing a request fails instead
      of simply closing the connection. */
  #ifndef LWIP_HTTPD_SUPPORT_EXTSTATUS
  #define LWIP_HTTPD_SUPPORT_EXTSTATUS        0
  #endif
  
  /** Set this to 0 to drop support for HTTP/0.9 clients (to save some bytes) */
  #ifndef LWIP_HTTPD_SUPPORT_V09
  #define LWIP_HTTPD_SUPPORT_V09              1
  #endif
  
  /** Set this to 1 to enable HTTP/1.1 persistent connections.
   * ATTENTION: If the generated file system includes HTTP headers, these must
   * include the "Connection: keep-alive" header (pass argument "-11" to makefsdata).
   */
  #ifndef LWIP_HTTPD_SUPPORT_11_KEEPALIVE
  #define LWIP_HTTPD_SUPPORT_11_KEEPALIVE     0
  #endif
  
  /** Set this to 1 to support HTTP request coming in in multiple packets/pbufs */
  #ifndef LWIP_HTTPD_SUPPORT_REQUESTLIST
  #define LWIP_HTTPD_SUPPORT_REQUESTLIST      1
  #endif
  
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
  /** Number of rx pbufs to enqueue to parse an incoming request (up to the first
      newline) */
  #ifndef LWIP_HTTPD_REQ_QUEUELEN
  #define LWIP_HTTPD_REQ_QUEUELEN             5
  #endif
  
  /** Number of (TCP payload-) bytes (in pbufs) to enqueue to parse and incoming
      request (up to the first double-newline) */
  #ifndef LWIP_HTTPD_REQ_BUFSIZE
  #define LWIP_HTTPD_REQ_BUFSIZE              LWIP_HTTPD_MAX_REQ_LENGTH
  #endif
  
  /** Defines the maximum length of a HTTP request line (up to the first CRLF,
      copied from pbuf into this a global buffer when pbuf- or packet-queues
      are received - otherwise the input pbuf is used directly) */
  #ifndef LWIP_HTTPD_MAX_REQ_LENGTH
  #define LWIP_HTTPD_MAX_REQ_LENGTH           LWIP_MIN(1023, (LWIP_HTTPD_REQ_QUEUELEN * PBUF_POOL_BUFSIZE))
  #endif
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
  
  /** Maximum length of the filename to send as response to a POST request,
   * filled in by the application when a POST is finished.
   */
  #ifndef LWIP_HTTPD_POST_MAX_RESPONSE_URI_LEN
  #define LWIP_HTTPD_POST_MAX_RESPONSE_URI_LEN 63
  #endif
  
  /** Set this to 0 to not send the SSI tag (default is on, so the tag will
   * be sent in the HTML page */
  #ifndef LWIP_HTTPD_SSI_INCLUDE_TAG
  #define LWIP_HTTPD_SSI_INCLUDE_TAG           1
  #endif
  
  /** Set this to 1 to call tcp_abort when tcp_close fails with memory error.
   * This can be used to prevent consuming all memory in situations where the
   * HTTP server has low priority compared to other communication. */
  #ifndef LWIP_HTTPD_ABORT_ON_CLOSE_MEM_ERROR
  #define LWIP_HTTPD_ABORT_ON_CLOSE_MEM_ERROR  0
  #endif
  
  /** Set this to 1 to kill the oldest connection when running out of
   * memory for 'struct http_state' or 'struct http_ssi_state'.
   * ATTENTION: This puts all connections on a linked list, so may be kind of slow.
   */
  #ifndef LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
  #define LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED 0
  #endif
  
  /** Minimum length for a valid HTTP/0.9 request: "GET /\r\n" -> 7 bytes */
  #define MIN_REQ_LEN   7
  
  #define CRLF "\r\n"
  #define HTTP11_CONNECTIONKEEPALIVE "Connection: keep-alive"
  
  #if LWIP_HTTPD_SSI
  #define LWIP_HTTPD_IS_SSI(hs) ((hs)->ssi)
  #else /* LWIP_HTTPD_SSI */
  #define LWIP_HTTPD_IS_SSI(hs) 0
  #endif /* LWIP_HTTPD_SSI */
  
  /** These defines check whether tcp_write has to copy data or not */
  
  /** This was TI's check whether to let TCP copy data or not
  #define HTTP_IS_DATA_VOLATILE(hs) ((hs->file < (char *)0x20000000) ? 0 : TCP_WRITE_FLAG_COPY)*/
  #ifndef HTTP_IS_DATA_VOLATILE
  #if LWIP_HTTPD_SSI
  /* Copy for SSI files, no copy for non-SSI files */
  #define HTTP_IS_DATA_VOLATILE(hs)   ((hs)->ssi ? TCP_WRITE_FLAG_COPY : 0)
  #else /* LWIP_HTTPD_SSI */
  /** Default: don't copy if the data is sent from file-system directly */
  #define HTTP_IS_DATA_VOLATILE(hs) (((hs->file != NULL) && (hs->handle != NULL) && (hs->file == \
                                     (char*)hs->handle->data + hs->handle->len - hs->left)) \
                                     ? 0 : TCP_WRITE_FLAG_COPY)
  #endif /* LWIP_HTTPD_SSI */
  #endif
  
  /** Default: headers are sent from ROM */
  #ifndef HTTP_IS_HDR_VOLATILE
  #define HTTP_IS_HDR_VOLATILE(hs, ptr) 0
  #endif
  
  #if LWIP_HTTPD_SSI
  /** Default: Tags are sent from struct http_state and are therefore volatile */
  #ifndef HTTP_IS_TAG_VOLATILE
  #define HTTP_IS_TAG_VOLATILE(ptr) TCP_WRITE_FLAG_COPY
  #endif
  #endif /* LWIP_HTTPD_SSI */
  
  /* Return values for http_send_*() */
  #define HTTP_DATA_TO_SEND_BREAK    2
  #define HTTP_DATA_TO_SEND_CONTINUE 1
  #define HTTP_NO_DATA_TO_SEND       0
  
  #if HTTPD_USE_MEM_POOL
  #define HTTP_ALLOC_SSI_STATE()  (struct http_ssi_state *)memp_malloc(MEMP_HTTPD_SSI_STATE)
  #define HTTP_ALLOC_HTTP_STATE() (struct http_state *)memp_malloc(MEMP_HTTPD_STATE)
  #else /* HTTPD_USE_MEM_POOL */
  #define HTTP_ALLOC_SSI_STATE()  (struct http_ssi_state *)mem_malloc(sizeof(struct http_ssi_state))
  #define HTTP_ALLOC_HTTP_STATE() (struct http_state *)mem_malloc(sizeof(struct http_state))
  #endif /* HTTPD_USE_MEM_POOL */
  
  typedef struct
  {
    const char *name;
    u8_t shtml;
  } default_filename;
  
  const default_filename g_psDefaultFilenames[] = {
    {"/index.shtml", 1 },
    {"/index.ssi",   1 },
    {"/index.shtm",  1 },
    {"/index.html",  0 },
    {"/index.htm",   0 }
  };
  
  #define NUM_DEFAULT_FILENAMES (sizeof(g_psDefaultFilenames) /   \
                                 sizeof(default_filename))
  
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
  /** HTTP request is copied here from pbufs for simple parsing */
  static char httpd_req_buf[LWIP_HTTPD_MAX_REQ_LENGTH+1];
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
  
  #if LWIP_HTTPD_SUPPORT_POST
  /** Filename for response file to send when POST is finished */
  static char http_post_response_filename[LWIP_HTTPD_POST_MAX_RESPONSE_URI_LEN+1];
  #endif /* LWIP_HTTPD_SUPPORT_POST */
  
  #if LWIP_HTTPD_DYNAMIC_HEADERS
  /* The number of individual strings that comprise the headers sent before each
   * requested file.
   */
  #define NUM_FILE_HDR_STRINGS 3
  #endif /* LWIP_HTTPD_DYNAMIC_HEADERS */
  
  #if LWIP_HTTPD_SSI
  
  #define HTTPD_LAST_TAG_PART 0xFFFF
  
  enum tag_check_state {
    TAG_NONE,       /* Not processing an SSI tag */
    TAG_LEADIN,     /* Tag lead in "<!--#" being processed */
    TAG_FOUND,      /* Tag name being read, looking for lead-out start */
    TAG_LEADOUT,    /* Tag lead out "-->" being processed */
    TAG_SENDING     /* Sending tag replacement string */
  };
  
  struct http_ssi_state {
    const char *parsed;     /* Pointer to the first unparsed byte in buf. */
  #if !LWIP_HTTPD_SSI_INCLUDE_TAG
    const char *tag_started;/* Pointer to the first opening '<' of the tag. */
  #endif /* !LWIP_HTTPD_SSI_INCLUDE_TAG */
    const char *tag_end;    /* Pointer to char after the closing '>' of the tag. */
    u32_t parse_left; /* Number of unparsed bytes in buf. */
    u16_t tag_index;   /* Counter used by tag parsing state machine */
    u16_t tag_insert_len; /* Length of insert in string tag_insert */
  #if LWIP_HTTPD_SSI_MULTIPART
    u16_t tag_part; /* Counter passed to and changed by tag insertion function to insert multiple times */
  #endif /* LWIP_HTTPD_SSI_MULTIPART */
    u8_t tag_name_len; /* Length of the tag name in string tag_name */
    char tag_name[LWIP_HTTPD_MAX_TAG_NAME_LEN + 1]; /* Last tag name extracted */
    char tag_insert[LWIP_HTTPD_MAX_TAG_INSERT_LEN + 1]; /* Insert string for tag_name */
    enum tag_check_state tag_state; /* State of the tag processor */
  };
  #endif /* LWIP_HTTPD_SSI */
  
  struct http_state {
  #if LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
    struct http_state *next;
  #endif /* LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED */
    struct fs_file file_handle;
    struct fs_file *handle;
    char *file;       /* Pointer to first unsent byte in buf. */
  
    struct tcp_pcb *pcb;
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
    struct pbuf *req;
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
  
  #if LWIP_HTTPD_DYNAMIC_FILE_READ
    char *buf;        /* File read buffer. */
    int buf_len;      /* Size of file read buffer, buf. */
  #endif /* LWIP_HTTPD_DYNAMIC_FILE_READ */
    u32_t left;       /* Number of unsent bytes in buf. */
    u8_t retries;
  #if LWIP_HTTPD_SUPPORT_11_KEEPALIVE
    u8_t keepalive;
  #endif /* LWIP_HTTPD_SUPPORT_11_KEEPALIVE */
  #if LWIP_HTTPD_SSI
    struct http_ssi_state *ssi;
  #endif /* LWIP_HTTPD_SSI */
  #if LWIP_HTTPD_CGI
    char *params[LWIP_HTTPD_MAX_CGI_PARAMETERS]; /* Params extracted from the request URI */
    char *param_vals[LWIP_HTTPD_MAX_CGI_PARAMETERS]; /* Values for each extracted param */
  #endif /* LWIP_HTTPD_CGI */
  #if LWIP_HTTPD_DYNAMIC_HEADERS
    const char *hdrs[NUM_FILE_HDR_STRINGS]; /* HTTP headers to be sent. */
    u16_t hdr_pos;     /* The position of the first unsent header byte in the
                          current string */
    u16_t hdr_index;   /* The index of the hdr string currently being sent. */
  #endif /* LWIP_HTTPD_DYNAMIC_HEADERS */
  #if LWIP_HTTPD_TIMING
    u32_t time_started;
  #endif /* LWIP_HTTPD_TIMING */
  #if LWIP_HTTPD_SUPPORT_POST
    u32_t post_content_len_left;
  #if LWIP_HTTPD_POST_MANUAL_WND
    u32_t unrecved_bytes;
    u8_t no_auto_wnd;
    u8_t post_finished;
  #endif /* LWIP_HTTPD_POST_MANUAL_WND */
  #endif /* LWIP_HTTPD_SUPPORT_POST*/
  };
  
  static err_t http_close_conn(struct tcp_pcb *pcb, struct http_state *hs);
  static err_t http_close_or_abort_conn(struct tcp_pcb *pcb, struct http_state *hs, u8_t abort_conn);
  static err_t http_find_file(struct http_state *hs, const char *uri, int is_09);
  static err_t http_init_file(struct http_state *hs, struct fs_file *file, int is_09, const char *uri, u8_t tag_check);
  static err_t http_poll(void *arg, struct tcp_pcb *pcb);
  #if LWIP_HTTPD_FS_ASYNC_READ
  static void http_continue(void *connection);
  #endif /* LWIP_HTTPD_FS_ASYNC_READ */
  
  #if LWIP_HTTPD_SSI
  /* SSI insert handler function pointer. */
  tSSIHandler g_pfnSSIHandler = NULL;
  int g_iNumTags = 0;
  const char **g_ppcTags = NULL;
  
  #define LEN_TAG_LEAD_IN 5
  const char * const g_pcTagLeadIn = "<!--#";
  
  #define LEN_TAG_LEAD_OUT 3
  const char * const g_pcTagLeadOut = "-->";
  #endif /* LWIP_HTTPD_SSI */
  
  #if LWIP_HTTPD_CGI
  /* CGI handler information */
  const tCGI *g_pCGIs;
  int g_iNumCGIs;
  #endif /* LWIP_HTTPD_CGI */
  
  #if LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
  /** global list of active HTTP connections, use to kill the oldest when
      running out of memory */
  static struct http_state *http_connections;
  #endif /* LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED */
  
  #if LWIP_HTTPD_STRNSTR_PRIVATE
  /** Like strstr but does not need 'buffer' to be NULL-terminated */
  static char*
  strnstr(const char* buffer, const char* token, size_t n)
  {
    const char* p;
    int tokenlen = (int)strlen(token);
    if (tokenlen == 0) {
      return (char *)buffer;
    }
    for (p = buffer; *p && (p + tokenlen <= buffer + n); p++) {
      if ((*p == *token) && (strncmp(p, token, tokenlen) == 0)) {
        return (char *)p;
      }
    }
    return NULL;
  } 
  #endif /* LWIP_HTTPD_STRNSTR_PRIVATE */
  
  #if LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
  static void
  http_kill_oldest_connection(u8_t ssi_required)
  {
    struct http_state *hs = http_connections;
    struct http_state *hs_free_next = NULL;
    while(hs && hs->next) {
      if (ssi_required) {
        if (hs->next->ssi != NULL) {
          hs_free_next = hs;
        }
      } else {
        hs_free_next = hs;
      }
      hs = hs->next;
    }
    if (hs_free_next != NULL) {
      LWIP_ASSERT("hs_free_next->next != NULL", hs_free_next->next != NULL);
      LWIP_ASSERT("hs_free_next->next->pcb != NULL", hs_free_next->next->pcb != NULL);
      /* send RST when killing a connection because of memory shortage */
      http_close_or_abort_conn(hs_free_next->next->pcb, hs_free_next->next, 1); /* this also unlinks the http_state from the list */
    }
  }
  #endif /* LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED */
  
  #if LWIP_HTTPD_SSI
  /** Allocate as struct http_ssi_state. */
  static struct http_ssi_state*
  http_ssi_state_alloc(void)
  {
    struct http_ssi_state *ret = HTTP_ALLOC_SSI_STATE();
  #if LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
    if (ret == NULL) {
      http_kill_oldest_connection(1);
      ret = HTTP_ALLOC_SSI_STATE();
    }
  #endif /* LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED */
    if (ret != NULL) {
      memset(ret, 0, sizeof(struct http_ssi_state));
    }
    return ret;
  }
  
  /** Free a struct http_ssi_state. */
  static void
  http_ssi_state_free(struct http_ssi_state *ssi)
  {
    if (ssi != NULL) {
  #if HTTPD_USE_MEM_POOL
      memp_free(MEMP_HTTPD_SSI_STATE, ssi);
  #else /* HTTPD_USE_MEM_POOL */
      mem_free(ssi);
  #endif /* HTTPD_USE_MEM_POOL */
    }
  }
  #endif /* LWIP_HTTPD_SSI */
  
  /** Initialize a struct http_state.
   */
  static void
  http_state_init(struct http_state* hs)
  {
    /* Initialize the structure. */
    memset(hs, 0, sizeof(struct http_state));
  #if LWIP_HTTPD_DYNAMIC_HEADERS
    /* Indicate that the headers are not yet valid */
    hs->hdr_index = NUM_FILE_HDR_STRINGS;
  #endif /* LWIP_HTTPD_DYNAMIC_HEADERS */
  }
  
  /** Allocate a struct http_state. */
  static struct http_state*
  http_state_alloc(void)
  {
    struct http_state *ret = HTTP_ALLOC_HTTP_STATE();
  #if LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
    if (ret == NULL) {
      http_kill_oldest_connection(0);
      ret = HTTP_ALLOC_HTTP_STATE();
    }
  #endif /* LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED */
    if (ret != NULL) {
      http_state_init(ret);
  #if LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
      /* add the connection to the list */
      if (http_connections == NULL) {
        http_connections = ret;
      } else {
        struct http_state *last;
        for(last = http_connections; last->next != NULL; last = last->next);
        LWIP_ASSERT("last != NULL", last != NULL);
        last->next = ret;
      }
  #endif /* LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED */
    }
    return ret;
  }
  
  /** Free a struct http_state.
   * Also frees the file data if dynamic.
   */
  static void
  http_state_eof(struct http_state *hs)
  {
    if(hs->handle) {
  #if LWIP_HTTPD_TIMING
      u32_t ms_needed = sys_now() - hs->time_started;
      u32_t needed = LWIP_MAX(1, (ms_needed/100));
      LWIP_DEBUGF(HTTPD_DEBUG_TIMING, ("httpd: needed %"U32_F" ms to send file of %d bytes -> %"U32_F" bytes/sec\n",
        ms_needed, hs->handle->len, ((((u32_t)hs->handle->len) * 10) / needed)));
  #endif /* LWIP_HTTPD_TIMING */
      fs_close(hs->handle);
      hs->handle = NULL;
    }
  #if LWIP_HTTPD_DYNAMIC_FILE_READ
    if (hs->buf != NULL) {
      mem_free(hs->buf);
      hs->buf = NULL;
    }
  #endif /* LWIP_HTTPD_DYNAMIC_FILE_READ */
  #if LWIP_HTTPD_SSI
    if (hs->ssi) {
      http_ssi_state_free(hs->ssi);
      hs->ssi = NULL;
    }
  #endif /* LWIP_HTTPD_SSI */
  }
  
  /** Free a struct http_state.
   * Also frees the file data if dynamic.
   */
  static void
  http_state_free(struct http_state *hs)
  {
    if (hs != NULL) {
      http_state_eof(hs);
  #if LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED
      /* take the connection off the list */
      if (http_connections) {
        if (http_connections == hs) {
          http_connections = hs->next;
        } else {
          struct http_state *last;
          for(last = http_connections; last->next != NULL; last = last->next) {
            if (last->next == hs) {
              last->next = hs->next;
              break;
            }
          }
        }
      }
  #endif /* LWIP_HTTPD_KILL_OLD_ON_CONNECTIONS_EXCEEDED */
  #if HTTPD_USE_MEM_POOL
      memp_free(MEMP_HTTPD_STATE, hs);
  #else /* HTTPD_USE_MEM_POOL */
      mem_free(hs);
  #endif /* HTTPD_USE_MEM_POOL */
    }
  }
  
  /** Call tcp_write() in a loop trying smaller and smaller length
   *
   * @param pcb tcp_pcb to send
   * @param ptr Data to send
   * @param length Length of data to send (in/out: on return, contains the
   *        amount of data sent)
   * @param apiflags directly passed to tcp_write
   * @return the return value of tcp_write
   */
  static err_t
  http_write(struct tcp_pcb *pcb, const void* ptr, u16_t *length, u8_t apiflags)
  {
     u16_t len;
     err_t err;
     LWIP_ASSERT("length != NULL", length != NULL);
     len = *length;
     if (len == 0) {
       return ERR_OK;
     }
     do {
       LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("Trying go send %d bytes\n", len));
       err = tcp_write(pcb, ptr, len, apiflags);
       if (err == ERR_MEM) {
         if ((tcp_sndbuf(pcb) == 0) ||
             (tcp_sndqueuelen(pcb) >= TCP_SND_QUEUELEN)) {
           /* no need to try smaller sizes */
           len = 1;
         } else {
           len /= 2;
         }
         LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, 
                     ("Send failed, trying less (%d bytes)\n", len));
       }
     } while ((err == ERR_MEM) && (len > 1));
  
     if (err == ERR_OK) {
       LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("Sent %d bytes\n", len));
     } else {
       LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("Send failed with err %d (\"%s\")\n", err, lwip_strerr(err)));
     }
  
     *length = len;
     return err;
  }
  
  /**
   * The connection shall be actively closed (using RST to close from fault states).
   * Reset the sent- and recv-callbacks.
   *
   * @param pcb the tcp pcb to reset callbacks
   * @param hs connection state to free
   */
  static err_t
  http_close_or_abort_conn(struct tcp_pcb *pcb, struct http_state *hs, u8_t abort_conn)
  {
    err_t err;
    LWIP_DEBUGF(HTTPD_DEBUG, ("Closing connection %p\n", (void*)pcb));
  
  #if LWIP_HTTPD_SUPPORT_POST
    if (hs != NULL) {
      if ((hs->post_content_len_left != 0)
  #if LWIP_HTTPD_POST_MANUAL_WND
         || ((hs->no_auto_wnd != 0) && (hs->unrecved_bytes != 0))
  #endif /* LWIP_HTTPD_POST_MANUAL_WND */
         ) {
        /* make sure the post code knows that the connection is closed */
        http_post_response_filename[0] = 0;
        httpd_post_finished(hs, http_post_response_filename, LWIP_HTTPD_POST_MAX_RESPONSE_URI_LEN);
      }
    }
  #endif /* LWIP_HTTPD_SUPPORT_POST*/
  
  
    tcp_arg(pcb, NULL);
    tcp_recv(pcb, NULL);
    tcp_err(pcb, NULL);
    tcp_poll(pcb, NULL, 0);
    tcp_sent(pcb, NULL);
    if (hs != NULL) {
      http_state_free(hs);
    }
  
    if (abort_conn) {
      tcp_abort(pcb);
      return ERR_OK;
    }
    err = tcp_close(pcb);
    if (err != ERR_OK) {
      LWIP_DEBUGF(HTTPD_DEBUG, ("Error %d closing %p\n", err, (void*)pcb));
      /* error closing, try again later in poll */
      tcp_poll(pcb, http_poll, HTTPD_POLL_INTERVAL);
    }
    return err;
  }
  
  /**
   * The connection shall be actively closed.
   * Reset the sent- and recv-callbacks.
   *
   * @param pcb the tcp pcb to reset callbacks
   * @param hs connection state to free
   */
  static err_t
  http_close_conn(struct tcp_pcb *pcb, struct http_state *hs)
  {
     return http_close_or_abort_conn(pcb, hs, 0);
  }
  
  /** End of file: either close the connection (Connection: close) or
   * close the file (Connection: keep-alive)
   */
  static void
  http_eof(struct tcp_pcb *pcb, struct http_state *hs)
  {
    /* HTTP/1.1 persistent connection? (Not supported for SSI) */
  #if LWIP_HTTPD_SUPPORT_11_KEEPALIVE
    if (hs->keepalive && !LWIP_HTTPD_IS_SSI(hs)) {
      http_state_eof(hs);
      http_state_init(hs);
      hs->keepalive = 1;
    } else
  #endif /* LWIP_HTTPD_SUPPORT_11_KEEPALIVE */
    {
      http_close_conn(pcb, hs);
    }
  }
  
  #if LWIP_HTTPD_CGI
  /**
   * Extract URI parameters from the parameter-part of an URI in the form
   * "test.cgi?x=y" @todo: better explanation!
   * Pointers to the parameters are stored in hs->param_vals.
   *
   * @param hs http connection state
   * @param params pointer to the NULL-terminated parameter string from the URI
   * @return number of parameters extracted
   */
  static int
  extract_uri_parameters(struct http_state *hs, char *params)
  {
    char *pair;
    char *equals;
    int loop;
  
    /* If we have no parameters at all, return immediately. */
    if(!params || (params[0] == '\0')) {
        return(0);
    }
  
    /* Get a pointer to our first parameter */
    pair = params;
  
    /* Parse up to LWIP_HTTPD_MAX_CGI_PARAMETERS from the passed string and ignore the
     * remainder (if any) */
    for(loop = 0; (loop < LWIP_HTTPD_MAX_CGI_PARAMETERS) && pair; loop++) {
  
      /* Save the name of the parameter */
      hs->params[loop] = pair;
  
      /* Remember the start of this name=value pair */
      equals = pair;
  
      /* Find the start of the next name=value pair and replace the delimiter
       * with a 0 to terminate the previous pair string. */
      pair = strchr(pair, '&');
      if(pair) {
        *pair = '\0';
        pair++;
      } else {
         /* We didn't find a new parameter so find the end of the URI and
          * replace the space with a '\0' */
          pair = strchr(equals, ' ');
          if(pair) {
              *pair = '\0';
          }
  
          /* Revert to NULL so that we exit the loop as expected. */
          pair = NULL;
      }
  
      /* Now find the '=' in the previous pair, replace it with '\0' and save
       * the parameter value string. */
      equals = strchr(equals, '=');
      if(equals) {
        *equals = '\0';
        hs->param_vals[loop] = equals + 1;
      } else {
        hs->param_vals[loop] = NULL;
      }
    }
  
    return loop;
  }
  #endif /* LWIP_HTTPD_CGI */
  
  #if LWIP_HTTPD_SSI
  /**
   * Insert a tag (found in an shtml in the form of "<!--#tagname-->" into the file.
   * The tag's name is stored in ssi->tag_name (NULL-terminated), the replacement
   * should be written to hs->tag_insert (up to a length of LWIP_HTTPD_MAX_TAG_INSERT_LEN).
   * The amount of data written is stored to ssi->tag_insert_len.
   *
   * @todo: return tag_insert_len - maybe it can be removed from struct http_state?
   *
   * @param hs http connection state
   */
  static void
  get_tag_insert(struct http_state *hs)
  {
    int loop;
    size_t len;
    struct http_ssi_state *ssi;
    LWIP_ASSERT("hs != NULL", hs != NULL);
    ssi = hs->ssi;
    LWIP_ASSERT("ssi != NULL", ssi != NULL);
  #if LWIP_HTTPD_SSI_MULTIPART
    u16_t current_tag_part = ssi->tag_part;
    ssi->tag_part = HTTPD_LAST_TAG_PART;
  #endif /* LWIP_HTTPD_SSI_MULTIPART */
  
    if(g_pfnSSIHandler && g_ppcTags && g_iNumTags) {
  
      /* Find this tag in the list we have been provided. */
      for(loop = 0; loop < g_iNumTags; loop++) {
        if(strcmp(ssi->tag_name, g_ppcTags[loop]) == 0) {
          ssi->tag_insert_len = g_pfnSSIHandler(loop, ssi->tag_insert,
             LWIP_HTTPD_MAX_TAG_INSERT_LEN
  #if LWIP_HTTPD_SSI_MULTIPART
             , current_tag_part, &ssi->tag_part
  #endif /* LWIP_HTTPD_SSI_MULTIPART */
  #if LWIP_HTTPD_FILE_STATE
             , hs->handle->state
  #endif /* LWIP_HTTPD_FILE_STATE */
             );
          return;
        }
      }
    }
  
    /* If we drop out, we were asked to serve a page which contains tags that
     * we don't have a handler for. Merely echo back the tags with an error
     * marker. */
  #define UNKNOWN_TAG1_TEXT "<b>***UNKNOWN TAG "
  #define UNKNOWN_TAG1_LEN  18
  #define UNKNOWN_TAG2_TEXT "***</b>"
  #define UNKNOWN_TAG2_LEN  7
    len = LWIP_MIN(strlen(ssi->tag_name),
      LWIP_HTTPD_MAX_TAG_INSERT_LEN - (UNKNOWN_TAG1_LEN + UNKNOWN_TAG2_LEN));
    MEMCPY(ssi->tag_insert, UNKNOWN_TAG1_TEXT, UNKNOWN_TAG1_LEN);
    MEMCPY(&ssi->tag_insert[UNKNOWN_TAG1_LEN], ssi->tag_name, len);
    MEMCPY(&ssi->tag_insert[UNKNOWN_TAG1_LEN + len], UNKNOWN_TAG2_TEXT, UNKNOWN_TAG2_LEN);
    ssi->tag_insert[UNKNOWN_TAG1_LEN + len + UNKNOWN_TAG2_LEN] = 0;
  
    len = strlen(ssi->tag_insert);
    LWIP_ASSERT("len <= 0xffff", len <= 0xffff);
    ssi->tag_insert_len = (u16_t)len;
  }
  #endif /* LWIP_HTTPD_SSI */
  
  #if LWIP_HTTPD_DYNAMIC_HEADERS
  /**
   * Generate the relevant HTTP headers for the given filename and write
   * them into the supplied buffer.
   */
  static void
  get_http_headers(struct http_state *pState, char *pszURI)
  {
    unsigned int iLoop;
    char *pszWork;
    char *pszExt;
    char *pszVars;
  
    /* Ensure that we initialize the loop counter. */
    iLoop = 0;
  
    /* In all cases, the second header we send is the server identification
       so set it here. */
    pState->hdrs[1] = g_psHTTPHeaderStrings[HTTP_HDR_SERVER];
  
    /* Is this a normal file or the special case we use to send back the
       default "404: Page not found" response? */
    if (pszURI == NULL) {
      pState->hdrs[0] = g_psHTTPHeaderStrings[HTTP_HDR_NOT_FOUND];
      pState->hdrs[2] = g_psHTTPHeaderStrings[DEFAULT_404_HTML];
  
      /* Set up to send the first header string. */
      pState->hdr_index = 0;
      pState->hdr_pos = 0;
      return;
    } else {
      /* We are dealing with a particular filename. Look for one other
         special case.  We assume that any filename with "404" in it must be
         indicative of a 404 server error whereas all other files require
         the 200 OK header. */
      if (strstr(pszURI, "404")) {
        pState->hdrs[0] = g_psHTTPHeaderStrings[HTTP_HDR_NOT_FOUND];
      } else if (strstr(pszURI, "400")) {
        pState->hdrs[0] = g_psHTTPHeaderStrings[HTTP_HDR_BAD_REQUEST];
      } else if (strstr(pszURI, "501")) {
        pState->hdrs[0] = g_psHTTPHeaderStrings[HTTP_HDR_NOT_IMPL];
      } else {
        pState->hdrs[0] = g_psHTTPHeaderStrings[HTTP_HDR_OK];
      }
  
      /* Determine if the URI has any variables and, if so, temporarily remove 
         them. */
      pszVars = strchr(pszURI, '?');
      if(pszVars) {
        *pszVars = '\0';
      }
  
      /* Get a pointer to the file extension.  We find this by looking for the
         last occurrence of "." in the filename passed. */
      pszExt = NULL;
      pszWork = strchr(pszURI, '.');
      while(pszWork) {
        pszExt = pszWork + 1;
        pszWork = strchr(pszExt, '.');
      }
  
      /* Now determine the content type and add the relevant header for that. */
      for(iLoop = 0; (iLoop < NUM_HTTP_HEADERS) && pszExt; iLoop++) {
        /* Have we found a matching extension? */
        if(!strcmp(g_psHTTPHeaders[iLoop].extension, pszExt)) {
          pState->hdrs[2] =
            g_psHTTPHeaderStrings[g_psHTTPHeaders[iLoop].headerIndex];
          break;
        }
      }
  
      /* Reinstate the parameter marker if there was one in the original URI. */
      if(pszVars) {
        *pszVars = '?';
      }
    }
  
    /* Does the URL passed have any file extension?  If not, we assume it
       is a special-case URL used for control state notification and we do
       not send any HTTP headers with the response. */
    if(!pszExt) {
      /* Force the header index to a value indicating that all headers
         have already been sent. */
      pState->hdr_index = NUM_FILE_HDR_STRINGS;
    } else {
      /* Did we find a matching extension? */
      if(iLoop == NUM_HTTP_HEADERS) {
        /* No - use the default, plain text file type. */
        pState->hdrs[2] = g_psHTTPHeaderStrings[HTTP_HDR_DEFAULT_TYPE];
      }
  
      /* Set up to send the first header string. */
      pState->hdr_index = 0;
      pState->hdr_pos = 0;
    }
  }
  
  /** Sub-function of http_send(): send dynamic headers
   *
   * @returns: - HTTP_NO_DATA_TO_SEND: no new data has been enqueued
   *           - HTTP_DATA_TO_SEND_CONTINUE: continue with sending HTTP body
   *           - HTTP_DATA_TO_SEND_BREAK: data has been enqueued, headers pending,
   *                                      so don't send HTTP body yet
   */
  static u8_t
  http_send_headers(struct tcp_pcb *pcb, struct http_state *hs)
  {
    err_t err;
    u16_t len;
    u8_t data_to_send = HTTP_NO_DATA_TO_SEND;
    u16_t hdrlen, sendlen;
  
    /* How much data can we send? */
    len = tcp_sndbuf(pcb);
    sendlen = len;
  
    while(len && (hs->hdr_index < NUM_FILE_HDR_STRINGS) && sendlen) {
      const void *ptr;
      u16_t old_sendlen;
      /* How much do we have to send from the current header? */
      hdrlen = (u16_t)strlen(hs->hdrs[hs->hdr_index]);
  
      /* How much of this can we send? */
      sendlen = (len < (hdrlen - hs->hdr_pos)) ? len : (hdrlen - hs->hdr_pos);
  
      /* Send this amount of data or as much as we can given memory
      * constraints. */
      ptr = (const void *)(hs->hdrs[hs->hdr_index] + hs->hdr_pos);
      old_sendlen = sendlen;
      err = http_write(pcb, ptr, &sendlen, HTTP_IS_HDR_VOLATILE(hs, ptr));
      if ((err == ERR_OK) && (old_sendlen != sendlen)) {
        /* Remember that we added some more data to be transmitted. */
        data_to_send = HTTP_DATA_TO_SEND_CONTINUE;
      } else if (err != ERR_OK) {
         /* special case: http_write does not try to send 1 byte */
        sendlen = 0;
      }
  
      /* Fix up the header position for the next time round. */
      hs->hdr_pos += sendlen;
      len -= sendlen;
  
      /* Have we finished sending this string? */
      if(hs->hdr_pos == hdrlen) {
        /* Yes - move on to the next one */
        hs->hdr_index++;
        hs->hdr_pos = 0;
      }
    }
    /* If we get here and there are still header bytes to send, we send
     * the header information we just wrote immediately. If there are no
     * more headers to send, but we do have file data to send, drop through
     * to try to send some file data too. */
    if((hs->hdr_index < NUM_FILE_HDR_STRINGS) || !hs->file) {
      LWIP_DEBUGF(HTTPD_DEBUG, ("tcp_output\n"));
      return HTTP_DATA_TO_SEND_BREAK;
    }
    return data_to_send;
  }
  #endif /* LWIP_HTTPD_DYNAMIC_HEADERS */
  
  /** Sub-function of http_send(): end-of-file (or block) is reached,
   * either close the file or read the next block (if supported).
   *
   * @returns: 0 if the file is finished or no data has been read
   *           1 if the file is not finished and data has been read
   */
  static u8_t
  http_check_eof(struct tcp_pcb *pcb, struct http_state *hs)
  {
  #if LWIP_HTTPD_DYNAMIC_FILE_READ
    int count;
  #endif /* LWIP_HTTPD_DYNAMIC_FILE_READ */
  
    /* Do we have a valid file handle? */
    if (hs->handle == NULL) {
      /* No - close the connection. */
      http_eof(pcb, hs);
      return 0;
    }
    if (fs_bytes_left(hs->handle) <= 0) {
      /* We reached the end of the file so this request is done. */
      LWIP_DEBUGF(HTTPD_DEBUG, ("End of file.\n"));
      http_eof(pcb, hs);
      return 0;
    }
  #if LWIP_HTTPD_DYNAMIC_FILE_READ
    /* Do we already have a send buffer allocated? */
    if(hs->buf) {
      /* Yes - get the length of the buffer */
      count = hs->buf_len;
    } else {
      /* We don't have a send buffer so allocate one up to 2mss bytes long. */
      count = 2 * tcp_mss(pcb);
      do {
        hs->buf = (char*)mem_malloc((mem_size_t)count);
        if (hs->buf != NULL) {
          hs->buf_len = count;
          break;
        }
        count = count / 2;
      } while (count > 100);
  
      /* Did we get a send buffer? If not, return immediately. */
      if (hs->buf == NULL) {
        LWIP_DEBUGF(HTTPD_DEBUG, ("No buff\n"));
        return 0;
      }
    }
  
    /* Read a block of data from the file. */
    LWIP_DEBUGF(HTTPD_DEBUG, ("Trying to read %d bytes.\n", count));
  
  #if LWIP_HTTPD_FS_ASYNC_READ
    count = fs_read_async(hs->handle, hs->buf, count, http_continue, hs);
  #else /* LWIP_HTTPD_FS_ASYNC_READ */
    count = fs_read(hs->handle, hs->buf, count);
  #endif /* LWIP_HTTPD_FS_ASYNC_READ */
    if (count < 0) {
      if (count == FS_READ_DELAYED) {
        /* Delayed read, wait for FS to unblock us */
        return 0;
      }
      /* We reached the end of the file so this request is done.
       * @todo: don't close here for HTTP/1.1? */
      LWIP_DEBUGF(HTTPD_DEBUG, ("End of file.\n"));
      http_eof(pcb, hs);
      return 0;
    }
  
    /* Set up to send the block of data we just read */
    LWIP_DEBUGF(HTTPD_DEBUG, ("Read %d bytes.\n", count));
    hs->left = count;
    hs->file = hs->buf;
  #if LWIP_HTTPD_SSI
    if (hs->ssi) {
      hs->ssi->parse_left = count;
      hs->ssi->parsed = hs->buf;
    }
  #endif /* LWIP_HTTPD_SSI */
  #else /* LWIP_HTTPD_DYNAMIC_FILE_READ */
    LWIP_ASSERT("SSI and DYNAMIC_HEADERS turned off but eof not reached", 0);
  #endif /* LWIP_HTTPD_SSI || LWIP_HTTPD_DYNAMIC_HEADERS */
    return 1;
  }
  
  /** Sub-function of http_send(): This is the normal send-routine for non-ssi files
   *
   * @returns: - 1: data has been written (so call tcp_ouput)
   *           - 0: no data has been written (no need to call tcp_output)
   */
  static u8_t
  http_send_data_nonssi(struct tcp_pcb *pcb, struct http_state *hs)
  {
    err_t err;
    u16_t len;
    u16_t mss;
    u8_t data_to_send = 0;
  
    /* We are not processing an SHTML file so no tag checking is necessary.
     * Just send the data as we received it from the file. */
  
    /* We cannot send more data than space available in the send
       buffer. */
    if (tcp_sndbuf(pcb) < hs->left) {
      len = tcp_sndbuf(pcb);
    } else {
      len = (u16_t)hs->left;
      LWIP_ASSERT("hs->left did not fit into u16_t!", (len == hs->left));
    }
    mss = tcp_mss(pcb);
    if (len > (2 * mss)) {
      len = 2 * mss;
    }
  
    err = http_write(pcb, hs->file, &len, HTTP_IS_DATA_VOLATILE(hs));
    if (err == ERR_OK) {
      data_to_send = 1;
      hs->file += len;
      hs->left -= len;
    }
  
    return data_to_send;
  }
  
  #if LWIP_HTTPD_SSI
  /** Sub-function of http_send(): This is the send-routine for ssi files
   *
   * @returns: - 1: data has been written (so call tcp_ouput)
   *           - 0: no data has been written (no need to call tcp_output)
   */
  static u8_t
  http_send_data_ssi(struct tcp_pcb *pcb, struct http_state *hs)
  {
    err_t err = ERR_OK;
    u16_t len;
    u16_t mss;
    u8_t data_to_send = 0;
  
    struct http_ssi_state *ssi = hs->ssi;
    LWIP_ASSERT("ssi != NULL", ssi != NULL);
    /* We are processing an SHTML file so need to scan for tags and replace
     * them with insert strings. We need to be careful here since a tag may
     * straddle the boundary of two blocks read from the file and we may also
     * have to split the insert string between two tcp_write operations. */
  
    /* How much data could we send? */
    len = tcp_sndbuf(pcb);
  
    /* Do we have remaining data to send before parsing more? */
    if(ssi->parsed > hs->file) {
      /* We cannot send more data than space available in the send
         buffer. */
      if (tcp_sndbuf(pcb) < (ssi->parsed - hs->file)) {
        len = tcp_sndbuf(pcb);
      } else {
        LWIP_ASSERT("Data size does not fit into u16_t!",
                    (ssi->parsed - hs->file) <= 0xffff);
        len = (u16_t)(ssi->parsed - hs->file);
      }
      mss = tcp_mss(pcb);
      if(len > (2 * mss)) {
        len = 2 * mss;
      }
  
      err = http_write(pcb, hs->file, &len, HTTP_IS_DATA_VOLATILE(hs));
      if (err == ERR_OK) {
        data_to_send = 1;
        hs->file += len;
        hs->left -= len;
      }
  
      /* If the send buffer is full, return now. */
      if(tcp_sndbuf(pcb) == 0) {
        return data_to_send;
      }
    }
  
    LWIP_DEBUGF(HTTPD_DEBUG, ("State %d, %d left\n", ssi->tag_state, (int)ssi->parse_left));
  
    /* We have sent all the data that was already parsed so continue parsing
     * the buffer contents looking for SSI tags. */
    while((ssi->parse_left) && (err == ERR_OK)) {
      /* @todo: somewhere in this loop, 'len' should grow again... */
      if (len == 0) {
        return data_to_send;
      }
      switch(ssi->tag_state) {
        case TAG_NONE:
          /* We are not currently processing an SSI tag so scan for the
           * start of the lead-in marker. */
          if(*ssi->parsed == g_pcTagLeadIn[0]) {
            /* We found what could be the lead-in for a new tag so change
             * state appropriately. */
            ssi->tag_state = TAG_LEADIN;
            ssi->tag_index = 1;
  #if !LWIP_HTTPD_SSI_INCLUDE_TAG
            ssi->tag_started = ssi->parsed;
  #endif /* !LWIP_HTTPD_SSI_INCLUDE_TAG */
          }
  
          /* Move on to the next character in the buffer */
          ssi->parse_left--;
          ssi->parsed++;
          break;
  
        case TAG_LEADIN:
          /* We are processing the lead-in marker, looking for the start of
           * the tag name. */
  
          /* Have we reached the end of the leadin? */
          if(ssi->tag_index == LEN_TAG_LEAD_IN) {
            ssi->tag_index = 0;
            ssi->tag_state = TAG_FOUND;
          } else {
            /* Have we found the next character we expect for the tag leadin? */
            if(*ssi->parsed == g_pcTagLeadIn[ssi->tag_index]) {
              /* Yes - move to the next one unless we have found the complete
               * leadin, in which case we start looking for the tag itself */
              ssi->tag_index++;
            } else {
              /* We found an unexpected character so this is not a tag. Move
               * back to idle state. */
              ssi->tag_state = TAG_NONE;
            }
  
            /* Move on to the next character in the buffer */
            ssi->parse_left--;
            ssi->parsed++;
          }
          break;
  
        case TAG_FOUND:
          /* We are reading the tag name, looking for the start of the
           * lead-out marker and removing any whitespace found. */
  
          /* Remove leading whitespace between the tag leading and the first
           * tag name character. */
          if((ssi->tag_index == 0) && ((*ssi->parsed == ' ') ||
             (*ssi->parsed == '\t') || (*ssi->parsed == '\n') ||
             (*ssi->parsed == '\r'))) {
            /* Move on to the next character in the buffer */
            ssi->parse_left--;
            ssi->parsed++;
            break;
          }
  
          /* Have we found the end of the tag name? This is signalled by
           * us finding the first leadout character or whitespace */
          if((*ssi->parsed == g_pcTagLeadOut[0]) ||
             (*ssi->parsed == ' ')  || (*ssi->parsed == '\t') ||
             (*ssi->parsed == '\n') || (*ssi->parsed == '\r')) {
  
            if(ssi->tag_index == 0) {
              /* We read a zero length tag so ignore it. */
              ssi->tag_state = TAG_NONE;
            } else {
              /* We read a non-empty tag so go ahead and look for the
               * leadout string. */
              ssi->tag_state = TAG_LEADOUT;
              LWIP_ASSERT("ssi->tag_index <= 0xff", ssi->tag_index <= 0xff);
              ssi->tag_name_len = (u8_t)ssi->tag_index;
              ssi->tag_name[ssi->tag_index] = '\0';
              if(*ssi->parsed == g_pcTagLeadOut[0]) {
                ssi->tag_index = 1;
              } else {
                ssi->tag_index = 0;
              }
            }
          } else {
            /* This character is part of the tag name so save it */
            if(ssi->tag_index < LWIP_HTTPD_MAX_TAG_NAME_LEN) {
              ssi->tag_name[ssi->tag_index++] = *ssi->parsed;
            } else {
              /* The tag was too long so ignore it. */
              ssi->tag_state = TAG_NONE;
            }
          }
  
          /* Move on to the next character in the buffer */
          ssi->parse_left--;
          ssi->parsed++;
  
          break;
  
        /* We are looking for the end of the lead-out marker. */
        case TAG_LEADOUT:
          /* Remove leading whitespace between the tag leading and the first
           * tag leadout character. */
          if((ssi->tag_index == 0) && ((*ssi->parsed == ' ') ||
             (*ssi->parsed == '\t') || (*ssi->parsed == '\n') ||
             (*ssi->parsed == '\r'))) {
            /* Move on to the next character in the buffer */
            ssi->parse_left--;
            ssi->parsed++;
            break;
          }
  
          /* Have we found the next character we expect for the tag leadout? */
          if(*ssi->parsed == g_pcTagLeadOut[ssi->tag_index]) {
            /* Yes - move to the next one unless we have found the complete
             * leadout, in which case we need to call the client to process
             * the tag. */
  
            /* Move on to the next character in the buffer */
            ssi->parse_left--;
            ssi->parsed++;
  
            if(ssi->tag_index == (LEN_TAG_LEAD_OUT - 1)) {
              /* Call the client to ask for the insert string for the
               * tag we just found. */
  #if LWIP_HTTPD_SSI_MULTIPART
              ssi->tag_part = 0; /* start with tag part 0 */
  #endif /* LWIP_HTTPD_SSI_MULTIPART */
              get_tag_insert(hs);
  
              /* Next time through, we are going to be sending data
               * immediately, either the end of the block we start
               * sending here or the insert string. */
              ssi->tag_index = 0;
              ssi->tag_state = TAG_SENDING;
              ssi->tag_end = ssi->parsed;
  #if !LWIP_HTTPD_SSI_INCLUDE_TAG
              ssi->parsed = ssi->tag_started;
  #endif /* !LWIP_HTTPD_SSI_INCLUDE_TAG*/
  
              /* If there is any unsent data in the buffer prior to the
               * tag, we need to send it now. */
              if (ssi->tag_end > hs->file) {
                /* How much of the data can we send? */
  #if LWIP_HTTPD_SSI_INCLUDE_TAG
                if(len > ssi->tag_end - hs->file) {
                  len = (u16_t)(ssi->tag_end - hs->file);
                }
  #else /* LWIP_HTTPD_SSI_INCLUDE_TAG*/
                if(len > ssi->tag_started - hs->file) {
                  /* we would include the tag in sending */
                  len = (u16_t)(ssi->tag_started - hs->file);
                }
  #endif /* LWIP_HTTPD_SSI_INCLUDE_TAG*/
  
                err = http_write(pcb, hs->file, &len, HTTP_IS_DATA_VOLATILE(hs));
                if (err == ERR_OK) {
                  data_to_send = 1;
  #if !LWIP_HTTPD_SSI_INCLUDE_TAG
                  if(ssi->tag_started <= hs->file) {
                    /* pretend to have sent the tag, too */
                    len += ssi->tag_end - ssi->tag_started;
                  }
  #endif /* !LWIP_HTTPD_SSI_INCLUDE_TAG*/
                  hs->file += len;
                  hs->left -= len;
                }
              }
            } else {
              ssi->tag_index++;
            }
          } else {
            /* We found an unexpected character so this is not a tag. Move
             * back to idle state. */
            ssi->parse_left--;
            ssi->parsed++;
            ssi->tag_state = TAG_NONE;
          }
          break;
  
        /*
         * We have found a valid tag and are in the process of sending
         * data as a result of that discovery. We send either remaining data
         * from the file prior to the insert point or the insert string itself.
         */
        case TAG_SENDING:
          /* Do we have any remaining file data to send from the buffer prior
           * to the tag? */
          if(ssi->tag_end > hs->file) {
            /* How much of the data can we send? */
  #if LWIP_HTTPD_SSI_INCLUDE_TAG
            if(len > ssi->tag_end - hs->file) {
              len = (u16_t)(ssi->tag_end - hs->file);
            }
  #else /* LWIP_HTTPD_SSI_INCLUDE_TAG*/
            LWIP_ASSERT("hs->started >= hs->file", ssi->tag_started >= hs->file);
            if (len > ssi->tag_started - hs->file) {
              /* we would include the tag in sending */
              len = (u16_t)(ssi->tag_started - hs->file);
            }
  #endif /* LWIP_HTTPD_SSI_INCLUDE_TAG*/
            if (len != 0) {
              err = http_write(pcb, hs->file, &len, HTTP_IS_DATA_VOLATILE(hs));
            } else {
              err = ERR_OK;
            }
            if (err == ERR_OK) {
              data_to_send = 1;
  #if !LWIP_HTTPD_SSI_INCLUDE_TAG
              if(ssi->tag_started <= hs->file) {
                /* pretend to have sent the tag, too */
                len += ssi->tag_end - ssi->tag_started;
              }
  #endif /* !LWIP_HTTPD_SSI_INCLUDE_TAG*/
              hs->file += len;
              hs->left -= len;
            }
          } else {
  #if LWIP_HTTPD_SSI_MULTIPART
            if(ssi->tag_index >= ssi->tag_insert_len) {
              /* Did the last SSIHandler have more to send? */
              if (ssi->tag_part != HTTPD_LAST_TAG_PART) {
                /* If so, call it again */
                ssi->tag_index = 0;
                get_tag_insert(hs);
              }
            }
  #endif /* LWIP_HTTPD_SSI_MULTIPART */
  
            /* Do we still have insert data left to send? */
            if(ssi->tag_index < ssi->tag_insert_len) {
              /* We are sending the insert string itself. How much of the
               * insert can we send? */
              if(len > (ssi->tag_insert_len - ssi->tag_index)) {
                len = (ssi->tag_insert_len - ssi->tag_index);
              }
  
              /* Note that we set the copy flag here since we only have a
               * single tag insert buffer per connection. If we don't do
               * this, insert corruption can occur if more than one insert
               * is processed before we call tcp_output. */
              err = http_write(pcb, &(ssi->tag_insert[ssi->tag_index]), &len,
                               HTTP_IS_TAG_VOLATILE(hs));
              if (err == ERR_OK) {
                data_to_send = 1;
                ssi->tag_index += len;
                /* Don't return here: keep on sending data */
              }
            } else {
  #if LWIP_HTTPD_SSI_MULTIPART
              if (ssi->tag_part == HTTPD_LAST_TAG_PART)
  #endif /* LWIP_HTTPD_SSI_MULTIPART */
              {
                /* We have sent all the insert data so go back to looking for
                 * a new tag. */
                LWIP_DEBUGF(HTTPD_DEBUG, ("Everything sent.\n"));
                ssi->tag_index = 0;
                ssi->tag_state = TAG_NONE;
  #if !LWIP_HTTPD_SSI_INCLUDE_TAG
                ssi->parsed = ssi->tag_end;
  #endif /* !LWIP_HTTPD_SSI_INCLUDE_TAG*/
              }
            }
            break;
        }
      }
    }
  
    /* If we drop out of the end of the for loop, this implies we must have
     * file data to send so send it now. In TAG_SENDING state, we've already
     * handled this so skip the send if that's the case. */
    if((ssi->tag_state != TAG_SENDING) && (ssi->parsed > hs->file)) {
      /* We cannot send more data than space available in the send
         buffer. */
      if (tcp_sndbuf(pcb) < (ssi->parsed - hs->file)) {
        len = tcp_sndbuf(pcb);
      } else {
        LWIP_ASSERT("Data size does not fit into u16_t!",
                    (ssi->parsed - hs->file) <= 0xffff);
        len = (u16_t)(ssi->parsed - hs->file);
      }
      if(len > (2 * tcp_mss(pcb))) {
        len = 2 * tcp_mss(pcb);
      }
  
      err = http_write(pcb, hs->file, &len, HTTP_IS_DATA_VOLATILE(hs));
      if (err == ERR_OK) {
        data_to_send = 1;
        hs->file += len;
        hs->left -= len;
      }
    }
    return data_to_send;
  }
  #endif /* LWIP_HTTPD_SSI */
  
  /**
   * Try to send more data on this pcb.
   *
   * @param pcb the pcb to send data
   * @param hs connection state
   */
  static u8_t
  http_send(struct tcp_pcb *pcb, struct http_state *hs)
  {
    u8_t data_to_send = HTTP_NO_DATA_TO_SEND;
  
    LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("http_send: pcb=%p hs=%p left=%d\n", (void*)pcb,
      (void*)hs, hs != NULL ? (int)hs->left : 0));
  
  #if LWIP_HTTPD_SUPPORT_POST && LWIP_HTTPD_POST_MANUAL_WND
    if (hs->unrecved_bytes != 0) {
      return 0;
    }
  #endif /* LWIP_HTTPD_SUPPORT_POST && LWIP_HTTPD_POST_MANUAL_WND */
  
    /* If we were passed a NULL state structure pointer, ignore the call. */
    if (hs == NULL) {
      return 0;
    }
  
  #if LWIP_HTTPD_FS_ASYNC_READ
    /* Check if we are allowed to read from this file.
       (e.g. SSI might want to delay sending until data is available) */
    if (!fs_is_file_ready(hs->handle, http_continue, hs)) {
      return 0;
    }
  #endif /* LWIP_HTTPD_FS_ASYNC_READ */
  
  #if LWIP_HTTPD_DYNAMIC_HEADERS
    /* Do we have any more header data to send for this file? */
    if(hs->hdr_index < NUM_FILE_HDR_STRINGS) {
      data_to_send = http_send_headers(pcb, hs);
      if (data_to_send != HTTP_DATA_TO_SEND_CONTINUE) {
        return data_to_send;
      }
    }
  #endif /* LWIP_HTTPD_DYNAMIC_HEADERS */
  
    /* Have we run out of file data to send? If so, we need to read the next
     * block from the file. */
    if (hs->left == 0) {
      if (!http_check_eof(pcb, hs)) {
        return 0;
      }
    }
  
  #if LWIP_HTTPD_SSI
    if(hs->ssi) {
      data_to_send = http_send_data_ssi(pcb, hs);
    } else
  #endif /* LWIP_HTTPD_SSI */
    {
      data_to_send = http_send_data_nonssi(pcb, hs);
    }
  
    if((hs->left == 0) && (fs_bytes_left(hs->handle) <= 0)) {
      /* We reached the end of the file so this request is done.
       * This adds the FIN flag right into the last data segment. */
      LWIP_DEBUGF(HTTPD_DEBUG, ("End of file.\n"));
      http_eof(pcb, hs);
      return 0;
    }
    LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("send_data end.\n"));
    return data_to_send;
  }
  
  #if LWIP_HTTPD_SUPPORT_EXTSTATUS
  /** Initialize a http connection with a file to send for an error message
   *
   * @param hs http connection state
   * @param error_nr HTTP error number
   * @return ERR_OK if file was found and hs has been initialized correctly
   *         another err_t otherwise
   */
  static err_t
  http_find_error_file(struct http_state *hs, u16_t error_nr)
  {
    const char *uri1, *uri2, *uri3;
    err_t err;
  
    if (error_nr == 501) {
      uri1 = "/501.html";
      uri2 = "/501.htm";
      uri3 = "/501.shtml";
    } else {
      /* 400 (bad request is the default) */
      uri1 = "/400.html";
      uri2 = "/400.htm";
      uri3 = "/400.shtml";
    }
    err = fs_open(&hs->file_handle, uri1);
    if (err != ERR_OK) {
      err = fs_open(&hs->file_handle, uri2);
      if (err != ERR_OK) {
        err = fs_open(&hs->file_handle, uri3);
        if (err != ERR_OK) {
          LWIP_DEBUGF(HTTPD_DEBUG, ("Error page for error %"U16_F" not found\n",
            error_nr));
          return ERR_ARG;
        }
      }
    }
    return http_init_file(hs, &hs->file_handle, 0, NULL, 0);
  }
  #else /* LWIP_HTTPD_SUPPORT_EXTSTATUS */
  #define http_find_error_file(hs, error_nr) ERR_ARG
  #endif /* LWIP_HTTPD_SUPPORT_EXTSTATUS */
  
  /**
   * Get the file struct for a 404 error page.
   * Tries some file names and returns NULL if none found.
   *
   * @param uri pointer that receives the actual file name URI
   * @return file struct for the error page or NULL no matching file was found
   */
  static struct fs_file *
  http_get_404_file(struct http_state *hs, const char **uri)
  {
    err_t err;
  
    *uri = "/404.html";
    err = fs_open(&hs->file_handle, *uri);
    if (err != ERR_OK) {
      /* 404.html doesn't exist. Try 404.htm instead. */
      *uri = "/404.htm";
      err = fs_open(&hs->file_handle, *uri);
      if (err != ERR_OK) {
        /* 404.htm doesn't exist either. Try 404.shtml instead. */
        *uri = "/404.shtml";
        err = fs_open(&hs->file_handle, *uri);
        if (err != ERR_OK) {
          /* 404.htm doesn't exist either. Indicate to the caller that it should
           * send back a default 404 page.
           */
          *uri = NULL;
          return NULL;
        }
      }
    }
  
    return &hs->file_handle;
  }
  
  #if LWIP_HTTPD_SUPPORT_POST
  static err_t
  http_handle_post_finished(struct http_state *hs)
  {
  #if LWIP_HTTPD_POST_MANUAL_WND
    /* Prevent multiple calls to httpd_post_finished, since it might have already
       been called before from httpd_post_data_recved(). */
    if (hs->post_finished) {
      return ERR_OK;
    }
    hs->post_finished = 1;
  #endif /* LWIP_HTTPD_POST_MANUAL_WND */
    /* application error or POST finished */
    /* NULL-terminate the buffer */
    http_post_response_filename[0] = 0;
    httpd_post_finished(hs, http_post_response_filename, LWIP_HTTPD_POST_MAX_RESPONSE_URI_LEN);
    return http_find_file(hs, http_post_response_filename, 0);
  }
  
  /** Pass received POST body data to the application and correctly handle
   * returning a response document or closing the connection.
   * ATTENTION: The application is responsible for the pbuf now, so don't free it!
   *
   * @param hs http connection state
   * @param p pbuf to pass to the application
   * @return ERR_OK if passed successfully, another err_t if the response file
   *         hasn't been found (after POST finished)
   */
  static err_t
  http_post_rxpbuf(struct http_state *hs, struct pbuf *p)
  {
    err_t err;
  
    /* adjust remaining Content-Length */
    if (hs->post_content_len_left < p->tot_len) {
      hs->post_content_len_left = 0;
    } else {
      hs->post_content_len_left -= p->tot_len;
    }
    err = httpd_post_receive_data(hs, p);
    if ((err != ERR_OK) || (hs->post_content_len_left == 0)) {
  #if LWIP_HTTPD_SUPPORT_POST && LWIP_HTTPD_POST_MANUAL_WND
      if (hs->unrecved_bytes != 0) {
         return ERR_OK;
      }
  #endif /* LWIP_HTTPD_SUPPORT_POST && LWIP_HTTPD_POST_MANUAL_WND */
      /* application error or POST finished */
      return http_handle_post_finished(hs);
    }
  
    return ERR_OK;
  }
  
  /** Handle a post request. Called from http_parse_request when method 'POST'
   * is found.
   *
   * @param p The input pbuf (containing the POST header and body).
   * @param hs The http connection state.
   * @param data HTTP request (header and part of body) from input pbuf(s).
   * @param data_len Size of 'data'.
   * @param uri The HTTP URI parsed from input pbuf(s).
   * @param uri_end Pointer to the end of 'uri' (here, the rest of the HTTP
   *                header starts).
   * @return ERR_OK: POST correctly parsed and accepted by the application.
   *         ERR_INPROGRESS: POST not completely parsed (no error yet)
   *         another err_t: Error parsing POST or denied by the application
   */
  static err_t
  http_post_request(struct pbuf **inp, struct http_state *hs,
                    char *data, u16_t data_len, char *uri, char *uri_end)
  {
    err_t err;
    /* search for end-of-header (first double-CRLF) */
    char* crlfcrlf = strnstr(uri_end + 1, CRLF CRLF, data_len - (uri_end + 1 - data));
  
    if (crlfcrlf != NULL) {
      /* search for "Content-Length: " */
  #define HTTP_HDR_CONTENT_LEN                "Content-Length: "
  #define HTTP_HDR_CONTENT_LEN_LEN            16
  #define HTTP_HDR_CONTENT_LEN_DIGIT_MAX_LEN  10
      char *scontent_len = strnstr(uri_end + 1, HTTP_HDR_CONTENT_LEN, crlfcrlf - (uri_end + 1));
      if (scontent_len != NULL) {
        char *scontent_len_end = strnstr(scontent_len + HTTP_HDR_CONTENT_LEN_LEN, CRLF, HTTP_HDR_CONTENT_LEN_DIGIT_MAX_LEN);
        if (scontent_len_end != NULL) {
          int content_len;
          char *conten_len_num = scontent_len + HTTP_HDR_CONTENT_LEN_LEN;
          *scontent_len_end = 0;
          content_len = atoi(conten_len_num);
          if (content_len > 0) {
            /* adjust length of HTTP header passed to application */
            const char *hdr_start_after_uri = uri_end + 1;
            u16_t hdr_len = LWIP_MIN(data_len, crlfcrlf + 4 - data);
            u16_t hdr_data_len = LWIP_MIN(data_len, crlfcrlf + 4 - hdr_start_after_uri);
            u8_t post_auto_wnd = 1;
            http_post_response_filename[0] = 0;
            err = httpd_post_begin(hs, uri, hdr_start_after_uri, hdr_data_len, content_len,
              http_post_response_filename, LWIP_HTTPD_POST_MAX_RESPONSE_URI_LEN, &post_auto_wnd);
            if (err == ERR_OK) {
              /* try to pass in data of the first pbuf(s) */
              struct pbuf *q = *inp;
              u16_t start_offset = hdr_len;
  #if LWIP_HTTPD_POST_MANUAL_WND
              hs->no_auto_wnd = !post_auto_wnd;
  #endif /* LWIP_HTTPD_POST_MANUAL_WND */
              /* set the Content-Length to be received for this POST */
              hs->post_content_len_left = (u32_t)content_len;
  
              /* get to the pbuf where the body starts */
              while((q != NULL) && (q->len <= start_offset)) {
                struct pbuf *head = q;
                start_offset -= q->len;
                q = q->next;
                /* free the head pbuf */
                head->next = NULL;
                pbuf_free(head);
              }
              *inp = NULL;
              if (q != NULL) {
                /* hide the remaining HTTP header */
                pbuf_header(q, -(s16_t)start_offset);
  #if LWIP_HTTPD_POST_MANUAL_WND
                if (!post_auto_wnd) {
                  /* already tcp_recved() this data... */
                  hs->unrecved_bytes = q->tot_len;
                }
  #endif /* LWIP_HTTPD_POST_MANUAL_WND */
                return http_post_rxpbuf(hs, q);
              } else {
                return ERR_OK;
              }
            } else {
              /* return file passed from application */
              return http_find_file(hs, http_post_response_filename, 0);
            }
          } else {
            LWIP_DEBUGF(HTTPD_DEBUG, ("POST received invalid Content-Length: %s\n",
              conten_len_num));
            return ERR_ARG;
          }
        }
      }
    }
    /* if we come here, the POST is incomplete */
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
    return ERR_INPROGRESS;
  #else /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
    return ERR_ARG;
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
  }
  
  #if LWIP_HTTPD_POST_MANUAL_WND
  /** A POST implementation can call this function to update the TCP window.
   * This can be used to throttle data reception (e.g. when received data is
   * programmed to flash and data is received faster than programmed).
   *
   * @param connection A connection handle passed to httpd_post_begin for which
   *        httpd_post_finished has *NOT* been called yet!
   * @param recved_len Length of data received (for window update)
   */
  void httpd_post_data_recved(void *connection, u16_t recved_len)
  {
    struct http_state *hs = (struct http_state*)connection;
    if (hs != NULL) {
      if (hs->no_auto_wnd) {
        u16_t len = recved_len;
        if (hs->unrecved_bytes >= recved_len) {
          hs->unrecved_bytes -= recved_len;
        } else {
          LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_LEVEL_WARNING, ("httpd_post_data_recved: recved_len too big\n"));
          len = (u16_t)hs->unrecved_bytes;
          hs->unrecved_bytes = 0;
        }
        if (hs->pcb != NULL) {
          if (len != 0) {
            tcp_recved(hs->pcb, len);
          }
          if ((hs->post_content_len_left == 0) && (hs->unrecved_bytes == 0)) {
            /* finished handling POST */
            http_handle_post_finished(hs);
            http_send(hs->pcb, hs);
          }
        }
      }
    }
  }
  #endif /* LWIP_HTTPD_POST_MANUAL_WND */
  
  #endif /* LWIP_HTTPD_SUPPORT_POST */
  
  #if LWIP_HTTPD_FS_ASYNC_READ
  /** Try to send more data if file has been blocked before
   * This is a callback function passed to fs_read_async().
   */
  static void
  http_continue(void *connection)
  {
    struct http_state *hs = (struct http_state*)connection;
    if (hs && (hs->pcb) && (hs->handle)) {
      LWIP_ASSERT("hs->pcb != NULL", hs->pcb != NULL);
      LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("httpd_continue: try to send more data\n"));
      if (http_send(hs->pcb, hs)) {
        /* If we wrote anything to be sent, go ahead and send it now. */
        LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("tcp_output\n"));
        tcp_output(hs->pcb);
      }
    }
  }
  #endif /* LWIP_HTTPD_FS_ASYNC_READ */
  
  /**
   * When data has been received in the correct state, try to parse it
   * as a HTTP request.
   *
   * @param p the received pbuf
   * @param hs the connection state
   * @param pcb the tcp_pcb which received this packet
   * @return ERR_OK if request was OK and hs has been initialized correctly
   *         ERR_INPROGRESS if request was OK so far but not fully received
   *         another err_t otherwise
   */
  static err_t
  http_parse_request(struct pbuf **inp, struct http_state *hs, struct tcp_pcb *pcb)
  {
    char *data;
    char *crlf;
    u16_t data_len;
    struct pbuf *p = *inp;
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
    u16_t clen;
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
  #if LWIP_HTTPD_SUPPORT_POST
    err_t err;
  #endif /* LWIP_HTTPD_SUPPORT_POST */
  
    LWIP_UNUSED_ARG(pcb); /* only used for post */
    LWIP_ASSERT("p != NULL", p != NULL);
    LWIP_ASSERT("hs != NULL", hs != NULL);
  
    if ((hs->handle != NULL) || (hs->file != NULL)) {
      LWIP_DEBUGF(HTTPD_DEBUG, ("Received data while sending a file\n"));
      /* already sending a file */
      /* @todo: abort? */
      return ERR_USE;
    }
  
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
  
    LWIP_DEBUGF(HTTPD_DEBUG, ("Received %"U16_F" bytes\n", p->tot_len));
  
    /* first check allowed characters in this pbuf? */
  
    /* enqueue the pbuf */
    if (hs->req == NULL) {
      LWIP_DEBUGF(HTTPD_DEBUG, ("First pbuf\n"));
      hs->req = p;
    } else {
      LWIP_DEBUGF(HTTPD_DEBUG, ("pbuf enqueued\n"));
      pbuf_cat(hs->req, p);
    }
  
    if (hs->req->next != NULL) {
      data_len = LWIP_MIN(hs->req->tot_len, LWIP_HTTPD_MAX_REQ_LENGTH);
      pbuf_copy_partial(hs->req, httpd_req_buf, data_len, 0);
      data = httpd_req_buf;
    } else
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
    {
      data = (char *)p->payload;
      data_len = p->len;
      if (p->len != p->tot_len) {
        LWIP_DEBUGF(HTTPD_DEBUG, ("Warning: incomplete header due to chained pbufs\n"));
      }
    }
  
    /* received enough data for minimal request? */
    if (data_len >= MIN_REQ_LEN) {
      /* wait for CRLF before parsing anything */
      crlf = strnstr(data, CRLF, data_len);
      if (crlf != NULL) {
  #if LWIP_HTTPD_SUPPORT_POST
        int is_post = 0;
  #endif /* LWIP_HTTPD_SUPPORT_POST */
        int is_09 = 0;
        char *sp1, *sp2;
        u16_t left_len, uri_len;
        LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("CRLF received, parsing request\n"));
        /* parse method */
        if (!strncmp(data, "GET ", 4)) {
          sp1 = data + 3;
          /* received GET request */
          LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("Received GET request\"\n"));
  #if LWIP_HTTPD_SUPPORT_POST
        } else if (!strncmp(data, "POST ", 5)) {
          /* store request type */
          is_post = 1;
          sp1 = data + 4;
          /* received GET request */
          LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("Received POST request\n"));
  #endif /* LWIP_HTTPD_SUPPORT_POST */
        } else {
          /* null-terminate the METHOD (pbuf is freed anyway wen returning) */
          data[4] = 0;
          /* unsupported method! */
          LWIP_DEBUGF(HTTPD_DEBUG, ("Unsupported request method (not implemented): \"%s\"\n",
            data));
          return http_find_error_file(hs, 501);
        }
        /* if we come here, method is OK, parse URI */
        left_len = data_len - ((sp1 +1) - data);
        sp2 = strnstr(sp1 + 1, " ", left_len);
  #if LWIP_HTTPD_SUPPORT_V09
        if (sp2 == NULL) {
          /* HTTP 0.9: respond with correct protocol version */
          sp2 = strnstr(sp1 + 1, CRLF, left_len);
          is_09 = 1;
  #if LWIP_HTTPD_SUPPORT_POST
          if (is_post) {
            /* HTTP/0.9 does not support POST */
            goto badrequest;
          }
  #endif /* LWIP_HTTPD_SUPPORT_POST */
        }
  #endif /* LWIP_HTTPD_SUPPORT_V09 */
        uri_len = sp2 - (sp1 + 1);
        if ((sp2 != 0) && (sp2 > sp1)) {
          /* wait for CRLFCRLF (indicating end of HTTP headers) before parsing anything */
          if (strnstr(data, CRLF CRLF, data_len) != NULL) {
            char *uri = sp1 + 1;
  #if LWIP_HTTPD_SUPPORT_11_KEEPALIVE
            if (!is_09 && strnstr(data, HTTP11_CONNECTIONKEEPALIVE, data_len)) {
              hs->keepalive = 1;
            }
  #endif /* LWIP_HTTPD_SUPPORT_11_KEEPALIVE */
            /* null-terminate the METHOD (pbuf is freed anyway wen returning) */
            *sp1 = 0;
            uri[uri_len] = 0;
            LWIP_DEBUGF(HTTPD_DEBUG, ("Received \"%s\" request for URI: \"%s\"\n",
                        data, uri));
  #if LWIP_HTTPD_SUPPORT_POST
            if (is_post) {
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
              struct pbuf **q = &hs->req;
  #else /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
              struct pbuf **q = inp;
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
              err = http_post_request(q, hs, data, data_len, uri, sp2);
              if (err != ERR_OK) {
                /* restore header for next try */
                *sp1 = ' ';
                *sp2 = ' ';
                uri[uri_len] = ' ';
              }
              if (err == ERR_ARG) {
                goto badrequest;
              }
              return err;
            } else
  #endif /* LWIP_HTTPD_SUPPORT_POST */
            {
              return http_find_file(hs, uri, is_09);
            }
          }
        } else {
          LWIP_DEBUGF(HTTPD_DEBUG, ("invalid URI\n"));
        }
      }
    }
  
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
    clen = pbuf_clen(hs->req);
    if ((hs->req->tot_len <= LWIP_HTTPD_REQ_BUFSIZE) &&
      (clen <= LWIP_HTTPD_REQ_QUEUELEN)) {
      /* request not fully received (too short or CRLF is missing) */
      return ERR_INPROGRESS;
    } else
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
    {
  #if LWIP_HTTPD_SUPPORT_POST
  badrequest:
  #endif /* LWIP_HTTPD_SUPPORT_POST */
      LWIP_DEBUGF(HTTPD_DEBUG, ("bad request\n"));
      /* could not parse request */
      return http_find_error_file(hs, 400);
    }
  }
  
  /** Try to find the file specified by uri and, if found, initialize hs
   * accordingly.
   *
   * @param hs the connection state
   * @param uri the HTTP header URI
   * @param is_09 1 if the request is HTTP/0.9 (no HTTP headers in response)
   * @return ERR_OK if file was found and hs has been initialized correctly
   *         another err_t otherwise
   */
  static err_t
  http_find_file(struct http_state *hs, const char *uri, int is_09)
  {
    size_t loop;
    struct fs_file *file = NULL;
    char *params;
    err_t err;
  #if LWIP_HTTPD_CGI
    int i;
    int count;
  #endif /* LWIP_HTTPD_CGI */
  #if !LWIP_HTTPD_SSI
    const
  #endif /* !LWIP_HTTPD_SSI */
    /* By default, assume we will not be processing server-side-includes tags */
    u8_t tag_check = 0;
  
    /* Have we been asked for the default root file? */
    if((uri[0] == '/') &&  (uri[1] == 0)) {
      /* Try each of the configured default filenames until we find one
         that exists. */
      for (loop = 0; loop < NUM_DEFAULT_FILENAMES; loop++) {
        LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("Looking for %s...\n", g_psDefaultFilenames[loop].name));
        err = fs_open(&hs->file_handle, (char *)g_psDefaultFilenames[loop].name);
        uri = (char *)g_psDefaultFilenames[loop].name;
        if(err == ERR_OK) {
          file = &hs->file_handle;
          LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("Opened.\n"));
  #if LWIP_HTTPD_SSI
          tag_check = g_psDefaultFilenames[loop].shtml;
  #endif /* LWIP_HTTPD_SSI */
          break;
        }
      }
      if (file == NULL) {
        /* None of the default filenames exist so send back a 404 page */
        file = http_get_404_file(hs, &uri);
  #if LWIP_HTTPD_SSI
        tag_check = 0;
  #endif /* LWIP_HTTPD_SSI */
      }
    } else {
      /* No - we've been asked for a specific file. */
      /* First, isolate the base URI (without any parameters) */
      params = (char *)strchr(uri, '?');
      if (params != NULL) {
        /* URI contains parameters. NULL-terminate the base URI */
        *params = '\0';
        params++;
      }
  
  #if LWIP_HTTPD_CGI
      /* Does the base URI we have isolated correspond to a CGI handler? */
      if (g_iNumCGIs && g_pCGIs) {
        for (i = 0; i < g_iNumCGIs; i++) {
          if (strcmp(uri, g_pCGIs[i].pcCGIName) == 0) {
            /*
             * We found a CGI that handles this URI so extract the
             * parameters and call the handler.
             */
             count = extract_uri_parameters(hs, params);
             uri = g_pCGIs[i].pfnCGIHandler(i, count, hs->params,
                                            hs->param_vals);
             break;
          }
        }
      }
  #endif /* LWIP_HTTPD_CGI */
  
      LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("Opening %s\n", uri));
  
      err = fs_open(&hs->file_handle, uri);
      if (err == ERR_OK) {
         file = &hs->file_handle;
      } else {
        file = http_get_404_file(hs, &uri);
      }
  #if LWIP_HTTPD_SSI
      if (file != NULL) {
        /* See if we have been asked for an shtml file and, if so,
           enable tag checking. */
        tag_check = 0;
        for (loop = 0; loop < NUM_SHTML_EXTENSIONS; loop++) {
          if (strstr(uri, g_pcSSIExtensions[loop])) {
            tag_check = 1;
            break;
          }
        }
      }
  #endif /* LWIP_HTTPD_SSI */
    }
    return http_init_file(hs, file, is_09, uri, tag_check);
  }
  
  /** Initialize a http connection with a file to send (if found).
   * Called by http_find_file and http_find_error_file.
   *
   * @param hs http connection state
   * @param file file structure to send (or NULL if not found)
   * @param is_09 1 if the request is HTTP/0.9 (no HTTP headers in response)
   * @param uri the HTTP header URI
   * @param tag_check enable SSI tag checking
   * @return ERR_OK if file was found and hs has been initialized correctly
   *         another err_t otherwise
   */
  static err_t
  http_init_file(struct http_state *hs, struct fs_file *file, int is_09, const char *uri, u8_t tag_check)
  {
    if (file != NULL) {
      /* file opened, initialise struct http_state */
  #if LWIP_HTTPD_SSI
      if (tag_check) {
        struct http_ssi_state *ssi = http_ssi_state_alloc();
        if (ssi != NULL) {
          ssi->tag_index = 0;
          ssi->tag_state = TAG_NONE;
          ssi->parsed = file->data;
          ssi->parse_left = file->len;
          ssi->tag_end = file->data;
          hs->ssi = ssi;
        }
      }
  #else /* LWIP_HTTPD_SSI */
      LWIP_UNUSED_ARG(tag_check);
  #endif /* LWIP_HTTPD_SSI */
      hs->handle = file;
      hs->file = (char*)file->data;
      LWIP_ASSERT("File length must be positive!", (file->len >= 0));
      hs->left = file->len;
      hs->retries = 0;
  #if LWIP_HTTPD_TIMING
      hs->time_started = sys_now();
  #endif /* LWIP_HTTPD_TIMING */
  #if !LWIP_HTTPD_DYNAMIC_HEADERS
      LWIP_ASSERT("HTTP headers not included in file system", hs->handle->http_header_included);
  #endif /* !LWIP_HTTPD_DYNAMIC_HEADERS */
  #if LWIP_HTTPD_SUPPORT_V09
      if (hs->handle->http_header_included && is_09) {
        /* HTTP/0.9 responses are sent without HTTP header,
           search for the end of the header. */
        char *file_start = strnstr(hs->file, CRLF CRLF, hs->left);
        if (file_start != NULL) {
          size_t diff = file_start + 4 - hs->file;
          hs->file += diff;
          hs->left -= (u32_t)diff;
        }
      }
  #endif /* LWIP_HTTPD_SUPPORT_V09*/
    } else {
      hs->handle = NULL;
      hs->file = NULL;
      hs->left = 0;
      hs->retries = 0;
    }
  #if LWIP_HTTPD_DYNAMIC_HEADERS
      /* Determine the HTTP headers to send based on the file extension of
     * the requested URI. */
    if ((hs->handle == NULL) || !hs->handle->http_header_included) {
      get_http_headers(hs, (char*)uri);
    }
  #else /* LWIP_HTTPD_DYNAMIC_HEADERS */
    LWIP_UNUSED_ARG(uri);
  #endif /* LWIP_HTTPD_DYNAMIC_HEADERS */
    return ERR_OK;
  }
  
  /**
   * The pcb had an error and is already deallocated.
   * The argument might still be valid (if != NULL).
   */
  static void
  http_err(void *arg, err_t err)
  {
    struct http_state *hs = (struct http_state *)arg;
    LWIP_UNUSED_ARG(err);
  
    LWIP_DEBUGF(HTTPD_DEBUG, ("http_err: %s", lwip_strerr(err)));
  
    if (hs != NULL) {
      http_state_free(hs);
    }
  }
  
  /**
   * Data has been sent and acknowledged by the remote host.
   * This means that more data can be sent.
   */
  static err_t
  http_sent(void *arg, struct tcp_pcb *pcb, u16_t len)
  {
    struct http_state *hs = (struct http_state *)arg;
  
    LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("http_sent %p\n", (void*)pcb));
  
    LWIP_UNUSED_ARG(len);
  
    if (hs == NULL) {
      return ERR_OK;
    }
  
    hs->retries = 0;
  
    http_send(pcb, hs);
  
    return ERR_OK;
  }
  
  /**
   * The poll function is called every 2nd second.
   * If there has been no data sent (which resets the retries) in 8 seconds, close.
   * If the last portion of a file has not been sent in 2 seconds, close.
   *
   * This could be increased, but we don't want to waste resources for bad connections.
   */
  static err_t
  http_poll(void *arg, struct tcp_pcb *pcb)
  {
    struct http_state *hs = (struct http_state *)arg;
    LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("http_poll: pcb=%p hs=%p pcb_state=%s\n",
      (void*)pcb, (void*)hs, tcp_debug_state_str(pcb->state)));
  
    if (hs == NULL) {
      err_t closed;
      /* arg is null, close. */
      LWIP_DEBUGF(HTTPD_DEBUG, ("http_poll: arg is NULL, close\n"));
      closed = http_close_conn(pcb, NULL);
      LWIP_UNUSED_ARG(closed);
  #if LWIP_HTTPD_ABORT_ON_CLOSE_MEM_ERROR
      if (closed == ERR_MEM) {
         tcp_abort(pcb);
         return ERR_ABRT;
      }
  #endif /* LWIP_HTTPD_ABORT_ON_CLOSE_MEM_ERROR */
      return ERR_OK;
    } else {
      hs->retries++;
      if (hs->retries == HTTPD_MAX_RETRIES) {
        LWIP_DEBUGF(HTTPD_DEBUG, ("http_poll: too many retries, close\n"));
        http_close_conn(pcb, hs);
        return ERR_OK;
      }
  
      /* If this connection has a file open, try to send some more data. If
       * it has not yet received a GET request, don't do this since it will
       * cause the connection to close immediately. */
      if(hs && (hs->handle)) {
        LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("http_poll: try to send more data\n"));
        if(http_send(pcb, hs)) {
          /* If we wrote anything to be sent, go ahead and send it now. */
          LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("tcp_output\n"));
          tcp_output(pcb);
        }
      }
    }
  
    return ERR_OK;
  }
  
  /**
   * Data has been received on this pcb.
   * For HTTP 1.0, this should normally only happen once (if the request fits in one packet).
   */
  static err_t
  http_recv(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
  {
    err_t parsed = ERR_ABRT;
    struct http_state *hs = (struct http_state *)arg;
    LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("http_recv: pcb=%p pbuf=%p err=%s\n", (void*)pcb,
      (void*)p, lwip_strerr(err)));
  
    if ((err != ERR_OK) || (p == NULL) || (hs == NULL)) {
      /* error or closed by other side? */
      if (p != NULL) {
        /* Inform TCP that we have taken the data. */
        tcp_recved(pcb, p->tot_len);
        pbuf_free(p);
      }
      if (hs == NULL) {
        /* this should not happen, only to be robust */
        LWIP_DEBUGF(HTTPD_DEBUG, ("Error, http_recv: hs is NULL, close\n"));
      }
      http_close_conn(pcb, hs);
      return ERR_OK;
    }
  
  #if LWIP_HTTPD_SUPPORT_POST && LWIP_HTTPD_POST_MANUAL_WND
    if (hs->no_auto_wnd) {
       hs->unrecved_bytes += p->tot_len;
    } else
  #endif /* LWIP_HTTPD_SUPPORT_POST && LWIP_HTTPD_POST_MANUAL_WND */
    {
      /* Inform TCP that we have taken the data. */
      tcp_recved(pcb, p->tot_len);
    }
  
  #if LWIP_HTTPD_SUPPORT_POST
    if (hs->post_content_len_left > 0) {
      /* reset idle counter when POST data is received */
      hs->retries = 0;
      /* this is data for a POST, pass the complete pbuf to the application */
      http_post_rxpbuf(hs, p);
      /* pbuf is passed to the application, don't free it! */
      if (hs->post_content_len_left == 0) {
        /* all data received, send response or close connection */
        http_send(pcb, hs);
      }
      return ERR_OK;
    } else
  #endif /* LWIP_HTTPD_SUPPORT_POST */
    {
      if (hs->handle == NULL) {
        parsed = http_parse_request(&p, hs, pcb);
        LWIP_ASSERT("http_parse_request: unexpected return value", parsed == ERR_OK
          || parsed == ERR_INPROGRESS ||parsed == ERR_ARG || parsed == ERR_USE);
      } else {
        LWIP_DEBUGF(HTTPD_DEBUG, ("http_recv: already sending data\n"));
      }
  #if LWIP_HTTPD_SUPPORT_REQUESTLIST
      if (parsed != ERR_INPROGRESS) {
        /* request fully parsed or error */
        if (hs->req != NULL) {
          pbuf_free(hs->req);
          hs->req = NULL;
        }
      }
  #else /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
      if (p != NULL) {
        /* pbuf not passed to application, free it now */
        pbuf_free(p);
      }
  #endif /* LWIP_HTTPD_SUPPORT_REQUESTLIST */
      if (parsed == ERR_OK) {
  #if LWIP_HTTPD_SUPPORT_POST
        if (hs->post_content_len_left == 0)
  #endif /* LWIP_HTTPD_SUPPORT_POST */
        {
          LWIP_DEBUGF(HTTPD_DEBUG | LWIP_DBG_TRACE, ("http_recv: data %p len %"S32_F"\n", hs->file, hs->left));
          http_send(pcb, hs);
        }
      } else if (parsed == ERR_ARG) {
        /* @todo: close on ERR_USE? */
        http_close_conn(pcb, hs);
      }
    }
    return ERR_OK;
  }
  
  /**
   * A new incoming connection has been accepted.
   */
  static err_t
  http_accept(void *arg, struct tcp_pcb *pcb, err_t err)
  {
    struct http_state *hs;
    struct tcp_pcb_listen *lpcb = (struct tcp_pcb_listen*)arg;
    LWIP_UNUSED_ARG(err);
    LWIP_DEBUGF(HTTPD_DEBUG, ("http_accept %p / %p\n", (void*)pcb, arg));
  
    /* Decrease the listen backlog counter */
    tcp_accepted(lpcb);
    /* Set priority */
    tcp_setprio(pcb, HTTPD_TCP_PRIO);
  
    /* Allocate memory for the structure that holds the state of the
       connection - initialized by that function. */
    hs = http_state_alloc();
    if (hs == NULL) {
      LWIP_DEBUGF(HTTPD_DEBUG, ("http_accept: Out of memory, RST\n"));
      return ERR_MEM;
    }
    hs->pcb = pcb;
  
    /* Tell TCP that this is the structure we wish to be passed for our
       callbacks. */
    tcp_arg(pcb, hs);
  
    /* Set up the various callback functions */
    tcp_recv(pcb, http_recv);
    tcp_err(pcb, http_err);
    tcp_poll(pcb, http_poll, HTTPD_POLL_INTERVAL);
    tcp_sent(pcb, http_sent);
  
    return ERR_OK;
  }
  
  /**
   * Initialize the httpd with the specified local address.
   */
  static void
  httpd_init_addr(ip_addr_t *local_addr)
  {
    struct tcp_pcb *pcb;
    err_t err;
  
    pcb = tcp_new();
    LWIP_ASSERT("httpd_init: tcp_new failed", pcb != NULL);
    tcp_setprio(pcb, HTTPD_TCP_PRIO);
    /* set SOF_REUSEADDR here to explicitly bind httpd to multiple interfaces */
    err = tcp_bind(pcb, local_addr, HTTPD_SERVER_PORT);
    LWIP_ASSERT("httpd_init: tcp_bind failed", err == ERR_OK);
    pcb = tcp_listen(pcb);
    LWIP_ASSERT("httpd_init: tcp_listen failed", pcb != NULL);
    /* initialize callback arg and accept callback */
    tcp_arg(pcb, pcb);
    tcp_accept(pcb, http_accept);
  }
  
  /**
   * Initialize the httpd: set up a listening PCB and bind it to the defined port
   */
  void
  httpd_init(void)
  {
  #if HTTPD_USE_MEM_POOL
    LWIP_ASSERT("memp_sizes[MEMP_HTTPD_STATE] >= sizeof(http_state)",
       memp_sizes[MEMP_HTTPD_STATE] >= sizeof(http_state));
    LWIP_ASSERT("memp_sizes[MEMP_HTTPD_SSI_STATE] >= sizeof(http_ssi_state)",
       memp_sizes[MEMP_HTTPD_SSI_STATE] >= sizeof(http_ssi_state));
  #endif
    LWIP_DEBUGF(HTTPD_DEBUG, ("httpd_init\n"));
  
    httpd_init_addr(IP_ADDR_ANY);
  }
  
  #if LWIP_HTTPD_SSI
  /**
   * Set the SSI handler function.
   *
   * @param ssi_handler the SSI handler function
   * @param tags an array of SSI tag strings to search for in SSI-enabled files
   * @param num_tags number of tags in the 'tags' array
   */
  void
  http_set_ssi_handler(tSSIHandler ssi_handler, const char **tags, int num_tags)
  {
    LWIP_DEBUGF(HTTPD_DEBUG, ("http_set_ssi_handler\n"));
  
    LWIP_ASSERT("no ssi_handler given", ssi_handler != NULL);
    LWIP_ASSERT("no tags given", tags != NULL);
    LWIP_ASSERT("invalid number of tags", num_tags > 0);
  
    g_pfnSSIHandler = ssi_handler;
    g_ppcTags = tags;
    g_iNumTags = num_tags;
  }
  #endif /* LWIP_HTTPD_SSI */
  
  #if LWIP_HTTPD_CGI
  /**
   * Set an array of CGI filenames/handler functions
   *
   * @param cgis an array of CGI filenames/handler functions
   * @param num_handlers number of elements in the 'cgis' array
   */
  void
  http_set_cgi_handlers(const tCGI *cgis, int num_handlers)
  {
    LWIP_ASSERT("no cgis given", cgis != NULL);
    LWIP_ASSERT("invalid number of handlers", num_handlers > 0);
    
    g_pCGIs = cgis;
    g_iNumCGIs = num_handlers;
  }
  #endif /* LWIP_HTTPD_CGI */
  
  #endif /* LWIP_TCP */
  