text: #ifndef _BUFFER_H_
  #define _BUFFER_H_
  #include "first.h"
  
  struct tm;              /* declaration */
  
  /* generic string + binary data container; contains a terminating 0 in both
   * cases
   *
   * used == 0 indicates a special "empty" state (unset config values); ptr
   * might be NULL too then. otherwise an empty string has used == 1 (and ptr[0]
   * == 0);
   *
   * copy/append functions will ensure used >= 1 (i.e. never leave it in the
   * special empty state); only buffer_copy_buffer will copy the special empty
   * state.
   */
  typedef struct {
  	char *ptr;
  
  	/* "used" includes a terminating 0 */
  	size_t used;
  	/* size of allocated buffer at *ptr */
  	size_t size;
  } buffer;
  
  /* create new buffer; either empty or copy given data */
  buffer* buffer_init(void);
  buffer* buffer_init_buffer(const buffer *src); /* src can  be NULL */
  buffer* buffer_init_string(const char *str); /* str can  be NULL */
  
  void buffer_free(buffer *b); /* b can be NULL */
  /* truncates to used == 0; frees large buffers, might keep smaller ones for reuse */
  void buffer_reset(buffer *b); /* b can be NULL */
  
  /* reset b. if NULL != b && NULL != src, move src content to b. reset src. */
  void buffer_move(buffer *b, buffer *src);
  
  /* make sure buffer is large enough to store a string of given size
   * and a terminating zero.
   * sets b to an empty string, and may drop old content.
   * @return b->ptr
   */
  char* buffer_string_prepare_copy(buffer *b, size_t size);
  
  /* allocate buffer large enough to be able to append a string of given size
   * if b was empty (used == 0) it will contain an empty string (used == 1)
   * afterwards
   * "used" data is preserved; if not empty buffer must contain a
   * zero terminated string.
   */
  char* buffer_string_prepare_append(buffer *b, size_t size);
  
  /* use after prepare_(copy,append) when you have written data to the buffer
   * to increase the buffer length by size. also sets the terminating zero.
   * requires enough space is present for the terminating zero (prepare with the
   * same size to be sure).
   */
  void buffer_commit(buffer *b, size_t size);
  
  /* sets string length:
   * - always stores a terminating zero to terminate the "new" string
   * - does not modify the string data apart from terminating zero
   * - reallocates the buffer iff needed
   */
  void buffer_string_set_length(buffer *b, size_t len);
  
  /* clear buffer
   * - invalidate buffer contents
   * - unsets used chars but does not modify existing ptr contents
   *   (b->ptr *is not* set to an empty, '\0'-terminated string "")
   */
  static inline void buffer_clear(buffer *b);
  
  void buffer_copy_string(buffer *b, const char *s);
  void buffer_copy_string_len(buffer *b, const char *s, size_t s_len);
  static inline void buffer_copy_buffer(buffer *b, const buffer *src);
  
  void buffer_append_string(buffer *b, const char *s);
  void buffer_append_string_len(buffer *b, const char *s, size_t s_len);
  static inline void buffer_append_string_buffer(buffer *b, const buffer *src);
  
  #define buffer_append_uint_hex(b,len) buffer_append_uint_hex_lc((b),(len))
  void buffer_append_uint_hex_lc(buffer *b, uintmax_t len);
  void buffer_append_int(buffer *b, intmax_t val);
  void buffer_copy_int(buffer *b, intmax_t val);
  
  void buffer_append_strftime(buffer *b, const char *format, const struct tm *tm);
  
  /* '-', log_10 (2^bits) = bits * log 2 / log 10 < bits * 0.31, terminating 0 */
  #define LI_ITOSTRING_LENGTH (2 + (8 * sizeof(intmax_t) * 31 + 99) / 100)
  
  void li_itostrn(char *buf, size_t buf_len, intmax_t val);
  void li_utostrn(char *buf, size_t buf_len, uintmax_t val);
  
  /* buf must be (at least) 2*s_len + 1 big. uses lower-case hex letters. */
  #define li_tohex(buf,buf_len,s,s_len) li_tohex_lc((buf),(buf_len),(s),(s_len))
  void li_tohex_lc(char *buf, size_t buf_len, const char *s, size_t s_len);
  void li_tohex_uc(char *buf, size_t buf_len, const char *s, size_t s_len);
  
  /* NULL buffer or empty buffer (used == 0);
   * unset "string" (buffer) config options are initialized to used == 0,
   * while setting an empty string leads to used == 1
   */
  static inline int buffer_is_empty(const buffer *b);
  /* NULL buffer, empty buffer (used == 0) or empty string (used == 1) */
  static inline int buffer_string_is_empty(const buffer *b);
  
  int buffer_is_equal(const buffer *a, const buffer *b);
  int buffer_is_equal_right_len(const buffer *a, const buffer *b, size_t len);
  int buffer_is_equal_string(const buffer *a, const char *s, size_t b_len);
  int buffer_is_equal_caseless_string(const buffer *a, const char *s, size_t b_len);
  int buffer_caseless_compare(const char *a, size_t a_len, const char *b, size_t b_len);
  
  void buffer_substr_replace (buffer *b, size_t offset, size_t len, const buffer *replace);
  
  void buffer_append_string_encoded_hex_lc(buffer *b, const char *s, size_t len);
  void buffer_append_string_encoded_hex_uc(buffer *b, const char *s, size_t len);
  
  typedef enum {
  	ENCODING_REL_URI, /* for coding a rel-uri (/with space/and%percent) nicely as part of a href */
  	ENCODING_REL_URI_PART, /* same as ENC_REL_URL plus coding / too as %2F */
  	ENCODING_HTML,         /* & becomes &amp; and so on */
  	ENCODING_MINIMAL_XML   /* minimal encoding for xml */
  } buffer_encoding_t;
  
  void buffer_append_string_encoded(buffer *b, const char *s, size_t s_len, buffer_encoding_t encoding);
  
  /* escape non-printable characters; simple escapes for \t, \r, \n; fallback to \xCC */
  void buffer_append_string_c_escaped(buffer *b, const char *s, size_t s_len);
  
  /* to upper case, replace non alpha-numerics with '_'; if is_http_header prefix with "HTTP_" unless s is "content-type" */
  void buffer_copy_string_encoded_cgi_varnames(buffer *b, const char *s, size_t s_len, int is_http_header);
  
  void buffer_urldecode_path(buffer *url);
  void buffer_urldecode_query(buffer *url);
  int buffer_is_valid_UTF8(const buffer *b);
  void buffer_path_simplify(buffer *dest, buffer *src);
  
  void buffer_to_lower(buffer *b);
  void buffer_to_upper(buffer *b);
  
  
  /** deprecated */
  char hex2int(unsigned char c);
  char int2hex(char i);
  
  static inline int light_isdigit(int c);
  static inline int light_isxdigit(int c);
  static inline int light_isalpha(int c);
  static inline int light_isalnum(int c);
  
  static inline int light_isdigit(int c) {
  	return (c >= '0' && c <= '9');
  }
  
  static inline int light_isxdigit(int c) {
  	return light_isdigit(c) || (c |= 32, c >= 'a' && c <= 'f');
  }
  
  static inline int light_isalpha(int c) {
  	return (c |= 32, c >= 'a' && c <= 'z');
  }
  
  static inline int light_isalnum(int c) {
  	return light_isdigit(c) || light_isalpha(c);
  }
  
  
  static inline size_t buffer_string_length(const buffer *b); /* buffer string length without terminating 0 */
  static inline size_t buffer_string_space(const buffer *b); /* maximum length of string that can be stored without reallocating */
  static inline void buffer_append_slash(buffer *b); /* append '/' no non-empty strings not ending in '/' */
  void buffer_append_path_len(buffer *b, const char *a, size_t alen); /* join strings with '/', if '/' not present */
  
  #define BUFFER_APPEND_STRING_CONST(x, y) \
  	buffer_append_string_len(x, y, sizeof(y) - 1)
  
  #define BUFFER_COPY_STRING_CONST(x, y) \
  	buffer_copy_string_len(x, y, sizeof(y) - 1)
  
  #define BUFFER_INTLEN_PTR(x) (x)->used ? (int)((x)->used - 1) : 0, (x)->ptr
  
  #define CONST_STR_LEN(x) x, (x) ? sizeof(x) - 1 : 0
  #define CONST_BUF_LEN(x) ((x) ? (x)->ptr : NULL), buffer_string_length(x)
  
  
  #define LI_NORETURN __attribute_noreturn__
  
  __attribute_cold__
  void log_failed_assert(const char *filename, unsigned int line, const char *msg) LI_NORETURN;
  #define force_assert(x) do { if (!(x)) log_failed_assert(__FILE__, __LINE__, "assertion failed: " #x); } while(0)
  #define SEGFAULT() log_failed_assert(__FILE__, __LINE__, "aborted");
  
  /* inline implementations */
  
  static inline int buffer_is_empty(const buffer *b) {
  	return NULL == b || 0 == b->used;
  }
  static inline int buffer_string_is_empty(const buffer *b) {
  	return NULL == b || b->used < 2;
  }
  
  static inline size_t buffer_string_length(const buffer *b) {
  	return NULL != b && 0 != b->used ? b->used - 1 : 0;
  }
  
  static inline size_t buffer_string_space(const buffer *b) {
  	return NULL != b && b->size ? b->size - (b->used | (0 == b->used)) : 0;
  }
  
  static inline void buffer_copy_buffer(buffer *b, const buffer *src) {
  	buffer_copy_string_len(b, CONST_BUF_LEN(src));
  }
  
  static inline void buffer_append_string_buffer(buffer *b, const buffer *src) {
  	buffer_append_string_len(b, CONST_BUF_LEN(src));
  }
  
  static inline void buffer_append_slash(buffer *b) {
  	size_t len = buffer_string_length(b);
  	if (len > 0 && '/' != b->ptr[len-1]) BUFFER_APPEND_STRING_CONST(b, "/");
  }
  
  static inline void buffer_clear(buffer *b) {
  	b->used = 0;
  }
  
  #endif
  