#ifndef __PERF_STRBUF_H
  #define __PERF_STRBUF_H
  
  /*
   * Strbuf's can be use in many ways: as a byte array, or to store arbitrary
   * long, overflow safe strings.
   *
   * Strbufs has some invariants that are very important to keep in mind:
   *
   * 1. the ->buf member is always malloc-ed, hence strbuf's can be used to
   *    build complex strings/buffers whose final size isn't easily known.
   *
   *    It is NOT legal to copy the ->buf pointer away.
   *    `strbuf_detach' is the operation that detachs a buffer from its shell
   *    while keeping the shell valid wrt its invariants.
   *
   * 2. the ->buf member is a byte array that has at least ->len + 1 bytes
   *    allocated. The extra byte is used to store a '\0', allowing the ->buf
   *    member to be a valid C-string. Every strbuf function ensure this
   *    invariant is preserved.
   *
   *    Note that it is OK to "play" with the buffer directly if you work it
   *    that way:
   *
   *    strbuf_grow(sb, SOME_SIZE);
   *       ... Here, the memory array starting at sb->buf, and of length
   *       ... strbuf_avail(sb) is all yours, and you are sure that
   *       ... strbuf_avail(sb) is at least SOME_SIZE.
   *    strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE);
   *
   *    Of course, SOME_OTHER_SIZE must be smaller or equal to strbuf_avail(sb).
   *
   *    Doing so is safe, though if it has to be done in many places, adding the
   *    missing API to the strbuf module is the way to go.
   *
   *    XXX: do _not_ assume that the area that is yours is of size ->alloc - 1
   *         even if it's true in the current implementation. Alloc is somehow a
   *         "private" member that should not be messed with.
   */
  
  #include <assert.h>
  
  extern char strbuf_slopbuf[];
  struct strbuf {
  	size_t alloc;
  	size_t len;
  	char *buf;
  };
  
  #define STRBUF_INIT  { 0, 0, strbuf_slopbuf }
  
  /*----- strbuf life cycle -----*/
  extern void strbuf_init(struct strbuf *buf, ssize_t hint);
  extern void strbuf_release(struct strbuf *);
  extern char *strbuf_detach(struct strbuf *, size_t *);
  
  /*----- strbuf size related -----*/
  static inline ssize_t strbuf_avail(const struct strbuf *sb) {
  	return sb->alloc ? sb->alloc - sb->len - 1 : 0;
  }
  
  extern void strbuf_grow(struct strbuf *, size_t);
  
  static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
  	if (!sb->alloc)
  		strbuf_grow(sb, 0);
  	assert(len < sb->alloc);
  	sb->len = len;
  	sb->buf[len] = '\0';
  }
  
  /*----- add data in your buffer -----*/
  static inline void strbuf_addch(struct strbuf *sb, int c) {
  	strbuf_grow(sb, 1);
  	sb->buf[sb->len++] = c;
  	sb->buf[sb->len] = '\0';
  }
  
  extern void strbuf_remove(struct strbuf *, size_t pos, size_t len);
  
  extern void strbuf_add(struct strbuf *, const void *, size_t);
  static inline void strbuf_addstr(struct strbuf *sb, const char *s) {
  	strbuf_add(sb, s, strlen(s));
  }
  
  __attribute__((format(printf,2,3)))
  extern void strbuf_addf(struct strbuf *sb, const char *fmt, ...);
  
  /* XXX: if read fails, any partial read is undone */
  extern ssize_t strbuf_read(struct strbuf *, int fd, ssize_t hint);
  
  #endif /* __PERF_STRBUF_H */