typedef void * strbuff_t;

/*  Creates and returns a pointer to a new string buffer of size 0 and
 *  capacity 1.
 *
 *  Returns NULL if out of memory.
 */
strbuff_t mk_strbuff(void);

/*  Returns a pointer to a newly allocated string whose contents is
 *  a copy of the entire contents of the buffer.  The client may modify
 *  or free the returned string without affecting the string buffer.
 *
 *  Returns NULL if out of memory or if sb is NULL.
 */
char *strbuff_to_string(strbuff_t sb);

/*  Returns the character at position given by index (0-based) of the
 *  contents. 
 * 
 *  Returns -1 if index is out of range or sb is NULL.
 */
int strbuff_getchar(strbuff_t sb, int index);

/*  Sets the character at position given by index (0-based) of the 
 *  contents to c and returns c.
 * 
 *  Returns -1 if index is out of range or sb is NULL.
 */
int strbuff_setchar(strbuff_t sb, int index, char c);

/*  Returns the current size of sb or -1 if sb is NULL.
 */
inline int strbuff_size(strbuff_t sb);

/*  Returns the current capacity of sb or -1 if sb is NULL.
 */
inline int strbuff_capacity(strbuff_t sb);

/*  Appends the character c to the contents of the buffer.
 * 
 *  Returns 0 on success, ENOMEM if there is insufficient memory,
 *  EINVAL if sb is NULL.
 */
int strbuff_append(strbuff_t sb, char c);

/*  Appends the contents of the NUL-terminated string s (excluding the
 *  terminating NUL character) to the contents of sb.  Subsequent
 *  modifications to the contents of the string pointed to by s have
 *  no effect on the contents of the string buffer, i.e., the data are
 *  copied out.  Returns 0 on success, ENOMEM if there is insufficient
 *  memory, EINVAL if either sb or s is NULL.
 */
int strbuff_append_str(strbuff_t sb, char *s);

/*  Truncates the string buffer to given size and returns 0.
 *  Returns EINVAL if newsize is negative or larger than the current
 *  size or if sb is NULL.
 */
int strbuff_truncate(strbuff_t sb, int newsize);

/*  Frees sb and all its associated space.
 */
void strbuff_destroy(strbuff_t sb);