petidomo/libtext/easy_sprintf.c

/*
 * Copyright (c) 1995-2019 Peter Simons <simons@cryp.to>
 * Copyright (c) 2000-2001 Cable & Wireless GmbH
 * Copyright (c) 1999-2000 CyberSolutions GmbH
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include <config.h>
#include <stdarg.h>
#include <string.h>
#include "text.h"

#if !defined HAVE_VSNPRINTF && defined HAVE___VSNPRINTF
#  define vsnprintf __vsnprintf
#endif

/* Use sprintf() without worrying about buffer size.

   One problem when dealing a lot with texts and strings is the buffer
   handling. Usually a programmer will frequently have to format
   several strings into a new one using sprintf(3), without knowing
   how long the resulting string will become.

   text_easy_sprintf() will solve this problem. The syntax is very much
   like sprintf(), except for that the target buffer is allocated by
   the routine and returned to the caller.

   RETURNS: A buffer holding the formatted string or NULL if the
   memory allocation failed.

   NOTE: The returned buffer has been allocated with malloc(3) and
   should be freed when not needed anymore.

   AUTHOR: Peter Simons <simons@rhein.de>

 */

char *
text_easy_sprintf(const char * fmt  /* Format string in printf(3) syntax. */,
                  ... /* Parameter list. */)
{
    char *    buffer,
         *    result;
    size_t    buffer_size;
    va_list   ap;
    int       rc;

    /* Sanity checks. */

    assert(fmt != NULL);
    if (fmt == NULL)
      return NULL;

    /* Do the work. */

    va_start(ap, fmt);
    for (buffer_size = 0, result = NULL; TRUE; free(buffer)) { /* forever */

        /* Allocate the internal buffer. */

        buffer_size += 8 * 1024;
        buffer = malloc(buffer_size);
        if (buffer == NULL)
          goto leave;

        /* Format the string into it. */

        rc = vsnprintf(buffer, buffer_size, fmt, ap);

        /* Success? */

        if (rc < buffer_size) {
            /* Yes. */

            result = strdup(buffer);
            free(buffer);
            goto leave;
        }

        /* No. */
    }

leave:
    va_end(ap);
    return result;
}