lib/libc/stdio/vsnprintf.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)vsnprintf.c      8.1 (Berkeley) 6/4/93
  33  * $FreeBSD: src/lib/libc/stdio/vsnprintf.c,v 1.24 2008/04/17 22:17:54 jhb Exp $
  34  * $DragonFly: src/lib/libc/stdio/vsnprintf.c,v 1.9 2008/05/15 03:59:59 dillon Exp $
  35  */
  36
  37 #include <limits.h>
  38 #include <stdio.h>
  39 #include "local.h"
  40 #include "priv_stdio.h"
  41
  42 int
  43 vsnprintf(char * __restrict str, size_t n, const char * __restrict fmt,
  44           __va_list ap)
  45 {
  46         size_t on;
  47         int ret;
  48         char dummy[2];
  49         FILE f;
  50
  51         on = n;
  52         if (n != 0)
  53                 n--;
  54         if (n > INT_MAX)
  55                 n = INT_MAX;
  56         /* Stdio internals do not deal correctly with zero length buffer */
  57         if (n == 0) {
  58                 if (on > 0)
  59                         *str = '\0';
  60                 str = dummy;
  61                 n = 1;
  62         }
  63         f.pub._fileno = -1;
  64         f.pub._flags = __SWR | __SSTR;
  65         f._bf._base = f.pub._p = (unsigned char *)str;
  66         f._bf._size = f.pub._w = n;
  67         memset(WCIO_GET(&f), 0, sizeof(struct wchar_io_data));
  68         ret = __vfprintf(&f, fmt, ap);
  69         if (on > 0)
  70                 *f.pub._p = '\0';
  71         return (ret);
  72 }