stdio/FreeBSD/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  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)vsnprintf.c 8.1 (Berkeley) 6/4/93";
  39 #endif /* LIBC_SCCS and not lint */
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: src/lib/libc/stdio/vsnprintf.c,v 1.22 2003/07/02 07:08:44 jkh Exp $");
  42
  43 #include <limits.h>
  44 #include <stdio.h>
  45 #include "local.h"
  46
  47 int
  48 vsnprintf(char * __restrict str, size_t n, const char * __restrict fmt,
  49     __va_list ap)
  50 {
  51         size_t on;
  52         int ret;
  53         char dummy[2];
  54         FILE f;
  55         struct __sFILEX ext;
  56
  57         on = n;
  58         if (n != 0)
  59                 n--;
  60         if (n > INT_MAX)
  61                 n = INT_MAX;
  62         /* Stdio internals do not deal correctly with zero length buffer */
  63         if (n == 0) {
  64                 if (on > 0)
  65                         *str = '\0';
  66                 str = dummy;
  67                 n = 1;
  68         }
  69         f._file = -1;
  70         f._flags = __SWR | __SSTR;
  71         f._bf._base = f._p = (unsigned char *)str;
  72         f._bf._size = f._w = n;
  73         f._extra = &ext;
  74         INITEXTRA(&f);
  75         ret = __vfprintf(&f, fmt, ap);
  76         if (on > 0)
  77                 *f._p = '\0';
  78         return (ret);
  79 }