stdio/vsnprintf.c

   1 /* Copyright (C) 1991, 1992, 1995, 1997 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <stdarg.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22
  23
  24 /*
  25  * Write formatted output to S according to the format string
  26  * FORMAT, using the argument list in ARG, writing no more
  27  * than MAXLEN characters.
  28  */
  29 int
  30 __vsnprintf (char *s, size_t maxlen, const char *format, va_list arg)
  31 {
  32   int done;
  33   FILE f;
  34
  35   /* We have to handle the case of MAXLEN == 0 special.  */
  36   if (maxlen == 0)
  37     return 0;
  38
  39   memset ((void *) &f, 0, sizeof (f));
  40   f.__magic = _IOMAGIC;
  41   f.__mode.__write = 1;
  42   /* The buffer size is one less than MAXLEN
  43      so we have space for the null terminator.  */
  44   f.__bufp = f.__buffer = (char *) s;
  45   f.__bufsize = maxlen - 1;
  46   f.__put_limit = f.__buffer + f.__bufsize;
  47   f.__get_limit = f.__buffer;
  48   /* After the buffer is full (MAXLEN characters have been written),
  49      any more characters written will go to the bit bucket.  */
  50   f.__room_funcs = __default_room_functions;
  51   f.__io_funcs.__write = NULL;
  52   f.__seen = 1;
  53
  54   done = vfprintf (&f, format, arg);
  55   *f.__bufp = '\0';
  56
  57   return done;
  58 }
  59 weak_alias (__vsnprintf, vsnprintf)