stdio/vsnprintf.c

   1 /* Copyright (C) 1991, 1992 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 Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 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 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <stdarg.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23
  24
  25 /*
  26  * Write formatted output to S according to the format string
  27  * FORMAT, using the argument list in ARG, writing no more
  28  * than MAXLEN characters.
  29  */
  30 int
  31 DEFUN(vsnprintf, (s, maxlen, format, arg),
  32         char *s AND size_t maxlen AND CONST char *format AND va_list arg)
  33 {
  34   int done;
  35   FILE f;
  36
  37   memset((PTR) &f, 0, sizeof(f));
  38   f.__magic = _IOMAGIC;
  39   f.__mode.__write = 1;
  40   /* The buffer size is one less than MAXLEN
  41      so we have space for the null terminator.  */
  42   f.__bufp = f.__buffer = (char *) s;
  43   f.__bufsize = maxlen - 1;
  44   f.__put_limit = f.__buffer + f.__bufsize;
  45   f.__get_limit = f.__buffer;
  46   /* After the buffer is full (MAXLEN characters have been written),
  47      any more characters written will go to the bit bucket.  */
  48   f.__room_funcs = __default_room_functions;
  49   f.__io_funcs.__write = NULL;
  50   f.__seen = 1;
  51
  52   done = vfprintf(&f, format, arg);
  53   *f.__bufp = '\0';
  54
  55   return done;
  56 }