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[glibc.git] / stdio / vsnprintf.c
blob278711ab663d5333accae09ff27eb0d5fb028c9c
1 /* Copyright (C) 1991, 1992, 1995, 1997 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
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.
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.
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 not,
16 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 Boston, MA 02111-1307, USA. */
19 #include <stdarg.h>
20 #include <stdio.h>
21 #include <string.h>
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.
29 int
30 __vsnprintf (char *s, size_t maxlen, const char *format, va_list arg)
32 int done;
33 FILE f;
35 /* We have to handle the case of MAXLEN == 0 special. */
36 if (maxlen == 0)
37 return 0;
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;
54 done = vfprintf (&f, format, arg);
55 *f.__bufp = '\0';
57 return done;
59 weak_alias (__vsnprintf, vsnprintf)