1 /*
2  * Copyright (c) 2000-2001 Sendmail, Inc. and its suppliers.
3  *      All rights reserved.
4  * Copyright (c) 1990, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * Chris Torek.
9  *
10  * By using this file, you agree to the terms and conditions set
11  * forth in the LICENSE file which can be found at the top level of
12  * the sendmail distribution.
13  */
14 
15 #include <sm/gen.h>
16 SM_RCSID("@(#)$Id: vsnprintf.c,v 1.21 2001/03/04 23:28:41 ca Exp $")
17 #include <limits.h>
18 #include <sm/io.h>
19 #include "local.h"
20 
21 /*
22 **  SM_VSNPRINTF -- format data for "output" into a string
23 **
24 **	Assigned 'str' to a "fake" file pointer. This allows common
25 **	o/p formatting function sm_vprintf() to be used.
26 **
27 **	Parameters:
28 **		str -- location for output
29 **		n -- maximum size for o/p
30 **		fmt -- format directives
31 **		ap -- data unit vectors for use by 'fmt'
32 **
33 **	Results:
34 **		result from sm_io_vfprintf()
35 **
36 **	Side Effects:
37 **		Limits the size ('n') to INT_MAX.
38 */
39 
40 int
41 sm_vsnprintf(str, n, fmt, ap)
42 	char *str;
43 	size_t n;
44 	const char *fmt;
45 	SM_VA_LOCAL_DECL
46 {
47 	int ret;
48 	char dummy;
49 	SM_FILE_T fake;
50 
51 	/* While snprintf(3) specifies size_t stdio uses an int internally */
52 	if (n > INT_MAX)
53 		n = INT_MAX;
54 
55 	/* Stdio internals do not deal correctly with zero length buffer */
56 	if (n == 0)
57 	{
58 		str = &dummy;
59 		n = 1;
60 	}
61 	fake.sm_magic = SmFileMagic;
62 	fake.f_timeout = SM_TIME_FOREVER;
63 	fake.f_timeoutstate = SM_TIME_BLOCK;
64 	fake.f_file = -1;
65 	fake.f_flags = SMWR | SMSTR;
66 	fake.f_bf.smb_base = fake.f_p = (unsigned char *)str;
67 	fake.f_bf.smb_size = fake.f_w = n - 1;
68 	fake.f_close = NULL;
69 	fake.f_open = NULL;
70 	fake.f_read = NULL;
71 	fake.f_write = NULL;
72 	fake.f_seek = NULL;
73 	fake.f_setinfo = fake.f_getinfo = NULL;
74 	fake.f_type = "sm_vsnprintf:fake";
75 	ret = sm_io_vfprintf(&fake, SM_TIME_FOREVER, fmt, ap);
76 	*fake.f_p = 0;
77 	return ret;
78 }
79