xref: /illumos-gate/usr/src/lib/libc/port/print/snprintf.c (revision 7257d1b4)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
28 /*	  All Rights Reserved	*/
29 
30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
31 
32 #include "lint.h"
33 #include <mtlib.h>
34 #include <stdarg.h>
35 #include <values.h>
36 #include <thread.h>
37 #include <synch.h>
38 #include <errno.h>
39 #include <sys/types.h>
40 #include "print.h"
41 #include "libc.h"
42 
43 /*VARARGS2*/
44 int
snprintf(char * string,size_t n,const char * format,...)45 snprintf(char *string, size_t n, const char *format, ...)
46 {
47 	ssize_t count;
48 	FILE siop;
49 	va_list ap;
50 	size_t	max = MAXINT;
51 	unsigned char tmpbuf[1]; /* dummy buffer for _doprnt() if NULL string */
52 
53 	siop._cnt = n - 1;
54 	siop._base = siop._ptr = (unsigned char *)string;
55 	siop._flag = _IOREAD;   /* distinguish dummy file descriptor */
56 #ifdef _LP64
57 	/*
58 	 * _bufend() (_realbufend()) should return NULL for v/snprintf,
59 	 * so PUT() macro in _doprnt() will bounds check.  For 32-bit,
60 	 * there is no _end field, and _realbufend() will return NULL
61 	 * since it cannot find the dummy FILE structure in the linked
62 	 * list of FILE strucutres.  See bug 4274368.
63 	 */
64 	siop._end = NULL;
65 #endif	/* _LP64 */
66 
67 	if (n == 0) {
68 		/*
69 		 * When n==0, string may be NULL, so always use tmpbuf to
70 		 * guard for this case.  No bytes should be transmitted to
71 		 * the buffer when n==0, so using tmpbuf instead of string
72 		 * (ie, if string is not NULL) should not matter.
73 		 */
74 		siop._base = siop._ptr = tmpbuf;
75 		siop._cnt = 0;
76 	} else if (n > max) {
77 		errno = EOVERFLOW;
78 		return (EOF);
79 	}
80 
81 	va_start(ap, format);
82 	count = _ndoprnt(format, ap, &siop, 0);
83 	va_end(ap);
84 
85 	*siop._ptr = '\0';   /* plant terminating null character */
86 
87 	if (count == EOF)
88 		return (EOF);
89 
90 	/* overflow check */
91 	if ((size_t)count > max) {
92 		errno = EOVERFLOW;
93 		return (EOF);
94 	} else {
95 		return ((int)count);
96 	}
97 }
98 
99 #ifndef _LP64
100 
101 /*
102  * 32-bit shadow function of snprintf().
103  * When using the c89 compiler to build 32-bit applications, the size
104  * of intmax_t is 32-bits, otherwise the size of intmax_t is 64-bits.
105  * The shadow function uses 32-bit size of intmax_t for %j conversion.
106  * The #pragma redefine_extname in <stdio.h> selects the proper routine
107  * at compile time for the user application.
108  * NOTE: this function is only available in the 32-bit library.
109  */
110 
111 int
_snprintf_c89(char * string,size_t n,const char * format,...)112 _snprintf_c89(char *string, size_t n, const char *format, ...)
113 {
114 	ssize_t count;
115 	va_list ap;
116 
117 	va_start(ap, format);
118 	count = _vsnprintf_c89(string, n, format, ap);
119 	va_end(ap);
120 	return ((int)count);
121 }
122 
123 #endif	/* _LP64 */
124