usr/src/lib/libc/port/print/snprintf.c

   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
  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
 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 */