usr/src/lib/libc/port/print/vsnprintf.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 <errno.h>
  37 #include <synch.h>
  38 #include <thread.h>
  39 #include <sys/types.h>
  40 #include "print.h"
  41 #include "libc.h"
  42
  43 /*
  44  * 32-bit shadow function _vsnprintf_c89() is included here.
  45  * When using the c89 compiler to build 32-bit applications, the size
  46  * of intmax_t is 32-bits, otherwise the size of intmax_t is 64-bits.
  47  * The shadow function uses 32-bit size of intmax_t for j conversion.
  48  * The #pragma redefine_extname in <stdio.h> selects the proper routine
  49  * at compile time for the user application.
  50  * NOTE: the shadow function only exists in the 32-bit library.
  51  */
  52
  53 /*VARARGS2*/
  54 int
  55 #ifdef _C89_INTMAX32            /* _C89_INTMAX32 version in 32-bit libc only */
  56 _vsnprintf_c89(char *string, size_t n, const char *format, va_list ap)
  57 #else
  58 vsnprintf(char *string, size_t n, const char *format, va_list ap)
  59 #endif
  60 {
  61         ssize_t count;
  62         FILE siop;
  63         size_t  max = MAXINT;
  64         unsigned char tmpbuf[1]; /* dummy buffer for _doprnt() if NULL string */
  65
  66         siop._cnt = n - 1;
  67         siop._base = siop._ptr = (unsigned char *)string;
  68         siop._flag = _IOREAD;   /* distinguish dummy file descriptor */
  69 #ifdef _LP64
  70         /*
  71          * _bufend() (_realbufend()) should return NULL for v/snprintf,
  72          * so PUT() macro in _doprnt() will bounds check.  For 32-bit,
  73          * there is no _end field, and _realbufend() will return NULL
  74          * since it cannot find the dummy FILE structure in the linked
  75          * list of FILE strucutres.  See bug 4274368.
  76          */
  77         siop._end = NULL;
  78 #endif  /* _LP64 */
  79
  80         if (n == 0) {
  81                 /*
  82                  * When n==0, string may be NULL, so always use tmpbuf to
  83                  * guard for this case.  No bytes should be transmitted to
  84                  * the buffer when n==0, so using tmpbuf instead of string
  85                  * (ie, if string is not NULL) should not matter.
  86                  */
  87                 siop._base = siop._ptr = tmpbuf;
  88                 siop._cnt = 0;
  89         } else if (n > max) {
  90                 errno = EOVERFLOW;
  91                 return (EOF);
  92         }
  93
  94
  95 #ifdef _C89_INTMAX32
  96         count = _ndoprnt(format, ap, &siop, _F_INTMAX32);
  97 #else
  98         count = _ndoprnt(format, ap, &siop, 0);
  99 #endif  /* _C89_INTMAX32 */
 100
 101         *siop._ptr = '\0';      /* plant terminating null character */
 102
 103         /* overflow check */
 104         if ((size_t)count > max) {
 105                 errno = EOVERFLOW;
 106                 return (EOF);
 107         } else {
 108                 return ((int)count);
 109         }
 110 }