stdio/freopen.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1990, 1993
  27  *      The Regents of the University of California.  All rights reserved.
  28  *
  29  * This code is derived from software contributed to Berkeley by
  30  * Chris Torek.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 3. All advertising materials mentioning features or use of this software
  41  *    must display the following acknowledgement:
  42  *      This product includes software developed by the University of
  43  *      California, Berkeley and its contributors.
  44  * 4. Neither the name of the University nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  */
  60
  61
  62 #include <sys/types.h>
  63 #include <sys/stat.h>
  64 #include <fcntl.h>
  65 #include <errno.h>
  66 #include <unistd.h>
  67 #include <stdio.h>
  68 #include <stdlib.h>
  69 #include "local.h"
  70
  71 /*
  72  * Re-direct an existing, open (probably) file to some other file.
  73  * ANSI is written such that the original file gets closed if at
  74  * all possible, no matter what.
  75  */
  76 FILE *
  77 freopen(file, mode, fp)
  78         const char *file, *mode;
  79         register FILE *fp;
  80 {
  81         register int f;
  82         int flags, isopen, oflags, sverrno, wantfd;
  83
  84         if ((flags = __sflags(mode, &oflags)) == 0) {
  85                 (void) fclose(fp);
  86                 return (NULL);
  87         }
  88
  89         if (!__sdidinit)
  90                 __sinit();
  91
  92         /*
  93          * There are actually programs that depend on being able to "freopen"
  94          * descriptors that weren't originally open.  Keep this from breaking.
  95          * Remember whether the stream was open to begin with, and which file
  96          * descriptor (if any) was associated with it.  If it was attached to
  97          * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
  98          * should work.  This is unnecessary if it was not a Unix file.
  99          */
 100         if (fp->_flags == 0) {
 101                 fp->_flags = __SEOF;    /* hold on to it */
 102                 isopen = 0;
 103                 wantfd = -1;
 104         } else {
 105                 /* flush the stream; ANSI doesn't require this. */
 106                 if (fp->_flags & __SWR)
 107                         (void) __sflush(fp);
 108                 /* if close is NULL, closing is a no-op, hence pointless */
 109                 isopen = fp->_close != NULL;
 110                 if ((wantfd = fp->_file) < 0 && isopen) {
 111                         (void) (*fp->_close)(fp->_cookie);
 112                         isopen = 0;
 113                 }
 114         }
 115
 116         /* Get a new descriptor to refer to the new file. */
 117         f = open(file, oflags, DEFFILEMODE);
 118         if (f < 0 && isopen) {
 119                 /* If out of fd's close the old one and try again. */
 120                 if (errno == ENFILE || errno == EMFILE) {
 121                         (void) (*fp->_close)(fp->_cookie);
 122                         isopen = 0;
 123                         f = open(file, oflags, DEFFILEMODE);
 124                 }
 125         }
 126         sverrno = errno;
 127
 128         /*
 129          * Finish closing fp.  Even if the open succeeded above, we cannot
 130          * keep fp->_base: it may be the wrong size.  This loses the effect
 131          * of any setbuffer calls, but stdio has always done this before.
 132          */
 133         if (isopen)
 134                 (void) (*fp->_close)(fp->_cookie);
 135         if (fp->_flags & __SMBF)
 136                 free((char *)fp->_bf._base);
 137         fp->_w = 0;
 138         fp->_r = 0;
 139         fp->_p = NULL;
 140         fp->_bf._base = NULL;
 141         fp->_bf._size = 0;
 142         fp->_lbfsize = 0;
 143         if (HASUB(fp))
 144                 FREEUB(fp);
 145         fp->_ub._size = 0;
 146         if (HASLB(fp))
 147                 FREELB(fp);
 148         fp->_lb._size = 0;
 149
 150         if (f < 0) {                    /* did not get it after all */
 151                 fp->_flags = 0;         /* set it free */
 152                 errno = sverrno;        /* restore in case _close clobbered */
 153                 return (NULL);
 154         }
 155
 156         /*
 157          * If reopening something that was open before on a real file, try
 158          * to maintain the descriptor.  Various C library routines (perror)
 159          * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
 160          */
 161         if (wantfd >= 0 && f != wantfd) {
 162                 if (dup2(f, wantfd) >= 0) {
 163                         (void) close(f);
 164                         f = wantfd;
 165                 }
 166         }
 167
 168         fp->_flags = flags;
 169         fp->_file = f;
 170         fp->_cookie = fp;
 171         fp->_read = __sread;
 172         fp->_write = __swrite;
 173         fp->_seek = __sseek;
 174         fp->_close = __sclose;
 175         return (fp);
 176 }