stdio/freopen.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1990, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * This code is derived from software contributed to Berkeley by
  27  * Chris Torek.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  */
  57
  58
  59 #include <sys/types.h>
  60 #include <sys/stat.h>
  61 #include <fcntl.h>
  62 #include <errno.h>
  63 #include <unistd.h>
  64 #include <stdio.h>
  65 #include <stdlib.h>
  66 #include "local.h"
  67
  68 /*
  69  * Re-direct an existing, open (probably) file to some other file.
  70  * ANSI is written such that the original file gets closed if at
  71  * all possible, no matter what.
  72  */
  73 FILE *
  74 freopen(file, mode, fp)
  75         const char *file, *mode;
  76         register FILE *fp;
  77 {
  78         register int f;
  79         int flags, isopen, oflags, sverrno, wantfd;
  80
  81         if ((flags = __sflags(mode, &oflags)) == 0) {
  82                 (void) fclose(fp);
  83                 return (NULL);
  84         }
  85
  86         if (!__sdidinit)
  87                 __sinit();
  88
  89         /*
  90          * There are actually programs that depend on being able to "freopen"
  91          * descriptors that weren't originally open.  Keep this from breaking.
  92          * Remember whether the stream was open to begin with, and which file
  93          * descriptor (if any) was associated with it.  If it was attached to
  94          * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
  95          * should work.  This is unnecessary if it was not a Unix file.
  96          */
  97         if (fp->_flags == 0) {
  98                 fp->_flags = __SEOF;    /* hold on to it */
  99                 isopen = 0;
 100                 wantfd = -1;
 101         } else {
 102                 /* flush the stream; ANSI doesn't require this. */
 103                 if (fp->_flags & __SWR)
 104                         (void) __sflush(fp);
 105                 /* if close is NULL, closing is a no-op, hence pointless */
 106                 isopen = fp->_close != NULL;
 107                 if ((wantfd = fp->_file) < 0 && isopen) {
 108                         (void) (*fp->_close)(fp->_cookie);
 109                         isopen = 0;
 110                 }
 111         }
 112
 113         /* Get a new descriptor to refer to the new file. */
 114         f = open(file, oflags, DEFFILEMODE);
 115         if (f < 0 && isopen) {
 116                 /* If out of fd's close the old one and try again. */
 117                 if (errno == ENFILE || errno == EMFILE) {
 118                         (void) (*fp->_close)(fp->_cookie);
 119                         isopen = 0;
 120                         f = open(file, oflags, DEFFILEMODE);
 121                 }
 122         }
 123         sverrno = errno;
 124
 125         /*
 126          * Finish closing fp.  Even if the open succeeded above, we cannot
 127          * keep fp->_base: it may be the wrong size.  This loses the effect
 128          * of any setbuffer calls, but stdio has always done this before.
 129          */
 130         if (isopen)
 131                 (void) (*fp->_close)(fp->_cookie);
 132         if (fp->_flags & __SMBF)
 133                 free((char *)fp->_bf._base);
 134         fp->_w = 0;
 135         fp->_r = 0;
 136         fp->_p = NULL;
 137         fp->_bf._base = NULL;
 138         fp->_bf._size = 0;
 139         fp->_lbfsize = 0;
 140         if (HASUB(fp))
 141                 FREEUB(fp);
 142         fp->_ub._size = 0;
 143         if (HASLB(fp))
 144                 FREELB(fp);
 145         fp->_lb._size = 0;
 146
 147         if (f < 0) {                    /* did not get it after all */
 148                 fp->_flags = 0;         /* set it free */
 149                 errno = sverrno;        /* restore in case _close clobbered */
 150                 return (NULL);
 151         }
 152
 153         /*
 154          * If reopening something that was open before on a real file, try
 155          * to maintain the descriptor.  Various C library routines (perror)
 156          * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
 157          */
 158         if (wantfd >= 0 && f != wantfd) {
 159                 if (dup2(f, wantfd) >= 0) {
 160                         (void) close(f);
 161                         f = wantfd;
 162                 }
 163         }
 164
 165         fp->_flags = flags;
 166         fp->_file = f;
 167         fp->_cookie = fp;
 168         fp->_read = __sread;
 169         fp->_write = __swrite;
 170         fp->_seek = __sseek;
 171         fp->_close = __sclose;
 172         return (fp);
 173 }