stdio/FreeBSD/freopen.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)freopen.c   8.1 (Berkeley) 6/4/93";
  39 #endif /* LIBC_SCCS and not lint */
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: src/lib/libc/stdio/freopen.c,v 1.12 2003/01/26 11:45:54 tjr Exp $");
  42
  43 #include "namespace.h"
  44 #include <sys/types.h>
  45 #include <sys/stat.h>
  46 #include <fcntl.h>
  47 #include <errno.h>
  48 #include <unistd.h>
  49 #include <stdio.h>
  50 #include <stdlib.h>
  51 #include "un-namespace.h"
  52 #include "libc_private.h"
  53 #include "local.h"
  54
  55 /*
  56  * Re-direct an existing, open (probably) file to some other file.
  57  * ANSI is written such that the original file gets closed if at
  58  * all possible, no matter what.
  59  */
  60 FILE *
  61 freopen(file, mode, fp)
  62         const char * __restrict file;
  63         const char * __restrict mode;
  64         FILE *fp;
  65 {
  66         int f;
  67         int dflags, flags, isopen, oflags, sverrno, wantfd;
  68
  69         if ((flags = __sflags(mode, &oflags)) == 0) {
  70                 (void) fclose(fp);
  71                 return (NULL);
  72         }
  73
  74         FLOCKFILE(fp);
  75
  76         if (!__sdidinit)
  77                 __sinit();
  78
  79         /*
  80          * If the filename is a NULL pointer, the caller is asking us to
  81          * re-open the same file with a different mode. We allow this only
  82          * if the modes are compatible.
  83          */
  84         if (file == NULL) {
  85                 /* See comment below regarding freopen() of closed files. */
  86                 if (fp->_flags == 0) {
  87                         FUNLOCKFILE(fp);
  88                         errno = EINVAL;
  89                         return (NULL);
  90                 }
  91                 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) {
  92                         sverrno = errno;
  93                         fclose(fp);
  94                         FUNLOCKFILE(fp);
  95                         errno = sverrno;
  96                         return (NULL);
  97                 }
  98                 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
  99                     (oflags & O_ACCMODE)) {
 100                         fclose(fp);
 101                         FUNLOCKFILE(fp);
 102                         errno = EINVAL;
 103                         return (NULL);
 104                 }
 105                 if ((oflags ^ dflags) & O_APPEND) {
 106                         dflags &= ~O_APPEND;
 107                         dflags |= oflags & O_APPEND;
 108                         if (_fcntl(fp->_file, F_SETFL, dflags) < 0) {
 109                                 sverrno = errno;
 110                                 fclose(fp);
 111                                 FUNLOCKFILE(fp);
 112                                 errno = sverrno;
 113                                 return (NULL);
 114                         }
 115                 }
 116                 if (oflags & O_TRUNC)
 117                         ftruncate(fp->_file, 0);
 118                 if (_fseeko(fp, 0, oflags & O_APPEND ? SEEK_END : SEEK_SET,
 119                     0) < 0 && errno != ESPIPE) {
 120                         sverrno = errno;
 121                         fclose(fp);
 122                         FUNLOCKFILE(fp);
 123                         errno = sverrno;
 124                         return (NULL);
 125                 }
 126                 f = fp->_file;
 127                 isopen = 0;
 128                 wantfd = -1;
 129                 goto finish;
 130         }
 131
 132         /*
 133          * There are actually programs that depend on being able to "freopen"
 134          * descriptors that weren't originally open.  Keep this from breaking.
 135          * Remember whether the stream was open to begin with, and which file
 136          * descriptor (if any) was associated with it.  If it was attached to
 137          * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
 138          * should work.  This is unnecessary if it was not a Unix file.
 139          */
 140         if (fp->_flags == 0) {
 141                 fp->_flags = __SEOF;    /* hold on to it */
 142                 isopen = 0;
 143                 wantfd = -1;
 144         } else {
 145                 /* flush the stream; ANSI doesn't require this. */
 146                 if (fp->_flags & __SWR)
 147                         (void) __sflush(fp);
 148                 /* if close is NULL, closing is a no-op, hence pointless */
 149                 isopen = fp->_close != NULL;
 150                 if ((wantfd = fp->_file) < 0 && isopen) {
 151                         (void) (*fp->_close)(fp->_cookie);
 152                         isopen = 0;
 153                 }
 154         }
 155
 156         /* Get a new descriptor to refer to the new file. */
 157         f = _open(file, oflags, DEFFILEMODE);
 158         if (f < 0 && isopen) {
 159                 /* If out of fd's close the old one and try again. */
 160                 if (errno == ENFILE || errno == EMFILE) {
 161                         (void) (*fp->_close)(fp->_cookie);
 162                         isopen = 0;
 163                         f = _open(file, oflags, DEFFILEMODE);
 164                 }
 165         }
 166         sverrno = errno;
 167
 168 finish:
 169         /*
 170          * Finish closing fp.  Even if the open succeeded above, we cannot
 171          * keep fp->_base: it may be the wrong size.  This loses the effect
 172          * of any setbuffer calls, but stdio has always done this before.
 173          */
 174         if (isopen)
 175                 (void) (*fp->_close)(fp->_cookie);
 176         if (fp->_flags & __SMBF)
 177                 free((char *)fp->_bf._base);
 178         fp->_w = 0;
 179         fp->_r = 0;
 180         fp->_p = NULL;
 181         fp->_bf._base = NULL;
 182         fp->_bf._size = 0;
 183         fp->_lbfsize = 0;
 184         if (HASUB(fp))
 185                 FREEUB(fp);
 186         fp->_ub._size = 0;
 187         if (HASLB(fp))
 188                 FREELB(fp);
 189         fp->_lb._size = 0;
 190         fp->_extra->orientation = 0;
 191
 192         if (f < 0) {                    /* did not get it after all */
 193                 fp->_flags = 0;         /* set it free */
 194                 errno = sverrno;        /* restore in case _close clobbered */
 195                 FUNLOCKFILE(fp);
 196                 return (NULL);
 197         }
 198
 199         /*
 200          * If reopening something that was open before on a real file, try
 201          * to maintain the descriptor.  Various C library routines (perror)
 202          * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
 203          */
 204         if (wantfd >= 0 && f != wantfd) {
 205                 if (_dup2(f, wantfd) >= 0) {
 206                         (void)_close(f);
 207                         f = wantfd;
 208                 }
 209         }
 210
 211         fp->_flags = flags;
 212         fp->_file = f;
 213         fp->_cookie = fp;
 214         fp->_read = __sread;
 215         fp->_write = __swrite;
 216         fp->_seek = __sseek;
 217         fp->_close = __sclose;
 218         FUNLOCKFILE(fp);
 219         return (fp);
 220 }