lib/libc/stdio/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  * @(#)freopen.c        8.1 (Berkeley) 6/4/93
  37  * $FreeBSD: src/lib/libc/stdio/freopen.c,v 1.5.2.1 2001/03/05 10:54:53 obrien Exp $
  38  * $DragonFly: src/lib/libc/stdio/freopen.c,v 1.7 2005/11/20 11:07:30 swildner Exp $
  39  */
  40
  41 #include "namespace.h"
  42 #include <sys/types.h>
  43 #include <sys/stat.h>
  44 #include <fcntl.h>
  45 #include <errno.h>
  46 #include <unistd.h>
  47 #include <stdio.h>
  48 #include <stdlib.h>
  49 #include "un-namespace.h"
  50
  51 #include "libc_private.h"
  52 #include "local.h"
  53 #include "priv_stdio.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(const char *file, const char *mode, FILE *fp)
  62 {
  63         int f;
  64         int dflags, flags, isopen, oflags, sverrno, wantfd;
  65
  66         if ((flags = __sflags(mode, &oflags)) == 0) {
  67                 fclose(fp);
  68                 return (NULL);
  69         }
  70
  71         FLOCKFILE(fp);
  72
  73         if (!__sdidinit)
  74                 __sinit();
  75
  76         sverrno = 0;
  77
  78         /*
  79          * If the filename is a NULL pointer, the caller is asking us to
  80          * re-open the same file with a different mode. We allow this only
  81          * if the modes are compatible.
  82          */
  83         if (file == NULL) {
  84                 /* See comment below regarding freopen() of closed files. */
  85                 if (fp->pub._flags == 0) {
  86                         FUNLOCKFILE(fp);
  87                         errno = EINVAL;
  88                         return (NULL);
  89                 }
  90                 if ((dflags = _fcntl(fp->pub._fileno, F_GETFL)) < 0) {
  91                         sverrno = errno;
  92                         fclose(fp);
  93                         FUNLOCKFILE(fp);
  94                         errno = sverrno;
  95                         return (NULL);
  96                 }
  97                 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
  98                     (oflags & O_ACCMODE)) {
  99                         fclose(fp);
 100                         FUNLOCKFILE(fp);
 101                         errno = EINVAL;
 102                         return (NULL);
 103                 }
 104                 if ((oflags ^ dflags) & O_APPEND) {
 105                         dflags &= ~O_APPEND;
 106                         dflags |= oflags & O_APPEND;
 107                         if (_fcntl(fp->pub._fileno, F_SETFL, dflags) < 0) {
 108                                 sverrno = errno;
 109                                 fclose(fp);
 110                                 FUNLOCKFILE(fp);
 111                                 errno = sverrno;
 112                                 return (NULL);
 113                         }
 114                 }
 115                 if (oflags & O_TRUNC)
 116                         ftruncate(fp->pub._fileno, 0);
 117                 if (_fseeko(fp, 0, oflags & O_APPEND ? SEEK_END : SEEK_SET) < 0 &&
 118                     errno != ESPIPE) {
 119                         sverrno = errno;
 120                         fclose(fp);
 121                         FUNLOCKFILE(fp);
 122                         errno = sverrno;
 123                         return (NULL);
 124                 }
 125                 f = fp->pub._fileno;
 126                 isopen = 0;
 127                 wantfd = -1;
 128                 goto finish;
 129         }
 130
 131         /*
 132          * There are actually programs that depend on being able to "freopen"
 133          * descriptors that weren't originally open.  Keep this from breaking.
 134          * Remember whether the stream was open to begin with, and which file
 135          * descriptor (if any) was associated with it.  If it was attached to
 136          * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
 137          * should work.  This is unnecessary if it was not a Unix file.
 138          */
 139         if (fp->pub._flags == 0) {
 140                 fp->pub._flags = __SEOF;        /* hold on to it */
 141                 isopen = 0;
 142                 wantfd = -1;
 143         } else {
 144                 /* flush the stream; ANSI doesn't require this. */
 145                 if (fp->pub._flags & __SWR)
 146                         __sflush(fp);
 147                 /* if close is NULL, closing is a no-op, hence pointless */
 148                 isopen = fp->_close != NULL;
 149                 if ((wantfd = fp->pub._fileno) < 0 && isopen) {
 150                         (*fp->_close)(fp->_cookie);
 151                         isopen = 0;
 152                 }
 153         }
 154
 155         /* Get a new descriptor to refer to the new file. */
 156         f = _open(file, oflags, DEFFILEMODE);
 157         if (f < 0 && isopen) {
 158                 /* If out of fd's close the old one and try again. */
 159                 if (errno == ENFILE || errno == EMFILE) {
 160                         (*fp->_close)(fp->_cookie);
 161                         isopen = 0;
 162                         f = _open(file, oflags, DEFFILEMODE);
 163                 }
 164         }
 165         sverrno = errno;
 166
 167 finish:
 168         /*
 169          * Finish closing fp.  Even if the open succeeded above, we cannot
 170          * keep fp->_base: it may be the wrong size.  This loses the effect
 171          * of any setbuffer calls, but stdio has always done this before.
 172          */
 173         if (isopen)
 174                 (*fp->_close)(fp->_cookie);
 175         if (fp->pub._flags & __SMBF)
 176                 free((char *)fp->_bf._base);
 177         fp->pub._w = 0;
 178         fp->pub._r = 0;
 179         fp->pub._p = NULL;
 180         fp->_bf._base = NULL;
 181         fp->_bf._size = 0;
 182         fp->pub._lbfsize = 0;
 183         if (HASUB(fp))
 184                 FREEUB(fp);
 185         fp->_ub._size = 0;
 186         if (HASLB(fp))
 187                 FREELB(fp);
 188         fp->_lb._size = 0;
 189
 190         if (f < 0) {                    /* did not get it after all */
 191                 fp->pub._flags = 0;             /* set it free */
 192                 errno = sverrno;        /* restore in case _close clobbered */
 193                 FUNLOCKFILE(fp);
 194                 return (NULL);
 195         }
 196
 197         /*
 198          * If reopening something that was open before on a real file, try
 199          * to maintain the descriptor.  Various C library routines (perror)
 200          * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
 201          */
 202         if (wantfd >= 0 && f != wantfd) {
 203                 if (_dup2(f, wantfd) >= 0) {
 204                         _close(f);
 205                         f = wantfd;
 206                 }
 207         }
 208
 209         fp->pub._flags = flags;
 210         fp->pub._fileno = f;
 211         fp->_cookie = fp;
 212         fp->_read = __sread;
 213         fp->_write = __swrite;
 214         fp->_seek = __sseek;
 215         fp->_close = __sclose;
 216         FUNLOCKFILE(fp);
 217         return (fp);
 218 }