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  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)freopen.c   8.1 (Berkeley) 6/4/93";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/stdio/freopen.c,v 1.21 2008/04/17 22:17:54 jhb Exp $");
  38
  39 #include "namespace.h"
  40 #include <sys/types.h>
  41 #include <sys/stat.h>
  42 #include <fcntl.h>
  43 #include <errno.h>
  44 #include <limits.h>
  45 #include <unistd.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include "un-namespace.h"
  49 #include "libc_private.h"
  50 #include "local.h"
  51
  52 /*
  53  * Re-direct an existing, open (probably) file to some other file.
  54  * ANSI is written such that the original file gets closed if at
  55  * all possible, no matter what.
  56  */
  57 FILE *
  58 freopen(file, mode, fp)
  59         const char * __restrict file;
  60         const char * __restrict mode;
  61         FILE *fp;
  62 {
  63         int f;
  64         int dflags, flags, isopen, oflags, sverrno, wantfd;
  65
  66         if ((flags = __sflags(mode, &oflags)) == 0) {
  67                 sverrno = errno;
  68                 (void) fclose(fp);
  69                 errno = sverrno;
  70                 return (NULL);
  71         }
  72
  73         pthread_once(&__sdidinit, __sinit);
  74
  75         FLOCKFILE(fp);
  76
  77         /*
  78          * If the filename is a NULL pointer, the caller is asking us to
  79          * re-open the same file with a different mode. We allow this only
  80          * if the modes are compatible.
  81          */
  82         if (file == NULL) {
  83                 /* See comment below regarding freopen() of closed files. */
  84                 if (fp->_flags == 0) {
  85                         FUNLOCKFILE(fp);
  86                         errno = EINVAL;
  87                         return (NULL);
  88                 }
  89                 if ((dflags = _fcntl(fp->_file, F_GETFL)) < 0) {
  90                         sverrno = errno;
  91                         fclose(fp);
  92                         FUNLOCKFILE(fp);
  93                         errno = sverrno;
  94                         return (NULL);
  95                 }
  96                 if ((dflags & O_ACCMODE) != O_RDWR && (dflags & O_ACCMODE) !=
  97                     (oflags & O_ACCMODE)) {
  98                         fclose(fp);
  99                         FUNLOCKFILE(fp);
 100                         errno = EBADF;
 101                         return (NULL);
 102                 }
 103                 if (fp->_flags & __SWR)
 104                         (void) __sflush(fp);
 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                         (void) ftruncate(fp->_file, (off_t)0);
 118                 if (!(oflags & O_APPEND))
 119                         (void) _sseek(fp, (fpos_t)0, SEEK_SET);
 120                 f = fp->_file;
 121                 isopen = 0;
 122                 wantfd = -1;
 123                 goto finish;
 124         }
 125
 126         /*
 127          * There are actually programs that depend on being able to "freopen"
 128          * descriptors that weren't originally open.  Keep this from breaking.
 129          * Remember whether the stream was open to begin with, and which file
 130          * descriptor (if any) was associated with it.  If it was attached to
 131          * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
 132          * should work.  This is unnecessary if it was not a Unix file.
 133          *
 134          * For UNIX03, we always close if it was open.
 135          */
 136         if (fp->_flags == 0) {
 137                 fp->_flags = __SEOF;    /* hold on to it */
 138                 isopen = 0;
 139                 wantfd = -1;
 140         } else {
 141                 /* flush the stream; ANSI doesn't require this. */
 142                 if (fp->_flags & __SWR)
 143                         (void) __sflush(fp);
 144                 /* if close is NULL, closing is a no-op, hence pointless */
 145 #if __DARWIN_UNIX03
 146                 if (fp->_close)
 147                         (void) (*fp->_close)(fp->_cookie);
 148                 isopen = 0;
 149                 wantfd = -1;
 150 #else /* !__DARWIN_UNIX03 */
 151                 isopen = fp->_close != NULL;
 152                 if ((wantfd = fp->_file) < 0 && isopen) {
 153                         (void) (*fp->_close)(fp->_cookie);
 154                         isopen = 0;
 155                 }
 156 #endif /* __DARWIN_UNIX03 */
 157         }
 158
 159         /* Get a new descriptor to refer to the new file. */
 160         f = _open(file, oflags, DEFFILEMODE);
 161         if (f < 0 && isopen) {
 162                 /* If out of fd's close the old one and try again. */
 163                 if (errno == ENFILE || errno == EMFILE) {
 164                         (void) (*fp->_close)(fp->_cookie);
 165                         isopen = 0;
 166                         f = _open(file, oflags, DEFFILEMODE);
 167                 }
 168         }
 169         sverrno = errno;
 170
 171 finish:
 172         /*
 173          * Finish closing fp.  Even if the open succeeded above, we cannot
 174          * keep fp->_base: it may be the wrong size.  This loses the effect
 175          * of any setbuffer calls, but stdio has always done this before.
 176          */
 177         if (isopen)
 178                 (void) (*fp->_close)(fp->_cookie);
 179         if (fp->_flags & __SMBF)
 180                 free((char *)fp->_bf._base);
 181         fp->_w = 0;
 182         fp->_r = 0;
 183         fp->_p = NULL;
 184         fp->_bf._base = NULL;
 185         fp->_bf._size = 0;
 186         fp->_lbfsize = 0;
 187         if (HASUB(fp))
 188                 FREEUB(fp);
 189         fp->_ub._size = 0;
 190         if (HASLB(fp))
 191                 FREELB(fp);
 192         fp->_lb._size = 0;
 193         fp->_orientation = 0;
 194         memset(&fp->_mbstate, 0, sizeof(mbstate_t));
 195
 196         if (f < 0) {                    /* did not get it after all */
 197                 FUNLOCKFILE(fp);
 198                 __sfprelease(fp);       /* set it free */
 199                 errno = sverrno;        /* restore in case _close clobbered */
 200                 return (NULL);
 201         }
 202
 203         /*
 204          * If reopening something that was open before on a real file, try
 205          * to maintain the descriptor.  Various C library routines (perror)
 206          * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
 207          */
 208         if (wantfd >= 0 && f != wantfd) {
 209                 if (_dup2(f, wantfd) >= 0) {
 210                         (void)_close(f);
 211                         f = wantfd;
 212                 }
 213         }
 214
 215         /*
 216          * File descriptors are a full int, but _file is only a short.
 217          * If we get a valid file descriptor that is greater than
 218          * SHRT_MAX, then the fd will get sign-extended into an
 219          * invalid file descriptor.  Handle this case by failing the
 220          * open.
 221          */
 222         if (f > SHRT_MAX) {
 223                 FUNLOCKFILE(fp);
 224                 __sfprelease(fp);       /* set it free */
 225                 errno = EMFILE;
 226                 return (NULL);
 227         }
 228
 229         fp->_flags = flags;
 230         fp->_file = f;
 231         fp->_cookie = fp;
 232         fp->_read = __sread;
 233         fp->_write = __swrite;
 234         fp->_seek = __sseek;
 235         fp->_close = __sclose;
 236         /*
 237          * When opening in append mode, even though we use O_APPEND,
 238          * we need to seek to the end so that ftell() gets the right
 239          * answer.  If the user then alters the seek pointer, or
 240          * the file extends, this will fail, but there is not much
 241          * we can do about this.  (We could set __SAPP and check in
 242          * fseek and ftell.)
 243          */
 244         if (oflags & O_APPEND)
 245                 (void) _sseek(fp, (fpos_t)0, SEEK_END);
 246         FUNLOCKFILE(fp);
 247         return (fp);
 248 }