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         FLOCKFILE(fp);
  74
  75         if (!__sdidinit)
  76                 __sinit();
  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->_flags == 0) {
  86                         FUNLOCKFILE(fp);
  87                         errno = EINVAL;
  88                         return (NULL);
  89                 }
  90                 if ((dflags = _fcntl(fp->_file, 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 = EBADF;
 102                         return (NULL);
 103                 }
 104                 if (fp->_flags & __SWR)
 105                         (void) __sflush(fp);
 106                 if ((oflags ^ dflags) & O_APPEND) {
 107                         dflags &= ~O_APPEND;
 108                         dflags |= oflags & O_APPEND;
 109                         if (_fcntl(fp->_file, F_SETFL, dflags) < 0) {
 110                                 sverrno = errno;
 111                                 fclose(fp);
 112                                 FUNLOCKFILE(fp);
 113                                 errno = sverrno;
 114                                 return (NULL);
 115                         }
 116                 }
 117                 if (oflags & O_TRUNC)
 118                         (void) ftruncate(fp->_file, (off_t)0);
 119                 if (!(oflags & O_APPEND))
 120                         (void) _sseek(fp, (fpos_t)0, SEEK_SET);
 121                 f = fp->_file;
 122                 isopen = 0;
 123                 wantfd = -1;
 124                 goto finish;
 125         }
 126
 127         /*
 128          * There are actually programs that depend on being able to "freopen"
 129          * descriptors that weren't originally open.  Keep this from breaking.
 130          * Remember whether the stream was open to begin with, and which file
 131          * descriptor (if any) was associated with it.  If it was attached to
 132          * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
 133          * should work.  This is unnecessary if it was not a Unix file.
 134          *
 135          * For UNIX03, we always close if it was open.
 136          */
 137         if (fp->_flags == 0) {
 138                 fp->_flags = __SEOF;    /* hold on to it */
 139                 isopen = 0;
 140                 wantfd = -1;
 141         } else {
 142                 /* flush the stream; ANSI doesn't require this. */
 143                 if (fp->_flags & __SWR)
 144                         (void) __sflush(fp);
 145                 /* if close is NULL, closing is a no-op, hence pointless */
 146 #if __DARWIN_UNIX03
 147                 if (fp->_close)
 148                         (void) (*fp->_close)(fp->_cookie);
 149                 isopen = 0;
 150                 wantfd = -1;
 151 #else /* !__DARWIN_UNIX03 */
 152                 isopen = fp->_close != NULL;
 153                 if ((wantfd = fp->_file) < 0 && isopen) {
 154                         (void) (*fp->_close)(fp->_cookie);
 155                         isopen = 0;
 156                 }
 157 #endif /* __DARWIN_UNIX03 */
 158         }
 159
 160         /* Get a new descriptor to refer to the new file. */
 161         f = _open(file, oflags, DEFFILEMODE);
 162         if (f < 0 && isopen) {
 163                 /* If out of fd's close the old one and try again. */
 164                 if (errno == ENFILE || errno == EMFILE) {
 165                         (void) (*fp->_close)(fp->_cookie);
 166                         isopen = 0;
 167                         f = _open(file, oflags, DEFFILEMODE);
 168                 }
 169         }
 170         sverrno = errno;
 171
 172 finish:
 173         /*
 174          * Finish closing fp.  Even if the open succeeded above, we cannot
 175          * keep fp->_base: it may be the wrong size.  This loses the effect
 176          * of any setbuffer calls, but stdio has always done this before.
 177          */
 178         if (isopen)
 179                 (void) (*fp->_close)(fp->_cookie);
 180         if (fp->_flags & __SMBF)
 181                 free((char *)fp->_bf._base);
 182         fp->_w = 0;
 183         fp->_r = 0;
 184         fp->_p = NULL;
 185         fp->_bf._base = NULL;
 186         fp->_bf._size = 0;
 187         fp->_lbfsize = 0;
 188         if (HASUB(fp))
 189                 FREEUB(fp);
 190         fp->_ub._size = 0;
 191         if (HASLB(fp))
 192                 FREELB(fp);
 193         fp->_lb._size = 0;
 194         fp->_orientation = 0;
 195         memset(&fp->_mbstate, 0, sizeof(mbstate_t));
 196
 197         if (f < 0) {                    /* did not get it after all */
 198                 __sfprelease(fp);       /* set it free */
 199                 FUNLOCKFILE(fp);
 200                 errno = sverrno;        /* restore in case _close clobbered */
 201                 return (NULL);
 202         }
 203
 204         /*
 205          * If reopening something that was open before on a real file, try
 206          * to maintain the descriptor.  Various C library routines (perror)
 207          * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
 208          */
 209         if (wantfd >= 0 && f != wantfd) {
 210                 if (_dup2(f, wantfd) >= 0) {
 211                         (void)_close(f);
 212                         f = wantfd;
 213                 }
 214         }
 215
 216         /*
 217          * File descriptors are a full int, but _file is only a short.
 218          * If we get a valid file descriptor that is greater than
 219          * SHRT_MAX, then the fd will get sign-extended into an
 220          * invalid file descriptor.  Handle this case by failing the
 221          * open.
 222          */
 223         if (f > SHRT_MAX) {
 224                 __sfprelease(fp);       /* set it free */
 225                 FUNLOCKFILE(fp);
 226                 errno = EMFILE;
 227                 return (NULL);
 228         }
 229
 230         fp->_flags = flags;
 231         fp->_file = f;
 232         fp->_cookie = fp;
 233         fp->_read = __sread;
 234         fp->_write = __swrite;
 235         fp->_seek = __sseek;
 236         fp->_close = __sclose;
 237         /*
 238          * When opening in append mode, even though we use O_APPEND,
 239          * we need to seek to the end so that ftell() gets the right
 240          * answer.  If the user then alters the seek pointer, or
 241          * the file extends, this will fail, but there is not much
 242          * we can do about this.  (We could set __SAPP and check in
 243          * fseek and ftell.)
 244          */
 245         if (oflags & O_APPEND)
 246                 (void) _sseek(fp, (fpos_t)0, SEEK_END);
 247         FUNLOCKFILE(fp);
 248         return (fp);
 249 }