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 = EINVAL;
 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         if (fp->_flags == 0) {
 136                 fp->_flags = __SEOF;    /* hold on to it */
 137                 isopen = 0;
 138                 wantfd = -1;
 139         } else {
 140                 /* flush the stream; ANSI doesn't require this. */
 141                 if (fp->_flags & __SWR)
 142                         (void) __sflush(fp);
 143                 /* if close is NULL, closing is a no-op, hence pointless */
 144                 isopen = fp->_close != NULL;
 145                 if ((wantfd = fp->_file) < 0 && isopen) {
 146                         (void) (*fp->_close)(fp->_cookie);
 147                         isopen = 0;
 148                 }
 149         }
 150
 151         /* Get a new descriptor to refer to the new file. */
 152         f = _open(file, oflags, DEFFILEMODE);
 153         if (f < 0 && isopen) {
 154                 /* If out of fd's close the old one and try again. */
 155                 if (errno == ENFILE || errno == EMFILE) {
 156                         (void) (*fp->_close)(fp->_cookie);
 157                         isopen = 0;
 158                         f = _open(file, oflags, DEFFILEMODE);
 159                 }
 160         }
 161         sverrno = errno;
 162
 163 finish:
 164         /*
 165          * Finish closing fp.  Even if the open succeeded above, we cannot
 166          * keep fp->_base: it may be the wrong size.  This loses the effect
 167          * of any setbuffer calls, but stdio has always done this before.
 168          */
 169         if (isopen)
 170                 (void) (*fp->_close)(fp->_cookie);
 171         if (fp->_flags & __SMBF)
 172                 free((char *)fp->_bf._base);
 173         fp->_w = 0;
 174         fp->_r = 0;
 175         fp->_p = NULL;
 176         fp->_bf._base = NULL;
 177         fp->_bf._size = 0;
 178         fp->_lbfsize = 0;
 179         if (HASUB(fp))
 180                 FREEUB(fp);
 181         fp->_ub._size = 0;
 182         if (HASLB(fp))
 183                 FREELB(fp);
 184         fp->_lb._size = 0;
 185         fp->_orientation = 0;
 186         memset(&fp->_mbstate, 0, sizeof(mbstate_t));
 187
 188         if (f < 0) {                    /* did not get it after all */
 189                 fp->_flags = 0;         /* set it free */
 190                 FUNLOCKFILE(fp);
 191                 errno = sverrno;        /* restore in case _close clobbered */
 192                 return (NULL);
 193         }
 194
 195         /*
 196          * If reopening something that was open before on a real file, try
 197          * to maintain the descriptor.  Various C library routines (perror)
 198          * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
 199          */
 200         if (wantfd >= 0 && f != wantfd) {
 201                 if (_dup2(f, wantfd) >= 0) {
 202                         (void)_close(f);
 203                         f = wantfd;
 204                 }
 205         }
 206
 207         /*
 208          * File descriptors are a full int, but _file is only a short.
 209          * If we get a valid file descriptor that is greater than
 210          * SHRT_MAX, then the fd will get sign-extended into an
 211          * invalid file descriptor.  Handle this case by failing the
 212          * open.
 213          */
 214         if (f > SHRT_MAX) {
 215                 fp->_flags = 0;         /* set it free */
 216                 FUNLOCKFILE(fp);
 217                 errno = EMFILE;
 218                 return (NULL);
 219         }
 220
 221         fp->_flags = flags;
 222         fp->_file = f;
 223         fp->_cookie = fp;
 224         fp->_read = __sread;
 225         fp->_write = __swrite;
 226         fp->_seek = __sseek;
 227         fp->_close = __sclose;
 228         /*
 229          * When opening in append mode, even though we use O_APPEND,
 230          * we need to seek to the end so that ftell() gets the right
 231          * answer.  If the user then alters the seek pointer, or
 232          * the file extends, this will fail, but there is not much
 233          * we can do about this.  (We could set __SAPP and check in
 234          * fseek and ftell.)
 235          */
 236         if (oflags & O_APPEND)
 237                 (void) _sseek(fp, (fpos_t)0, SEEK_END);
 238         FUNLOCKFILE(fp);
 239         return (fp);
 240 }