diff options
Diffstat (limited to 'libc/stdio/freopen.c')
| -rw-r--r-- | libc/stdio/freopen.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/libc/stdio/freopen.c b/libc/stdio/freopen.c new file mode 100644 index 0000000..414d810 --- /dev/null +++ b/libc/stdio/freopen.c @@ -0,0 +1,158 @@ +/* $OpenBSD: freopen.c,v 1.9 2005/08/08 08:05:36 espie Exp $ */ +/*- + * Copyright (c) 1990, 1993 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Chris Torek. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <errno.h> +#include <unistd.h> +#include <stdio.h> +#include <stdlib.h> +#include "local.h" + +/* + * Re-direct an existing, open (probably) file to some other file. + * ANSI is written such that the original file gets closed if at + * all possible, no matter what. + */ +FILE * +freopen(const char *file, const char *mode, FILE *fp) +{ + int f; + int flags, isopen, oflags, sverrno, wantfd; + + if ((flags = __sflags(mode, &oflags)) == 0) { + (void) fclose(fp); + return (NULL); + } + + if (!__sdidinit) + __sinit(); + + /* + * There are actually programs that depend on being able to "freopen" + * descriptors that weren't originally open. Keep this from breaking. + * Remember whether the stream was open to begin with, and which file + * descriptor (if any) was associated with it. If it was attached to + * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin) + * should work. This is unnecessary if it was not a Unix file. + */ + if (fp->_flags == 0) { + fp->_flags = __SEOF; /* hold on to it */ + isopen = 0; + wantfd = -1; + } else { + /* flush the stream; ANSI doesn't require this. */ + if (fp->_flags & __SWR) + (void) __sflush(fp); + /* if close is NULL, closing is a no-op, hence pointless */ + isopen = fp->_close != NULL; + if ((wantfd = fp->_file) < 0 && isopen) { + (void) (*fp->_close)(fp->_cookie); + isopen = 0; + } + } + + /* Get a new descriptor to refer to the new file. */ + f = open(file, oflags, DEFFILEMODE); + if (f < 0 && isopen) { + /* If out of fd's close the old one and try again. */ + if (errno == ENFILE || errno == EMFILE) { + (void) (*fp->_close)(fp->_cookie); + isopen = 0; + f = open(file, oflags, DEFFILEMODE); + } + } + sverrno = errno; + + /* + * Finish closing fp. Even if the open succeeded above, we cannot + * keep fp->_base: it may be the wrong size. This loses the effect + * of any setbuffer calls, but stdio has always done this before. + */ + if (isopen && f != wantfd) + (void) (*fp->_close)(fp->_cookie); + if (fp->_flags & __SMBF) + free((char *)fp->_bf._base); + fp->_w = 0; + fp->_r = 0; + fp->_p = NULL; + fp->_bf._base = NULL; + fp->_bf._size = 0; + fp->_lbfsize = 0; + if (HASUB(fp)) + FREEUB(fp); + _UB(fp)._size = 0; + WCIO_FREE(fp); + if (HASLB(fp)) + FREELB(fp); + fp->_lb._size = 0; + + if (f < 0) { /* did not get it after all */ + fp->_flags = 0; /* set it free */ + errno = sverrno; /* restore in case _close clobbered */ + return (NULL); + } + + /* + * If reopening something that was open before on a real file, try + * to maintain the descriptor. Various C library routines (perror) + * assume stderr is always fd STDERR_FILENO, even if being freopen'd. + */ + if (wantfd >= 0 && f != wantfd) { + if (dup2(f, wantfd) >= 0) { + (void) close(f); + f = wantfd; + } + } + + fp->_flags = flags; + fp->_file = f; + fp->_cookie = fp; + fp->_read = __sread; + fp->_write = __swrite; + fp->_seek = __sseek; + fp->_close = __sclose; + + /* + * When opening in append mode, even though we use O_APPEND, + * we need to seek to the end so that ftell() gets the right + * answer. If the user then alters the seek pointer, or + * the file extends, this will fail, but there is not much + * we can do about this. (We could set __SAPP and check in + * fseek and ftell.) + */ + if (oflags & O_APPEND) + (void) __sseek((void *)fp, (fpos_t)0, SEEK_END); + return (fp); +} |