mirror of
https://github.com/jart/cosmopolitan.git
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65 lines
3.2 KiB
C
65 lines
3.2 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/calls.h"
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#include "libc/stdio/internal.h"
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#include "libc/stdio/stdio.h"
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#include "libc/sysv/consts/f.h"
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#include "libc/sysv/consts/fd.h"
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#include "libc/sysv/consts/o.h"
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/**
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* Overwrites existing stream.
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*
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* This function can be used in two ways. The first is sort of a
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* mutating assignment. The second behavior, if pathname is NULL, is
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* just changing the mode of an already open file descriptor.
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*
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* @param pathname is the file to open or NULL
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* @param mode is the mode string flags, see fopenflags()
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* @param stream is the existing allocated stream memory, which is
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* flushed and closed if already open
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* @return stream object if successful, or NULL w/ errno
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*/
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FILE *freopen(const char *pathname, const char *mode, FILE *stream) {
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int fd;
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FILE *res;
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unsigned flags;
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flags = fopenflags(mode);
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flockfile(stream);
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fflush_unlocked(stream);
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if (pathname) {
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/* open new stream, overwriting existing alloc */
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if ((fd = open(pathname, flags, 0666)) != -1) {
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dup3(fd, stream->fd, flags & O_CLOEXEC);
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close(fd);
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stream->iomode = flags;
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stream->beg = 0;
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stream->end = 0;
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res = stream;
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} else {
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res = NULL;
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}
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} else {
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fcntl(stream->fd, F_SETFD, !!(flags & O_CLOEXEC));
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fcntl(stream->fd, F_SETFL, flags & ~O_CLOEXEC);
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res = stream;
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}
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funlockfile(stream);
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return res;
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}
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