cosmopolitan/libc/stdio/fseeko.c
Justine Tunney d5910e2673
Fix bugs and make code tinier
- Fixed bug where stdio eof wasn't being sticky
- Fixed bug where fseeko() wasn't clearing eof state
- Removed assert() usage from libc favoring _unassert() / _npassert()
2022-10-09 23:21:34 -07:00

46 lines
2.7 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/intrin/describeflags.internal.h"
#include "libc/intrin/strace.internal.h"
#include "libc/stdio/lock.internal.h"
#include "libc/stdio/stdio.h"
/**
* Repositions open file stream.
*
* This function flushes the buffer (unless it's currently in the EOF
* state) and then calls lseek() on the underlying file. If the stream
* is in the EOF state, this function can be used to restore it without
* needing to reopen the file.
*
* @param f is a non-null stream handle
* @param offset is the byte delta
* @param whence can be SEET_SET, SEEK_CUR, or SEEK_END
* @returns 0 on success or -1 on error
* @threadsafe
*/
int fseeko(FILE *f, int64_t offset, int whence) {
int rc;
flockfile(f);
rc = fseeko_unlocked(f, offset, whence);
STDIOTRACE("fseeko(%p, %'ld, %s) → %d %s", f, offset, DescribeWhence(whence),
rc, DescribeStdioState(f->state));
funlockfile(f);
return rc;
}