cosmopolitan/libc/stdio/fseek_unlocked.c
Jōshin e16a7d8f3b
flip et / noet in modelines
`et` means `expandtab`.

```sh
rg 'vi: .* :vi' -l -0 | \
  xargs -0 sed -i '' 's/vi: \(.*\) et\(.*\)  :vi/vi: \1 xoet\2:vi/'
rg 'vi: .*  :vi' -l -0 | \
  xargs -0 sed -i '' 's/vi: \(.*\)noet\(.*\):vi/vi: \1et\2  :vi/'
rg 'vi: .*  :vi' -l -0 | \
  xargs -0 sed -i '' 's/vi: \(.*\)xoet\(.*\):vi/vi: \1noet\2:vi/'
```
2023-12-07 22:17:11 -05:00

82 lines
3.3 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et 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/calls/calls.h"
#include "libc/errno.h"
#include "libc/macros.internal.h"
#include "libc/stdio/internal.h"
#include "libc/stdio/stdio.h"
#include "libc/sysv/consts/o.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
*/
int fseek_unlocked(FILE *f, int64_t offset, int whence) {
int res;
int64_t pos;
if (f->fd != -1) {
if (__fflush_impl(f) == -1) return -1;
if (whence == SEEK_CUR && f->beg < f->end) {
offset -= f->end - f->beg;
}
if (lseek(f->fd, offset, whence) != -1) {
f->beg = 0;
f->end = 0;
f->state = 0;
res = 0;
} else {
f->state = errno == ESPIPE ? EBADF : errno;
res = -1;
}
} else {
switch (whence) {
case SEEK_SET:
pos = offset;
break;
case SEEK_CUR:
pos = f->beg + offset;
break;
case SEEK_END:
pos = f->end + offset;
break;
default:
pos = -1;
break;
}
f->end = MAX(f->beg, f->end);
if (0 <= pos && pos <= f->end) {
f->beg = pos;
f->state = 0;
res = 0;
} else {
f->state = errno = EINVAL;
res = -1;
}
}
return res;
}