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/*-*- 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/calls/calls.h"
#include "libc/errno.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 fseeko(FILE *f, int64_t offset, int whence) {
ssize_t rc;
int64_t pos;
if (f->fd != -1) {
if (f->beg && !f->end && (f->iomode & O_ACCMODE) != O_RDONLY) {
if ((rc = write(f->fd, f->buf, f->beg)) == -1) {
f->state = errno;
return -1;
}
if (rc != f->beg) abort();
f->beg = 0;
}
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;
return 0;
} else {
f->state = errno == ESPIPE ? EBADF : errno;
return -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;
}
if (0 <= pos && pos <= f->end) {
f->beg = pos;
return 0;
} else {
f->state = errno = EINVAL;
return -1;
}
}
}
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