libc-top-half/musl/src/stdio/fseek.c

   1 #include "stdio_impl.h"
   2
   3 int __fseeko_unlocked(FILE *f, off_t off, int whence)
   4 {
   5         /* Adjust relative offset for unread data in buffer, if any. */
   6         if (whence == SEEK_CUR && f->rend) off -= f->rend - f->rpos;
   7
   8         /* Flush write buffer, and report error on failure. */
   9         if (f->wpos != f->wbase) {
  10                 f->write(f, 0, 0);
  11                 if (!f->wpos) return -1;
  12         }
  13
  14         /* Leave writing mode */
  15         f->wpos = f->wbase = f->wend = 0;
  16
  17         /* Perform the underlying seek. */
  18         if (f->seek(f, off, whence) < 0) return -1;
  19
  20         /* If seek succeeded, file is seekable and we discard read buffer. */
  21         f->rpos = f->rend = 0;
  22         f->flags &= ~F_EOF;
  23
  24         return 0;
  25 }
  26
  27 int __fseeko(FILE *f, off_t off, int whence)
  28 {
  29         int result;
  30         FLOCK(f);
  31         result = __fseeko_unlocked(f, off, whence);
  32         FUNLOCK(f);
  33         return result;
  34 }
  35
  36 int fseek(FILE *f, long off, int whence)
  37 {
  38         return __fseeko(f, off, whence);
  39 }
  40
  41 weak_alias(__fseeko, fseeko);
  42
  43 weak_alias(fseeko, fseeko64);