src/stdio/ungetc.c

   1 #include "stdio_impl.h"
   2
   3 int ungetc(int c, FILE *f)
   4 {
   5         if (c == EOF) return c;
   6
   7         FLOCK(f);
   8
   9         if (!f->rpos) __toread(f);
  10         if (!f->rpos || f->rpos <= f->buf - UNGET) {
  11                 FUNLOCK(f);
  12                 return EOF;
  13         }
  14
  15         *--f->rpos = c;
  16         f->flags &= ~F_EOF;
  17
  18         FUNLOCK(f);
  19         return (unsigned char)c;
  20 }