sys/src/libstdio/ungetc.c

   1 /*
   2  * pANS stdio -- ungetc
   3  */
   4 #include "iolib.h"
   5 int ungetc(int c, FILE *f){
   6         if(c==EOF) return EOF;
   7         switch(f->state){
   8         default:        /* WR */
   9                 f->state=ERR;
  10                 return EOF;
  11         case CLOSED:
  12         case ERR:
  13                 return EOF;
  14         case OPEN:
  15                 _IO_setvbuf(f);
  16         case RDWR:
  17         case END:
  18                 f->rp=f->wp=f->buf+(f->bufl==0?1:f->bufl);
  19                 f->state=RD;
  20         case RD:
  21                 if(f->rp==f->buf) return EOF;
  22                 if(f->flags&STRING)
  23                         f->rp--;
  24                 else
  25                         *--f->rp=c;
  26                 return (char)c;
  27         }
  28 }