sys/src/libbio/bgetc.c

   1 #include        <u.h>
   2 #include        <libc.h>
   3 #include        <bio.h>
   4
   5 int
   6 Bgetc(Biobufhdr *bp)
   7 {
   8         int i;
   9
  10 loop:
  11         i = bp->icount;
  12         if(i != 0) {
  13                 bp->icount = i+1;
  14                 return bp->ebuf[i];
  15         }
  16         if(bp->state != Bractive) {
  17                 if(bp->state == Bracteof)
  18                         bp->state = Bractive;
  19                 return Beof;
  20         }
  21         /*
  22          * get next buffer, try to keep Bungetsize
  23          * characters pre-catenated from the previous
  24          * buffer to allow that many ungets.
  25          */
  26         memmove(bp->bbuf-Bungetsize, bp->ebuf-Bungetsize, Bungetsize);
  27         i = bp->iof(bp, bp->bbuf, bp->bsize);
  28         bp->gbuf = bp->bbuf;
  29         if(i <= 0) {
  30                 bp->state = Bracteof;
  31                 if(i < 0) {
  32                         bp->state = Binactive;
  33                         Berror(bp, "read error: %r");
  34                 }
  35                 return Beof;
  36         }
  37         if(i < bp->bsize) {
  38                 memmove(bp->ebuf-i-Bungetsize, bp->bbuf-Bungetsize, i+Bungetsize);
  39                 bp->gbuf = bp->ebuf-i;
  40         }
  41         bp->icount = -i;
  42         bp->offset += i;
  43         goto loop;
  44 }
  45
  46 int
  47 Bungetc(Biobufhdr *bp)
  48 {
  49
  50         if(bp->state == Bracteof)
  51                 bp->state = Bractive;
  52         if(bp->state != Bractive)
  53                 return Beof;
  54         bp->icount--;
  55         return 1;
  56 }