sys/src/boot/pc/queue.c

   1 #include        "u.h"
   2 #include        "lib.h"
   3 #include        "mem.h"
   4 #include        "dat.h"
   5 #include        "fns.h"
   6 #include        "io.h"
   7
   8 int
   9 qgetc(IOQ *q)
  10 {
  11         int c;
  12
  13         if(q->in == q->out)
  14                 return -1;
  15         c = *q->out;
  16         if(q->out == q->buf+sizeof(q->buf)-1)
  17                 q->out = q->buf;
  18         else
  19                 q->out++;
  20         return c;
  21 }
  22
  23 static int
  24 qputc(IOQ *q, int c)
  25 {
  26         uchar *nextin;
  27         if(q->in >= &q->buf[sizeof(q->buf)-1])
  28                 nextin = q->buf;
  29         else
  30                 nextin = q->in+1;
  31         if(nextin == q->out)
  32                 return -1;
  33         *q->in = c;
  34         q->in = nextin;
  35         return 0;
  36 }
  37
  38 void
  39 qinit(IOQ *q)
  40 {
  41         q->in = q->out = q->buf;
  42         q->getc = qgetc;
  43         q->putc = qputc;
  44 }