pipe.c

   1 #include "types.h"
   2 #include "defs.h"
   3 #include "param.h"
   4 #include "mmu.h"
   5 #include "proc.h"
   6 #include "fs.h"
   7 #include "file.h"
   8 #include "spinlock.h"
   9
  10 #define PIPESIZE 512
  11
  12 struct pipe {
  13   struct spinlock lock;
  14   char data[PIPESIZE];
  15   uint nread;     // number of bytes read
  16   uint nwrite;    // number of bytes written
  17   int readopen;   // read fd is still open
  18   int writeopen;  // write fd is still open
  19 };
  20
  21 int
  22 pipealloc(struct file **f0, struct file **f1)
  23 {
  24   struct pipe *p;
  25
  26   p = 0;
  27   *f0 = *f1 = 0;
  28   if((*f0 = filealloc()) == 0 || (*f1 = filealloc()) == 0)
  29     goto bad;
  30   if((p = (struct pipe*)kalloc()) == 0)
  31     goto bad;
  32   p->readopen = 1;
  33   p->writeopen = 1;
  34   p->nwrite = 0;
  35   p->nread = 0;
  36   initlock(&p->lock, "pipe");
  37   (*f0)->type = FD_PIPE;
  38   (*f0)->readable = 1;
  39   (*f0)->writable = 0;
  40   (*f0)->pipe = p;
  41   (*f1)->type = FD_PIPE;
  42   (*f1)->readable = 0;
  43   (*f1)->writable = 1;
  44   (*f1)->pipe = p;
  45   return 0;
  46
  47  bad:
  48   if(p)
  49     kfree((char*)p);
  50   if(*f0)
  51     fileclose(*f0);
  52   if(*f1)
  53     fileclose(*f1);
  54   return -1;
  55 }
  56
  57 void
  58 pipeclose(struct pipe *p, int writable)
  59 {
  60   acquire(&p->lock);
  61   if(writable){
  62     p->writeopen = 0;
  63     wakeup(&p->nread);
  64   } else {
  65     p->readopen = 0;
  66     wakeup(&p->nwrite);
  67   }
  68   if(p->readopen == 0 && p->writeopen == 0){
  69     release(&p->lock);
  70     kfree((char*)p);
  71   } else
  72     release(&p->lock);
  73 }
  74
  75 int
  76 pipewrite(struct pipe *p, char *addr, int n)
  77 {
  78   int i;
  79
  80   acquire(&p->lock);
  81   for(i = 0; i < n; i++){
  82     while(p->nwrite == p->nread + PIPESIZE){  //DOC: pipewrite-full
  83       if(p->readopen == 0 || proc->killed){
  84         release(&p->lock);
  85         return -1;
  86       }
  87       wakeup(&p->nread);
  88       sleep(&p->nwrite, &p->lock);  //DOC: pipewrite-sleep
  89     }
  90     p->data[p->nwrite++ % PIPESIZE] = addr[i];
  91   }
  92   wakeup(&p->nread);  //DOC: pipewrite-wakeup1
  93   release(&p->lock);
  94   return n;
  95 }
  96
  97 int
  98 piperead(struct pipe *p, char *addr, int n)
  99 {
 100   int i;
 101
 102   acquire(&p->lock);
 103   while(p->nread == p->nwrite && p->writeopen){  //DOC: pipe-empty
 104     if(proc->killed){
 105       release(&p->lock);
 106       return -1;
 107     }
 108     sleep(&p->nread, &p->lock); //DOC: piperead-sleep
 109   }
 110   for(i = 0; i < n; i++){  //DOC: piperead-copy
 111     if(p->nread == p->nwrite)
 112       break;
 113     addr[i] = p->data[p->nread++ % PIPESIZE];
 114   }
 115   wakeup(&p->nwrite);  //DOC: piperead-wakeup
 116   release(&p->lock);
 117   return i;
 118 }