25   struct pipe *p;  in pipealloc()  local
27   p = 0;  in pipealloc()
31   if((p = (struct pipe*)kalloc()) == 0)  in pipealloc()
33   p->readopen = 1;  in pipealloc()
34   p->writeopen = 1;  in pipealloc()
35   p->nwrite = 0;  in pipealloc()
36   p->nread = 0;  in pipealloc()
37   initlock(&p->lock, "pipe");  in pipealloc()
41   (*f0)->pipe = p;  in pipealloc()
45   (*f1)->pipe = p;  in pipealloc()
50   if(p)  in pipealloc()
51     kfree((char*)p);  in pipealloc()
60 pipeclose(struct pipe *p, int writable)  in pipeclose()  argument
62   acquire(&p->lock);  in pipeclose()
64     p->writeopen = 0;  in pipeclose()
65     wakeup(&p->nread);  in pipeclose()
67     p->readopen = 0;  in pipeclose()
68     wakeup(&p->nwrite);  in pipeclose()
70   if(p->readopen == 0 && p->writeopen == 0){  in pipeclose()
71     release(&p->lock);  in pipeclose()
72     kfree((char*)p);  in pipeclose()
74     release(&p->lock);  in pipeclose()
79 pipewrite(struct pipe *p, char *addr, int n)  in pipewrite()  argument
83   acquire(&p->lock);  in pipewrite()
85     while(p->nwrite == p->nread + PIPESIZE){  //DOC: pipewrite-full  in pipewrite()
86       if(p->readopen == 0 || myproc()->killed){  in pipewrite()
87         release(&p->lock);  in pipewrite()
90       wakeup(&p->nread);  in pipewrite()
91       sleep(&p->nwrite, &p->lock);  //DOC: pipewrite-sleep  in pipewrite()
93     p->data[p->nwrite++ % PIPESIZE] = addr[i];  in pipewrite()
95   wakeup(&p->nread);  //DOC: pipewrite-wakeup1  in pipewrite()
96   release(&p->lock);  in pipewrite()
101 piperead(struct pipe *p, char *addr, int n)  in piperead()  argument
105   acquire(&p->lock);  in piperead()
106   while(p->nread == p->nwrite && p->writeopen){  //DOC: pipe-empty  in piperead()
108       release(&p->lock);  in piperead()
111     sleep(&p->nread, &p->lock); //DOC: piperead-sleep  in piperead()
114     if(p->nread == p->nwrite)  in piperead()
116     addr[i] = p->data[p->nread++ % PIPESIZE];  in piperead()
118   wakeup(&p->nwrite);  //DOC: piperead-wakeup  in piperead()
119   release(&p->lock);  in piperead()