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pipe.c
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pipe.c
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#include "types.h"
#include "defs.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "spinlock.h"
#include "sleeplock.h"
#include "file.h"
#define PIPESIZE 512
struct pipe {
struct spinlock lock;
char data[PIPESIZE];
uint nread; // number of bytes read
uint nwrite; // number of bytes written
int readopen; // read fd is still open
int writeopen; // write fd is still open
};
int
pipealloc(struct file **f0, struct file **f1)
{
struct pipe *p;
p = 0;
*f0 = *f1 = 0;
if((*f0 = filealloc()) == 0 || (*f1 = filealloc()) == 0)
goto bad;
if((p = (struct pipe*)kalloc()) == 0)
goto bad;
p->readopen = 1;
p->writeopen = 1;
p->nwrite = 0;
p->nread = 0;
initlock(&p->lock, "pipe");
(*f0)->type = FD_PIPE;
(*f0)->readable = 1;
(*f0)->writable = 0;
(*f0)->pipe = p;
(*f1)->type = FD_PIPE;
(*f1)->readable = 0;
(*f1)->writable = 1;
(*f1)->pipe = p;
return 0;
//PAGEBREAK: 20
bad:
if(p)
kfree((char*)p);
if(*f0)
fileclose(*f0);
if(*f1)
fileclose(*f1);
return -1;
}
void
pipeclose(struct pipe *p, int writable)
{
acquire(&p->lock);
if(writable){
p->writeopen = 0;
wakeup(&p->nread);
} else {
p->readopen = 0;
wakeup(&p->nwrite);
}
if(p->readopen == 0 && p->writeopen == 0){
release(&p->lock);
kfree((char*)p);
} else
release(&p->lock);
}
//PAGEBREAK: 40
int
pipewrite(struct pipe *p, char *addr, int n)
{
int i;
acquire(&p->lock);
for(i = 0; i < n; i++){
while(p->nwrite == p->nread + PIPESIZE){ //DOC: pipewrite-full
if(p->readopen == 0 || myproc()->killed){
release(&p->lock);
return -1;
}
wakeup(&p->nread);
sleep(&p->nwrite, &p->lock); //DOC: pipewrite-sleep
}
p->data[p->nwrite++ % PIPESIZE] = addr[i];
}
wakeup(&p->nread); //DOC: pipewrite-wakeup1
release(&p->lock);
return n;
}
int
piperead(struct pipe *p, char *addr, int n)
{
int i;
acquire(&p->lock);
while(p->nread == p->nwrite && p->writeopen){ //DOC: pipe-empty
if(myproc()->killed){
release(&p->lock);
return -1;
}
sleep(&p->nread, &p->lock); //DOC: piperead-sleep
}
for(i = 0; i < n; i++){ //DOC: piperead-copy
if(p->nread == p->nwrite)
break;
addr[i] = p->data[p->nread++ % PIPESIZE];
}
wakeup(&p->nwrite); //DOC: piperead-wakeup
release(&p->lock);
return i;
}