xv6/pipe.c

122 lines
2.2 KiB
C

#include "types.h"
#include "defs.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "file.h"
#include "spinlock.h"
#define PIPESIZE 512
struct pipe {
int readopen; // read fd is still open
int writeopen; // write fd is still open
uint writep; // next index to write
uint readp; // next index to read
struct spinlock lock;
char data[PIPESIZE];
};
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(PAGE)) == 0)
goto bad;
p->readopen = 1;
p->writeopen = 1;
p->writep = 0;
p->readp = 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, PAGE);
if(*f0){
(*f0)->type = FD_NONE;
fileclose(*f0);
}
if(*f1){
(*f1)->type = FD_NONE;
fileclose(*f1);
}
return -1;
}
void
pipeclose(struct pipe *p, int writable)
{
acquire(&p->lock);
if(writable){
p->writeopen = 0;
wakeup(&p->readp);
} else {
p->readopen = 0;
wakeup(&p->writep);
}
release(&p->lock);
if(p->readopen == 0 && p->writeopen == 0)
kfree((char*)p, PAGE);
}
//PAGEBREAK: 30
int
pipewrite(struct pipe *p, char *addr, int n)
{
int i;
acquire(&p->lock);
for(i = 0; i < n; i++){
while(p->writep == p->readp + PIPESIZE) {
if(p->readopen == 0 || cp->killed){
release(&p->lock);
return -1;
}
wakeup(&p->readp);
sleep(&p->writep, &p->lock);
}
p->data[p->writep++ % PIPESIZE] = addr[i];
}
wakeup(&p->readp);
release(&p->lock);
return i;
}
int
piperead(struct pipe *p, char *addr, int n)
{
int i;
acquire(&p->lock);
while(p->readp == p->writep && p->writeopen){
if(cp->killed){
release(&p->lock);
return -1;
}
sleep(&p->readp, &p->lock);
}
for(i = 0; i < n; i++){
if(p->readp == p->writep)
break;
addr[i] = p->data[p->readp++ % PIPESIZE];
}
wakeup(&p->writep);
release(&p->lock);
return i;
}