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#include "types.h"
#include "param.h"
#include "x86.h"
#include "mmu.h"
#include "proc.h"
#include "defs.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
int writep; // next index to write
int readp; // next index to read
struct spinlock lock;
char data[PIPESIZE];
};
int
pipe_alloc(struct file **f0, struct file **f1)
{
*f0 = *f1 = 0;
struct pipe *p = 0;
if((*f0 = filealloc()) == 0)
goto oops;
if((*f1 = filealloc()) == 0)
goto oops;
if((p = (struct pipe*) kalloc(PAGE)) == 0)
goto oops;
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;
oops:
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
pipe_close(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);
}
int
pipe_write(struct pipe *p, char *addr, int n)
{
int i;
acquire(&p->lock);
for(i = 0; i < n; i++){
while(((p->writep + 1) % PIPESIZE) == p->readp){
if(p->readopen == 0){
release(&p->lock);
return -1;
}
wakeup(&p->readp);
sleep(&p->writep, &p->lock);
}
p->data[p->writep] = addr[i];
p->writep = (p->writep + 1) % PIPESIZE;
}
release(&p->lock);
wakeup(&p->readp);
return i;
}
int
pipe_read(struct pipe *p, char *addr, int n)
{
int i;
acquire(&p->lock);
while(p->readp == p->writep){
if(p->writeopen == 0){
release(&p->lock);
return 0;
}
sleep(&p->readp, &p->lock);
}
for(i = 0; i < n; i++){
if(p->readp == p->writep)
break;
addr[i] = p->data[p->readp];
p->readp = (p->readp + 1) % PIPESIZE;
}
release(&p->lock);
wakeup(&p->writep);
return i;
}
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