xv6-cs450/fd.c

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#include "types.h"
#include "param.h"
#include "x86.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "fd.h"
#include "spinlock.h"
#include "dev.h"
struct spinlock fd_table_lock;
struct devsw devsw[NDEV];
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struct fd fds[NFD];
/*
* allocate a file descriptor number for curproc.
*/
int
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fd_ualloc(void)
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{
int fd;
struct proc *p = curproc[cpu()];
for(fd = 0; fd < NOFILE; fd++)
if(p->fds[fd] == 0)
return fd;
return -1;
}
/*
* allocate a file descriptor structure
*/
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struct fd *
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fd_alloc(void)
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{
int i;
acquire(&fd_table_lock);
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for(i = 0; i < NFD; i++){
if(fds[i].type == FD_CLOSED){
fds[i].type = FD_NONE;
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fds[i].ref = 1;
release(&fd_table_lock);
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return fds + i;
}
}
release(&fd_table_lock);
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return 0;
}
/*
* addr is a kernel address, pointing into some process's p->mem.
*/
int
fd_write(struct fd *fd, char *addr, int n)
{
if(fd->writeable == 0)
return -1;
if(fd->type == FD_PIPE){
return pipe_write(fd->pipe, addr, n);
} else if (fd->type == FD_FILE) {
return writei (fd->ip, addr, n);
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} else {
panic("fd_write");
return -1;
}
}
int
fd_read(struct fd *fd, char *addr, int n)
{
if(fd->readable == 0)
return -1;
if(fd->type == FD_PIPE){
return pipe_read(fd->pipe, addr, n);
} else if(fd->type == FD_FILE){
ilock(fd->ip);
int cc = readi(fd->ip, addr, fd->off, n);
if(cc > 0)
fd->off += cc;
iunlock(fd->ip);
return cc;
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} else {
panic("fd_read");
return -1;
}
}
void
fd_close(struct fd *fd)
{
acquire(&fd_table_lock);
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if(fd->ref < 1 || fd->type == FD_CLOSED)
panic("fd_close");
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if(--fd->ref == 0){
if(fd->type == FD_PIPE){
pipe_close(fd->pipe, fd->writeable);
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} else if(fd->type == FD_FILE){
idecref(fd->ip);
} else {
panic("fd_close");
}
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fd->ref = 0;
fd->type = FD_CLOSED;
}
release(&fd_table_lock);
}
void
fd_incref(struct fd *fd)
{
acquire(&fd_table_lock);
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if(fd->ref < 1 || fd->type == FD_CLOSED)
panic("fd_incref");
fd->ref++;
release(&fd_table_lock);
}