xv6-cs450/file.c
2006-09-06 18:43:45 +00:00

150 lines
2.7 KiB
C

#include "types.h"
#include "stat.h"
#include "param.h"
#include "x86.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "file.h"
#include "spinlock.h"
#include "dev.h"
#include "fs.h"
#include "fsvar.h"
struct spinlock fd_table_lock;
struct devsw devsw[NDEV];
struct file file[NFILE];
void
fileinit(void)
{
initlock(&fd_table_lock, "fd_table");
}
// Allocate a file descriptor number for curproc.
int
fdalloc(void)
{
int fd;
struct proc *p = curproc[cpu()];
for(fd = 0; fd < NOFILE; fd++)
if(p->ofile[fd] == 0)
return fd;
return -1;
}
// Allocate a file descriptor structure
struct file*
filealloc(void)
{
int i;
acquire(&fd_table_lock);
for(i = 0; i < NFILE; i++){
if(file[i].type == FD_CLOSED){
file[i].type = FD_NONE;
file[i].ref = 1;
release(&fd_table_lock);
return file + i;
}
}
release(&fd_table_lock);
return 0;
}
// Write to file descriptor;
// addr is a kernel address, pointing into some process's p->mem.
int
filewrite(struct file *fd, char *addr, int n)
{
if(fd->writable == 0)
return -1;
if(fd->type == FD_PIPE){
return pipe_write(fd->pipe, addr, n);
} else if(fd->type == FD_FILE) {
ilock(fd->ip);
int r = writei(fd->ip, addr, fd->off, n);
if(r > 0) {
fd->off += r;
}
iunlock(fd->ip);
return r;
} else {
panic("filewrite");
return -1;
}
}
// Read from file descriptor.
int
fileread(struct file *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;
} else {
panic("fileread");
return -1;
}
}
// Close file descriptor.
void
fileclose(struct file *fd)
{
acquire(&fd_table_lock);
if(fd->ref < 1 || fd->type == FD_CLOSED)
panic("fileclose");
if(--fd->ref == 0){
struct file dummy = *fd;
fd->ref = 0;
fd->type = FD_CLOSED;
release(&fd_table_lock);
if(dummy.type == FD_PIPE){
pipe_close(dummy.pipe, dummy.writable);
} else if(dummy.type == FD_FILE){
idecref(dummy.ip);
} else {
panic("fileclose");
}
} else {
release(&fd_table_lock);
}
}
// Get metadata about file descriptor.
int
filestat(struct file *fd, struct stat *st)
{
if(fd->type == FD_FILE){
ilock(fd->ip);
stati(fd->ip, st);
iunlock(fd->ip);
return 0;
} else
return -1;
}
// Increment file descriptor reference count.
void
fileincref(struct file *fd)
{
acquire(&fd_table_lock);
if(fd->ref < 1 || fd->type == FD_CLOSED)
panic("fileincref");
fd->ref++;
release(&fd_table_lock);
}