xv6-cs450/file.c
2006-09-08 13:44:42 +00:00

137 lines
2.5 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 file_table_lock;
struct devsw devsw[NDEV];
struct file file[NFILE];
void
fileinit(void)
{
initlock(&file_table_lock, "file_table");
}
// Allocate a file structure
struct file*
filealloc(void)
{
int i;
acquire(&file_table_lock);
for(i = 0; i < NFILE; i++){
if(file[i].type == FD_CLOSED){
file[i].type = FD_NONE;
file[i].ref = 1;
release(&file_table_lock);
return file + i;
}
}
release(&file_table_lock);
return 0;
}
// Write to file f. Addr is kernel address.
int
filewrite(struct file *f, char *addr, int n)
{
if(f->writable == 0)
return -1;
if(f->type == FD_PIPE){
return pipe_write(f->pipe, addr, n);
} else if(f->type == FD_FILE) {
ilock(f->ip);
int r = writei(f->ip, addr, f->off, n);
if(r > 0) {
f->off += r;
}
iunlock(f->ip);
return r;
} else {
panic("filewrite");
return -1;
}
}
// Read from file f. Addr is kernel address.
int
fileread(struct file *f, char *addr, int n)
{
if(f->readable == 0)
return -1;
if(f->type == FD_PIPE){
return pipe_read(f->pipe, addr, n);
} else if(f->type == FD_FILE){
ilock(f->ip);
int cc = readi(f->ip, addr, f->off, n);
if(cc > 0)
f->off += cc;
iunlock(f->ip);
return cc;
} else {
panic("fileread");
return -1;
}
}
// Close file f. (Decrement ref count, close when reaches 0.)
void
fileclose(struct file *f)
{
acquire(&file_table_lock);
if(f->ref < 1 || f->type == FD_CLOSED)
panic("fileclose");
if(--f->ref == 0){
struct file dummy = *f;
f->ref = 0;
f->type = FD_CLOSED;
release(&file_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(&file_table_lock);
}
}
// Get metadata about file f.
int
filestat(struct file *f, struct stat *st)
{
if(f->type == FD_FILE){
ilock(f->ip);
stati(f->ip, st);
iunlock(f->ip);
return 0;
} else
return -1;
}
// Increment ref count for file f.
void
fileincref(struct file *f)
{
acquire(&file_table_lock);
if(f->ref < 1 || f->type == FD_CLOSED)
panic("fileincref");
f->ref++;
release(&file_table_lock);
}