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//
// File descriptors
//
#include "types.h"
#include "defs.h"
#include "param.h"
#include "fs.h"
#include "file.h"
#include "spinlock.h"
struct devsw devsw[NDEV];
struct {
struct spinlock lock;
struct file file[NFILE];
} ftable;
void
fileinit(void)
{
initlock(&ftable.lock, "ftable");
}
// Allocate a file structure.
struct file*
filealloc(void)
{
struct file *f;
acquire(&ftable.lock);
for(f = ftable.file; f < ftable.file + NFILE; f++){
if(f->ref == 0){
f->ref = 1;
release(&ftable.lock);
return f;
}
}
release(&ftable.lock);
return 0;
}
// Increment ref count for file f.
struct file*
filedup(struct file *f)
{
acquire(&ftable.lock);
if(f->ref < 1)
panic("filedup");
f->ref++;
release(&ftable.lock);
return f;
}
// Close file f. (Decrement ref count, close when reaches 0.)
void
fileclose(struct file *f)
{
struct file ff;
acquire(&ftable.lock);
if(f->ref < 1)
panic("fileclose");
if(--f->ref > 0){
release(&ftable.lock);
return;
}
ff = *f;
f->ref = 0;
f->type = FD_NONE;
release(&ftable.lock);
if(ff.type == FD_PIPE)
pipeclose(ff.pipe, ff.writable);
else if(ff.type == FD_INODE){
begin_trans();
iput(ff.ip);
commit_trans();
}
}
// Get metadata about file f.
int
filestat(struct file *f, struct stat *st)
{
if(f->type == FD_INODE){
ilock(f->ip);
stati(f->ip, st);
iunlock(f->ip);
return 0;
}
return -1;
}
// Read from file f.
int
fileread(struct file *f, char *addr, int n)
{
int r;
if(f->readable == 0)
return -1;
if(f->type == FD_PIPE)
return piperead(f->pipe, addr, n);
if(f->type == FD_INODE){
ilock(f->ip);
if((r = readi(f->ip, addr, f->off, n)) > 0)
f->off += r;
iunlock(f->ip);
return r;
}
panic("fileread");
}
//PAGEBREAK!
// Write to file f.
int
filewrite(struct file *f, char *addr, int n)
{
int r;
if(f->writable == 0)
return -1;
if(f->type == FD_PIPE)
return pipewrite(f->pipe, addr, n);
if(f->type == FD_INODE){
// write a few blocks at a time to avoid exceeding
// the maximum log transaction size, including
// i-node, indirect block, allocation blocks,
// and 2 blocks of slop for non-aligned writes.
// this really belongs lower down, since writei()
// might be writing a device like the console.
int max = ((LOGSIZE-1-1-2) / 2) * 512;
int i = 0;
while(i < n){
int n1 = n - i;
if(n1 > max)
n1 = max;
begin_trans();
ilock(f->ip);
if ((r = writei(f->ip, addr + i, f->off, n1)) > 0)
f->off += r;
iunlock(f->ip);
commit_trans();
if(r < 0)
break;
if(r != n1)
panic("short filewrite");
i += r;
}
return i == n ? n : -1;
}
panic("filewrite");
}