use io;
use types;

use fmt;

export const length: u64 = 512;

export fn lba(no: u64) size = {
	return no * length;
};

export type sector = struct {
	buf: []u8,
	fd: io::file,
	lba_begin: u64,
	lba_end: u64,
};

export fn map(fd: io::file, lba_begin: u64, lba_end: u64) sector = {
	let self = sector {
		buf = alloc([0...], (lba_end - lba_begin + 1)*length),
		fd = fd,
		lba_begin = lba_begin,
		lba_end = lba_end
	};

	return self;
};

export fn finish(self: *sector) void = {
	free(self.buf);
};

export fn fetch(self: *sector) void = {
	// XXX proper error
	io::seek(self.fd, (self.lba_begin * length): io::off, io::whence::SET)!;
	io::read(self.fd, self.buf)!;
};

export fn commit(self: *sector) void = {
	io::seek(self.fd, (self.lba_begin * length): io::off, io::whence::SET)!;
	io::write(self.fd, self.buf)!;
};

export fn commit_at(self: *sector, fd: io::file, lba: u64) void = {
	io::seek(fd, (lba * length): io::off, io::whence::SET)!;
	io::write(fd, self.buf)!;
};