gptman: implement convert

1 files changed, 36 insertions, 4 deletions

diff --git a/mbr/mbr.ha b/mbr/mbr.ha
index d0622d2..31a9534 100644
--- a/mbr/mbr.ha
+++ b/mbr/mbr.ha
@@ -8,24 +8,56 @@ def mbr_lba: size = 0;
 export type nombr = !void;
 
 export type mbr = struct {
+	bootsector_sec: sector::sector,
+	bootsector: *bootsector
+};
+
+export type bootsector = struct {
 	@offset(0) bootstrap: [440]u8,
 	@offset(440) udid: u32,
 	@offset(444) reserved: u16,
-	@offset(446) entries: [4]mbr_entry,
+	@offset(446) entries: [4]entry,
 	@offset(510) magic: u16,
 };
 
-export type mbr_entry = struct {
+export type entry = struct {
 	@offset(0) attributes: u8,
 	@offset(4) part_type: u8,
 	@offset(8) lba_begin: u32,
-	@offset(12) lba_end: u32, 
+	@offset(12) length: u32, 
 };
 
-export fn validate(self: *mbr) bool = {
+export fn bootsector_validate(self: *bootsector) bool = {
 	if (self.magic != 0xaa55) {
 		return false;
 	};
 
 	return true;
 };
+
+export fn from(fd: io::file) (*mbr | nombr | io::error) = {
+	const bootsector_sec = sector::map(fd, 0, 1);
+	sector::fetch(&bootsector_sec)?;
+
+	const bootsector = bootsector_sec.buf: *[*]u8: *bootsector;
+	if (!bootsector_validate(bootsector)) {
+		sector::finish(&bootsector_sec);
+		return nombr;
+	};
+
+	let self = alloc(mbr {
+		bootsector_sec = bootsector_sec,
+		bootsector = bootsector
+	});
+
+	return self;
+};
+
+export fn partstream_reader(self: *mbr, entry: *entry) (io::limitstream | io::error) = {
+	const fd = self.bootsector_sec.fd;
+	const part = entry.lba_begin * sector::sector_length;
+	const length = entry.length * sector::sector_length;
+
+	io::seek(fd, part: io::off, io::whence::SET)?;
+	return io::limitreader(fd, length);
+};