Further implementing everthing again.

Added Decompressor vtable interface.
Directory table parsing
Inode reading
Metadata Reader

src/util/metadata.zig

@@ -0,0 +1,76 @@
+const std = @import("std");
+const Reader = std.Io.Reader;
+const Writer = std.Io.Writer;
+const Limit = std.Io.Limit;
+
+const Decompressor = @import("../decomp.zig");
+
+const Header = packed struct {
+    size: u15,
+    uncompressed: bool,
+};
+
+const MetadataReader = @This();
+
+rdr: *Reader,
+decomp: *Decompressor,
+
+read_buf: [8192]u8 = undefined,
+interface: Reader = .{
+    .buffer = &([1]u8{undefined} ** 8192),
+    .end = 0,
+    .seek = 0,
+    .vtable = &.{
+        .stream = stream,
+        .discard = discard,
+        .readVec = readVec,
+    },
+},
+
+pub fn init(rdr: *Reader, decomp: *Decompressor) MetadataReader {
+    return .{ .rdr = rdr, .decomp = decomp };
+}
+fn advanceBuffer(self: *MetadataReader) Reader.Error!void {
+    self.interface.seek = 0;
+    var hdr: Header = undefined;
+    try self.rdr.readSliceEndian(Header, @ptrCast(&hdr), .little);
+    try self.rdr.readSliceAll(self.read_buf[0..hdr.size]);
+    if (hdr.uncompressed) {
+        @memcpy(self.interface.buffer[0..hdr.size], self.read_buf[0..hdr.size]);
+        self.interface.end = hdr.size;
+        return;
+    }
+    self.interface.end = self.decomp.decompress(self.read_buf[0..hdr.size], self.interface.buffer) catch |err| return switch (err) {
+        error.OutOfMemory => error.ReadFailed,
+        else => err,
+    };
+}
+
+fn stream(rdr: *Reader, wrt: *Writer, limit: Limit) Reader.StreamError!usize {
+    var self: *MetadataReader = @fieldParentPtr("interface", rdr);
+    if (rdr.seek == rdr.end) try self.advanceBuffer();
+    const to_write = @min(@intFromEnum(limit), rdr.end - rdr.seek);
+    const wrote = try wrt.write(rdr.buffer[rdr.seek .. rdr.seek + to_write]);
+    rdr.seek += wrote;
+    return wrote;
+}
+fn discard(rdr: *Reader, limit: Limit) Reader.Error!usize {
+    var self: *MetadataReader = @fieldParentPtr("interface", rdr);
+    if (rdr.seek == rdr.end) try self.advanceBuffer();
+    const to_adv = @min(@intFromEnum(limit), rdr.end - rdr.seek);
+    rdr.seek += to_adv;
+    return to_adv;
+}
+fn readVec(rdr: *Reader, vec: [][]u8) Reader.Error!usize {
+    var self: *MetadataReader = @fieldParentPtr("interface", rdr);
+    if (rdr.seek == rdr.end) try self.advanceBuffer();
+    var wrote = 0;
+    for (vec) |v| {
+        if (rdr.seek == rdr.end) break;
+        const to_write = @min(v.len, rdr.end - rdr.seek);
+        @memcpy(v[0..to_write], rdr.buffer[rdr.seek .. rdr.seek + to_write]);
+        wrote += to_write;
+        rdr.seek += to_write;
+    }
+    return wrote;
+}

src/util/offset_file.zig

@@ -11,3 +11,10 @@ pub fn readerAt(self: OffsetFile, offset: u64, buf: []u8) !FileReader {
     try rdr.seekTo(self.offset + offset);
     return rdr;
 }
+pub fn valueAt(self: OffsetFile, comptime T: type, offset: u64) !T {
+    var rdr = self.fil.reader(&[0]u8{});
+    try rdr.seekTo(self.offset + offset);
+    var new: T = undefined;
+    try rdr.interface.readSliceEndian(T, @ptrCast(&new), .little);
+    return new;
+}