Further work on making everything work

Directory table reading
Finished MetadataReader

src/archive.zig

@@ -1,9 +1,10 @@
 const std = @import("std");
 const Io = std.Io;
 
+const util = @import("utils/util.zig");
+
 const File = @import("file.zig");
 const Inode = @import("inode.zig");
-const Util = @import("utils/util.zig");
 const Decomp = @import("decomp.zig");
 
 const Options = @import("options.zig");
@@ -13,6 +14,7 @@ const Archive = @This();
 map: Io.File.MemoryMap,
 
 super: Super,
+root_inode_ref: Inode.Reference,
 
 pub fn open(io: Io, file: Io.File, offset: u64) !Archive {
     var map = try file.createMemoryMap(io, .{
@@ -21,22 +23,41 @@ pub fn open(io: Io, file: Io.File, offset: u64) !Archive {
         .protection = .{ .read = true },
     });
 
-    var superblock = Util.readValue(Superblock, map.memory[0..@sizeOf(Superblock)]);
-    const super = try superblock.check();
+    var superblock = util.readValue(Superblock, map.memory[0..@sizeOf(Superblock)]);
+    const super = try superblock.checkAndMinimize();
 
     return .{
         .map = map,
 
         .super = super,
+        .root_inode_ref = superblock.root_inode_ref,
     };
 }
 pub fn close(self: *Archive, io: Io) void {
     self.map.destroy(io);
 }
 
-pub fn root(self: *Archive) !File {
-    _ = self;
-    return error.TODO;
+pub fn root(self: *Archive, alloc: std.mem.Allocator) !File {
+    return .{
+        .alloc = alloc,
+
+        .data = self.map.memory,
+        .super = self.super,
+
+        .inode = try .fromRef(
+            alloc,
+            self.map.memory,
+            self.root_inode_ref,
+            self.super,
+        ),
+        .name = "",
+    };
+}
+pub fn openFile(self: *Archive, alloc: std.mem.Allocator, filepath: []const u8) !File {
+    var root_file = try self.root(alloc);
+    defer root_file.deinit();
+
+    return root.open(alloc, filepath);
 }
 pub fn extract(self: *Archive, alloc: std.mem.Allocator, io: Io, ext_loc: []const u8, options: Options) !void {
     _ = self;
@@ -59,11 +80,25 @@ const Superblock = extern struct {
     frag_count: u32,
     compression: Decomp.Enum,
     block_log: u16,
-    flags: u16, // TODO: break out into packed struct.
+    flags: packed struct(u16) {
+        inode_uncompressed: bool,
+        data_uncompressed: bool,
+        check: bool,
+        fragment_uncompressed: bool,
+        fragment_never: bool,
+        fragment_always: bool,
+        de_duplicate: bool,
+        exportable: bool,
+        xattr_uncompressed: bool,
+        xattr_never: bool,
+        compression_options: bool,
+        id_uncompressed: bool,
+        _: u4,
+    },
     id_count: u16,
     version_major: u16,
     version_minor: u16,
-    root_inode_ref: Inode.Reference, // TODO: Change to inode reference packed struct.
+    root_inode_ref: Inode.Reference,
     size: u64,
     id_table_start: u64,
     xattr_table_start: u64,
@@ -72,20 +107,21 @@ const Superblock = extern struct {
     frag_table_start: u64,
     export_table_start: u64,
 
-    fn check(self: Superblock) !Super {
+    fn checkAndMinimize(self: Superblock) !Super {
         if (self.magic != MAGIC)
             return error.InvalidMagic;
         if (self.version_major != 4 or self.version_minor != 0)
             return error.IncompatibleVersion;
         if (std.math.log2(self.block_size) != self.block_log)
             return error.BadBlockLog;
+        if (self.flags.check)
+            return error.BadCheckFlag;
 
         return .{
             .block_size = self.block_size,
             .frag_count = self.frag_count,
             .decomp_fn = try self.compression.func(),
             .id_count = self.id_count,
-            .root_inode_ref = self.root_inode_ref,
             .id_table_start = self.id_table_start,
             .xattr_table_start = self.xattr_table_start,
             .inode_table_start = self.inode_table_start,
@@ -100,7 +136,6 @@ pub const Super = struct {
     frag_count: u32,
     decomp_fn: Decomp.Fn,
     id_count: u16,
-    root_inode_ref: Inode.Reference,
     id_table_start: u64,
     xattr_table_start: u64,
     inode_table_start: u64,

src/decomp.zig

@@ -16,7 +16,7 @@ pub const Enum = enum(u16) {
         return switch (self) {
             .gzip => if (build.zig_decomp) zigZlib else cZlib,
             .lzma => if (build.zig_decomp) zigLzma else cLzma,
-            .lzo => if (build.zig_decomp) error.LzoUnsupported else cLzo,
+            .lzo => if (build.zig_decomp or !build.allow_lzo) error.LzoUnsupported else cLzo,
             .xz => if (build.zig_decomp) zigXz else cXz,
             .lz4 => if (build.zig_decomp) error.Lz4Unsupported else cLz4,
             .zstd => if (build.zig_decomp) zigZstd else cZstd,
@@ -25,7 +25,7 @@ pub const Enum = enum(u16) {
 };
 pub const Fn = *const fn (alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize;
 
-pub const Error = Io.Reader.Error;
+pub const Error = Io.Reader.Error || std.mem.Allocator.Error;
 
 // Actual decomp functions
 
@@ -45,56 +45,102 @@ fn cZlib(_: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
     const res = c.inflate(&stream, c.Z_FULL_FLUSH);
     if (res != c.Z_OK)
         return Error.ReadFailed;
-    return 0;
+    return stream.total_out;
 }
 
 fn zigLzma(alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
     var rdr: Io.Reader = .fixed(in);
-    var decomp: std.compress.lzma.Decompress = .initOptions(&rdr, alloc, out, .{}, 0);
+
+    var decomp: std.compress.lzma.Decompress = .initOptions(&rdr, alloc, &[0]u8{}, .{}, 0);
+    defer decomp.deinit();
+
+    return decomp.reader.readSliceShort(out);
 }
-fn cLzma(alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
-    _ = alloc;
-    _ = in;
-    _ = out;
-    return Error.ReadFailed;
+fn cLzma(_: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
+    var stream: c.lzma_stream = .{
+        .avail_in = in.len,
+        .next_in = in.ptr,
+        .avail_out = out.len,
+        .next_out = out.ptr,
+    };
+    defer c.lzma_end(&stream);
+
+    var res = c.lzma_alone_decoder(&stream, 0);
+    if (res != c.LZMA_OK)
+        return Error.ReadFailed;
+
+    while (res == c.LZMA_OK)
+        res = c.lzma_code(&stream, c.LZMA_RUN);
+    if (res != c.LZMA_FINISH)
+        return Error.ReadFailed;
+
+    return stream.total_out;
 }
 
-fn cLzo(alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
-    _ = alloc;
-    _ = in;
-    _ = out;
+fn cLzo(_: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
+    var res = c.lzo_init();
+    if (res != c.LZO_E_OK)
+        return Error.ReadFailed;
+
+    var len = out.len;
+    res = c.lzo1x_decompress(in.ptr, in.len, out.ptr, &len, null);
+    if (res != c.LZO_E_OK)
+        return Error.ReadFailed;
+
     return Error.ReadFailed;
 }
 
 fn zigXz(alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
-    _ = alloc;
-    _ = in;
-    _ = out;
-    return Error.ReadFailed;
+    var rdr: Io.Reader = .fixed(in);
+
+    var decomp: std.compress.xz.Decompress = .init(&rdr, alloc, &[0]u8{});
+    defer decomp.deinit();
+
+    return decomp.reader.readSliceShort(out);
 }
-fn cXz(alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
-    _ = alloc;
-    _ = in;
-    _ = out;
-    return Error.ReadFailed;
+fn cXz(_: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
+    var stream: c.lzma_stream = .{
+        .avail_in = in.len,
+        .next_in = in.ptr,
+        .avail_out = out.len,
+        .next_out = out.ptr,
+    };
+    defer c.lzma_end(&stream);
+
+    var res = c.lzma_stream_decoder(&stream, 0, 0);
+    if (res != c.LZMA_OK)
+        return Error.ReadFailed;
+
+    while (res == c.LZMA_OK)
+        res = c.lzma_code(&stream, c.LZMA_RUN);
+    if (res != c.LZMA_FINISH)
+        return Error.ReadFailed;
+
+    return stream.total_out;
 }
 
-fn cLz4(alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
-    _ = alloc;
-    _ = in;
-    _ = out;
-    return Error.ReadFailed;
+fn cLz4(_: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
+    const res = c.LZ4_decompress_safe(in.ptr, out.ptr, @intCast(in.len), @intCast(out.len));
+    if (res < 0) return Error.ReadFailed;
+
+    return @abs(res);
 }
 
 fn zigZstd(alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
-    _ = alloc;
-    _ = in;
-    _ = out;
-    return Error.ReadFailed;
+    var rdr: Io.Reader = .fixed(in);
+
+    const buf = try alloc.alloc(u8, 1024 * 1024);
+    defer alloc.free(buf);
+
+    var decomp: std.compress.zstd.Decompress = .init(&rdr, buf, .{
+        .window_len = 1024 * 1024,
+    });
+
+    return decomp.reader.readSliceShort(out);
 }
-fn cZstd(alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
-    _ = alloc;
-    _ = in;
-    _ = out;
-    return Error.ReadFailed;
+fn cZstd(_: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
+    const res = c.ZSTD_decompress(out.ptr, out.len, in.ptr, in.len);
+    if (c.ZSTD_isError(res) == 1)
+        return Error.ReadFailed;
+    return res;
 }

src/dir.zig

@@ -0,0 +1,74 @@
+const std = @import("std");
+const Io = std.Io;
+
+const utils = @import("utils/util.zig");
+
+const Inode = @import("inode.zig");
+
+const Directory = @This();
+
+entries: []Entry,
+
+pub fn read(alloc: std.mem.Allocator, rdr: *Io.Reader, size: u32) !Directory {
+    var red: u32 = 3;
+
+    var out: std.ArrayList(Entry) = try .initCapacity(alloc, 10);
+    errdefer out.deinit(alloc);
+
+    while (red < size) {
+        const hdr: Header = try utils.readValueRdr(Header, rdr);
+        red += @sizeOf(Header);
+
+        try out.ensureUnusedCapacity(alloc, hdr.count + 1);
+
+        for (hdr.count + 1) |_| {
+            const raw: RawEntry = try utils.readValueRdr(RawEntry, rdr);
+
+            const name = try alloc.alloc(u8, raw.name_size + 1);
+            errdefer alloc.free(name);
+
+            try rdr.readSliceAll(name);
+
+            out.addOneAssumeCapacity().* = .{
+                .start = hdr.start,
+                .offset = raw.offset,
+                .type = raw.type,
+                .name = name,
+            };
+
+            red += @sizeOf(RawEntry + raw.name_size + 1);
+        }
+    }
+
+    return out.toOwnedSlice(alloc);
+}
+pub fn deinit(self: Directory, alloc: std.mem.Allocator) void {
+    for (self.entries) |entry|
+        entry.deinit(alloc);
+
+    alloc.free(self.entries);
+}
+
+// Types
+
+pub const Entry = struct {
+    start: u32,
+    offset: u16,
+    type: Inode.Type,
+    name: []const u8,
+
+    pub fn deinit(self: Entry, alloc: std.mem.Allocator) void {
+        alloc.free(self.name);
+    }
+};
+const Header = extern struct {
+    count: u32,
+    start: u32,
+    inode_num: u32,
+};
+const RawEntry = extern struct {
+    offset: u16,
+    inode_num_offset: i16,
+    type: Inode.Type,
+    name_size: u16,
+};

src/file.zig

@@ -2,15 +2,75 @@ const std = @import("std");
 const Io = std.Io;
 
 const Inode = @import("inode.zig");
+const Directory = @import("dir.zig");
+const MetadataReader = @import("utils/meta.zig");
+const Super = @import("archive.zig").Super;
 
 const File = @This();
 
 alloc: std.mem.Allocator,
 
+data: []u8,
+super: Super,
+
 name: []const u8,
 inode: Inode,
 
-pub fn close(self: File) void {
+pub fn copy(self: File, alloc: std.mem.Allocator) !File {
+    const new_name = try alloc.dupe(u8, self.name);
+    errdefer alloc.free(new_name);
+
+    return .{
+        .alloc = alloc,
+
+        .data = self.data,
+        .super = self.super,
+
+        .name = new_name,
+        .inode = try self.inode.copy(alloc),
+    };
+}
+pub fn deinit(self: File) void {
     self.inode.deinit(self.alloc);
     self.alloc.free(self.name);
 }
+
+pub fn open(self: File, alloc: std.mem.Allocator, filepath: []const u8) !File {
+    switch (self.inode.header.type) {
+        .dir, .ext_dir => {},
+        else => return error.NotDirectory,
+    }
+
+    const path = std.mem.trim(u8, filepath, "/");
+
+    if (path.len == 0 or (path.len == 1 and path[0] == '.'))
+        return self.copy(alloc);
+
+    const first_element: []u8 = std.mem.sliceTo(path, '/');
+
+    var dir_size: u32 = undefined;
+    var dir_rdr: MetadataReader = undefined;
+
+    switch (self.inode.data) {
+        .dir => |d| {
+            dir_rdr = .init(alloc, self.data[d.block..], self.super.decomp_fn);
+            try dir_rdr.interface.discardAll(d.offset);
+
+            dir_size = d.size;
+        },
+        .ext_dir => |d| {
+            dir_rdr = .init(alloc, self.data[d.block..], self.super.decomp_fn);
+            try dir_rdr.interface.discardAll(d.offset);
+
+            dir_size = d.size;
+        },
+        else => unreachable,
+    }
+
+    const inode: Inode = {
+        var dir: Directory = try .read(alloc, &dir_rdr.interface, dir_size);
+        defer dir.deinit(alloc);
+    };
+
+    return error.TODO;
+}

src/inode.zig

@@ -1,11 +1,58 @@
 const std = @import("std");
 const Io = std.Io;
 
+const util = @import("utils/util.zig");
+
+const MetadataReader = @import("utils/meta.zig");
+const Super = @import("archive.zig").Super;
+
 const Inode = @This();
 
 header: Header,
 data: Data,
 
+pub fn fromRef(alloc: std.mem.Allocator, data: []u8, ref: Reference, super: Super) !Inode {
+    var meta: MetadataReader = .init(alloc, data[super.inode_table_start + ref.start ..], super.decomp_fn);
+    try meta.interface.discardAll(ref.offset);
+
+    return read(alloc, &meta.interface, super.block_size);
+}
+pub fn read(alloc: std.mem.Allocator, rdr: *Io.Reader, block_size: u32) !Inode {
+    const hdr = try util.readValueRdr(Header, rdr);
+
+    return .{
+        .header = hdr,
+        .data = switch (hdr.type) {
+            .dir => .{ .dir = try .read(rdr) },
+            .file => .{ .file = try .read(rdr, alloc, block_size) },
+            .symlink => .{ .symlink = try .read(rdr, alloc) },
+            .block_dev => .{ .block_dev = try .read(rdr) },
+            .char_dev => .{ .char_dev = try .read(rdr) },
+            .fifo => .{ .fifo = try .read(rdr) },
+            .socket => .{ .socket = try .read(rdr) },
+            .ext_dir => .{ .ext_dir = try .read(rdr) },
+            .ext_file => .{ .ext_file = try .read(rdr, alloc, block_size) },
+            .ext_symlink => .{ .ext_symlink = try .read(rdr, alloc) },
+            .ext_block_dev => .{ .ext_block_dev = try .read(rdr) },
+            .ext_char_dev => .{ .ext_char_dev = try .read(rdr) },
+            .ext_fifo => .{ .ext_fifo = try .read(rdr) },
+            .ext_socket => .{ .ext_socket = try .read(rdr) },
+        },
+    };
+}
+pub fn copy(self: Inode, alloc: std.mem.Allocator) !Inode {
+    var new_inode = self;
+
+    switch (new_inode.data) {
+        .file => |*f| f.blocks = try alloc.dupe(BlockSize, f.blocks),
+        .ext_file => |*f| f.blocks = try alloc.dupe(BlockSize, f.blocks),
+        .symlink => |*f| f.target = try alloc.dupe(u8, f.target),
+        .ext_symlink => |*f| f.target = try alloc.dupe(u8, f.target),
+        else => {},
+    }
+
+    return new_inode;
+}
 pub fn deinit(self: Inode, alloc: std.mem.Allocator) void {
     switch (self.data) {
         .file => |f| alloc.free(f.blocks),
@@ -20,10 +67,16 @@ pub fn deinit(self: Inode, alloc: std.mem.Allocator) void {
 
 pub const Reference = packed struct(u64) {
     offset: u16,
-    block: u32,
+    start: u32,
     _: u16,
 };
 
+pub const BlockSize = packed struct(u32) {
+    size: u23,
+    uncompressed: bool,
+    _: u8,
+};
+
 pub const Type = enum(u16) {
     dir,
     file,
@@ -42,7 +95,7 @@ pub const Type = enum(u16) {
 };
 
 pub const Header = extern struct {
-    type: Type, // TODO: enum
+    type: Type,
     permission: u16,
     uid_idx: u16,
     gid_idx: u16,
@@ -60,7 +113,7 @@ pub const Data = union(Type) {
     socket: Fifo,
     ext_dir: ExtDir,
     ext_file: ExtFile,
-    ext_symlink: ExtSymlink,
+    ext_symlink: Symlink,
     ext_block_dev: ExtDev,
     ext_char_dev: ExtDev,
     ext_fifo: ExtFifo,
@@ -70,38 +123,145 @@ pub const Data = union(Type) {
 // Inode data types
 
 pub const Dir = extern struct {
-    block: u32,
+    start: u32,
     hard_links: u32,
     size: u16,
     offset: u16,
     parent_inode_num: u32,
+
+    pub fn read(rdr: *Io.Reader) !Dir {
+        return util.readValueRdr(Dir, rdr);
+    }
 };
 pub const ExtDir = extern struct {
     hard_links: u32,
     size: u32,
-    block: u32,
+    start: u32,
     parent_inode_num: u32,
     idx_count: u16,
     offset: u16,
     xattr_idx: u32,
+
+    pub fn read(rdr: *Io.Reader) !ExtDir {
+        return util.readValueRdr(ExtDir, rdr);
+    }
 };
 
 pub const File = struct {
-    blocks: []u64,
+    start: u32,
+    frag_idx: u32,
+    frag_offset: u32,
+    size: u32,
+    blocks: []BlockSize,
+
+    pub fn read(rdr: *Io.Reader, alloc: std.mem.Allocator, block_size: u32) !File {
+        var raw: [16]u8 = undefined;
+        try rdr.readSliceAll(&raw);
+
+        const frag_idx = std.mem.readInt(u32, raw[4..8], .little);
+        const size = std.mem.readInt(u32, raw[12..16], .little);
+
+        var num = size / block_size;
+        if (frag_idx == 0xFFFFFFFF and size % block_size > 0)
+            num += 1;
+
+        const blocks = try alloc.alloc(BlockSize, num);
+        try rdr.readSliceEndian(BlockSize, blocks, .little);
+
+        return .{
+            .start = std.mem.readInt(u32, raw[0..4], .little),
+            .frag_idx = frag_idx,
+            .frag_offset = std.mem.readInt(u32, raw[8..12], .little),
+            .size = size,
+            .blocks = blocks,
+        };
+    }
 };
 pub const ExtFile = struct {
-    blocks: []u64,
+    start: u64,
+    size: u64,
+    hard_links: u32,
+    frag_idx: u32,
+    frag_offset: u32,
+    xattr_idx: u32,
+    blocks: []BlockSize,
+
+    pub fn read(rdr: *Io.Reader, alloc: std.mem.Allocator, block_size: u32) !ExtFile {
+        var raw: [40]u8 = undefined;
+        try rdr.readSliceAll(&raw);
+
+        const frag_idx = std.mem.readInt(u32, raw[28..32], .little);
+        const size = std.mem.readInt(u64, raw[8..16], .little);
+
+        var num = size / block_size;
+        if (frag_idx == 0xFFFFFFFF and size % block_size > 0)
+            num += 1;
+
+        const blocks = try alloc.alloc(BlockSize, num);
+        try rdr.readSliceEndian(BlockSize, blocks, .little);
+
+        return .{
+            .start = std.mem.readInt(u64, raw[0..8], .little),
+            .size = size,
+            .hard_links = std.mem.readInt(u32, raw[24..28], .little),
+            .frag_idx = frag_idx,
+            .frag_offset = std.mem.readInt(u32, raw[32..36], .little),
+            .xattr_idx = std.mem.readInt(u32, raw[36..], .little),
+            .blocks = blocks,
+        };
+    }
 };
 
 pub const Symlink = struct {
+    hard_links: u32,
     target: []const u8,
-};
-pub const ExtSymlink = struct {
-    target: []const u8,
+
+    pub fn read(rdr: *Io.Reader, alloc: std.mem.Allocator) !Symlink {
+        var raw: [8]u8 = undefined;
+        try rdr.readSliceAll(&raw);
+
+        const target = try alloc.alloc(u8, std.mem.readInt(u32, raw[4..], .little));
+        errdefer alloc.free(target);
+
+        try rdr.readSliceEndian(u8, target, .little);
+
+        return .{
+            .hard_links = std.mem.readInt(u32, raw[0..4], .little),
+            .target = target,
+        };
+    }
 };
 
-pub const Dev = extern struct {};
-pub const ExtDev = extern struct {};
+pub const Dev = extern struct {
+    hard_links: u32,
+    device: u32,
 
-pub const Fifo = extern struct {};
-pub const ExtFifo = extern struct {};
+    pub fn read(rdr: *Io.Reader) !Dev {
+        return util.readValueRdr(Dev, rdr);
+    }
+};
+pub const ExtDev = extern struct {
+    hard_links: u32,
+    device: u32,
+    xattr_idx: u32,
+
+    pub fn read(rdr: *Io.Reader) !ExtDev {
+        return util.readValue(ExtDev, rdr);
+    }
+};
+
+pub const Fifo = extern struct {
+    hard_links: u32,
+
+    pub fn read(rdr: *Io.Reader) !Fifo {
+        return util.readValueRdr(Fifo, rdr);
+    }
+};
+pub const ExtFifo = extern struct {
+    hard_links: u32,
+    xattr_idx: u32,
+
+    pub fn read(rdr: *Io.Reader) !ExtFifo {
+        return util.readValueRdr(ExtFifo, rdr);
+    }
+};

src/tests.zig

@@ -17,6 +17,6 @@ test "Open" {
 
     std.debug.print("{}\n", .{arc.super});
 
-    var root = try arc.root();
+    var root = try arc.root(alloc);
     defer root.close();
 }

src/utils/meta.zig

@@ -1,8 +1,109 @@
 const std = @import("std");
+const Io = std.Io;
+
+const util = @import("util.zig");
 
 const Decomp = @import("../decomp.zig");
 
 const MetadataReader = @This();
 
+alloc: std.mem.Allocator,
+
 data: []u8,
 decomp: Decomp.Fn,
+
+decomp_block: [8192]u8 = undefined,
+
+interface: Io.Reader = .{
+    .buffer = &[0]u8,
+    .end = 0,
+    .seek = 0,
+    .vtable = &.{
+        .stream = stream,
+        .discard = discard,
+        .readVec = readVec,
+    },
+},
+
+pub fn init(alloc: std.mem.Allocator, data: []u8, decomp: Decomp.Fn) MetadataReader {
+    return .{
+        .alloc = alloc,
+
+        .data = data,
+        .decomp = decomp,
+    };
+}
+
+fn advance(self: *MetadataReader) Io.Reader.Error!void {
+    self.interface.seek = 0;
+    errdefer self.interface.end = 0;
+
+    const hdr = util.readValue(Header, self.data[0..2]);
+
+    const block = self.data[2..][0..hdr.size];
+
+    self.data = self.data[hdr.size + 2 ..];
+
+    if (hdr.uncompressed) {
+        self.interface.end = hdr.size;
+        self.interface.buffer = block;
+        return;
+    }
+
+    self.interface.end = self.decomp(self.alloc, block, &self.decomp_block) catch return error.ReadFailed;
+    self.interface.buffer = self.decomp_block[0..self.interface.end];
+}
+
+fn stream(rdr: *Io.Reader, wrt: *Io.Writer, limit: Io.Limit) Io.Reader.StreamError!usize {
+    if (rdr.seek >= rdr.end) {
+        var meta: *MetadataReader = @fieldParentPtr("interface", rdr);
+        try meta.advance();
+    }
+    if (limit == .nothing) return 0;
+
+    const size = @min(@intFromEnum(limit), rdr.end - rdr.seek);
+
+    const wrote = try wrt.write(rdr.buffer[rdr.seek..][0..size]);
+    rdr.seek += wrote;
+
+    return wrote;
+}
+fn discard(rdr: *Io.Reader, limit: Io.Limit) Io.Reader.Error!usize {
+    if (rdr.seek >= rdr.end) {
+        var meta: *MetadataReader = @fieldParentPtr("interface", rdr);
+        try meta.advance();
+    }
+    if (limit == .nothing) return 0;
+
+    const size = @min(@intFromEnum(limit), rdr.end - rdr.seek);
+    rdr.seek += size;
+
+    return size;
+}
+fn readVec(rdr: *Io.Reader, vec: [][]u8) Io.Reader.Error!usize {
+    if (rdr.seek >= rdr.end) {
+        var meta: *MetadataReader = @fieldParentPtr("interface", rdr);
+        try meta.advance();
+    }
+
+    var wrote: usize = 0;
+    for (vec) |s| {
+        const size = @min(rdr.end - rdr.seek, s.len);
+
+        @memcpy(s[0..size], rdr.buffer[rdr.seek..][0..size]);
+
+        wrote += size;
+        rdr.seek += size;
+
+        if (rdr.seek >= rdr.end) break;
+    }
+
+    return wrote;
+}
+
+// Types
+
+const Header = packed struct(u16) {
+    size: u15,
+    uncompressed: bool,
+};

src/utils/util.zig

@@ -20,3 +20,9 @@ pub fn readValue(comptime T: type, bytes: []u8) T {
     }
     return res;
 }
+pub fn readValueRdr(comptime T: type, rdr: *std.Io.Reader) !T {
+    var tmp: [@sizeOf(T)]u8 = undefined;
+    try rdr.readSliceAll(&tmp);
+
+    return readValue(T, &tmp);
+}