Fixed using the wrong decompression function for gzip

Re-added errors from settings xattr values

.github/workflows/release-build.yml

@@ -0,0 +1,31 @@
+name: Release Build
+
+on:
+  push:
+    tags:
+      - "v*.*.*"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+      - uses: mlugg/setup-zig@v2
+      - name: Install deps
+        run: sudo apt update && sudo apt install -y zlib1g-dev libzstd-dev liblzma-dev liblz4-dev liblzo2-dev
+      - name: Build normal version
+        run: zig build --release=fast -Dversion=${{ github.ref_name }}
+      - name: Move normal build out
+        run: mv zig-out/bin/unsquashfs ./unsquashfs-x86_64-zig-libs
+      - name: Rebuild with C libraries
+        run: zig build --release=fast -Duse_c_libs=true -Dversion="${{ github.ref_name }}"
+      - name: Move C build out
+        run: mv zig-out/bin/unsquashfs ./unsquashfs-x86_64-c-libs
+      - name: Release
+        uses: softprops/action-gh-release@v2
+        with:
+          prerelease: true
+          files: |
+            unsquashfs-x86_64-zig-libs
+            unsquashfs-x86_64-c-libs

.gitignore

@@ -1,2 +1,4 @@
+testing/
+
 .zig-cache/
 zig-out/

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "extern/zstd"]
+	path = extern/zstd
+	url = https://github.com/facebook/zstd

.zed/debug.json

@@ -0,0 +1,25 @@
+// Project-local debug tasks
+//
+// For more documentation on how to configure debug tasks,
+// see: https://zed.dev/docs/debugger
+[
+	{
+		"label": "Build & Run",
+
+		"adapter": "CodeLLDB",
+		"request": "launch",
+
+		"build": {
+			"command": "zig",
+			"args": ["build", "-Duse_c_libs=true", "-Ddebug=true"],
+		},
+
+		"program": "zig-out/bin/unsquashfs",
+		"args": [
+			"--force",
+			"-d",
+			"testing/TestExtractUnsquashfs",
+			"testing/LinuxPATest.sfs",
+		],
+	},
+]

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2025 Caleb Gardner
+Copyright (c) 2026 Caleb Gardner
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -0,0 +1,75 @@
+# zig-squashfs
+
+This is my experiments to learn Zig. Might amount to something. Might not.
+
+A library and application to decompress or view squashfs archives.
+
+## Current State
+
+Overall works, but currently is missing some features ([see below](#capabilities)) and has significantly slow performance compared to `unsquashfs` ([see below](#performance)).
+
+## Build options
+
+> `-Duse_c_libs=true`
+
+Instead of using Zig's standard library for decompression, use the system's C libraries. Has the benefit of being much faster and enabling LZO and LZ4 decompression.
+
+> `-Dallow_lzo=true`
+
+Enable compiling with LZO decompression support. The LZO library currently has some issues with Zig when imported so it's easier to just disable it by default. Only has an effect when using `-Duse_c_libs=true`.
+
+> `-Ddebug=true`
+
+Sets various build options that make debugging easier. Specifically, debug optimization is forced, valgrind support is enabled, error tracing is enabled, stipping is disabled, and copmilation uses LLVM (this is due to some linking issues when on Debug optimization and is required for debugging tools such as `lldb`. In the future this may be removed from the debug flag).
+
+> `-Dversion=0.0.0`
+
+Sets the version of `unsquashfs` shown when `--version` is passed.
+
+## Capabilities
+
+Most features are present except for the following:
+
+* When using Zig decompression libraries then lzo and lz4 compression types are unavailable. I don't _currently_ plan on spending the time to find and validate a library since neither is popular.
+* When using C decompression libraries, lzo is not supported by default due to [some issues](#build-considerations). If it's needed it's trivial to fix, but it's easiest to just leave it disabled.
+
+## Performance
+
+This is some basic observation's I've made about this library's performance when compared to `unsquashfs`. Unless otherwise stated, most observations were made when extracting my test archive (which is fairly small and uses zstd compression) and with `--release=fast`.
+
+Currently, my only performance checks are checking execution time, nothing deeper.
+
+* Under ideal circumstances, my library is ~70% slower (.12s vs .20s).
+* Using Zig decompression libraries *significantly* increases decompression time by ~600%. Under ideal circumstances.
+* Performance improvements/regressions will be common. I'm still learning Zig.
+
+Example Times:
+
+* *unsquashfs, multi-threaded*: .12s
+* *unsquashfs, single-threaded*: .13s
+* *C-libs, single-threaded*: .45s
+* *C-libs, multi-threaded*: .20s
+* *Zig-libs, single-threaded*: 5.78s
+* *Zig-libs, multi-threaded*: 1.08s
+
+## Build considerations
+
+Compilation without `use_c_libs` works completely fine, but Zig has issues with some symbols from the lzo library that needs to be manually fixed. In particular you need to fix the definitions for `lzo_bytep` and `lzo_voidp` to be `*u8` and `?*anyopaque` respectively. Due to this, you have to manually enable LZO decompression using `-Dallow_lzo=true` when building.
+
+```zig
+pub const lzo_bytep = @compileError("unable to translate C expr: unexpected token ''");
+// /usr/include/lzo/lzoconf.h:148:9
+pub const lzo_charp = @compileError("unable to translate C expr: unexpected token ''");
+// /usr/include/lzo/lzoconf.h:149:9
+pub const lzo_voidp = @compileError("unable to translate C expr: unexpected token ''");
+```
+
+to
+
+```zig
+pub const lzo_bytep = *u8;
+// /usr/include/lzo/lzoconf.h:148:9
+pub const lzo_charp = @compileError("unable to translate C expr: unexpected token ''");
+// /usr/include/lzo/lzoconf.h:149:9
+pub const lzo_voidp = ?*anyopaque;
+```

build.zig

@@ -0,0 +1,163 @@
+const std = @import("std");
+const Compile = std.Build.Step.Compile;
+const ResolvedTarget = std.Build.ResolvedTarget;
+const OptimizeMode = std.builtin.OptimizeMode;
+const Module = std.Build.Module;
+
+pub fn build(b: *std.Build) !void {
+    const use_zig_decomp = b.option(bool, "use_zig_decomp", "Use Zig standard library for decompression instead of C libraries.") orelse false;
+    const allow_lzo = b.option(bool, "allow_lzo", "Compile with lzo support") orelse false;
+    const debug = b.option(bool, "debug", "Enable options to make debugging easier.");
+    const version_string_option = b.option([]const u8, "version", "Version of the library/binary");
+
+    const zig_squashfs_options = b.addOptions();
+    zig_squashfs_options.addOption(bool, "use_zig_decomp", use_zig_decomp);
+    zig_squashfs_options.addOption(bool, "allow_lzo", allow_lzo);
+
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+    const mod = b.addModule("zig_squashfs", .{
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = if (debug == true) .Debug else optimize,
+        .link_libc = !use_zig_decomp,
+        .valgrind = debug,
+        .error_tracing = debug,
+        .strip = if (debug == true) false else null,
+    });
+    mod.addOptions("config", zig_squashfs_options);
+
+    if (!use_zig_decomp) {
+        var zlib = b.dependency("zlib_ng", .{});
+        mod.linkLibrary(zlib.artifact("zng"));
+
+        mod.linkSystemLibrary("lzma", .{ .preferred_link_mode = .static });
+        if (allow_lzo == true)
+            mod.linkSystemLibrary("minilzo", .{ .preferred_link_mode = .static });
+        mod.linkSystemLibrary("lz4", .{ .preferred_link_mode = .static });
+
+        const zstd_lib = buildZstdLibrary(b, target, optimize, debug);
+        mod.linkLibrary(zstd_lib);
+        mod.addIncludePath(b.path("extern/zstd/lib/"));
+    }
+
+    var version = version_string_option orelse "0.0.0-testing";
+    if (version[0] == 'v') version = version[1..];
+    const unsquashfs_options = b.addOptions();
+    unsquashfs_options.addOption(
+        std.SemanticVersion,
+        "version",
+        try std.SemanticVersion.parse(version),
+    );
+
+    var exe_mod = b.createModule(.{
+        .root_source_file = b.path("src/bin/unsquashfs.zig"),
+        .target = target,
+        .optimize = if (debug == true) .Debug else optimize,
+        .link_libc = !use_zig_decomp,
+        .imports = &.{
+            .{ .name = "zig_squashfs", .module = mod },
+        },
+        .valgrind = debug,
+        .error_tracing = debug,
+        .strip = if (debug == true) false else null,
+    });
+    exe_mod.addOptions("config", unsquashfs_options);
+    const exe = b.addExecutable(.{
+        .name = "unsquashfs",
+        .root_module = exe_mod,
+        .use_llvm = debug,
+    });
+
+    const lib = b.addLibrary(.{
+        .name = "squashfs",
+        .root_module = mod,
+        .use_llvm = debug,
+    });
+
+    b.installArtifact(lib);
+    b.installArtifact(exe);
+
+    const mod_tests = b.addTest(.{
+        .root_module = mod,
+    });
+    const run_mod_tests = b.addRunArtifact(mod_tests);
+    const exe_tests = b.addTest(.{
+        .root_module = exe.root_module,
+    });
+    const run_exe_tests = b.addRunArtifact(exe_tests);
+    const test_step = b.step("test", "Run tests");
+    test_step.dependOn(&run_mod_tests.step);
+    test_step.dependOn(&run_exe_tests.step);
+
+    // zls build check steps
+    const lib_check = b.addLibrary(.{
+        .name = "squashfs",
+        .root_module = mod,
+    });
+    const exe_check = b.addExecutable(.{
+        .name = "unsquashfs",
+        .root_module = exe_mod,
+    });
+    const check = b.step("check", "Check if unsquashfs compiles");
+    check.dependOn(&lib_check.step);
+    check.dependOn(&exe_check.step);
+}
+
+fn buildZstdLibrary(b: *std.Build, target: ResolvedTarget, optimize: OptimizeMode, debug: ?bool) *Compile {
+    var zstd_lib = b.addLibrary(.{
+        .name = "zstd",
+        .linkage = .static,
+        .root_module = b.createModule(.{
+            .target = target,
+            .optimize = if (debug == true) .Debug else optimize,
+            .link_libc = true,
+        }),
+        .use_llvm = debug,
+    });
+    zstd_lib.root_module.addCSourceFiles(.{
+        .root = b.path("extern/zstd/lib/"),
+        .files = &.{
+            "common/debug.c",
+            "common/entropy_common.c",
+            "common/error_private.c",
+            "common/fse_decompress.c",
+            "common/pool.c",
+            "common/threading.c",
+            "common/xxhash.c",
+            "common/zstd_common.c",
+            "compress/fse_compress.c",
+            "compress/hist.c",
+            "compress/huf_compress.c",
+            "compress/zstd_compress.c",
+            "compress/zstd_compress_literals.c",
+            "compress/zstd_compress_sequences.c",
+            "compress/zstd_compress_superblock.c",
+            "compress/zstd_double_fast.c",
+            "compress/zstd_fast.c",
+            "compress/zstd_lazy.c",
+            "compress/zstd_ldm.c",
+            "compress/zstdmt_compress.c",
+            "compress/zstd_opt.c",
+            "compress/zstd_preSplit.c",
+            "decompress/huf_decompress.c",
+            "decompress/zstd_ddict.c",
+            "decompress/zstd_decompress_block.c",
+            "decompress/zstd_decompress.c",
+            "dictBuilder/cover.c",
+            "dictBuilder/divsufsort.c",
+            "dictBuilder/fastcover.c",
+            "dictBuilder/zdict.c",
+        },
+    });
+    zstd_lib.root_module.addCSourceFiles(.{
+        .root = b.path("extern/zstd/lib/decompress"),
+        .files = &.{"huf_decompress_amd64.S"},
+    });
+    zstd_lib.installHeadersDirectory(b.path("extern/zstd/lib/"), &.{}, .{});
+    zstd_lib.installHeadersDirectory(b.path("extern/zstd/lib/common/"), &.{}, .{});
+    zstd_lib.installHeadersDirectory(b.path("extern/zstd/lib/compress/"), &.{}, .{});
+    zstd_lib.installHeadersDirectory(b.path("extern/zstd/lib/dictBuilder/"), &.{}, .{});
+    zstd_lib.installHeadersDirectory(b.path("extern/zstd/lib/"), &.{}, .{});
+    return zstd_lib;
+}

build.zig.zon

@@ -0,0 +1,21 @@
+.{
+    .name = .squashfs,
+    .version = "0.0.6",
+    .fingerprint = 0x37ba29474b87f145, // Changing this has security and trust implications.
+    .minimum_zig_version = "0.15.2",
+    .dependencies = .{
+        .zlib_ng = .{
+            // .url = "https://github.com/CalebQ42/zig-zlib-ng/archive/refs/tags/2.3.3.tar.gz",
+            // .hash = "zlib_ng-2.3.3-2HYS4Bw_AADjgv7tkrqjjz2fVz5kRTvha8wN9LEcjYNp",
+            .path = "../zig-zlib-ng",
+        },
+    },
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+
+        "LICENSE",
+        "README.md",
+    },
+}

run_tests.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+zig test \
+	-lc \
+	-lz \
+	-llzma \
+	-lminilzo \
+	-llz4 \
+	-lzstd \
+		src/test.zig

src/archive.zig

@@ -0,0 +1,97 @@
+//! A squashfs archive read from a file.
+//! Can be used to directly access File's contents or extract to the filesystem.
+
+const std = @import("std");
+const File = std.fs.File;
+const builtin = @import("builtin");
+
+const Decomp = @import("decomp.zig");
+const ExtractionOptions = @import("options.zig");
+const Inode = @import("inode.zig");
+const InodeRef = Inode.Ref;
+const BlockSize = @import("inode_data/file.zig").BlockSize;
+const SfsFile = @import("file.zig");
+const Superblock = @import("super.zig").Superblock;
+const Tables = @import("tables.zig");
+const MetadataReader = @import("util/metadata.zig");
+const OffsetFile = @import("util/offset_file.zig");
+const XattrTable = @import("xattr.zig");
+
+const config = if (builtin.is_test) .{
+    .use_zig_decomp = builtin.link_libc != true,
+    .allow_lzo = false,
+} else @import("config");
+
+const Archive = @This();
+
+alloc: std.mem.Allocator,
+
+fil: OffsetFile,
+decomp: Decomp.DecompFn,
+
+super: Superblock,
+
+tables: ?Tables = null,
+
+/// Default settings using std.Thread.getCpuCount() threads and the minimum of 4gb or half of system memory for memory usage.
+pub fn init(alloc: std.mem.Allocator, fil: File, offset: u64) !Archive {
+    var super: Superblock = undefined;
+    const red = try fil.pread(@ptrCast(&super), offset);
+    std.debug.assert(red == @sizeOf(Superblock));
+    try super.validate();
+    const off_fil: OffsetFile = .init(fil, offset);
+    const decomp: Decomp.DecompFn = switch (super.compression) {
+        .gzip => Decomp.gzipDecompress,
+        .lzma => Decomp.lzmaDecompress,
+        .xz => Decomp.xzDecompress,
+        .zstd => Decomp.zstdDecompress,
+        .lz4 => if (!config.use_zig_decomp) Decomp.cLz4 else return error.Lz4Unsupported,
+        .lzo => if (!config.use_zig_decomp and config.allow_lzo) Decomp.lzoDecompress else return error.LzoUnsupported,
+    };
+    return .{
+        .alloc = alloc,
+        .fil = off_fil,
+        .decomp = decomp,
+        .super = super,
+    };
+}
+pub fn deinit(self: *Archive) void {
+    if (self.tables != null)
+        self.tables.?.deinit();
+}
+
+pub fn inode(self: *Archive, alloc: std.mem.Allocator, num: u32) !Inode {
+    if (self.tables == null)
+        self.tables = try .init(alloc, self);
+    const ref = try self.export_table.get(num - 1);
+    var rdr = try self.fil.readerAt(ref.block_start + self.super.inode_start, &[0]u8{});
+    var meta: MetadataReader = .init(alloc, &rdr.interface, &self.decomp);
+    try meta.interface.discardAll(ref.block_offset);
+    return try .read(alloc, &meta.interface, self.super.block_size);
+}
+
+pub fn root(self: *Archive, alloc: std.mem.Allocator) !SfsFile {
+    if (self.tables == null)
+        self.tables = try .init(alloc, self);
+    var rdr = try self.fil.readerAt(self.super.root_ref.block_start + self.super.inode_start, &[0]u8{});
+    var meta: MetadataReader = .init(alloc, &rdr.interface, self.decomp);
+    try meta.interface.discardAll(self.super.root_ref.block_offset);
+    const in: Inode = try .read(alloc, &meta.interface, self.super.block_size);
+    return .init(self, in, "");
+}
+
+pub fn open(self: *Archive, alloc: std.mem.Allocator, path: []const u8) !SfsFile {
+    if (self.tables == null)
+        self.tables = try .init(alloc, self);
+    var root_fil = try self.root(alloc);
+    defer if (!SfsFile.pathIsSelf(path)) root_fil.deinit();
+    return root_fil.open(path);
+}
+
+pub fn extract(self: Archive, alloc: std.mem.Allocator, path: []const u8, options: ExtractionOptions) !void {
+    var rdr = try self.fil.readerAt(self.super.root_ref.block_start + self.super.inode_start, &[0]u8{});
+    var meta: MetadataReader = .init(self.alloc, &rdr.interface, self.decomp);
+    try meta.interface.discardAll(self.super.root_ref.block_offset);
+    const in: Inode = try .read(self.alloc, &meta.interface, self.super.block_size);
+    try in.extractTo(alloc, self, path, options);
+}

src/bin/unsquashfs.zig

@@ -0,0 +1,133 @@
+const std = @import("std");
+const Writer = std.Io.Writer;
+const builtin = @import("builtin");
+
+const config = @import("config");
+const squashfs = @import("zig_squashfs");
+
+//TODO: Add more options
+const help_mgs =
+    \\
+    \\Usage: unsquashfs [options] <archive>
+    \\
+    \\Options:
+    \\  -d <location>   Extract to the given location instead of "squashfs-root"
+    \\
+    \\  -o <offset>     Start reading the archive at the given offset.
+    \\  -dx             Don't set xattr values
+    \\  -dp             Don't set permissions (includes setting uid & gid owner)
+    \\
+    \\  -p <threads>    Specify how many threads to use. If no present or zero, the system's logical cores count is used.
+    \\  -v              Verbose
+    \\
+    \\  --force         Force extraction. If the destination already exists, it will be deleted.
+    \\
+    \\  --help          Display this messages
+    \\  --version       Display the version
+    \\
+;
+
+const errors = error{InvalidArguments};
+
+var archive: []const u8 = "";
+var extLoc: []const u8 = "squashfs-root";
+var offset: u64 = 0;
+var threads: u32 = 0;
+var verbose: bool = false;
+var ignore_xattrs: bool = false;
+var ignore_permissions: bool = false;
+var force: bool = false;
+
+pub fn main() !void {
+    const alloc = std.heap.smp_allocator;
+    var stdout = std.fs.File.stdout();
+    var out = stdout.writer(&[0]u8{});
+    defer out.interface.flush() catch {};
+    try handleArgs(alloc, &out.interface);
+    if (archive.len == 0) {
+        try out.interface.print("You must provide a squashfs archive\n", .{});
+        try out.interface.print(help_mgs, .{});
+        return;
+    }
+    var fil: std.fs.File = try std.fs.cwd().openFile(archive, .{}); //TODO: Handle error gracefully.
+    defer fil.close();
+    var arc: squashfs.Archive = try .init(alloc, fil, offset); //TODO: Update when memory size matters. //TODO: Handle error gracefully.
+    defer arc.deinit();
+    const options: squashfs.ExtractionOptions = .{
+        .threads = if (threads == 0) try std.Thread.getCpuCount() else threads,
+        .verbose = verbose,
+        .verbose_writer = if (verbose) &out.interface else null,
+        .ignore_xattr = ignore_xattrs,
+        .ignore_permissions = ignore_permissions,
+    };
+    if (force)
+        try std.fs.cwd().deleteTree(extLoc);
+    try arc.extract(alloc, extLoc, options); //TODO: Handle error gracefully.
+}
+
+fn handleArgs(alloc: std.mem.Allocator, out: *Writer) !void {
+    var args = try std.process.argsWithAllocator(alloc);
+    defer args.deinit();
+    _ = args.next(); // args[0] is the application launch command.
+    while (args.next()) |arg| {
+        if (std.mem.eql(u8, arg, "-o")) {
+            const nxt = args.next();
+            if (nxt == null or nxt.?.len == 0) {
+                try out.print("-o must be followed by a number\n", .{});
+                return errors.InvalidArguments;
+            }
+            offset = std.fmt.parseInt(u64, nxt.?, 10) catch {
+                try out.print("-o must be followed by a number\n", .{});
+                return errors.InvalidArguments;
+            };
+            continue;
+        } else if (std.mem.eql(u8, arg, "-d")) {
+            const nxt = args.next();
+            if (nxt == null or nxt.?.len == 0) {
+                try out.print("-d must be followed by a location\n", .{});
+                return errors.InvalidArguments;
+            }
+            extLoc = nxt.?;
+            continue;
+        } else if (std.mem.eql(u8, arg, "-p")) {
+            const nxt = args.next();
+            if (nxt == null or nxt.?.len == 0) {
+                try out.print("-p must be followed by a number\n", .{});
+                return errors.InvalidArguments;
+            }
+            threads = std.fmt.parseInt(u32, nxt.?, 10) catch {
+                try out.print("-p must be followed by a number\n", .{});
+                return errors.InvalidArguments;
+            };
+            continue;
+        } else if (std.mem.eql(u8, arg, "-v")) {
+            verbose = true;
+            continue;
+        } else if (std.mem.eql(u8, arg, "-dx")) {
+            ignore_xattrs = true;
+            continue;
+        } else if (std.mem.eql(u8, arg, "-dp")) {
+            ignore_permissions = true;
+            continue;
+        } else if (std.mem.eql(u8, arg, "--force")) {
+            force = true;
+            continue;
+        } else if (std.mem.eql(u8, arg, "--version")) {
+            try out.print("zig-unsquashfs v", .{});
+            try config.version.format(out);
+            try out.print("\nBuilt using Zig {s} in {} mode\n", .{ builtin.zig_version_string, builtin.mode });
+            std.process.exit(0);
+            return;
+        } else if (std.mem.eql(u8, arg, "--help")) {
+            try out.print(help_mgs, .{});
+            std.process.exit(0);
+            return;
+        }
+        if (archive.len > 0) {
+            try out.print("you can only provide one file at a time\n", .{});
+            try out.print(help_mgs, .{});
+            return errors.InvalidArguments;
+        }
+        archive = arg;
+    }
+}

src/decomp.zig

@@ -0,0 +1,261 @@
+//! Implementations for decompression.
+//! TODO: change to vtable interface to allow for shared decompressors for better performance/resource usage.
+
+const std = @import("std");
+const Reader = std.Io.Reader;
+const builtin = @import("builtin");
+
+const config = if (builtin.is_test) .{
+    .use_zig_decomp = builtin.link_libc != true,
+    .allow_lzo = false, // Change once LZO compilation is fixed
+} else @import("config");
+
+const c = @cImport({
+    @cInclude("zlib-ng.h");
+    @cInclude("lzma.h");
+    @cInclude("lz4.h");
+    @cInclude("zstd.h");
+    @cInclude("zstd_errors.h");
+    if (config.allow_lzo)
+        @cInclude("lzo/minilzo.h");
+});
+
+pub const CompressionType = enum(u16) {
+    gzip = 1,
+    lzma,
+    lzo,
+    xz,
+    lz4,
+    zstd,
+};
+
+pub const DecompFn = *const fn (alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize; // TODO: replace anyerror to definitive error types.
+
+pub const gzipDecompress = if (!config.use_zig_decomp) cGzip else zigGzip;
+
+fn zigGzip(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    var rdr: Reader = .fixed(in);
+    const buf = try alloc.alloc(u8, out.len);
+    defer alloc.free(buf);
+    var decomp = std.compress.flate.Decompress.init(&rdr, .zlib, buf);
+    return decomp.reader.readSliceShort(out);
+}
+fn cGzip(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    _ = alloc;
+    var out_len: usize = out.len;
+    const res = c.zng_uncompress(out.ptr, &out_len, in.ptr, in.len);
+    return switch (res) {
+        c.Z_OK => out_len,
+        c.Z_MEM_ERROR => error.NotEnoughMemory,
+        c.Z_BUF_ERROR => error.OutBufferTooSmall,
+        c.Z_DATA_ERROR => error.BadData,
+        else => error.UnknownResult,
+    };
+}
+
+pub const lzmaDecompress = if (!config.use_zig_decomp) cLzma else zigLzma;
+
+fn zigLzma(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    var rdr: Reader = .fixed(in);
+    var decomp = try std.compress.lzma.decompress(alloc, rdr.adaptToOldInterface());
+    return decomp.read(out);
+}
+fn cLzma(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    _ = alloc;
+    var stream: c.lzma_stream = .{
+        .next_in = in.ptr,
+        .avail_in = in.len,
+        .next_out = out.ptr,
+        .avail_out = out.len,
+    };
+    var res = c.lzma_alone_decoder(&stream, in.len * 2);
+    switch (res) {
+        c.LZMA_OK => {},
+        c.LZMA_MEM_ERROR => return error.LzmaMemoryError,
+        c.LZMA_PROG_ERROR => return error.LzmaProgramError,
+        else => return error.UnknownResult,
+    }
+    defer c.lzma_end(&stream);
+    while (res == c.LZMA_OK)
+        res = c.lzma_code(&stream, c.LZMA_RUN);
+    return switch (res) {
+        c.LZMA_STREAM_END => stream.total_out,
+        c.LZMA_MEM_ERROR => error.LzmaMemoryError,
+        c.LZMA_MEMLIMIT_ERROR => error.LzmaMemoryLimit,
+        c.LZMA_FORMAT_ERROR => error.LzmaBadFormat,
+        c.LZMA_DATA_ERROR => error.LzmaDataCorrupt,
+        c.LZMA_BUF_ERROR => error.LzmaCannotProgress,
+        c.LZMA_PROG_ERROR => error.LzmaProgramError,
+        else => error.UnknownResult,
+    };
+}
+
+// pub const lzoDecompress = if (!config.use_zig_decomp) cLzo else zigLzo;
+
+// fn zigLzo(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+//     _ = alloc;
+//     _ = in;
+//     _ = out;
+//     return error.LzoUnsupported;
+// }
+pub fn cLzo(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    _ = alloc;
+    var res = c.lzo_init();
+    if (res != 0) return error.LzoInitFailed;
+    var out_len: usize = out.len;
+    res = c.lzo1x_decompress(in.ptr, in.len, out.ptr, &out_len, null);
+    return switch (res) {
+        c.LZO_E_OK => out_len,
+        c.LZO_E_ERROR => error.LzoError,
+        c.LZO_E_OUT_OF_MEMORY => error.LzoOutOfMemory,
+        c.LZO_E_NOT_COMPRESSIBLE => error.LzoNotCompressible,
+        c.LZO_E_INPUT_OVERRUN => error.LzoInputOverrun,
+        c.LZO_E_OUTPUT_OVERRUN => error.LzoOutputOverrun,
+        c.LZO_E_LOOKBEHIND_OVERRUN => error.LzoLookbehindOverrun,
+        c.LZO_E_EOF_NOT_FOUND => error.LzoEofNotFound,
+        c.LZO_E_INPUT_NOT_CONSUMED => error.LzoInputNotConsumed,
+        c.LZO_E_NOT_YET_IMPLEMENTED => error.LzoNotYetImplemented,
+        c.LZO_E_INVALID_ARGUMENT => error.LzoInvalidArgument,
+        c.LZO_E_INVALID_ALIGNMENT => error.LzoInvalidAlignment,
+        c.LZO_E_OUTPUT_NOT_CONSUMED => error.LzoOutputNotConsumed,
+        c.LZO_E_INTERNAL_ERROR => error.LzoInternalError,
+        else => error.UnknownResult,
+    };
+}
+
+pub const xzDecompress = if (!config.use_zig_decomp) cXz else zigXz;
+
+fn zigXz(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    var rdr: Reader = .fixed(in);
+    var decomp = try std.compress.xz.decompress(alloc, rdr.adaptToOldInterface());
+    return decomp.read(out);
+}
+fn cXz(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    _ = alloc;
+    var stream: c.lzma_stream = .{
+        .next_in = in.ptr,
+        .avail_in = in.len,
+        .next_out = out.ptr,
+        .avail_out = out.len,
+        // .allocator = _, TODO: create a custom allocator based on alloc,
+    };
+    var res = c.lzma_stream_decoder(&stream, in.len * 2, 0);
+    switch (res) {
+        c.LZMA_OK => {},
+        c.LZMA_MEM_ERROR => return error.LzmaMemoryError,
+        c.LZMA_PROG_ERROR => return error.LzmaProgramError,
+        else => return error.UnknownResult,
+    }
+    defer c.lzma_end(&stream);
+    while (res == c.LZMA_OK)
+        res = c.lzma_code(&stream, c.LZMA_RUN);
+    return switch (res) {
+        c.LZMA_STREAM_END => stream.total_out,
+        c.LZMA_MEM_ERROR => error.LzmaMemoryError,
+        c.LZMA_MEMLIMIT_ERROR => error.LzmaMemoryLimit,
+        c.LZMA_FORMAT_ERROR => error.LzmaBadFormat,
+        c.LZMA_DATA_ERROR => error.LzmaDataCorrupt,
+        c.LZMA_BUF_ERROR => error.LzmaCannotProgress,
+        c.LZMA_PROG_ERROR => error.LzmaProgramError,
+        else => error.UnknownResult,
+    };
+}
+
+// pub const lz4Decompress = if (!config.use_zig_decomp) cLz4 else zigLz4;
+
+// fn zigLz4(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+//     _ = alloc;
+//     _ = in;
+//     _ = out;
+//     return error.Lz4Unsupported;
+// }
+pub fn cLz4(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    _ = alloc;
+    const res = c.LZ4_decompress_safe(in.ptr, out.ptr, @intCast(in.len), @intCast(out.len));
+    if (res > 0) return @abs(res); // TODO: Find out what error values it can return.
+    return error.Lz4DecompressFailed;
+}
+
+pub const zstdDecompress = if (!config.use_zig_decomp) cZstd else zigZstd;
+
+pub fn zigZstd(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    var rdr: Reader = .fixed(in);
+    const buf = try alloc.alloc(u8, 1024 * 1024);
+    defer alloc.free(buf);
+    var decomp = std.compress.zstd.Decompress.init(&rdr, buf, .{});
+    return decomp.reader.readSliceShort(out) catch |err| {
+        return decomp.err orelse err;
+    };
+}
+fn cZstd(alloc: std.mem.Allocator, in: []u8, out: []u8) anyerror!usize {
+    _ = alloc;
+    const res = c.ZSTD_decompress(out.ptr, out.len, in.ptr, in.len);
+    if (c.ZSTD_isError(res) == 0) return res;
+    return switch (c.ZSTD_getErrorCode(res)) {
+        c.ZSTD_error_prefix_unknown => cZstdError.PrefixUnknown,
+        c.ZSTD_error_version_unsupported => cZstdError.VersionUnsupported,
+        c.ZSTD_error_frameParameter_unsupported => cZstdError.FrameParameterUnsupported,
+        c.ZSTD_error_frameParameter_windowTooLarge => cZstdError.FrameParameterWindowTooLarge,
+        c.ZSTD_error_corruption_detected => cZstdError.CorruptionDetected,
+        c.ZSTD_error_checksum_wrong => cZstdError.ChecksumWrong,
+        c.ZSTD_error_literals_headerWrong => cZstdError.LiteralsHeaderWrong,
+        c.ZSTD_error_dictionary_corrupted => cZstdError.DictionaryCorrupted,
+        c.ZSTD_error_dictionary_wrong => cZstdError.DictionaryWrong,
+        c.ZSTD_error_dictionaryCreation_failed => cZstdError.DictionaryCreationFailed,
+        c.ZSTD_error_parameter_unsupported => cZstdError.ParameterUnsupported,
+        c.ZSTD_error_parameter_combination_unsupported => cZstdError.ParameterCombinationUnsupported,
+        c.ZSTD_error_parameter_outOfBound => cZstdError.ParameterOutOfBound,
+        c.ZSTD_error_tableLog_tooLarge => cZstdError.TableLogTooLarge,
+        c.ZSTD_error_maxSymbolValue_tooLarge => cZstdError.MaxSymbolValueTooLarge,
+        c.ZSTD_error_maxSymbolValue_tooSmall => cZstdError.MaxSymbolValueTooSmall,
+        c.ZSTD_error_stabilityCondition_notRespected => cZstdError.StabilityConditionNotRespected,
+        c.ZSTD_error_stage_wrong => cZstdError.StageWrong,
+        c.ZSTD_error_init_missing => cZstdError.InitMissing,
+        c.ZSTD_error_memory_allocation => cZstdError.MemoryAllocation,
+        c.ZSTD_error_workSpace_tooSmall => cZstdError.WorkSpaceTooSmall,
+        c.ZSTD_error_dstSize_tooSmall => cZstdError.DstSizeTooSmall,
+        c.ZSTD_error_srcSize_wrong => cZstdError.SrcSizeWrong,
+        c.ZSTD_error_dstBuffer_null => cZstdError.DstBufferNull,
+        c.ZSTD_error_noForwardProgress_destFull => cZstdError.NoForwardProgressDestFull,
+        c.ZSTD_error_noForwardProgress_inputEmpty => cZstdError.NoForwardProgressInputEmpty,
+        else => cZstdError.Generic,
+    };
+}
+
+pub const cZstdError = error{
+    Generic,
+    PrefixUnknown,
+    VersionUnsupported,
+    FrameParameterUnsupported,
+    FrameParameterWindowTooLarge,
+    CorruptionDetected,
+    ChecksumWrong,
+    LiteralsHeaderWrong,
+    DictionaryCorrupted,
+    DictionaryWrong,
+    DictionaryCreationFailed,
+    ParameterUnsupported,
+    ParameterCombinationUnsupported,
+    ParameterOutOfBound,
+    TableLogTooLarge,
+    MaxSymbolValueTooLarge,
+    MaxSymbolValueTooSmall,
+    CannotProduceUncompressedBlock,
+    StabilityConditionNotRespected,
+    StageWrong,
+    InitMissing,
+    MemoryAllocation,
+    WorkSpaceTooSmall,
+    DstSizeTooSmall,
+    SrcSizeWrong,
+    DstBufferNull,
+    NoForwardProgressDestFull,
+    NoForwardProgressInputEmpty,
+    FrameIndexTooLarge,
+    SeekableIo,
+    DstBufferWrong,
+    SrcBufferWrong,
+    SequenceProducerFailed,
+    ExternalSequencesInvalid,
+    MaxCode,
+};

src/dir_entry.zig

@@ -0,0 +1,60 @@
+//! Directory entry from the directory table.
+
+const std = @import("std");
+const Reader = std.Io.Reader;
+
+const InodeType = @import("inode.zig").InodeType;
+
+const Entry = @This();
+
+const Header = extern struct { // use extern due to bad alignment with packed.
+    count: u32,
+    block_start: u32,
+    num: u32,
+};
+
+const RawEntry = packed struct {
+    offset: u16,
+    inode_offset: i16,
+    inode_type: InodeType,
+    name_size: u16,
+};
+
+block_start: u32,
+block_offset: u16,
+num: u32,
+inode_type: InodeType,
+name: []const u8,
+
+pub fn readDir(alloc: std.mem.Allocator, rdr: *Reader, size: u32) ![]Entry {
+    var cur_red: u32 = 3; // start at 3 due to "." & ".." being counted in the dir size.
+    var hdr: Header = undefined;
+    var raw: RawEntry = undefined;
+    var out: std.ArrayList(Entry) = try .initCapacity(alloc, 100); // Start out with a decent capacity instead of needing to allocate per header.
+    errdefer out.deinit(alloc);
+    while (cur_red < size) {
+        try rdr.readSliceEndian(Header, @ptrCast(&hdr), .little);
+        cur_red += @sizeOf(Header);
+        try out.ensureUnusedCapacity(alloc, hdr.count + 1);
+        for (0..hdr.count + 1) |_| {
+            try rdr.readSliceEndian(RawEntry, @ptrCast(&raw), .little);
+            const name = try alloc.alloc(u8, raw.name_size + 1);
+            errdefer alloc.free(name);
+            try rdr.readSliceEndian(u8, name, .little);
+            const val = out.addOneAssumeCapacity();
+            val.* = .{
+                .block_start = hdr.block_start,
+                .block_offset = raw.offset,
+                .num = @abs(hdr.num + raw.offset),
+                .inode_type = raw.inode_type,
+                .name = name,
+            };
+            cur_red += @sizeOf(RawEntry) + raw.name_size + 1;
+        }
+    }
+    return out.toOwnedSlice(alloc);
+}
+
+pub fn deinit(self: Entry, alloc: std.mem.Allocator) void {
+    alloc.free(self.name);
+}

src/file.zig

@@ -0,0 +1,202 @@
+//! A file/directory within the squashfs archive.
+
+const std = @import("std");
+const File = std.fs.File;
+const WaitGroup = std.Thread.WaitGroup;
+const Mutex = std.Thread.Mutex;
+
+const Archive = @import("archive.zig");
+const DirEntry = @import("dir_entry.zig");
+const ExtractionOptions = @import("options.zig");
+const Inode = @import("inode.zig");
+const BlockSize = @import("inode_data/file.zig").BlockSize;
+const DataReader = @import("util/data.zig");
+const MetadataReader = @import("util/metadata.zig");
+
+const FileError = error{
+    NotDirectory,
+    NotRegularFile,
+    NotSymlink,
+    NotDevice,
+    NotFound,
+    ExtractionPathExists,
+};
+
+const SfsFile = @This();
+
+archive: *Archive,
+
+inode: Inode,
+name: []const u8,
+
+/// Initialize a new File.
+/// name is copied to the File so can be safely freed afterwards.
+pub fn init(archive: *Archive, inode: Inode, name: []const u8) !SfsFile {
+    const new_name = try archive.allocator().alloc(u8, name.len);
+    @memcpy(new_name, name);
+    return .{
+        .archive = archive,
+        .inode = inode,
+        .name = new_name,
+    };
+}
+pub fn fromEntry(archive: *Archive, entry: DirEntry) !SfsFile {
+    var rdr = try archive.fil.readerAt(entry.block_start + archive.super.inode_start, &[0]u8{});
+    var meta: MetadataReader = .init(archive.allocator(), &rdr.interface, archive.decomp);
+    try meta.interface.discardAll(entry.block_offset);
+    const inode: Inode = try .read(archive.allocator(), &meta.interface, archive.super.block_size);
+    errdefer inode.deinit(archive.allocator());
+    return .init(archive, inode, entry.name);
+}
+
+pub fn deinit(self: SfsFile) void {
+    var alloc = self.archive.allocator();
+    alloc.free(self.name);
+    self.inode.deinit(alloc);
+}
+
+fn getEntries(self: SfsFile) ![]DirEntry {
+    return self.inode.dirEntries(self.archive.allocator(), self.archive.*);
+}
+
+pub fn ownerUid(self: SfsFile) !u16 {
+    return self.archive.id(self.inode.hdr.uid_idx);
+}
+pub fn ownerGid(self: SfsFile) !u16 {
+    return self.archive.id(self.inode.hdr.gid_idx);
+}
+pub fn permissions(self: SfsFile) u16 {
+    return self.inode.hdr.permissions;
+}
+
+pub fn isRegular(self: SfsFile) bool {
+    return switch (self.inode.hdr.inode_type) {
+        .file, .ext_file => true,
+        else => false,
+    };
+}
+/// The returned DataReader will no longer work if the File's deinit function is called
+/// or, more specifically, it's inode's deinit function is called.
+pub fn dataReader(self: SfsFile) !DataReader {
+    return self.inode.dataReader(self.archive);
+}
+
+pub fn isDir(self: SfsFile) bool {
+    return switch (self.inode.hdr.inode_type) {
+        .dir, .ext_dir => true,
+        else => false,
+    };
+}
+pub fn iterate(self: SfsFile) !Iterator {
+    if (!self.isDir()) return FileError.NotDirectory;
+    return .{
+        .entries = try self.getEntries(),
+        .archive = self.archive,
+    };
+}
+/// Open a sub-file/folder within a directory at the given path.
+/// If path is "", ".", "/", or "./", this File is returned.
+pub fn open(self: SfsFile, alloc: std.mem.Allocator, path: []const u8) !SfsFile {
+    if (!self.isDir()) return FileError.NotDirectory;
+    if (pathIsSelf(path)) return self;
+
+    // Recursively stip ending & leading path separators.
+    if (path[0] == '/') return self.open(path[1..]);
+    if (path[path.len - 1] == '/') return self.open(path[0 .. path.len - 1]);
+
+    const idx = std.mem.indexOf(u8, path, "/") orelse path.len;
+    const first_element = path[0..idx];
+    if (std.mem.eql(u8, first_element, ".")) return self.open(path[idx + 1 ..]);
+    const entries = try self.getEntries();
+    defer {
+        for (entries) |e| {
+            e.deinit(alloc);
+        }
+        alloc.free(entries);
+    }
+    var cur_slice = entries;
+    var split = cur_slice.len / 2;
+    while (cur_slice.len > 0) {
+        split = cur_slice.len / 2;
+        const comp = std.mem.order(u8, first_element, cur_slice[split].name);
+        switch (comp) {
+            .eq => {
+                var fil: SfsFile = try .fromEntry(self.archive, cur_slice[split]);
+                if (idx == path.len) {
+                    return fil;
+                }
+                defer fil.deinit();
+                return fil.open(alloc, path[idx + 1 ..]);
+            },
+            .lt => cur_slice = cur_slice[0..split],
+            .gt => cur_slice = cur_slice[split + 1 ..],
+        }
+    }
+    return FileError.NotFound;
+}
+
+pub fn isSymlink(self: SfsFile) bool {
+    return switch (self.inode.hdr.inode_type) {
+        .symlink, .ext_symlink => true,
+        else => false,
+    };
+}
+pub fn symlinkPath(self: SfsFile) ![]const u8 {
+    if (!self.isSymlink()) return FileError.NotSymlink;
+    return switch (self.inode.data) {
+        .symlink => |s| s.target,
+        .ext_symlink => |s| s.target,
+        else => unreachable,
+    };
+}
+
+/// Check if the File is a block or character device.
+pub fn isDevice(self: SfsFile) bool {
+    return switch (self.inode.hdr.inode_type) {
+        .block_dev, .char_dev, .ext_block_dev, .ext_char_dev => true,
+        else => false,
+    };
+}
+/// If the File is a block or character device, get's it's device number.
+pub fn devNum(self: SfsFile) !u32 {
+    if (!self.isDevice()) return FileError.NotDevice;
+    return switch (self.inode.data) {
+        .block_dev, .char_dev => |d| d.dev,
+        .ext_block_dev, .ext_char_dev => |d| d.dev,
+        else => unreachable,
+    };
+}
+
+/// Extract the given File to the path. If File is a regular file, the path must be a directory or not exist.
+/// If the gievn path is a folder, the File's contents will be extracted within.
+pub fn extract(self: *SfsFile, alloc: std.mem.Allocator, path: []const u8, options: ExtractionOptions) !void {
+    return self.inode.extractToThreaded(alloc, self.archive, path, options);
+}
+
+/// Utility function.
+pub fn pathIsSelf(path: []const u8) bool {
+    if (path.len == 0) return true;
+    if (path.len == 1 and (path[0] == '/' or path[0] == '.')) return true;
+    if (path.len == 2 and (path[0] == '.' and path[1] == '/')) return true;
+    return false;
+}
+
+pub const Iterator = struct {
+    entries: []DirEntry,
+    archive: *Archive,
+
+    idx: u32 = 0,
+
+    pub fn next(self: *Iterator) !?SfsFile {
+        if (self.idx >= self.entries.len) return null;
+        defer self.idx += 1;
+        return try SfsFile.fromEntry(self.archive, self.entries[self.idx]);
+    }
+    pub fn deinit(self: Iterator) void {
+        var alloc = self.archive.allocator();
+        for (self.entries) |e| {
+            e.deinit(alloc);
+        }
+        alloc.free(self.entries);
+    }
+};

src/inode.zig

@@ -0,0 +1,189 @@
+//! A file-system object. Represents a File or directory.
+
+const std = @import("std");
+const Reader = std.Io.Reader;
+const WaitGroup = std.Thread.WaitGroup;
+const Pool = std.Thread.Pool;
+const Mutex = std.Thread.Mutex;
+
+const Archive = @import("archive.zig");
+const DirEntry = @import("dir_entry.zig");
+const ExtractionOptions = @import("options.zig");
+const dir = @import("inode_data/dir.zig");
+const file = @import("inode_data/file.zig");
+const misc = @import("inode_data/misc.zig");
+const Tables = @import("tables.zig");
+const DataReader = @import("util/data.zig");
+const ThreadedDataReader = @import("util/data_threaded.zig");
+const InodeExtract = @import("util/extract.zig");
+const InodeFinish = @import("util/inode_finish.zig");
+const FinishUnion = InodeFinish.FinishUnion;
+const MetadataReader = @import("util/metadata.zig");
+
+pub const Ref = packed struct {
+    block_offset: u16,
+    block_start: u32,
+    _: u16,
+};
+
+pub const InodeType = enum(u16) {
+    dir = 1,
+    file,
+    symlink,
+    block_dev,
+    char_dev,
+    fifo,
+    socket,
+    ext_dir,
+    ext_file,
+    ext_symlink,
+    ext_block_dev,
+    ext_char_dev,
+    ext_fifo,
+    ext_socket,
+};
+
+pub const InodeData = union(InodeType) {
+    dir: dir.Dir,
+    file: file.File,
+    symlink: misc.Symlink,
+    block_dev: misc.Dev,
+    char_dev: misc.Dev,
+    fifo: misc.IPC,
+    socket: misc.IPC,
+    ext_dir: dir.ExtDir,
+    ext_file: file.ExtFile,
+    ext_symlink: misc.ExtSymlink,
+    ext_block_dev: misc.ExtDev,
+    ext_char_dev: misc.ExtDev,
+    ext_fifo: misc.ExtIPC,
+    ext_socket: misc.ExtIPC,
+};
+
+pub const Header = packed struct {
+    inode_type: InodeType,
+    permissions: u16,
+    uid_idx: u16,
+    gid_idx: u16,
+    mod_time: u32,
+    num: u32,
+};
+
+const Inode = @This();
+
+hdr: Header,
+data: InodeData,
+
+pub fn read(alloc: std.mem.Allocator, rdr: *Reader, block_size: u32) !Inode {
+    var hdr: Header = undefined;
+    try rdr.readSliceEndian(Header, @ptrCast(&hdr), .little);
+    return .{
+        .hdr = hdr,
+        .data = switch (hdr.inode_type) {
+            .dir => .{ .dir = try .read(rdr) },
+            .file => .{ .file = try .read(alloc, rdr, block_size) },
+            .symlink => .{ .symlink = try .read(alloc, rdr) },
+            .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(alloc, rdr, block_size) },
+            .ext_symlink => .{ .ext_symlink = try .read(alloc, rdr) },
+            .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 readFromEntry(alloc: std.mem.Allocator, archive: Archive, entry: DirEntry) !Inode {
+    var rdr = try archive.fil.readerAt(archive.super.inode_start + entry.block_start, &[0]u8{});
+    var meta: MetadataReader = .init(alloc, &rdr.interface, archive.decomp);
+    try meta.interface.discardAll(entry.block_offset);
+    return read(alloc, &meta.interface, archive.super.block_size);
+}
+
+pub fn deinit(self: Inode, alloc: std.mem.Allocator) void {
+    switch (self.data) {
+        .file => |f| alloc.free(f.block_sizes),
+        .ext_file => |f| alloc.free(f.block_sizes),
+        .symlink => |s| alloc.free(s.target),
+        .ext_symlink => |s| alloc.free(s.target),
+        else => {},
+    }
+}
+
+/// Get the data reader for a file inode.
+pub fn dataReader(self: Inode, alloc: std.mem.Allocator, archive: Archive, tables: *Tables) !DataReader {
+    return switch (self.hdr.inode_type) {
+        .file => readerFromData(alloc, archive, tables, self.data.file),
+        .ext_file => readerFromData(alloc, archive, tables, self.data.ext_file),
+        else => error.NotRegularFile,
+    };
+}
+fn readerFromData(alloc: std.mem.Allocator, archive: Archive, tables: *Tables, data: anytype) !DataReader {
+    var out: DataReader = .init(alloc, archive, data.block_sizes, data.block_start, data.size);
+    if (data.frag_idx != 0xFFFFFFFF)
+        out.addFragment(try tables.frag_table.get(data.frag_idx), data.frag_block_offset);
+    return out;
+}
+
+/// Get the directory entries for a directory inode.
+pub fn dirEntries(self: Inode, alloc: std.mem.Allocator, archive: Archive) ![]DirEntry {
+    return switch (self.hdr.inode_type) {
+        .dir => entriesFromData(alloc, archive, self.data.dir),
+        .ext_dir => entriesFromData(alloc, archive, self.data.ext_dir),
+        else => error.NotDirectory,
+    };
+}
+fn entriesFromData(alloc: std.mem.Allocator, archive: Archive, data: anytype) ![]DirEntry {
+    var rdr = try archive.fil.readerAt(archive.super.dir_start + data.block_start, &[0]u8{});
+    var meta: MetadataReader = .init(alloc, &rdr.interface, archive.decomp);
+    try meta.interface.discardAll(data.block_offset);
+    return DirEntry.readDir(alloc, &meta.interface, data.size);
+}
+
+/// Returns the xattr index for the given inode. If the inode isn't an extended variant or doesn't have any, the u32 max is returned (0xFFFFFFFF).
+pub fn xattrIdx(self: Inode) u32 {
+    return switch (self.data) {
+        .ext_dir => |d| d.xattr_id,
+        .ext_file => |f| f.xattr_idx,
+        .ext_symlink => |s| s.xattr_idx,
+        .ext_block_dev, .ext_char_dev => |d| d.xattr_idx,
+        .ext_fifo, .ext_socket => |i| i.xattr_idx,
+        else => 0xFFFFFFFF,
+    };
+}
+
+/// Applies the Inode's metadata to the given File.
+/// Mod time is always set, but permissions and xattrs are set based on the given ExtractionOptions.
+pub fn setMetadata(self: Inode, alloc: std.mem.Allocator, tables: *Tables, fil: std.fs.File, options: ExtractionOptions) !void {
+    const time = @as(i128, self.hdr.mod_time) * 1000000000;
+    try fil.updateTimes(time, time);
+    if (!options.ignore_permissions) {
+        try fil.chmod(self.hdr.permissions);
+        try fil.chown(try tables.id_table.get(self.hdr.uid_idx), try tables.id_table.get(self.hdr.gid_idx));
+    }
+    if (!options.ignore_xattr) {
+        const idx = self.xattrIdx();
+        if (idx == 0xFFFFFFFF) return;
+        const xattrs = try tables.xattr_table.get(alloc, idx);
+        defer alloc.free(xattrs);
+        for (xattrs) |kv| {
+            const res = std.os.linux.fsetxattr(fil.handle, kv.key, kv.value.ptr, kv.value.len, 0);
+            alloc.free(kv.key);
+            alloc.free(kv.value);
+            if (res != 0) {
+                if (options.verbose)
+                    options.verbose_writer.?.print("fsetxattr has result of: {}\n", .{res}) catch {};
+                return error.SetXattr;
+            }
+        }
+    }
+}
+
+/// Extract the inode to the given path.
+pub fn extractTo(self: Inode, alloc: std.mem.Allocator, archive: Archive, path: []const u8, options: ExtractionOptions) !void {
+    return InodeExtract.extractTo(alloc, self, archive, path, options);
+}

src/inode_data/dir.zig

@@ -0,0 +1,32 @@
+const Reader = @import("std").Io.Reader;
+
+pub const Dir = packed struct {
+    block_start: u32,
+    hard_links: u32,
+    size: u16,
+    block_offset: u16,
+    parent_num: u32,
+
+    pub fn read(rdr: *Reader) !Dir {
+        var d: Dir = undefined;
+        try rdr.readSliceEndian(Dir, @ptrCast(&d), .little);
+        return d;
+    }
+};
+
+pub const ExtDir = packed struct {
+    hard_links: u32,
+    size: u32,
+    block_start: u32,
+    parent_num: u32,
+    idx_count: u16,
+    block_offset: u16,
+    xattr_id: u32,
+    // index: []DirIndex
+
+    pub fn read(rdr: *Reader) !ExtDir {
+        var d: ExtDir = undefined;
+        try rdr.readSliceEndian(Dir, @ptrCast(&d), .little);
+        return d;
+    }
+};

src/inode_data/file.zig

@@ -0,0 +1,76 @@
+const std = @import("std");
+const Reader = std.Io.Reader;
+
+pub const BlockSize = packed struct {
+    size: u24,
+    uncompressed: bool,
+    _: u7,
+};
+
+pub const File = struct {
+    block_start: u32, // bytes 0-3
+    frag_idx: u32, // bytes 4-7
+    frag_block_offset: u32, // bytes 8-11
+    size: u32, // bytes 12-15
+    block_sizes: []BlockSize,
+
+    pub fn read(alloc: std.mem.Allocator, rdr: *Reader, block_size: u32) !File {
+        var start: [16]u8 = undefined;
+        try rdr.readSliceAll(&start);
+        const frag_idx: u32 = std.mem.readInt(u32, start[4..8], .little);
+        const size: u32 = std.mem.readInt(u32, start[12..16], .little);
+        var num_blocks: u32 = size / block_size;
+        if (size % block_size != 0 and frag_idx == 0xFFFFFFFF) num_blocks += 1;
+        const sizes = try alloc.alloc(BlockSize, num_blocks);
+        errdefer alloc.free(sizes);
+        try rdr.readSliceEndian(BlockSize, sizes, .little);
+        return .{
+            .block_start = std.mem.readInt(u32, start[0..4], .little),
+            .frag_idx = frag_idx,
+            .frag_block_offset = std.mem.readInt(u32, start[8..12], .little),
+            .size = size,
+            .block_sizes = sizes,
+        };
+    }
+
+    pub fn deinit(self: File, alloc: std.mem.Allocator) void {
+        alloc.free(self.block_sizes);
+    }
+};
+
+pub const ExtFile = struct {
+    block_start: u64, // bytes 0-7
+    size: u64, // bytes 8-15
+    sparse: u64, // bytes 16-23
+    hard_links: u32, // bytes 24-27
+    frag_idx: u32, // bytes 28-31
+    frag_block_offset: u32, // bytes 32-35
+    xattr_idx: u32, // bytes 36-39
+    block_sizes: []BlockSize,
+
+    pub fn read(alloc: std.mem.Allocator, rdr: *Reader, block_size: u32) !ExtFile {
+        var start: [40]u8 = undefined;
+        try rdr.readSliceAll(&start);
+        const frag_idx: u32 = std.mem.readInt(u32, start[28..32], .little);
+        const size: u64 = std.mem.readInt(u64, start[8..16], .little);
+        var num_blocks: u32 = @truncate(size / block_size);
+        if (size % block_size != 0 and frag_idx == 0xFFFFFFFF) num_blocks += 1;
+        const sizes = try alloc.alloc(BlockSize, num_blocks);
+        errdefer alloc.free(sizes);
+        try rdr.readSliceEndian(BlockSize, sizes, .little);
+        return .{
+            .block_start = std.mem.readInt(u64, start[0..8], .little),
+            .size = size,
+            .sparse = std.mem.readInt(u64, start[16..24], .little),
+            .hard_links = std.mem.readInt(u32, start[24..28], .little),
+            .frag_idx = frag_idx,
+            .frag_block_offset = std.mem.readInt(u32, start[32..36], .little),
+            .xattr_idx = std.mem.readInt(u32, start[36..40], .little),
+            .block_sizes = sizes,
+        };
+    }
+
+    pub fn deinit(self: ExtFile, alloc: std.mem.Allocator) void {
+        alloc.free(self.block_sizes);
+    }
+};

src/inode_data/misc.zig

@@ -0,0 +1,98 @@
+const std = @import("std");
+const Reader = std.Io.Reader;
+
+pub const Symlink = struct {
+    hard_links: u32,
+    target: []const u8,
+
+    pub fn read(alloc: std.mem.Allocator, rdr: *Reader) !Symlink {
+        var start: [8]u8 = undefined;
+        try rdr.readSliceAll(&start);
+        const target_size = std.mem.readInt(u32, start[4..8], .little);
+        const target = try alloc.alloc(u8, target_size + 1);
+        errdefer alloc.free(target);
+        try rdr.readSliceEndian(u8, target, .little);
+        return .{
+            .hard_links = std.mem.readInt(u32, start[0..4], .little),
+            .target = target,
+        };
+    }
+
+    pub fn deinit(self: Symlink, alloc: std.mem.Allocator) void {
+        alloc.free(self.target);
+    }
+};
+
+pub const ExtSymlink = struct {
+    hard_links: u32,
+    target: []const u8,
+    xattr_idx: u32,
+
+    pub fn read(alloc: std.mem.Allocator, rdr: *Reader) !ExtSymlink {
+        var start: [8]u8 = undefined;
+        try rdr.readSliceAll(&start);
+        const target_size = std.mem.readInt(u32, start[4..8], .little);
+        const target = try alloc.alloc(u8, target_size + 1);
+        errdefer alloc.free(target);
+        try rdr.readSliceEndian(u8, target, .little);
+        var xattr_idx: u32 = undefined;
+        try rdr.readSliceEndian(u32, @ptrCast(&xattr_idx), .little);
+        return .{
+            .hard_links = std.mem.readInt(u32, start[0..4], .little),
+            .target = target,
+            .xattr_idx = xattr_idx,
+        };
+    }
+
+    pub fn deinit(self: ExtSymlink, alloc: std.mem.Allocator) void {
+        alloc.free(self.target);
+    }
+};
+
+/// A block or character device.
+pub const Dev = packed struct {
+    hard_links: u32,
+    dev: u32,
+
+    pub fn read(rdr: *Reader) !Dev {
+        var d: Dev = undefined;
+        try rdr.readSliceEndian(Dev, @ptrCast(&d), .little);
+        return d;
+    }
+};
+
+/// An extended block or character device.
+pub const ExtDev = packed struct {
+    hard_links: u32,
+    dev: u32,
+    xattr_idx: u32,
+
+    pub fn read(rdr: *Reader) !ExtDev {
+        var d: ExtDev = undefined;
+        try rdr.readSliceEndian(ExtDev, @ptrCast(&d), .little);
+        return d;
+    }
+};
+
+/// A socket or FIFO file.
+pub const IPC = packed struct {
+    hard_links: u32,
+
+    pub fn read(rdr: *Reader) !IPC {
+        var d: IPC = undefined;
+        try rdr.readSliceEndian(IPC, @ptrCast(&d), .little);
+        return d;
+    }
+};
+
+/// An extended socket or FIFO file.
+pub const ExtIPC = packed struct {
+    hard_links: u32,
+    xattr_idx: u32,
+
+    pub fn read(rdr: *Reader) !ExtIPC {
+        var d: ExtIPC = undefined;
+        try rdr.readSliceEndian(ExtIPC, @ptrCast(&d), .little);
+        return d;
+    }
+};

src/options.zig

@@ -0,0 +1,33 @@
+//! Options for file/directory extraction.
+
+const std = @import("std");
+const Writer = std.Io.Writer;
+
+const ExtractionOptions = @This();
+
+/// The number of threads used for extraction. 0 implies single threaded.
+threads: usize = 1,
+/// Don't set the file's owner & permissions after extraction
+ignore_permissions: bool = false,
+/// Don't set xattr values. Currently xattrs are never set anyway.
+ignore_xattr: bool = false,
+/// Replace symlinks with their target.
+dereference_symlinks: bool = false,
+/// Verbose logging. If true, verbose_writer must be set
+verbose: bool = false,
+/// Where to print verbose log.
+verbose_writer: ?*Writer = null,
+
+pub const SingleThreadedDefault: ExtractionOptions = .{};
+pub fn Default() !ExtractionOptions {
+    return .{
+        .threads = try std.Thread.getCpuCount(),
+    };
+}
+pub fn VerboseDefault(wrt: *Writer) !ExtractionOptions {
+    return .{
+        .verbose = true,
+        .verbose_writer = wrt,
+        .threads = try std.Thread.getCpuCount(),
+    };
+}

src/root.zig

@@ -0,0 +1,2 @@
+pub const Archive = @import("archive.zig");
+pub const ExtractionOptions = @import("options.zig");

src/super.zig

@@ -0,0 +1,63 @@
+const std = @import("std");
+const math = std.math;
+
+const CompressionType = @import("decomp.zig").CompressionType;
+const InodeRef = @import("inode.zig").Ref;
+
+const SQUASHFS_MAGIC: u32 = std.mem.readInt(u32, "hsqs", .little);
+
+const SuperblockError = error{
+    InvalidMagic,
+    InvalidBlockLog,
+    InvalidVersion,
+    InvalidCheck,
+};
+
+/// A squashfs Superblock
+pub const Superblock = packed struct {
+    magic: u32,
+    inode_count: u32,
+    mod_time: u32,
+    block_size: u32,
+    frag_count: u32,
+    compression: CompressionType,
+    block_log: u16,
+    flags: packed struct {
+        inode_uncompressed: bool,
+        data_uncompressed: bool,
+        check: bool,
+        frag_uncompressed: bool,
+        fragment_never: bool,
+        fragment_always: bool,
+        duplicates: bool,
+        exportable: bool,
+        xattr_uncompressed: bool,
+        xattr_never: bool,
+        compression_options: bool,
+        ids_uncompressed: bool,
+        _: u4,
+    },
+    id_count: u16,
+    ver_maj: u16,
+    ver_min: u16,
+    root_ref: InodeRef,
+    size: u64,
+    id_start: u64,
+    xattr_start: u64,
+    inode_start: u64,
+    dir_start: u64,
+    frag_start: u64,
+    export_start: u64,
+
+    /// Validate the Superblock. If an error is returned, it's likely the archive is corrupted or not a squashfs archive.
+    pub fn validate(self: Superblock) !void {
+        if (self.magic != SQUASHFS_MAGIC)
+            return SuperblockError.InvalidMagic;
+        if (self.flags.check)
+            return SuperblockError.InvalidCheck;
+        if (self.ver_maj != 4 or self.ver_min != 0)
+            return SuperblockError.InvalidVersion;
+        if (math.log2(self.block_size) != self.block_log)
+            return SuperblockError.InvalidBlockLog;
+    }
+};

src/tables.zig

@@ -0,0 +1,108 @@
+const std = @import("std");
+const Mutex = std.Thread.Mutex;
+
+const Archive = @import("archive.zig");
+const DecompFn = @import("decomp.zig").DecompFn;
+const BlockSize = @import("inode_data/file.zig").BlockSize;
+const InodeRef = @import("inode.zig").Ref;
+const Superblock = @import("super.zig").Superblock;
+const MetadataReader = @import("util/metadata.zig");
+const OffsetFile = @import("util/offset_file.zig");
+const XattrTable = @import("xattr.zig");
+
+/// Information about a fragment section. Multiple fragments are contained in the block described by a single FragEntry.
+/// The offset into the block and fragment size is stored in the file's inode.
+pub const FragEntry = packed struct {
+    start: u64,
+    size: BlockSize,
+    _: u32,
+};
+
+const Tables = @This();
+
+frag_table: Table(FragEntry),
+id_table: Table(u16),
+export_table: Table(InodeRef),
+xattr_table: XattrTable,
+
+pub fn init(alloc: std.mem.Allocator, archive: Archive) !Tables {
+    return .{
+        .frag_table = try .init(alloc, archive.fil, archive.decomp, archive.super.frag_start, archive.super.frag_count),
+        .id_table = try .init(alloc, archive.fil, archive.decomp, archive.super.id_start, archive.super.id_count),
+        .export_table = try .init(alloc, archive.fil, archive.decomp, archive.super.export_start, archive.super.inode_count),
+        .xattr_table = try .init(alloc, archive.fil, archive.decomp, archive.super.xattr_start),
+    };
+}
+pub fn deinit(self: *Tables) void {
+    self.frag_table.deinit();
+    self.id_table.deinit();
+    self.export_table.deinit();
+    self.xattr_table.deinit();
+}
+
+/// A two-layer metadata table.
+pub fn Table(T: anytype) type {
+    return struct {
+        const Self = @This();
+
+        const VALS_PER_BLOCK = 8192 / @sizeOf(T);
+
+        alloc: std.mem.Allocator,
+        fil: OffsetFile,
+        decomp: DecompFn,
+        tab_start: u64,
+
+        tab: std.AutoHashMap(u32, []T),
+        values: u32,
+
+        mut: Mutex = .{},
+
+        pub fn init(alloc: std.mem.Allocator, fil: OffsetFile, decomp: DecompFn, tab_start: u64, values: u32) !Self {
+            return .{
+                .alloc = alloc,
+                .fil = fil,
+                .decomp = decomp,
+                .tab_start = tab_start,
+
+                .tab = .init(alloc),
+                .values = values,
+            };
+        }
+
+        pub fn deinit(self: *Self) void {
+            var iter = self.tab.valueIterator();
+            while (iter.next()) |s| {
+                self.alloc.free(s.*);
+            }
+            self.tab.deinit();
+        }
+
+        pub fn get(self: *Self, idx: u32) !T {
+            if (idx >= self.values) return error.InvalidIndex;
+            const block_num = idx / VALS_PER_BLOCK;
+            const idx_offset = idx - (block_num * VALS_PER_BLOCK);
+            if (self.tab.contains(block_num)) {
+                const block = self.tab.get(block_num).?;
+                return block[idx_offset];
+            }
+            self.mut.lock();
+            defer self.mut.unlock();
+            // Double check in case of race condition..
+            if (self.tab.contains(block_num)) {
+                const block = self.tab.get(block_num).?;
+                return block[idx_offset];
+            }
+            const is_last = (self.values - 1) / VALS_PER_BLOCK == block_num;
+            const slice_size = if (is_last) self.values - (block_num * VALS_PER_BLOCK) else VALS_PER_BLOCK;
+            const slice = try self.alloc.alloc(T, slice_size);
+            var rdr = try self.fil.readerAt(self.tab_start + (8 * block_num), &[0]u8{});
+            var offset: u64 = 0;
+            try rdr.interface.readSliceEndian(u64, @ptrCast(&offset), .little);
+            rdr = try self.fil.readerAt(offset, &[0]u8{});
+            var meta: MetadataReader = .init(self.alloc, &rdr.interface, self.decomp);
+            try meta.interface.readSliceEndian(T, @ptrCast(slice), .little);
+            try self.tab.put(block_num, slice);
+            return slice[idx_offset];
+        }
+    };
+}

src/test.zig

@@ -0,0 +1,84 @@
+const std = @import("std");
+const stuff = @import("builtin");
+
+const Archive = @import("archive.zig");
+const Superblock = @import("super.zig").Superblock;
+
+const TestArchive = "testing/LinuxPATest.sfs";
+
+test "Basics" {
+    var fil = try std.fs.cwd().openFile(TestArchive, .{});
+    defer fil.close();
+    var sfs: Archive = try .init(std.testing.allocator, fil);
+    defer sfs.deinit();
+    if (sfs.super != LinuxPATestCorrectSuperblock) {
+        std.debug.print("Superblock wrong\nShould be: {}\n\nis: {}\n", .{ LinuxPATestCorrectSuperblock, sfs.super });
+        return error.BadSuperblock;
+    }
+}
+
+const TestFile = "Start.exe";
+const TestFileExtractLocation = "testing/Start.exe";
+
+test "ExtractSingleFile" {
+    std.fs.cwd().deleteFile(TestFileExtractLocation) catch {};
+    var fil = try std.fs.cwd().openFile(TestArchive, .{});
+    defer fil.close();
+    var sfs: Archive = try .init(std.testing.allocator, fil);
+    defer sfs.deinit();
+    var test_fil = try sfs.open(TestFile);
+    defer test_fil.deinit();
+    try test_fil.extract(TestFileExtractLocation, .Default);
+    //TODO: validate extracted file.
+}
+
+const TestFullExtractLocation = "testing/TestExtract";
+
+test "ExtractCompleteArchive" {
+    std.fs.cwd().deleteTree(TestFullExtractLocation) catch {};
+    var fil = try std.fs.cwd().openFile(TestArchive, .{});
+    defer fil.close();
+    var sfs: Archive = try .init(std.testing.allocator, fil);
+    defer sfs.deinit();
+    try sfs.extract(TestFullExtractLocation, .Default);
+}
+
+const LinuxPATestCorrectSuperblock: Superblock = .{
+    .magic = std.mem.readInt(u32, "hsqs", .little),
+    .inode_count = 2974,
+    .mod_time = 1632696724,
+    .block_size = 131072,
+    .frag_count = 264,
+    .compression = .zstd,
+    .block_log = 17,
+    .flags = .{
+        .inode_uncompressed = false,
+        .data_uncompressed = false,
+        .check = false,
+        .frag_uncompressed = false,
+        .fragment_never = false,
+        .fragment_always = false,
+        .duplicates = true,
+        .exportable = true,
+        .xattr_uncompressed = false,
+        .xattr_never = false,
+        .compression_options = false,
+        .ids_uncompressed = false,
+        ._ = 0,
+    },
+    .id_count = 1,
+    .ver_maj = 4,
+    .ver_min = 0,
+    .root_ref = .{
+        .block_offset = 1363,
+        .block_start = 29237,
+        ._ = 0,
+    },
+    .size = 106841744,
+    .id_start = 106841632,
+    .xattr_start = 106841720,
+    .inode_start = 106778274,
+    .dir_start = 106807998,
+    .frag_start = 106837747,
+    .export_start = 106841602,
+};

src/util/data.zig

@@ -0,0 +1,174 @@
+//! A reader for a regular file.
+
+const std = @import("std");
+const Reader = std.Io.Reader;
+const Writer = std.Io.Writer;
+const Limit = std.Io.Limit;
+
+const Archive = @import("../archive.zig");
+const DecompFn = @import("../decomp.zig").DecompFn;
+const BlockSize = @import("../inode_data/file.zig").BlockSize;
+const FragEntry = @import("../tables.zig").FragEntry;
+const OffsetFile = @import("offset_file.zig");
+
+const DataReader = @This();
+
+alloc: std.mem.Allocator,
+fil: OffsetFile,
+decomp: DecompFn,
+block_size: u32,
+
+blocks: []BlockSize,
+
+frag: ?FragEntry = null, // TODO: do something better?
+frag_offset: u32 = 0,
+size: u64,
+
+interface: Reader,
+
+cur_offset: u64,
+block_idx: u32 = 0,
+
+pub fn init(alloc: std.mem.Allocator, archive: Archive, blocks: []BlockSize, start: u64, size: u64) DataReader {
+    return .{
+        .alloc = alloc,
+        .fil = archive.fil,
+        .decomp = archive.decomp,
+        .block_size = archive.super.block_size,
+        .blocks = blocks,
+        .size = size,
+        .cur_offset = start,
+        .interface = .{
+            .end = 0,
+            .seek = 0,
+            .buffer = &[0]u8{},
+            .vtable = &.{
+                .stream = stream,
+                .discard = discard,
+                .readVec = readVec,
+            },
+        },
+    };
+}
+pub fn deinit(self: *DataReader) void {
+    self.alloc.free(self.interface.buffer);
+    self.interface.end = 0;
+    self.interface.seek = 0;
+}
+
+pub fn addFragment(self: *DataReader, entry: FragEntry, frag_offset: u32) void {
+    self.frag = entry;
+    self.frag_offset = frag_offset;
+}
+
+fn numBlocks(self: DataReader) usize {
+    var res = self.blocks.len;
+    if (self.frag != null) res += 1;
+    return res;
+}
+
+fn advance(self: *DataReader) !void {
+    if (self.block_idx > self.blocks.len or (self.block_idx == self.blocks.len and self.frag == null)) {
+        if (self.interface.buffer.len > 0) {
+            self.alloc.free(self.interface.buffer);
+            self.interface.buffer = &[0]u8{};
+            self.interface.end = 0;
+            self.interface.seek = 0;
+        }
+        return Reader.Error.EndOfStream;
+    }
+    defer self.block_idx += 1;
+    const cur_block_size = if (self.block_idx == self.numBlocks() - 1) self.size % self.block_size else self.block_size;
+    try self.resizeBuffer(cur_block_size);
+    self.interface.seek = 0;
+    self.interface.end = cur_block_size;
+    if (self.block_idx == self.blocks.len) { // fragment
+        var rdr = try self.fil.readerAt(self.frag.?.start, &[0]u8{});
+        if (self.frag.?.size.uncompressed) {
+            try rdr.interface.discardAll(self.frag_offset);
+            try rdr.interface.readSliceAll(self.interface.buffer);
+            return;
+        }
+        const tmp_buf = try self.alloc.alloc(u8, self.frag.?.size.size);
+        defer self.alloc.free(tmp_buf);
+        try rdr.interface.readSliceAll(tmp_buf);
+        const needed_block = try self.alloc.alloc(u8, self.block_size);
+        defer self.alloc.free(needed_block);
+        _ = try self.decomp(self.alloc, tmp_buf, needed_block);
+        @memcpy(self.interface.buffer, needed_block[self.frag_offset .. self.frag_offset + cur_block_size]);
+        return;
+    }
+    const block = self.blocks[self.block_idx];
+    if (block.size == 0) {
+        @memset(self.interface.buffer, 0);
+        return;
+    }
+    var rdr = try self.fil.readerAt(self.cur_offset, &[0]u8{});
+    self.cur_offset += block.size;
+    if (block.uncompressed) {
+        try rdr.interface.readSliceAll(self.interface.buffer);
+        return;
+    }
+    const tmp_buf = try self.alloc.alloc(u8, block.size);
+    defer self.alloc.free(tmp_buf);
+    try rdr.interface.readSliceAll(tmp_buf);
+    _ = try self.decomp(self.alloc, tmp_buf, self.interface.buffer);
+}
+/// Does not guarentee that data currently in the buffer is retained.
+fn resizeBuffer(self: *DataReader, size: usize) !void {
+    if (self.interface.buffer.len == size) return;
+    if (!self.alloc.resize(self.interface.buffer, size)) {
+        self.alloc.free(self.interface.buffer);
+        self.interface.buffer = self.alloc.alloc(u8, size) catch |err| {
+            self.interface.buffer = &[0]u8{};
+            return err;
+        };
+    } else {
+        self.interface.buffer.len = size;
+    }
+}
+
+fn stream(rdr: *Reader, wrt: *Writer, limit: Limit) Reader.StreamError!usize {
+    var self: *DataReader = @alignCast(@fieldParentPtr("interface", rdr));
+    if (rdr.seek >= rdr.end) self.advance() catch |err| {
+        if (err == error.EndOfStream) return error.EndOfStream;
+        std.log.err("Error advancing data reader: {}\n", .{err});
+        return Reader.Error.ReadFailed;
+    };
+    if (limit == .nothing) return 0;
+    const to_read = @min(rdr.end - rdr.seek, @intFromEnum(limit));
+    const res = try wrt.write(rdr.buffer[rdr.seek .. rdr.seek + to_read]);
+    rdr.seek += res;
+    return res;
+}
+
+fn discard(rdr: *Reader, limit: Limit) Reader.Error!usize {
+    var self: *DataReader = @alignCast(@fieldParentPtr("interface", rdr));
+    if (rdr.seek >= rdr.end) self.advance() catch |err| {
+        if (err == error.EndOfStream) return error.EndOfStream;
+        std.log.err("Error advancing data reader: {}\n", .{err});
+        return Reader.Error.ReadFailed;
+    };
+    if (limit == .nothing) return 0;
+    const to_adv = @min(rdr.end - rdr.seek, @intFromEnum(limit));
+    rdr.seek += to_adv;
+    return to_adv;
+}
+
+fn readVec(rdr: *Reader, vec: [][]u8) Reader.Error!usize {
+    var self: *DataReader = @alignCast(@fieldParentPtr("interface", rdr));
+    if (rdr.seek >= rdr.end) self.advance() catch |err| {
+        if (err == error.EndOfStream) return error.EndOfStream;
+        std.log.err("Error advancing data reader: {}\n", .{err});
+        return Reader.Error.ReadFailed;
+    };
+    var cur_red: usize = 0;
+    for (vec) |s| {
+        const to_copy: usize = @min(rdr.end - rdr.seek, s.len);
+        @memcpy(s[0..to_copy], rdr.buffer[rdr.seek .. rdr.seek + to_copy]);
+        rdr.seek += to_copy;
+        cur_red += to_copy;
+        if (rdr.end == rdr.seek) break;
+    }
+    return cur_red;
+}

src/util/data_threaded.zig

@@ -0,0 +1,207 @@
+//! Similiar to DataReader, but set-up for threaded writing to files.
+
+const std = @import("std");
+const Reader = std.Io.Reader;
+const Writer = std.Io.Writer;
+const Limit = std.Io.Limit;
+const WaitGroup = std.Thread.WaitGroup;
+const Pool = std.Thread.Pool;
+
+const Archive = @import("../archive.zig");
+const DecompFn = @import("../decomp.zig").DecompFn;
+const BlockSize = @import("../inode_data/file.zig").BlockSize;
+const FragEntry = @import("../tables.zig").FragEntry;
+const InodeFinish = @import("inode_finish.zig");
+const OffsetFile = @import("offset_file.zig");
+
+const ThreadedDataReader = @This();
+
+alloc: std.mem.Allocator,
+fil: OffsetFile,
+decomp: DecompFn,
+block_size: u32,
+
+blocks: []BlockSize,
+
+frag: ?FragEntry = null, // TODO: do something better?
+frag_offset: u32 = 0,
+size: u64,
+num_blocks: usize,
+
+start_offset: u64,
+
+pub fn init(alloc: std.mem.Allocator, archive: Archive, blocks: []BlockSize, start: u64, size: u64) ThreadedDataReader {
+    return .{
+        .alloc = alloc,
+        .fil = archive.fil,
+        .decomp = archive.decomp,
+        .block_size = archive.super.block_size,
+
+        .blocks = blocks,
+
+        .size = size,
+        .num_blocks = blocks.len,
+
+        .start_offset = start,
+    };
+}
+
+pub fn addFragment(self: *ThreadedDataReader, entry: FragEntry, frag_offset: u32) void {
+    self.frag = entry;
+    self.frag_offset = frag_offset;
+    self.num_blocks = self.blocks.len + 1;
+}
+
+/// Extract the data to the file threadedly, using pool to spawn threads.
+/// If errors occur, they are set to finish.out_err.
+pub fn extractThreaded(self: ThreadedDataReader, file: std.fs.File, pool: *Pool, finish: *InodeFinish) void {
+    var cur_write_offset: u64 = 0;
+    var cur_read_offset: u64 = self.start_offset;
+    for (0..self.blocks.len) |i| {
+        const cur_block_size = if (i == self.num_blocks - 1) self.size % self.block_size else self.block_size;
+        pool.spawn(workThreadBlocks, .{ self, file, cur_write_offset, cur_read_offset, self.blocks[i], cur_block_size, finish }) catch |res_err| {
+            finish.logError("Can't spawn pool task: {}", .{res_err});
+            finish.out_err.* = res_err;
+            finish.finish();
+        };
+        cur_write_offset += cur_block_size;
+        cur_read_offset += self.blocks[i].size;
+    }
+    if (self.frag != null)
+        pool.spawn(workThreadFragment, .{ self, file, cur_write_offset, finish }) catch |res_err| {
+            finish.logError("Can't spawn pool task: {}", .{res_err});
+            finish.out_err.* = res_err;
+            finish.finish();
+        };
+}
+
+fn workThreadBlocks(
+    self: ThreadedDataReader,
+    fil: std.fs.File,
+    write_offset: u64,
+    read_offset: u64,
+    block: BlockSize,
+    cur_block_size: u64,
+    finish: *InodeFinish,
+) void {
+    defer finish.finish();
+    var wrt = fil.writer(&[0]u8{});
+    wrt.seekTo(write_offset) catch |err| {
+        finish.logError("Error seeking file writer: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    defer wrt.interface.flush() catch |err| {
+        finish.logError("Error flushing file writer: {}", .{err});
+        finish.out_err.* = err;
+    };
+    if (block.size == 0) {
+        wrt.interface.splatByteAll(0, cur_block_size) catch |err| {
+            finish.logError("Error writing zeroes: {}", .{err});
+            finish.out_err.* = err;
+            return;
+        };
+        return;
+    }
+    var rdr = self.fil.readerAt(read_offset, &[0]u8{}) catch |err| {
+        finish.logError("Error creating file reader: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    if (block.uncompressed) {
+        rdr.interface.streamExact(&wrt.interface, block.size) catch |err| {
+            finish.logError("Error streaming data: {}", .{err});
+            finish.out_err.* = err;
+            return;
+        };
+        return;
+    }
+    // TODO: shared buffers
+    const read_buf = self.alloc.alloc(u8, block.size) catch |err| {
+        finish.logError("Error creating reader buffer: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    defer self.alloc.free(read_buf);
+    rdr.interface.readSliceAll(read_buf) catch |err| {
+        finish.logError("Error reading data into reader buffer: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    // TODO: shared buffers
+    const res_buf = self.alloc.alloc(u8, cur_block_size) catch |err| {
+        finish.logError("Error creating result buffer: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    defer self.alloc.free(res_buf);
+    _ = self.decomp(self.alloc, read_buf, res_buf) catch |err| {
+        finish.logError("Error decompressing data block: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    wrt.interface.writeAll(res_buf) catch |err| {
+        finish.logError("Error writing to file: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+}
+fn workThreadFragment(self: ThreadedDataReader, fil: std.fs.File, write_offset: u64, finish: *InodeFinish) void {
+    defer finish.finish();
+
+    var wrt = fil.writer(&[0]u8{});
+    wrt.seekTo(write_offset) catch |err| {
+        finish.logError("Error seeking file writer for file fragment: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    defer wrt.interface.flush() catch |err| {
+        finish.out_err.* = err;
+    };
+
+    var rdr = self.fil.readerAt(self.frag.?.start, &[0]u8{}) catch |err| {
+        finish.logError("Error creating file reader for file fragment: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    if (self.frag.?.size.uncompressed) {
+        rdr.interface.discardAll(self.frag_offset) catch |err| {
+            finish.logError("Error discarding useless fragment data: {}", .{err});
+            finish.out_err.* = err;
+            return;
+        };
+        rdr.interface.streamExact(&wrt.interface, self.size % self.block_size) catch |err| {
+            finish.logError("Error streaming fragment data: {}", .{err});
+            finish.out_err.* = err;
+            return;
+        };
+        return;
+    }
+    const tmp_buf = self.alloc.alloc(u8, self.frag.?.size.size) catch |err| {
+        finish.logError("Error creating a temporary buffer for a file fragment: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    defer self.alloc.free(tmp_buf);
+    rdr.interface.readSliceAll(tmp_buf) catch |err| {
+        finish.logError("Error reading data into fragment buffer: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    const needed_block = self.alloc.alloc(u8, self.block_size) catch |err| {
+        finish.logError("Error allocating fragment decompression results: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    defer self.alloc.free(needed_block);
+    _ = self.decomp(self.alloc, tmp_buf, needed_block) catch |err| {
+        finish.logError("Error decompressing fragment: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+    wrt.interface.writeAll(needed_block[self.frag_offset .. self.frag_offset + (self.size % self.block_size)]) catch |err| {
+        finish.logError("Error writing fragment: {}", .{err});
+        finish.out_err.* = err;
+        return;
+    };
+}

src/util/extract.zig

@@ -0,0 +1,353 @@
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+const Pool = std.Thread.Pool;
+const WaitGroup = std.Thread.WaitGroup;
+
+const Archive = @import("../archive.zig");
+const DirEntry = @import("../dir_entry.zig");
+const Inode = @import("../inode.zig");
+const ExtractionOptions = @import("../options.zig");
+const Tables = @import("../tables.zig");
+const InodeFinish = @import("inode_finish.zig");
+const FinishUnion = InodeFinish.FinishUnion;
+const ThreadedDataReader = @import("data_threaded.zig");
+
+// 1 MB
+const STACK_ALLOC_SIZE = 1024 * 1024;
+
+pub fn extractTo(
+    allocator: Allocator,
+    inode: Inode,
+    archive: Archive,
+    path: []const u8,
+    options: ExtractionOptions,
+) !void {
+    if (path[path.len - 1] == '/')
+        return extractTo(allocator, inode, archive, path[0 .. path.len - 2], options);
+
+    var stack_alloc = std.heap.stackFallback(STACK_ALLOC_SIZE, allocator);
+    var arena: std.heap.ArenaAllocator = .init(stack_alloc.get());
+    defer arena.deinit();
+    if (options.threads <= 1) {
+        const alloc = arena.allocator();
+        var tables: Tables = try .init(alloc, archive);
+        return extractSingleThread(arena.allocator(), inode, archive, &tables, path, options);
+    }
+
+    var thread_alloc = std.heap.ThreadSafeAllocator{ .child_allocator = arena.allocator() };
+    const alloc = thread_alloc.allocator();
+    var tables: Tables = try .init(alloc, archive);
+
+    var pool_alloc = std.heap.stackFallback(10 * 1024, alloc);
+    var pool: Pool = undefined;
+    try pool.init(.{ .allocator = pool_alloc.get(), .n_jobs = options.threads - 1 });
+
+    var wg: WaitGroup = .{};
+    var err: ?anyerror = null;
+    wg.start();
+    try pool.spawn(extractMultiThread, .{
+        alloc,
+        inode,
+        archive,
+        &tables,
+        path,
+        options,
+        &pool,
+        FinishUnion{ .wg = &wg },
+        &err,
+    });
+    pool.waitAndWork(&wg);
+    if (err != null) return err.?;
+}
+
+fn extractSingleThread(
+    alloc: Allocator,
+    inode: Inode,
+    archive: Archive,
+    tables: *Tables,
+    path: []const u8,
+    options: ExtractionOptions,
+) !void {
+    switch (inode.hdr.inode_type) {
+        .dir, .ext_dir => {
+            _ = std.fs.cwd().makeDir(path) catch |err| switch (err) {
+                std.fs.Dir.MakeError.PathAlreadyExists => {},
+                else => return err,
+            };
+
+            // Currently we are ignoring any deinit or free calls since we know we are under an ArenaAllocator.
+            // Possibly in the future, do some simple math to see if it would be safe to ONLY deinit via Arena,
+            // otherwise be more conscientious about freeing memory.
+            // For now, this is good enough.
+
+            const entries = try inode.dirEntries(alloc, archive);
+            for (entries) |ent| {
+                const sub_inode: Inode = try .readFromEntry(alloc, archive, ent);
+                const new_path = try std.mem.concat(alloc, u8, &[_][]const u8{ path, "/", ent.name });
+                try extractSingleThread(alloc, sub_inode, archive, tables, new_path, options);
+            }
+
+            const fil = try std.fs.cwd().openFile(path, .{});
+            defer fil.close();
+            try inode.setMetadata(alloc, tables, fil, options);
+        },
+        .file, .ext_file => {
+            var fil = try std.fs.cwd().createFile(path, .{ .exclusive = true });
+            defer fil.close();
+            var wrt = fil.writer(&[0]u8{});
+            var dat_rdr = try inode.dataReader(alloc, archive, tables);
+            defer dat_rdr.deinit();
+            _ = try dat_rdr.interface.streamRemaining(&wrt.interface);
+            try wrt.interface.flush();
+
+            try inode.setMetadata(alloc, tables, fil, options);
+        },
+        .symlink, .ext_symlink => return extractSymlink(inode, path),
+        else => return extractDeviceAndIPC(inode, alloc, tables, path, options),
+    }
+}
+
+fn extractMultiThread(
+    alloc: Allocator,
+    inode: Inode,
+    archive: Archive,
+    tables: *Tables,
+    path: []const u8,
+    options: ExtractionOptions,
+    pool: *Pool,
+    fin: FinishUnion,
+    err: *?anyerror,
+) void {
+    if (err.* != null) {
+        fin.finish();
+        return;
+    }
+    switch (inode.hdr.inode_type) {
+        .dir, .ext_dir => {
+            _ = std.fs.cwd().makeDir(path) catch |res_err| switch (res_err) {
+                std.fs.Dir.MakeError.PathAlreadyExists => {},
+                else => {
+                    err.* = res_err;
+                    fin.finish();
+                    return;
+                },
+            };
+
+            // Currently we are ignoring any deinit or free calls since we know we are under an ArenaAllocator.
+            // Possibly in the future, do some simple math to see if it would be safe to ONLY deinit via Arena,
+            // otherwise be more conscientious about freeing memory.
+            // For now, this is good enough.
+
+            const entries = inode.dirEntries(alloc, archive) catch |res_err| {
+                err.* = res_err;
+                fin.finish();
+                return;
+            };
+
+            if (entries.len == 0) {
+                fin.finish();
+                return;
+            }
+
+            var dir_fin = InodeFinish.create(
+                alloc,
+                inode,
+                path,
+                tables,
+                options,
+                fin,
+                err,
+                null,
+                entries.len,
+            ) catch |res_err| {
+                err.* = res_err;
+                fin.finish();
+                return;
+            };
+
+            for (entries) |ent| {
+                if (ent.inode_type == .dir) {
+                    extractEntry(
+                        alloc,
+                        ent,
+                        archive,
+                        tables,
+                        path,
+                        options,
+                        pool,
+                        .{ .fin = dir_fin },
+                        err,
+                    );
+                    continue;
+                }
+
+                pool.spawn(
+                    extractEntry,
+                    .{ alloc, ent, archive, tables, path, options, pool, FinishUnion{ .fin = dir_fin }, err },
+                ) catch |res_err| {
+                    err.* = res_err;
+                    dir_fin.finish();
+                    return;
+                };
+            }
+        },
+        .file, .ext_file => {
+            const fil = std.fs.cwd().createFile(path, .{ .exclusive = true }) catch |res_err| {
+                if (options.verbose)
+                    options.verbose_writer.?.print("Can't create file at {s}: {}\n", .{ path, res_err }) catch {};
+                err.* = res_err;
+                fin.finish();
+                return;
+            };
+
+            var data_rdr = threadedDataReader(inode, alloc, archive, tables) catch |res_err| {
+                if (options.verbose)
+                    options.verbose_writer.?.print("Can't create data reader for inode #{} (extracting to {s}): {}\n", .{ inode.hdr.num, path, res_err }) catch {};
+                err.* = res_err;
+                fin.finish();
+                return;
+            };
+            if (data_rdr == null) {
+                inode.setMetadata(alloc, tables, fil, options) catch |res_err| {
+                    if (options.verbose)
+                        options.verbose_writer.?.print("Can't set metadata to {s}: {}\n", .{ path, res_err }) catch {};
+                    err.* = res_err;
+                };
+                fin.finish();
+                return;
+            }
+            const file_fin = InodeFinish.create(
+                alloc,
+                inode,
+                path,
+                tables,
+                options,
+                fin,
+                err,
+                fil,
+                data_rdr.?.num_blocks,
+            ) catch |res_err| {
+                if (options.verbose)
+                    options.verbose_writer.?.print("Can't create callback for inode #{} (extracting to {s}): {}\n", .{ inode.hdr.num, path, res_err }) catch {};
+                err.* = res_err;
+                fin.finish();
+                return;
+            };
+
+            data_rdr.?.extractThreaded(fil, pool, file_fin);
+        },
+        .symlink, .ext_symlink => {
+            extractSymlink(inode, path) catch |res_err| {
+                err.* = res_err;
+            };
+            fin.finish();
+        },
+        else => {
+            extractDeviceAndIPC(inode, alloc, tables, path, options) catch |res_err| {
+                err.* = res_err;
+            };
+            fin.finish();
+        },
+    }
+}
+
+fn extractEntry(
+    alloc: Allocator,
+    ent: DirEntry,
+    archive: Archive,
+    tables: *Tables,
+    path: []const u8,
+    options: ExtractionOptions,
+    pool: *Pool,
+    fin: FinishUnion,
+    err: *?anyerror,
+) void {
+    const new_path = std.mem.concat(alloc, u8, &[_][]const u8{ path, "/", ent.name }) catch |res_err| {
+        err.* = res_err;
+        fin.finish();
+        return;
+    };
+
+    const inode = Inode.readFromEntry(alloc, archive, ent) catch |res_err| {
+        err.* = res_err;
+        fin.finish();
+        return;
+    };
+    extractMultiThread(alloc, inode, archive, tables, new_path, options, pool, fin, err);
+}
+
+/// Get a threaded data reader for a file inode.
+fn threadedDataReader(self: Inode, alloc: std.mem.Allocator, archive: Archive, tables: *Tables) !?ThreadedDataReader {
+    return switch (self.hdr.inode_type) {
+        .file => threadedReaderFromData(alloc, archive, tables, self.data.file),
+        .ext_file => threadedReaderFromData(alloc, archive, tables, self.data.ext_file),
+        else => error.NotRegularFile,
+    };
+}
+fn threadedReaderFromData(alloc: std.mem.Allocator, archive: Archive, tables: *Tables, data: anytype) !?ThreadedDataReader {
+    if (data.block_sizes.len == 0 and data.frag_idx == 0xFFFFFFFF) return null;
+    var out: ThreadedDataReader = .init(alloc, archive, data.block_sizes, data.block_start, data.size);
+    if (data.frag_idx != 0xFFFFFFFF)
+        out.addFragment(try tables.frag_table.get(data.frag_idx), data.frag_block_offset);
+    return out;
+}
+
+/// Creates the symlink described by the inode.
+/// Sets metadata.
+fn extractSymlink(self: Inode, path: []const u8) !void {
+    const target = switch (self.data) {
+        .symlink => |s| s.target,
+        .ext_symlink => |s| s.target,
+        else => unreachable,
+    };
+    try std.fs.cwd().symLink(target, path, .{});
+}
+/// Creates the device described by the inode.
+/// Sets metadata.
+fn extractDeviceAndIPC(self: Inode, alloc: std.mem.Allocator, tables: *Tables, path: []const u8, options: ExtractionOptions) !void {
+    var mode: u32 = undefined;
+    var dev: u32 = 0;
+    switch (self.data) {
+        .char_dev => |d| {
+            mode = std.posix.S.IFCHR;
+            dev = d.dev;
+        },
+        .ext_char_dev => |d| {
+            mode = std.posix.S.IFCHR;
+            dev = d.dev;
+        },
+        .block_dev => |d| {
+            mode = std.posix.S.IFBLK;
+            dev = d.dev;
+        },
+        .ext_block_dev => |d| {
+            mode = std.posix.S.IFBLK;
+            dev = d.dev;
+        },
+        .fifo, .ext_fifo => mode = std.posix.S.IFIFO,
+        .socket, .ext_socket => mode = std.posix.S.IFSOCK,
+        else => unreachable,
+    }
+    const res: std.os.linux.E = @enumFromInt(std.os.linux.mknod(@ptrCast(path), mode, dev));
+    switch (res) {
+        .SUCCESS => {},
+        .ACCES => return std.fs.Dir.MakeError.AccessDenied,
+        .DQUOT => return std.fs.Dir.MakeError.DiskQuota,
+        .EXIST => return std.fs.Dir.MakeError.PathAlreadyExists,
+        .FAULT, .NOENT => return std.fs.Dir.MakeError.BadPathName,
+        .LOOP => return std.fs.Dir.MakeError.SymLinkLoop,
+        .NAMETOOLONG => return std.fs.Dir.MakeError.NameTooLong,
+        .NOMEM => return std.fs.Dir.MakeError.SystemResources,
+        .NOSPC => return std.fs.Dir.MakeError.NoSpaceLeft,
+        .NOTDIR => return std.fs.Dir.MakeError.NotDir,
+        .PERM => return std.fs.Dir.MakeError.PermissionDenied,
+        .ROFS => return std.fs.Dir.MakeError.ReadOnlyFileSystem,
+        else => return blk: {
+            std.debug.print("unhandled mknod result: {}\n", .{res});
+            break :blk std.fs.Dir.MakeError.Unexpected;
+        },
+    }
+    var fil = try std.fs.cwd().openFile(path, .{});
+    defer fil.close();
+    try self.setMetadata(alloc, tables, fil, options);
+}

src/util/inode_finish.zig

@@ -0,0 +1,101 @@
+const std = @import("std");
+const WaitGroup = std.Thread.WaitGroup;
+const Mutex = std.Thread.Mutex;
+
+const Archive = @import("../archive.zig");
+const Inode = @import("../inode.zig");
+const ExtractionOptions = @import("../options.zig");
+const Tables = @import("../tables.zig");
+
+const InodeFinish = @This();
+
+const FinishEnum = enum {
+    wg,
+    fin,
+};
+pub const FinishUnion = union(FinishEnum) {
+    wg: *WaitGroup,
+    fin: *InodeFinish,
+
+    pub fn finish(self: FinishUnion) void {
+        switch (self) {
+            .wg => |wg| wg.finish(),
+            .fin => |fin| fin.finish(),
+        }
+    }
+};
+
+alloc: std.mem.Allocator,
+
+inode: Inode,
+path: []const u8,
+tables: *Tables,
+options: ExtractionOptions,
+parent_finish: FinishUnion,
+fil: ?std.fs.File,
+out_err: *?anyerror,
+
+wg: WaitGroup = .{},
+mut: Mutex = .{},
+
+pub fn create(
+    alloc: std.mem.Allocator,
+    inode: Inode,
+    path: []const u8,
+    tables: *Tables,
+    options: ExtractionOptions,
+    parent_finish: FinishUnion,
+    out_err: *?anyerror,
+    fil: ?std.fs.File,
+    work_size: usize,
+) !*InodeFinish {
+    if (work_size == 0)
+        return error.InvalidWorkSize;
+    const out = try alloc.create(InodeFinish);
+    errdefer alloc.destroy(out);
+    out.* = .{
+        .alloc = alloc,
+
+        .inode = inode,
+        .path = path,
+        .tables = tables,
+        .options = options,
+        .parent_finish = parent_finish,
+        .out_err = out_err,
+        .fil = fil,
+    };
+    out.wg.startMany(work_size);
+    return out;
+}
+
+pub fn logError(self: *InodeFinish, comptime fmt: []const u8, args: anytype) void {
+    if (self.options.verbose)
+        self.options.verbose_writer.?.print(fmt, args) catch {};
+}
+
+pub fn finish(self: *InodeFinish) void {
+    self.mut.lock();
+    {
+        defer self.mut.unlock();
+        self.wg.finish();
+        if (!self.wg.isDone()) return;
+    }
+    defer {
+        self.parent_finish.finish();
+        self.alloc.destroy(self);
+    }
+    if (self.fil == null)
+        self.fil = std.fs.cwd().openFile(self.path, .{}) catch |err| {
+            if (self.options.verbose)
+                self.options.verbose_writer.?.print("Error opening {s} to set metadata: {}\n", .{ self.path, err }) catch {};
+            self.out_err.* = err;
+            return;
+        };
+    defer self.fil.?.close();
+    self.inode.setMetadata(self.alloc, self.tables, self.fil.?, self.options) catch |err| {
+        if (self.options.verbose)
+            self.options.verbose_writer.?.print("Error setting metadata to {s}: {}\n", .{ self.path, err }) catch {};
+        self.out_err.* = err;
+        return;
+    };
+}

src/util/meta_cache.zig

@@ -0,0 +1,41 @@
+const std = @import("std");
+
+const OffsetFile = @import("offset_file.zig");
+
+const MetadataCache = @This();
+
+alloc: std.mem.Allocator,
+
+buf: []u8,
+fixed_alloc: std.heap.FixedBufferAllocator,
+
+cache: std.AutoArrayHashMap(u64, [8192]u8),
+
+mut: std.Thread.Mutex = .{},
+cache_mut: std.AutoArrayHashMap(u64, std.Thread.Mutex),
+
+fil: OffsetFile,
+
+pub fn init(alloc: std.mem.Allocator, cache_size: u64) !MetadataCache {}
+pub fn deinit(self: *MetadataCache) void {
+    self.mut.lock();
+    defer self.mut.unlock();
+    self.cache.deinit();
+    self.cache_mut.deinit();
+    self.alloc.free(self.buf);
+}
+
+pub fn getChunk(self: *MetadataCache, offset: u64) ![8192]u8 {
+    var res = self.cache.get(offset);
+    if (res != null) return res.?;
+    var offset_mut = blk: {
+        self.mut.lock();
+        defer self.mut.unlock();
+        const mut = try self.cache_mut.getOrPut(offset);
+        if (!mut.found_existing)
+            mut.value_ptr.* = .{};
+        break :blk mut.value_ptr;
+    };
+    offset_mut.lock();
+    defer offset_mut.unlock();
+}

src/util/metadata.zig

@@ -0,0 +1,97 @@
+const std = @import("std");
+const Reader = std.Io.Reader;
+const Writer = std.Io.Writer;
+const Limit = std.Io.Limit;
+const StreamError = std.Io.Reader.StreamError;
+
+const DecompFn = @import("../decomp.zig").DecompFn;
+
+const BlockHeader = packed struct {
+    size: u15,
+    uncompressed: bool,
+};
+
+const This = @This();
+
+alloc: std.mem.Allocator,
+rdr: *Reader,
+decomp: DecompFn,
+
+buf: [8192]u8 = undefined,
+
+interface: Reader,
+err: ?anyerror = null,
+
+pub fn init(alloc: std.mem.Allocator, rdr: *Reader, decomp: DecompFn) This {
+    return .{
+        .alloc = alloc,
+        .rdr = rdr,
+        .decomp = decomp,
+        .interface = .{
+            .buffer = &[0]u8{},
+            .end = 0,
+            .seek = 0,
+            .vtable = &.{
+                .stream = stream,
+                .discard = discard,
+                .readVec = readVec,
+            },
+        },
+    };
+}
+
+fn advance(self: *This) !void {
+    self.interface.seek = 0;
+    var hdr: BlockHeader = undefined;
+    try self.rdr.readSliceEndian(BlockHeader, @ptrCast(&hdr), .little);
+    if (hdr.uncompressed) {
+        try self.rdr.readSliceEndian(u8, self.buf[0..hdr.size], .little);
+        self.interface.end = hdr.size;
+        self.interface.buffer = self.buf[0..hdr.size];
+        return;
+    }
+    var tmp_buf: [8192]u8 = undefined;
+    try self.rdr.readSliceAll(tmp_buf[0..hdr.size]);
+    self.interface.end = try self.decomp(self.alloc, tmp_buf[0..hdr.size], &self.buf);
+    self.interface.buffer = self.buf[0..self.interface.end];
+}
+
+fn stream(rdr: *Reader, wrt: *Writer, limit: Limit) StreamError!usize {
+    const self: *This = @fieldParentPtr("interface", rdr);
+    if (rdr.end == rdr.seek) self.advance() catch |err| {
+        self.err = err;
+        return StreamError.ReadFailed;
+    };
+    if (@intFromEnum(limit) == 0) return 0;
+    const to_write = @min(rdr.end - rdr.seek, @intFromEnum(limit));
+    const wrote = try wrt.write(self.buf[rdr.seek .. rdr.seek + to_write]);
+    self.interface.seek += wrote;
+    return wrote;
+}
+fn discard(rdr: *Reader, limit: Limit) error{ EndOfStream, ReadFailed }!usize {
+    const self: *This = @fieldParentPtr("interface", rdr);
+    if (rdr.end == rdr.seek) self.advance() catch |err| {
+        self.err = err;
+        return StreamError.ReadFailed;
+    };
+    if (@intFromEnum(limit) == 0) return 0;
+    const to_skip = @min(rdr.end - rdr.seek, @intFromEnum(limit));
+    rdr.seek += to_skip;
+    return to_skip;
+}
+fn readVec(rdr: *Reader, vec: [][]u8) error{ EndOfStream, ReadFailed }!usize {
+    const self: *This = @fieldParentPtr("interface", rdr);
+    if (rdr.end == rdr.seek) self.advance() catch |err| {
+        self.err = err;
+        return StreamError.ReadFailed;
+    };
+    var cur_red: usize = 0;
+    for (vec) |s| {
+        const to_copy: usize = @min(rdr.end - rdr.seek, s.len);
+        @memcpy(s[0..to_copy], self.buf[rdr.seek .. rdr.seek + to_copy]);
+        rdr.seek += to_copy;
+        cur_red += to_copy;
+        if (rdr.end == rdr.seek) break;
+    }
+    return cur_red;
+}

src/util/offset_file.zig

@@ -0,0 +1,20 @@
+//! A File where it's meaningful (to us) content starts at a given offset.
+
+const std = @import("std");
+const File = std.fs.File;
+const Reader = std.fs.File.Reader;
+
+const OffsetFile = @This();
+
+fil: File,
+offset: u64,
+
+pub fn init(fil: File, init_offset: u64) OffsetFile {
+    return .{ .fil = fil, .offset = init_offset };
+}
+
+pub fn readerAt(self: OffsetFile, offset: u64, buffer: []u8) !Reader {
+    var rdr = self.fil.reader(buffer);
+    try rdr.seekTo(self.offset + offset);
+    return rdr;
+}

src/xattr.zig

@@ -0,0 +1,117 @@
+const std = @import("std");
+
+const DecompFn = @import("decomp.zig").DecompFn;
+const Table = @import("tables.zig").Table;
+const MetadataReader = @import("util/metadata.zig");
+const OffsetFile = @import("util/offset_file.zig");
+
+const Ref = packed struct {
+    block_offset: u16,
+    block_start: u32,
+    _: u16,
+};
+const Entry = packed struct {
+    ref: Ref,
+    count: u32,
+    size: u32,
+};
+const KeyPrefix = enum(u8) {
+    user,
+    trusted,
+    security,
+};
+const KeyRaw = packed struct {
+    type: packed struct {
+        prefix: KeyPrefix,
+        out_of_line: bool,
+        _: u7,
+    },
+    name_size: u16,
+};
+
+pub const KeyValue = struct {
+    key: [:0]u8,
+    value: []u8,
+};
+
+const XattrTable = @This();
+
+alloc: std.mem.Allocator,
+fil: OffsetFile,
+decomp: DecompFn,
+
+count: u32,
+start: u64,
+
+table: Table(Entry),
+
+pub fn init(alloc: std.mem.Allocator, fil: OffsetFile, decomp: DecompFn, table_start: u64) !XattrTable {
+    var info = packed struct {
+        start: u64 = undefined,
+        count: u32 = undefined,
+        _: u32 = undefined,
+    }{};
+    var rdr = try fil.readerAt(table_start, &[0]u8{});
+    try rdr.interface.readSliceEndian(@TypeOf(info), @ptrCast(&info), .little);
+    return .{
+        .alloc = alloc,
+        .fil = fil,
+        .decomp = decomp,
+        .count = info.count,
+        .start = info.start,
+        .table = try .init(alloc, fil, decomp, table_start + 16, info.count),
+    };
+}
+pub fn deinit(self: *XattrTable) void {
+    self.table.deinit();
+}
+
+pub fn get(self: *XattrTable, alloc: std.mem.Allocator, idx: u32) ![]KeyValue {
+    const entry: Entry = try self.table.get(idx);
+    const out = try alloc.alloc(KeyValue, entry.count);
+
+    for (out) |*kv| {
+        var rdr = try self.fil.readerAt(self.start + entry.ref.block_start, &[0]u8{});
+        var meta: MetadataReader = .init(alloc, &rdr.interface, self.decomp);
+        try meta.interface.discardAll(entry.ref.block_offset);
+
+        var key_raw: KeyRaw = undefined;
+        try meta.interface.readSliceEndian(KeyRaw, @ptrCast(&key_raw), .little);
+
+        switch (key_raw.type.prefix) {
+            .user => {
+                kv.key = @ptrCast(try alloc.alloc(u8, key_raw.name_size + 5 + 1));
+                @memcpy(kv.key[0..5], "user.");
+                try meta.interface.readSliceAll(kv.key[5 .. kv.key.len - 1]);
+                kv.key[kv.key.len - 1] = 0;
+            },
+            .security => {
+                kv.key = @ptrCast(try alloc.alloc(u8, key_raw.name_size + 9 + 1));
+                @memcpy(kv.key[0..9], "security.");
+                try meta.interface.readSliceAll(kv.key[9 .. kv.key.len - 1]);
+                kv.key[kv.key.len - 1] = 0;
+            },
+            .trusted => {
+                kv.key = @ptrCast(try alloc.alloc(u8, key_raw.name_size + 8 + 1));
+                @memcpy(kv.key[0..8], "trusted.");
+                try meta.interface.readSliceAll(kv.key[8 .. kv.key.len - 1]);
+                kv.key[kv.key.len - 1] = 0;
+            },
+        }
+        if (key_raw.type.out_of_line) {
+            try meta.interface.discardAll(4);
+            var ref: Ref = undefined;
+            try meta.interface.readSliceEndian(Ref, @ptrCast(&ref), .little);
+
+            rdr = try self.fil.readerAt(self.start + ref.block_start, &[0]u8{});
+            meta = .init(alloc, &rdr.interface, self.decomp);
+            try meta.interface.discardAll(ref.block_offset);
+        }
+        var value_size: u32 = undefined;
+        try meta.interface.readSliceEndian(u32, @ptrCast(&value_size), .little);
+        kv.value = try alloc.alloc(u8, value_size);
+        try meta.interface.readSliceAll(kv.value);
+    }
+
+    return out;
+}