Finished work (theoretically) on single threaded extraction

Started work on Multi-threaded extraction
Added decompression cache.
Added XattrTable

src/util/cache.zig

@@ -0,0 +1,52 @@
+const std = @import("std");
+const Io = std.Io;
+
+const Decomp = @import("../decomp.zig");
+
+const CacheMap = @import("protected_map.zig").ProtectedMap(u64, CachedBlock, decompressBlock);
+
+const Cache = @This();
+
+alloc: std.mem.Allocator,
+
+data: []u8,
+decomp: Decomp.Fn,
+
+cache: CacheMap,
+
+pub fn init(alloc: std.mem.Allocator, data: []u8, decomp: Decomp.Fn) Cache {
+    return .{
+        .alloc = alloc,
+
+        .data = data,
+        .decomp = decomp,
+
+        .cache = .init(alloc),
+    };
+}
+pub fn deinit(self: *Cache) void {
+    self.cache.deinit();
+}
+
+pub fn get(self: *Cache, io: Io, offset: u64, compressed_size: u32) Error![]u8 {
+    const res: CachedBlock = try self.cache.getOrPut(io, offset, .{ self.alloc, self.data, self.decomp, offset, compressed_size });
+    return res.block[0..res.size];
+}
+
+fn decompressBlock(alloc: std.mem.Allocator, data: []u8, decomp: Decomp.Fn, offset: u64, compressed_size: u32) !CachedBlock {
+    const block = data[offset..][0..compressed_size];
+    var new_cache: CachedBlock = undefined;
+
+    new_cache.size = @truncate(try decomp(alloc, block, &new_cache.block));
+
+    return new_cache;
+}
+
+// Types
+
+pub const Error = CacheMap.Error;
+
+const CachedBlock = struct {
+    block: [1024 * 1024]u8,
+    size: u32,
+};