Small tweaks

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();
+}