Re-added all C decompressors

Some cleanup
Remove inode arena
Added deinit to Archive to destroy the File.MemoryMap

src/decomp/c_zstd.zig

@@ -0,0 +1,71 @@
+const std = @import("std");
+const Io = std.Io;
+const Reader = std.Io.Reader;
+const zstd = std.compress.zstd;
+const Node = std.SinglyLinkedList.Node;
+
+const c = @import("c");
+
+const Decompressor = @import("../util/decompressor.zig");
+const Error = Decompressor.Error;
+
+const Queue = std.Io.Queue([]u8);
+
+const Self = @This();
+
+interface: Decompressor = .{ .decomp_fn = decomp },
+
+io: Io,
+
+ctx: []?*c.ZSTD_DCtx,
+ctx_queue: Queue,
+
+pub fn init(alloc: std.mem.Allocator, io: Io, block_size: u32) !Self {
+    const buf = try alloc.alloc(?*c.ZSTD_DCtx, 20); // TODO: Choose a better number instead of a random one.
+    var queue: Queue = .init(buf);
+    for (0..20) |_|
+        try queue.putOne(io, c.ZSTD_createDCtx());
+
+    return .{
+        .alloc = alloc,
+        .io = io,
+
+        .block_size = block_size,
+        .ctx = buf,
+        .ctx_queue = queue,
+    };
+}
+pub fn deinit(self: *Self, alloc: std.mem.Allocator) void {
+    self.ctx_queue.close(self.io);
+    for (self.ctx) |ctx|
+        c.ZSTD_freeDCtx(ctx);
+    alloc.free(self.ctx);
+}
+
+fn decomp(d: ?*const Decompressor, alloc: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
+    if (d == null) {
+        return statelessDecomp(d, alloc, in, out);
+    }
+    var self: *Self = @fieldParentPtr("interface", @constCast(d.?));
+
+    const ctx = self.ctx_queue.getOne(self.io) catch return Error.ReadFailed;
+    defer self.ctx_queue.putOne(self.io, ctx) catch {};
+
+    _ = c.ZSTD_DCtx_reset(ctx, c.ZSTD_reset_session_only);
+
+    const res = c.ZSTD_decompressDCtx(ctx, out.ptr, out.len, in.ptr, in.len);
+    if (c.ZSTD_isError(res) != 0)
+        return Error.ReadFailed;
+    return res;
+}
+
+// Stateless
+
+pub const stateless_decompressor: Decompressor = .{ .decomp_fn = statelessDecomp };
+
+fn statelessDecomp(_: ?*const Decompressor, _: std.mem.Allocator, in: []u8, out: []u8) Error!usize {
+    const res = c.ZSTD_decompress(out.ptr, out.len, in.ptr, in.len);
+    if (c.ZSTD_isError(res) != 0)
+        return Error.ReadFailed;
+    return res;
+}