LibCompress: Add support for LZMA2

Userland/Libraries/LibCompress/Lzma2.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2023, Tim Schumacher <timschumi@gmx.de>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/CircularBuffer.h>
+#include <AK/MaybeOwned.h>
+#include <AK/Stream.h>
+#include <LibCompress/Lzma.h>
+
+namespace Compress {
+
+// This is based on the human-language description of the LZMA2 format on the English Wikipedia.
+// https://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Markov_chain_algorithm#LZMA2_format
+
+class Lzma2Decompressor : public Stream {
+public:
+    /// Creates a decompressor that does not require the leading byte indicating the dictionary size.
+    static ErrorOr<NonnullOwnPtr<Lzma2Decompressor>> create_from_raw_stream(MaybeOwned<Stream>, u32 dictionary_size);
+
+    virtual ErrorOr<Bytes> read_some(Bytes) override;
+    virtual ErrorOr<size_t> write_some(ReadonlyBytes) override;
+    virtual bool is_eof() const override;
+    virtual bool is_open() const override;
+    virtual void close() override;
+
+private:
+    Lzma2Decompressor(MaybeOwned<Stream>, CircularBuffer dictionary);
+
+    MaybeOwned<Stream> m_stream;
+    CircularBuffer m_dictionary;
+    // Our dictionary is always initialized, but LZMA2 requires that the first chunk resets the dictionary.
+    bool m_dictionary_initialized { false };
+    bool m_found_end_of_stream { false };
+
+    Optional<MaybeOwned<Stream>> m_current_chunk_stream;
+    bool m_in_uncompressed_chunk { false };
+
+    Optional<NonnullOwnPtr<LzmaDecompressor>> m_last_lzma_stream;
+    Optional<LzmaDecompressorOptions> m_last_lzma_options;
+};
+
+}