Implement Zlib Compression Backend

[toymak3r]

Overview

Add Zlib compression backend to the Goethe dialog system to provide a widely-compatible compression option with good balance of speed and compression ratio.

Background

Zlib is a widely-used compression library that provides good compression ratios with reasonable speed. Adding Zlib support ensures compatibility with existing systems and provides a reliable fallback option.

Requirements

Core Implementation

• Implement ZlibCompressionBackend class in src/engine/core/compression/implementations/zlib.cpp
• Add corresponding header in include/goethe/zlib.hpp
• Register Zlib backend in src/engine/core/compression/register_backends.cpp
• Update factory to include Zlib in backend selection

Features

• Support for compression levels 0-9 (0=no compression, 9=best compression)
• Configurable memory level (1-9)
• Support for different compression strategies (default, filtered, huffman_only, rle)
• Error handling and validation
• Streaming compression support

Testing

• Unit tests for Zlib backend in src/tests/test_compression.cpp
• Performance benchmarks vs Zstd and LZ4 backends
• Memory usage tests
• Error condition tests
• Compatibility tests with existing Zlib tools

Integration

• Update CompressionManager to support Zlib
• Add Zlib to automatic backend selection logic
• Update statistics tracking for Zlib metrics
• Update command-line tools to support Zlib

Documentation

• Update API documentation
• Add Zlib usage examples
• Update performance comparison documentation
• Add Zlib configuration guide

Technical Details

Dependencies

• Zlib library (system package or bundled)
• Update CMakeLists.txt to detect/find Zlib

Performance Targets

• Compression speed: >100 MB/s
• Decompression speed: >200 MB/s
• Compression ratio: 2.5:1 to 4:1 (depending on data and level)

API Design

class ZlibCompressionBackend : public CompressionBackend {
public:
    ZlibCompressionBackend();
    ~ZlibCompressionBackend() override;
    
    void set_compression_level(int level) override;
    void set_memory_level(int level);
    void set_strategy(CompressionStrategy strategy);
    
    std::vector<uint8_t> compress(const std::vector<uint8_t>& data) override;
    std::vector<uint8_t> decompress(const std::vector<uint8_t>& data) override;
    
private:
    int compression_level_;
    int memory_level_;
    CompressionStrategy strategy_;
};

enum class CompressionStrategy {
    DEFAULT,
    FILTERED,
    HUFFMAN_ONLY,
    RLE
};

Acceptance Criteria

• Zlib backend compiles and links successfully
• All tests pass
• Performance benchmarks show reasonable performance vs other backends
• Integration tests verify Zlib works with existing systems
• Documentation is complete and accurate
• Compatibility with standard Zlib tools verified

Priority

High - This is part of the short-term roadmap and provides compatibility with existing systems.

Labels

• enhancement
• compression
• compatibility
• short-term
• high-priority

Estimated Effort

• Development: 2-3 weeks
• Testing: 1 week
• Documentation: 3-5 days