Initial fixed huffman coding for png.

src/compression/huffman/HuffmanCodeLengthTable.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include "HuffmanTree.h"
+
+#include <vector>
+#include <string>
+#include <optional>
+
+class HuffmanCodeLengthTable
+{
+public:
+    void buildPrefixCodes();
+
+    void buildCompressedLengthSequence();
+
+    std::string dumpPrefixCodes() const;
+
+    std::optional<HuffmanTree::Symbol> findMatch(std::size_t treeIndex, uint32_t code) const;
+
+    const HuffmanTree& getTree() const;
+
+    const PrefixCode& getCode(std::size_t index) const;
+
+    using CompressedSequenceEntry = std::pair<unsigned, unsigned>;
+    const std::vector<CompressedSequenceEntry>& getCompressedLengthSequence() const;
+
+    const std::vector<unsigned> getCompressedLengthCounts() const;
+
+    unsigned getNumCodeLengths() const;
+
+    unsigned getCodeLength(std::size_t treeIndex) const;
+
+    unsigned mapToDeflateIndex(unsigned index) const;
+
+    void setInputLengthSequence(const std::vector<unsigned char>& sequence, bool targetDeflate = true);
+
+private:
+
+    HuffmanTree mTree;
+    bool mTargetDeflate{true};
+
+    std::vector<unsigned char> mInputLengthSequence;
+    std::vector<PrefixCode> mCodes;
+
+    std::vector<CompressedSequenceEntry> mCompressedLengthSequence;
+    std::vector<unsigned> mCompressedLengthCounts;
+
+    static constexpr unsigned DEFLATE_PERMUTATION_SIZE{19};
+    static constexpr unsigned DEFLATE_PERMUTATION[DEFLATE_PERMUTATION_SIZE]{16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
+};