Initial fixed huffman coding for png.

src/compression/huffman/HuffmanTree.h

@@ -0,0 +1,52 @@
+#pragma once
+
+#include <vector>
+#include <string>
+#include <optional>
+
+class PrefixCode
+{
+public:
+    PrefixCode(uint32_t data, unsigned length);
+
+    std::string toString(bool bitsAsRightToLeft = true) const;
+
+    bool matches(unsigned length, uint32_t code) const;
+
+    uint32_t getData() const
+    {
+        return mData;
+    }
+
+    unsigned getLength() const
+    {
+        return mLength;
+    }
+
+private:
+    unsigned mLength{0};
+    uint32_t mData{0};
+};
+
+class HuffmanTree
+{
+public:
+    using Symbol = unsigned;
+    using CodeLength = unsigned;
+    using CodeSymbolPair = std::pair<PrefixCode, Symbol>;
+    using CodeLengthData = std::pair<CodeLength, std::vector<CodeSymbolPair> >;
+
+    void addCodeLengthEntry(unsigned length, const CodeSymbolPair& data);
+
+    std::string dump(bool bitsAsRightToLeft = true) const;
+
+    std::optional<HuffmanTree::Symbol> findMatch(std::size_t treeIndex, uint32_t code) const;
+
+    std::size_t getNumCodeLengths() const;
+
+    unsigned getCodeLength(std::size_t idx) const;
+
+    void sortTable();
+private:
+    std::vector<CodeLengthData> mTable;
+};