Initial fixed huffman coding for png.

src/compression/huffman/HuffmanEncoder.h

@@ -0,0 +1,67 @@
+#pragma once
+
+#include "RawTree.h"
+
+#include "HuffmanCodeLengthTable.h"
+#include "HuffmanFixedCodes.h"
+
+#include <vector>
+#include <unordered_map>
+
+class PrefixCodeGenerator
+{
+public:
+    virtual ~PrefixCodeGenerator() = default;
+    virtual const PrefixCode& getLiteralValue(unsigned char value) const = 0;
+
+    virtual const PrefixCode& getEndOfStreamValue() const = 0;
+
+};
+
+class HuffmanEncoder : public PrefixCodeGenerator
+{
+using DataStream = std::vector<unsigned char>;
+using CountPair = std::pair<unsigned char, unsigned>;
+
+public:
+    void encode(const DataStream& stream);
+    void encode(const std::unordered_map<unsigned char, unsigned>& counts);
+
+    void setUseFixedCode(bool useFixed)
+    {
+        mUseFixedCode = useFixed;
+    }
+
+    uint32_t getLengthValue(unsigned length)
+    {
+        return 0;
+    }
+
+    const PrefixCode& getLiteralValue(unsigned char value) const override
+    {
+        return mLiteralLengthTable.getCode(value);
+    }
+
+    const PrefixCode& getEndOfStreamValue() const override
+    {
+        return mLiteralLengthTable.getCode(256);
+    }
+
+    void initializeLiteralLengthTable()
+    {
+        if(mUseFixedCode)
+        {
+            mLiteralLengthTable.setInputLengthSequence(HuffmanFixedCodes::getDeflateFixedHuffmanCodes(), false);
+            mLiteralLengthTable.buildPrefixCodes();
+        }
+    }
+
+private:
+    void dumpTree(const RawTree<CountPair>& tree) const;
+    void dumpNode(RawNode<CountPair>* node, unsigned depth) const;
+
+    bool mUseFixedCode{false};
+    bool mTableIsInitialized{false};
+    HuffmanCodeLengthTable mLiteralLengthTable;
+    HuffmanCodeLengthTable mDistanceTable;
+};