stuff-from-scratch/src/compression/huffman/HuffmanEncoder.cpp

#include "HuffmanEncoder.h"

#include "RawTree.h"

#include "HuffmanFixedCodes.h"

#include <unordered_map>
#include <queue>
#include <tuple>
#include <iostream>

void HuffmanEncoder::dumpNode(RawNode<CountPair>* node, unsigned depth) const
{
    if (!node)
    {
        return;
    }

    auto data = node->getData();

    std::string prefix(depth, '_');

    if (node->isLeaf())
    {
        //std::cout << prefix << "Leaf with value: " << data.first << " and sum " << data.second << std::endl;
    }
    else
    {
        //std::cout << prefix << "Intermediate with sum " << data.second << std::endl;
        //std::cout << prefix << "Doing Left.." << std::endl;
        dumpNode(node->getLeftChild(), depth+1);

        //std::cout << prefix << "Doing Right.." << std::endl;
        dumpNode(node->getRightChild(), depth+1);

        //std::cout << prefix << "*****" << std::endl;
    }
}

void HuffmanEncoder::dumpTree(const RawTree<CountPair>& tree) const
{
    dumpNode(tree.getRootNode(), 0);
}

void HuffmanEncoder::encode(const std::vector<unsigned>& counts)
{
    auto cmp = [](RawNode<CountPair>* left, RawNode<CountPair>* right)
        {
            return left->getData().second > right->getData().second;
        };

    std::priority_queue<RawNode<CountPair>*, std::vector<RawNode<CountPair>* >, decltype(cmp)> q(cmp);
    unsigned offset{0};
    for (auto count : counts)
    {
        if (count > 0)
        {
            q.push(new RawNode<CountPair>({offset, count}));
        }
        offset++;
    }

    while(q.size() > 1)
    {
        auto node0 = q.top();
        q.pop();

        auto node1 = q.top();
        q.pop();

        const auto sum = node0->getData().second + node1->getData().second;
        auto new_node = new RawNode<CountPair>(CountPair{0, sum});

        new_node->addChild(node0);
        new_node->addChild(node1);
        q.push(new_node);
    }

    auto root = q.top();
    q.pop();

    RawTree<CountPair> tree;
    tree.addRootNode(root);

    //using TableEntry = std::tuple<>

    //dumpTree(tree);

    //std::cout << "********" << std::endl;
}

void HuffmanEncoder::encode(const std::unordered_map<unsigned char, unsigned>& counts)
{
    std::vector<unsigned> just_counts;
    for (const auto& data: counts)
    {
        mSymbolMapping.push_back(data.first);
        just_counts.push_back(data.second);
    }

    encode(just_counts);
}

void HuffmanEncoder::setUseFixedCode(bool useFixed)
{
    mUseFixedCode = useFixed;
}

uint32_t HuffmanEncoder::getLengthValue(unsigned length)
{
    return 0;
}

std::optional<PrefixCode> HuffmanEncoder::getLiteralValue(unsigned char value) const
{
    return mLiteralLengthTable.getCodeForSymbol(value);
}

std::optional<PrefixCode> HuffmanEncoder::getLengthValue(unsigned length) const
{
    return mLiteralLengthTable.getCodeForSymbol(length);
}

std::optional<PrefixCode> HuffmanEncoder::getDistanceValue(unsigned distance) const
{
    return mDistanceTable.getCodeForSymbol(distance);
}

std::optional<PrefixCode> HuffmanEncoder::getEndOfStreamValue() const
{
    return mLiteralLengthTable.getCodeForSymbol(256);
}

void HuffmanEncoder::initializeTrees(const std::vector<Hit>& hits)
{
    initializeLiteralLengthTable(hits);
}

void HuffmanEncoder::initializeLiteralLengthTable(const std::vector<Hit>& hits)
{
    if(mUseFixedCode)
    {
        mLiteralLengthTable.setInputLengthSequence(HuffmanFixedCodes::getDeflateFixedHuffmanCodes(), false);
        mLiteralLengthTable.buildPrefixCodes();
        return;
    }

    std::vector<unsigned> counts(285, 0);
    counts[256] = 1;
    for (const auto& hit : hits)
    {
        const auto& [length, distance, next_char] = hit;
        if (length > 0 )
        {
            const auto& [code, extra_bits, num_extra_bits] = HuffmanFixedCodes::getCodeForLength(length);
            counts[code]++;
        }
        else
        {
            counts[next_char]++;
        }
    }

    for(unsigned idx=0; idx<counts.size(); idx++)
    {
        if (counts[idx]>0)
        {
            //std::cout << "Count for " << idx << " is " << counts[idx] << std::endl;
        }
    }

    encode(counts);
}