Convert lz77 to use fixed buffer sizes.
This commit is contained in:
James Grogan
parent
a6e31c8d39
commit
af6fad72eb
9 changed files with 362 additions and 110 deletions
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@ -8,55 +8,102 @@
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#include <iostream>
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Lz77Encoder::Lz77Encoder(BitStream* inputStream, BitStream* outputStream)
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: AbstractEncoder(inputStream, outputStream)
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: AbstractEncoder(inputStream, outputStream),
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mSearchBuffer(mSearchBufferSize),
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mLookaheadBuffer(mLookAheadBufferSize)
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{
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}
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unsigned Lz77Encoder::lookAheadForMatchingChars(std::vector<char>& matchBuffer, unsigned searchIndex, unsigned hitOffset, const std::string& stream, unsigned streamLoc)
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void Lz77Encoder::setPrefixCodeGenerator(std::unique_ptr<PrefixCodeGenerator> generator)
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{
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auto remaining_size = stream.size() - streamLoc;
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mCodeGenerator = std::move(generator);
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}
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unsigned num_hits{1};
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for (unsigned jdx=1; jdx< remaining_size; jdx++)
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bool Lz77Encoder::hitBufferFull() const
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{
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return mHitBuffer.size() == mMaxHitBufferSize;
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}
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void Lz77Encoder::populateSearchBuffer(const Hit& hit)
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{
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const auto& [length, distance, next_char] = hit;
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if (length == 0)
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{
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char buffer_char{0};
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if (searchIndex + jdx < mSearchBuffer.size())
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{
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buffer_char = mSearchBuffer[searchIndex + jdx];
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mSearchBuffer.addItem(next_char);
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}
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else
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{
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buffer_char = stream[jdx - hitOffset];
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std::vector<unsigned char> new_items(distance, 0);
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for(unsigned idx=0 ;idx<distance; idx++)
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{
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new_items[idx] = getSearchBufferItem(idx);
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}
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for(auto item : new_items)
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{
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mSearchBuffer.addItem(item);
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}
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auto lookahead_char = stream[streamLoc + jdx];
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if (lookahead_char == buffer_char)
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int difference = int(length) - distance;
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if (difference > 0)
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{
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matchBuffer.push_back(buffer_char);
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num_hits++;
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for(unsigned idx=0; idx<difference; idx++)
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{
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mSearchBuffer.addItem(mLookaheadBuffer.getItem(idx));
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}
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}
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}
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}
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unsigned char Lz77Encoder::getSearchBufferItem(unsigned index) const
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{
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return mSearchBuffer.getItem(mSearchBuffer.getNumItems() - 1 - index);
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}
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unsigned Lz77Encoder::lookAheadForMatchingChars(unsigned distance)
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{
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unsigned length{0};
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std::cout << "In hit check at distance " << distance << " max buffer index is: " << mMaxLookAheadBufferIndex << std::endl;
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for(unsigned idx=0; idx<mMaxLookAheadBufferIndex + 1; idx++)
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{
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int search_offset = int(distance-1) - idx;
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std::cout << "Have search offet " << search_offset << std::endl;
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unsigned char search_char{0};
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if (search_offset < 0)
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{
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search_char = mLookaheadBuffer.getItem(-search_offset - 1);
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}
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else
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{
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search_char = getSearchBufferItem(static_cast<unsigned>(search_offset));
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}
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unsigned char lookahead_char = mLookaheadBuffer.getItem(idx);
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std::cout << "Checking search char " << static_cast<int>(search_char) << " and lookup char " << static_cast<int>(lookahead_char) << std::endl;
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if ((lookahead_char != search_char) || (idx == mMaxLookAheadBufferIndex))
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{
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if (idx + 1>= mMinLengthMatchSize)
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{
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length = idx + 1;
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}
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break;
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}
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}
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return num_hits;
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return length;
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}
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void Lz77Encoder::lookThroughSearchBuffer(char searchChar, unsigned& hitLength, unsigned& hitOffset, const std::string& stream, unsigned streamLoc)
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void Lz77Encoder::lookForMatches(unsigned char searchChar, unsigned& hitLength, unsigned& hitOffset)
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{
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for(unsigned idx=0; idx<mSearchBuffer.size(); idx++)
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for (unsigned idx = 0; idx< mSearchBuffer.getNumItems(); idx++)
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{
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auto search_index = mSearchBuffer.size() - idx - 1;
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if (auto buffer_char = mSearchBuffer[search_index]; buffer_char == searchChar)
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if (mSearchBuffer.getItem(mSearchBuffer.getNumItems() - 1 - idx) == searchChar)
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{
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std::vector<char> match_buffer{buffer_char};
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auto num_hits = lookAheadForMatchingChars(match_buffer, search_index, idx, stream, streamLoc);
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std::cout << "Looking for hits " << std::endl;
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auto num_hits = lookAheadForMatchingChars(idx + 1);
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if (num_hits >= hitLength)
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if (num_hits > 0 && num_hits >= hitLength)
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{
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hitLength = num_hits;
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hitOffset = idx + 1;
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@ -65,75 +112,163 @@ void Lz77Encoder::lookThroughSearchBuffer(char searchChar, unsigned& hitLength,
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}
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}
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void Lz77Encoder::setPrefixCodeGenerator(std::unique_ptr<PrefixCodeGenerator> generator)
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bool Lz77Encoder::lookAheadSourceEmpty() const
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{
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mCodeGenerator = std::move(generator);
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if (mLookaheadBuffer.getNumItems() < mLookAheadBufferSize)
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{
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return true;
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}
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if (mMaxLookAheadBufferIndex < mLookAheadBufferSize - 1)
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{
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return true;
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}
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return false;
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}
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void Lz77Encoder::populateLookaheadBuffer(unsigned size, bool firstPass)
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{
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if (!firstPass && lookAheadSourceEmpty())
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{
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for(unsigned idx=0; idx<size; idx++)
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{
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mLookaheadBuffer.addItem(0);
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mMaxLookAheadBufferIndex--;
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}
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return;
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}
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bool stream_finished{false};
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unsigned stream_end_id{0};
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for(unsigned idx=0; idx<size; idx++)
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{
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if (!stream_finished)
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{
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auto byte = mInputStream->readNextByte();
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if (!byte)
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{
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stream_finished = true;
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stream_end_id = idx -1;
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mLookaheadBuffer.addItem(0);
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mMaxLookAheadBufferIndex--;
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continue;
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}
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else
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{
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mLookaheadBuffer.addItem(*byte);
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}
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}
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else
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{
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mLookaheadBuffer.addItem(0);
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mMaxLookAheadBufferIndex--;
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}
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}
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if (stream_finished && firstPass)
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{
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mMaxLookAheadBufferIndex = stream_end_id;
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}
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}
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bool Lz77Encoder::encode()
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{
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if (!mCodeGenerator)
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{
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auto code_generator = std::make_unique<HuffmanEncoder>();
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auto huffman_encoder = code_generator.get();
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mCodeGenerator = std::move(code_generator);
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huffman_encoder->setUseFixedCode(true);
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huffman_encoder->initializeLiteralLengthTable();
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mCodeGenerator = std::make_unique<HuffmanEncoder>();
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}
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while(auto byte = mInputStream->readNextByte())
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// Fill the lookahead buffer
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mMaxLookAheadBufferIndex = mLookAheadBufferSize - 1;
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populateLookaheadBuffer(mLookAheadBufferSize, true);
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if(mMaxLookAheadBufferIndex < 0)
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{
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const auto code = mCodeGenerator->getLiteralValue(*byte);
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std::cout << "Writing value " << static_cast<int>(*byte) << " with code " << ByteUtils::toString(code.getData(), code.getLength()) << "\n";
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mOutputStream->writeNBits(code.getData(), code.getLength());
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return true;
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}
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auto eos_code = mCodeGenerator->getEndOfStreamValue();
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std::cout << "Writing EOS value with code " << ByteUtils::toString(eos_code.getData(), eos_code.getLength()) << "\n";
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mOutputStream->writeNBits(eos_code.getData(), eos_code.getLength());
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/*
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unsigned loc{0};
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std::string ret;
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while(!mInputStream->isFinished())
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bool input_stream_ended{false};
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while(!hitBufferFull())
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{
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auto search_char = stream[loc];
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if (mMaxLookAheadBufferIndex < 0)
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{
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input_stream_ended = true;
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break;
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}
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const auto working_byte = mLookaheadBuffer.getItem(0);
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std::cout << "Working byte is " << static_cast<int>(working_byte) << std::endl;
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unsigned hit_length{0};
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unsigned hit_offset{0};
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lookThroughSearchBuffer(search_char, hit_length, hit_offset, stream, loc);
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unsigned hit_distance{0};
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lookForMatches(working_byte, hit_length, hit_distance);
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if (hit_length > 0)
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{
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ret += "@" + std::to_string(hit_offset) + "L" + std::to_string(hit_length);
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loc+=hit_length;
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std::cout << "Got hit length " << hit_length << " and distance " << hit_distance << std::endl;
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auto hit_loc = mSearchBuffer.size() - hit_offset;
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for(unsigned idx=hit_loc; idx<hit_loc + hit_length; idx++)
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const Hit hit{hit_length, hit_distance, working_byte};
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mHitBuffer.push_back(hit);
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populateSearchBuffer(hit);
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if (hit_length == 0)
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{
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mSearchBuffer.push_back(mSearchBuffer[idx]);
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}
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populateLookaheadBuffer(1);
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}
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else
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{
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ret += search_char;
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mSearchBuffer.push_back(search_char);
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loc++;
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populateLookaheadBuffer(hit_length);
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}
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}
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return ret;
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*/
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return false;
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return input_stream_ended;
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}
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const std::vector<Lz77Encoder::Hit>& Lz77Encoder::getHitBuffer() const
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{
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return mHitBuffer;
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}
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/*
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void Lz77Encoder::flushHitBuffer()
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{
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// If dynamic huffman build trees
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if (!mCodeGenerator)
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{
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mCodeGenerator = std::make_unique<HuffmanEncoder>();
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}
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// Convert hit buffer to prefix codes and write to output stream
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for (const auto& hit : mHitBuffer)
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{
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const auto& [length, distance, next_char] = hit;
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PrefixCode code;
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if (length == 0)
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{
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code = *mCodeGenerator->getLiteralValue(next_char);
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std::cout << "Writing symbol " << static_cast<int>(next_char) << " with code " << ByteUtils::toString(code.getData(), code.getLength()) << "\n";
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mOutputStream->writeNBits(code.getData(), code.getLength());
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}
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else
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{
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code = *mCodeGenerator->getLengthValue(length);
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const auto distance_code = mCodeGenerator->getDistanceValue(distance);
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std::cout << "Writing length " << length << " with code " << ByteUtils::toString(code.getData(), code.getLength()) << "\n";
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mOutputStream->writeNBits(code.getData(), code.getLength());
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std::cout << "Writing distance " << distance << " with code " << ByteUtils::toString(distance_code.getData(), distance_code.getLength()) << "\n";
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mOutputStream->writeNBits(distance_code.getData(), distance_code.getLength());
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}
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}
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auto eos_code = mCodeGenerator->getEndOfStreamValue();
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std::cout << "Writing EOS value with code " << ByteUtils::toString(eos_code->getData(), eos_code->getLength()) << "\n";
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mOutputStream->writeNBits(eos_code->getData(), eos_code->getLength());
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}
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*/
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bool Lz77Encoder::decode()
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{
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/*
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@ -203,3 +338,4 @@ bool Lz77Encoder::decode()
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*/
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return false;
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}
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@ -2,40 +2,59 @@
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#include "AbstractEncoder.h"
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#include "HuffmanEncoder.h"
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#include "CircleBuffer.h"
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#include <string>
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#include <vector>
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#include <memory>
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#include <tuple>
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class PrefixCodeGenerator;
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class Lz77Encoder : public AbstractEncoder
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{
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public:
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using Buffer = std::vector<unsigned char>;
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using Hit = std::tuple<unsigned, unsigned, unsigned char>;
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Lz77Encoder(BitStream* inputStream, BitStream* outputStream);
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unsigned lookAheadForMatchingChars(std::vector<char>& matchBuffer, unsigned searchIndex, unsigned hitOffset, const std::string& stream, unsigned streamLoc);
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void lookThroughSearchBuffer(char searchChar, unsigned& hitLength, unsigned& hitOffset, const std::string& stream, unsigned streamLoc);
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bool encode() override;
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bool decode() override;
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const std::vector<Hit>& getHitBuffer() const;
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void setSearchBufferSize(unsigned size);
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void setLookAheadBufferSize(unsigned size);
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void setPrefixCodeGenerator(std::unique_ptr<PrefixCodeGenerator> generator);
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bool hitBufferFull() const;
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private:
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bool lookAheadSourceEmpty() const;
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unsigned char getSearchBufferItem(unsigned index) const;
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unsigned lookAheadForMatchingChars(unsigned searchIndex);
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void lookForMatches(unsigned char searchChar, unsigned& hitLength, unsigned& hitOffset);
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void populateLookaheadBuffer(unsigned size, bool firstPass = false);
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void populateSearchBuffer(const Hit& hit);
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unsigned mMaxHitBufferSize{32000};
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std::vector<Hit> mHitBuffer;
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unsigned mSearchBufferSize{32000};
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Buffer mSearchBuffer;
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CircleBuffer<unsigned char> mSearchBuffer;
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unsigned mLookAheadBufferSize{256};
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Buffer mLookaheadBuffer;
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int mMaxLookAheadBufferIndex{0};
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unsigned mMinLengthMatchSize{1};
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CircleBuffer<unsigned char> mLookaheadBuffer;
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std::unique_ptr<PrefixCodeGenerator> mCodeGenerator;
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};
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@ -98,3 +98,47 @@ void HuffmanEncoder::encode(const std::unordered_map<unsigned char, unsigned>& c
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std::cout << "********" << std::endl;
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}
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void HuffmanEncoder::setUseFixedCode(bool useFixed)
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{
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mUseFixedCode = useFixed;
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}
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uint32_t HuffmanEncoder::getLengthValue(unsigned length)
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{
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return 0;
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}
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std::optional<PrefixCode> HuffmanEncoder::getLiteralValue(unsigned char value) const
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{
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return mLiteralLengthTable.getCodeForSymbol(value);
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}
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std::optional<PrefixCode> HuffmanEncoder::getLengthValue(unsigned length) const
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{
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return mLiteralLengthTable.getCodeForSymbol(length);
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}
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std::optional<PrefixCode> HuffmanEncoder::getDistanceValue(unsigned distance) const
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{
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return mDistanceTable.getCodeForSymbol(distance);
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}
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std::optional<PrefixCode> HuffmanEncoder::getEndOfStreamValue() const
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{
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return mLiteralLengthTable.getCodeForSymbol(256);
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}
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void HuffmanEncoder::initializeTrees()
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{
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initializeLiteralLengthTable();
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}
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void HuffmanEncoder::initializeLiteralLengthTable()
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{
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if(mUseFixedCode)
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{
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mLiteralLengthTable.setInputLengthSequence(HuffmanFixedCodes::getDeflateFixedHuffmanCodes(), false);
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mLiteralLengthTable.buildPrefixCodes();
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}
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}
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@ -12,10 +12,11 @@ class PrefixCodeGenerator
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{
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public:
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virtual ~PrefixCodeGenerator() = default;
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virtual const PrefixCode& getLiteralValue(unsigned char value) const = 0;
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virtual const PrefixCode& getEndOfStreamValue() const = 0;
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virtual std::optional<PrefixCode> getLiteralValue(unsigned char symbol) const = 0;
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virtual std::optional<PrefixCode> getLengthValue(unsigned length) const = 0;
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virtual std::optional<PrefixCode> getDistanceValue(unsigned distance) const = 0;
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virtual std::optional<PrefixCode> getEndOfStreamValue() const = 0;
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};
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class HuffmanEncoder : public PrefixCodeGenerator
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@ -27,36 +28,23 @@ public:
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void encode(const DataStream& stream);
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void encode(const std::unordered_map<unsigned char, unsigned>& counts);
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void setUseFixedCode(bool useFixed)
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{
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mUseFixedCode = useFixed;
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}
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uint32_t getLengthValue(unsigned length);
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uint32_t getLengthValue(unsigned length)
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{
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return 0;
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}
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std::optional<PrefixCode> getLiteralValue(unsigned char symbol) const override;
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const PrefixCode& getLiteralValue(unsigned char value) const override
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{
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return mLiteralLengthTable.getCode(value);
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}
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std::optional<PrefixCode> getLengthValue(unsigned length) const override;
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const PrefixCode& getEndOfStreamValue() const override
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{
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return mLiteralLengthTable.getCode(256);
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}
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std::optional<PrefixCode> getDistanceValue(unsigned distance) const override;
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void initializeLiteralLengthTable()
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{
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if(mUseFixedCode)
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{
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mLiteralLengthTable.setInputLengthSequence(HuffmanFixedCodes::getDeflateFixedHuffmanCodes(), false);
|
||||
mLiteralLengthTable.buildPrefixCodes();
|
||||
}
|
||||
}
|
||||
std::optional<PrefixCode> getEndOfStreamValue() const override;
|
||||
|
||||
void initializeTrees();
|
||||
|
||||
void setUseFixedCode(bool useFixed);
|
||||
|
||||
private:
|
||||
void initializeLiteralLengthTable();
|
||||
|
||||
void dumpTree(const RawTree<CountPair>& tree) const;
|
||||
void dumpNode(RawNode<CountPair>* node, unsigned depth) const;
|
||||
|
||||
|
|
|
|||
|
|
@ -9,6 +9,7 @@
|
|||
#include "PngFilter.h"
|
||||
#include "Lz77Encoder.h"
|
||||
#include "ZlibEncoder.h"
|
||||
#include "HuffmanEncoder.h"
|
||||
#include "CyclicRedundancyChecker.h"
|
||||
|
||||
#include "ByteUtils.h"
|
||||
|
|
@ -181,10 +182,6 @@ void PngWriter::write(const std::unique_ptr<Image<unsigned char> >& image)
|
|||
auto filter_out_stream = std::make_unique<BufferBitStream>();
|
||||
PngFilter filter(raw_image_stream, filter_out_stream.get());
|
||||
filter.encode();
|
||||
//while(!filter_out_stream->isFinished())
|
||||
//{
|
||||
//std::cout << "Got pix " << static_cast<int>(*filter_out_stream->readNextByte()) << std::endl;
|
||||
//}
|
||||
|
||||
filter_out_stream->resetOffsets();
|
||||
|
||||
|
|
@ -199,9 +196,12 @@ void PngWriter::write(const std::unique_ptr<Image<unsigned char> >& image)
|
|||
lz77_out_stream = std::make_unique<BufferBitStream>();
|
||||
Lz77Encoder lz77_encoder(filter_out_stream.get(), lz77_out_stream.get());
|
||||
|
||||
if (mCompressionMethod == Deflate::CompressionMethod::DYNAMIC_HUFFMAN)
|
||||
if (mCompressionMethod == Deflate::CompressionMethod::FIXED_HUFFMAN)
|
||||
{
|
||||
// Set up custom encoder;
|
||||
auto huffman_encoder = std::make_unique<HuffmanEncoder>();
|
||||
huffman_encoder->setUseFixedCode(true);
|
||||
huffman_encoder->initializeTrees();
|
||||
lz77_encoder.setPrefixCodeGenerator(std::move(huffman_encoder));
|
||||
}
|
||||
lz77_encoder.encode();
|
||||
lz77_out_stream->resetOffsets();
|
||||
|
|
|
|||
|
|
@ -50,7 +50,7 @@ private:
|
|||
PngInfo mPngInfo;
|
||||
PngHeader mPngHeader;
|
||||
|
||||
Deflate::CompressionMethod mCompressionMethod{Deflate::CompressionMethod::NONE};
|
||||
Deflate::CompressionMethod mCompressionMethod{Deflate::CompressionMethod::DYNAMIC_HUFFMAN};
|
||||
};
|
||||
|
||||
using PngWriterPtr = std::unique_ptr<PngWriter>;
|
||||
|
|
|
|||
|
|
@ -19,6 +19,7 @@ list(APPEND TestFiles
|
|||
compiler/TestTemplatingEngine.cpp
|
||||
compression/TestStreamCompressor.cpp
|
||||
compression/TestHuffmanStream.cpp
|
||||
compression/TestLz77Encoder.cpp
|
||||
database/TestDatabase.cpp
|
||||
fonts/TestFontReader.cpp
|
||||
graphics/TestRasterizer.cpp
|
||||
|
|
|
|||
32
test/compression/TestLz77Encoder.cpp
Normal file
32
test/compression/TestLz77Encoder.cpp
Normal file
|
|
@ -0,0 +1,32 @@
|
|||
#include <iostream>
|
||||
|
||||
#include "Lz77Encoder.h"
|
||||
#include "BufferBitStream.h"
|
||||
|
||||
int main()
|
||||
{
|
||||
std::vector<unsigned> values {0, 10, 11, 12, 10, 11, 12, 0, 13, 14, 15, 10, 11, 12};
|
||||
|
||||
//std::vector<unsigned> values {0, 1, 2, 3, 0, 1, 2, 3, 0,1};
|
||||
|
||||
BufferBitStream input_stream;
|
||||
for (auto value : values)
|
||||
{
|
||||
input_stream.writeByte(value);
|
||||
}
|
||||
|
||||
BufferBitStream output_stream;
|
||||
|
||||
Lz77Encoder encoder(&input_stream, &output_stream);
|
||||
|
||||
encoder.encode();
|
||||
|
||||
auto hit_buffer = encoder.getHitBuffer();
|
||||
for(const auto& hit : hit_buffer)
|
||||
{
|
||||
const auto& [length, distance, next_char] = hit;
|
||||
std::cout << "Got hit " << length << " | " << distance << " | " << static_cast<int>(next_char) << std::endl;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
@ -28,6 +28,7 @@ void testCompressedPng()
|
|||
|
||||
PngWriter writer;
|
||||
writer.setPath("test_compressed.png");
|
||||
writer.setCompressionMethod(Deflate::CompressionMethod::NONE);
|
||||
writer.write(image);
|
||||
|
||||
return;
|
||||
|
|
@ -72,9 +73,40 @@ void testFixedPng()
|
|||
|
||||
}
|
||||
|
||||
void testDynamicCompressedPng()
|
||||
{
|
||||
unsigned width = 10;
|
||||
unsigned height = 10;
|
||||
unsigned numChannels = 1;
|
||||
auto image = Image<unsigned char>::Create(width, height);
|
||||
image->setNumChannels(numChannels);
|
||||
image->setBitDepth(8);
|
||||
|
||||
std::vector<unsigned char> data(width*height, 0);
|
||||
for (unsigned idx=0; idx<width*height; idx++)
|
||||
{
|
||||
//unsigned char val = 100 * idx /(width*height);
|
||||
unsigned char val = 10;
|
||||
data[idx] = val;
|
||||
}
|
||||
|
||||
image->setData(data);
|
||||
|
||||
PngWriter writer;
|
||||
writer.setPath("test_dynamic.png");
|
||||
writer.write(image);
|
||||
|
||||
//return;
|
||||
File test_file("test_dynamic.png");
|
||||
std::cout << test_file.dumpBinary();
|
||||
|
||||
}
|
||||
|
||||
int main()
|
||||
{
|
||||
//testCompressedPng();
|
||||
testFixedPng();
|
||||
//testFixedPng();
|
||||
testDynamicCompressedPng();
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in a new issue