79 lines
2.1 KiB
C++
79 lines
2.1 KiB
C++
/* Copyright (C) Teemu Suutari */
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#include "FASTDecompressor.hpp"
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#include "InputStream.hpp"
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#include "OutputStream.hpp"
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#include "common/Common.hpp"
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namespace ancient::internal
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{
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bool FASTDecompressor::detectHeaderXPK(uint32_t hdr) noexcept
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{
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return hdr==FourCC("FAST");
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}
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std::shared_ptr<XPKDecompressor> FASTDecompressor::create(uint32_t hdr,uint32_t recursionLevel,const Buffer &packedData,std::shared_ptr<XPKDecompressor::State> &state,bool verify)
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{
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return std::make_shared<FASTDecompressor>(hdr,recursionLevel,packedData,state,verify);
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}
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FASTDecompressor::FASTDecompressor(uint32_t hdr,uint32_t recursionLevel,const Buffer &packedData,std::shared_ptr<XPKDecompressor::State> &state,bool verify) :
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XPKDecompressor(recursionLevel),
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_packedData(packedData)
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{
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if (!detectHeaderXPK(hdr)) throw Decompressor::InvalidFormatError();
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}
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FASTDecompressor::~FASTDecompressor()
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{
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// nothing needed
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}
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const std::string &FASTDecompressor::getSubName() const noexcept
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{
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static std::string name="XPK-FAST: Fast LZ77 compressor";
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return name;
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}
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void FASTDecompressor::decompressImpl(Buffer &rawData,const Buffer &previousData,bool verify)
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{
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ForwardInputStream forwardInputStream(_packedData,0,_packedData.size());
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BackwardInputStream backwardInputStream(_packedData,0,_packedData.size());
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forwardInputStream.link(backwardInputStream);
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backwardInputStream.link(forwardInputStream);
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MSBBitReader<BackwardInputStream> bitReader(backwardInputStream);
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auto readBit=[&]()->uint32_t
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{
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return bitReader.readBitsBE16(1);
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};
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auto readByte=[&]()->uint8_t
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{
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return forwardInputStream.readByte();
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};
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auto readShort=[&]()->uint16_t
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{
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const uint8_t *buf=backwardInputStream.consume(2);
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uint16_t ret=uint16_t(buf[0])<<8;
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return ret|uint16_t(buf[1]);
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};
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ForwardOutputStream outputStream(rawData,0,rawData.size());
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while (!outputStream.eof())
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{
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if (!readBit())
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{
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outputStream.writeByte(readByte());
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} else {
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uint16_t ld=readShort();
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uint32_t count=std::min(18U-(ld&0xf),uint32_t(outputStream.getEndOffset()-outputStream.getOffset()));
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uint32_t distance=ld>>4;
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outputStream.copy(distance,count);
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}
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}
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}
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}
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