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/* Copyright (C) Teemu Suutari */
#ifndef DYNAMICHUFFMANDECODER_HPP
#define DYNAMICHUFFMANDECODER_HPP
#include <cstddef>
#include <cstdint>
// For exception
#include "Decompressor.hpp"
namespace ancient::internal
{
template<uint32_t maxCount>
class DynamicHuffmanDecoder
{
public:
DynamicHuffmanDecoder(uint32_t initialCount=maxCount) :
_initialCount(initialCount)
{
if (_initialCount>maxCount) throw Decompressor::DecompressionError();
reset();
}
~DynamicHuffmanDecoder()
{
// nothing needed
}
void reset()
{
_count=_initialCount;
if (!_count) return;
for (uint32_t i=0;i<_count;i++)
{
_nodes[i].frequency=1;
_nodes[i].index=i+(maxCount-_count)*2;
_nodes[i].parent=maxCount*2-_count+(i>>1);
_nodes[i].leaves[0]=0;
_nodes[i].leaves[1]=0;
_codeMap[i+(maxCount-_count)*2]=i;
}
for (uint32_t i=maxCount*2-_count,j=0;i<maxCount*2-1;i++,j+=2)
{
uint32_t l=(j>=_count)?j+(maxCount-_count)*2:j;
uint32_t r=(j+1>=_count)?j+1+(maxCount-_count)*2:(j+1);
_nodes[i].frequency=_nodes[l].frequency+_nodes[r].frequency;
_nodes[i].index=i;
_nodes[i].parent=maxCount+(i>>1);
_nodes[i].leaves[0]=l;
_nodes[i].leaves[1]=r;
_codeMap[i]=i;
}
}
template<typename F>
uint32_t decode(F bitReader) const
{
if (!_count) throw Decompressor::DecompressionError();
if (_count==1) return 0;
uint32_t code=maxCount*2-2;
while (code>=maxCount)
code=_nodes[code].leaves[bitReader()?1:0];
return code;
}
void update(uint32_t code)
{
if (code>=_count) throw Decompressor::DecompressionError();
// this is a bug in LH2. Nobody else uses this codepath, so we can let it be...
if (_count==1)
{
_nodes[0].frequency=1;
return;
}
while (code!=maxCount*2-2)
{
_nodes[code].frequency++;
uint32_t index=_nodes[code].index;
uint32_t destIndex=index;
uint32_t freq=_nodes[code].frequency;
while (destIndex!=maxCount*2-2 && freq>_nodes[_codeMap[destIndex+1]].frequency) destIndex++;
if (index!=destIndex)
{
auto getParentLeaf=[&](uint32_t currentCode)->uint32_t&
{
Node &parent=_nodes[_nodes[currentCode].parent];
return parent.leaves[(parent.leaves[0]==currentCode)?0:1];
};
uint32_t destCode=_codeMap[destIndex];
std::swap(_nodes[code].index,_nodes[destCode].index);
std::swap(_codeMap[index],_codeMap[destIndex]);
std::swap(getParentLeaf(code),getParentLeaf(destCode));
std::swap(_nodes[code].parent,_nodes[destCode].parent);
}
code=_nodes[code].parent;
}
_nodes[code].frequency++;
}
// halve the frequencies rounding upwards
void halve()
{
if (!_count) return;
else if (_count==1)
{
_nodes[0].frequency=(_nodes[0].frequency+1)>>1;
return;
}
for (uint32_t i=(maxCount-_count)*2,j=(maxCount-_count)*2;i<maxCount*2-1&&j<maxCount*2-_count;i++)
if (_codeMap[i]<maxCount) _nodes[_codeMap[i]].index=j++;
for (uint32_t i=0;i<_count;i++)
{
_nodes[i].frequency=(_nodes[i].frequency+1)>>1;
_nodes[i].parent=maxCount+(_nodes[i].index>>1);
_codeMap[_nodes[i].index]=i;
}
for (uint32_t i=maxCount*2-_count,j=(maxCount-_count)*2;i<maxCount*2-1;i++,j+=2)
{
uint32_t l=_codeMap[j];
uint32_t r=_codeMap[j+1];
uint32_t freq=_nodes[l].frequency+_nodes[r].frequency;
_nodes[i].frequency=freq;
_nodes[i].index=i;
_nodes[i].parent=maxCount+(i>>1);
_nodes[i].leaves[0]=l;
_nodes[i].leaves[1]=r;
_codeMap[i]=i;
for (uint32_t k=i;freq<_nodes[_codeMap[k-1]].frequency;k--)
{
uint32_t &code=_codeMap[k];
uint32_t &destCode=_codeMap[k-1];
std::swap(_nodes[code].index,_nodes[destCode].index);
std::swap(_nodes[code].parent,_nodes[destCode].parent);
std::swap(code,destCode);
}
}
}
// Defined as in LH2
void addCode()
{
if (_count>=maxCount) throw Decompressor::DecompressionError();
uint32_t newIndex=(maxCount-_count-1)*2;
if (!_count)
{
_nodes[0].frequency=0;
_nodes[0].index=newIndex-1;
_nodes[0].parent=maxCount*2-2;
_nodes[0].leaves[0]=0;
_nodes[0].leaves[1]=0;
_codeMap[newIndex-1]=0;
_count++;
} else {
_nodes[_count].frequency=0;
_nodes[_count].index=newIndex;
_nodes[_count].parent=maxCount*2-_count-1;
_nodes[_count].leaves[0]=0;
_nodes[_count].leaves[1]=0;
_codeMap[newIndex]=_count;
uint32_t insertIndex=newIndex+2;
uint32_t repNode;
uint32_t parentNode;
uint32_t insertNode=maxCount*2-_count-1;
if (_count>1)
{
_codeMap[insertIndex-1]=_codeMap[insertIndex];
_nodes[_codeMap[insertIndex-1]].index--;
repNode=_codeMap[(maxCount-_count)*2];
parentNode=_nodes[repNode].parent;
_nodes[parentNode].leaves[(_nodes[parentNode].leaves[0]==repNode)?0:1]=insertNode;
_nodes[repNode].parent=insertNode;
} else {
repNode=0;
parentNode=maxCount*2-1;
}
_nodes[insertNode].frequency=_nodes[repNode].frequency;
_nodes[insertNode].index=insertIndex;
_nodes[insertNode].parent=parentNode;
_nodes[insertNode].leaves[0]=_count;
_nodes[insertNode].leaves[1]=repNode;
_codeMap[insertIndex]=insertNode;
Node &parent=_nodes[parentNode];
if (_count>1 && _nodes[parent.leaves[0]].index>_nodes[parent.leaves[1]].index)
std::swap(parent.leaves[0],parent.leaves[1]);
_count++;
}
}
uint32_t getMaxFrequency() const
{
return _nodes[maxCount*2-2].frequency;
}
private:
struct Node
{
uint32_t frequency;
uint32_t index;
uint32_t parent;
uint32_t leaves[2];
};
uint32_t _initialCount;
uint32_t _count;
Node _nodes[maxCount*2-1];
uint32_t _codeMap[maxCount*2-1];
};
}
#endif
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