mirror of https://github.com/dwsJason/gsla.git
334 lines
8.2 KiB
C++
334 lines
8.2 KiB
C++
//
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// LZB Encode / Decode
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//
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#include "lzb.h"
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#include <stdio.h>
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#include <vector>
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#include "bctypes.h"
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#define DICTIONARY_SIZE (32 * 1024)
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//
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// Yes This is a 32K Buffer, of bytes, with no structure to it
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//
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static unsigned char Dictionary[ DICTIONARY_SIZE ];
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static int AddDictionary(const std::vector<unsigned char>&data, int dictionarySize);
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static int EmitLiteral(unsigned char *pDest, std::vector<unsigned char>& data);
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static int ConcatLiteral(unsigned char *pDest, std::vector<unsigned char>& data);
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static int EmitReference(unsigned char *pDest, int dictionaryOffset, std::vector<unsigned char>& data);
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static int DictionaryMatch(const std::vector<unsigned char>& data, int dictionarySize);
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int LZB_Compress(unsigned char* pDest, unsigned char* pSource, int sourceSize)
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{
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printf("LZB_Compress %d bytes\n", sourceSize);
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// anything less than 3 bytes, is going to be a literal match
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int processedBytes = 0;
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int bytesInDictionary = 0;
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int bytesEmitted = 0;
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// dumb last emit is a literal stuff
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bool bLastEmitIsLiteral = false;
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int lastEmittedLiteralOffset = 0;
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std::vector<unsigned char> candidate_data;
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while (processedBytes < sourceSize)
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{
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unsigned char byte_data = pSource[ processedBytes++ ];
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candidate_data.push_back(byte_data);
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// If there's a match, then add to the candidate data, and see if
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// there's a bigger match (use previous result to speed up search)
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// (KMP is probably the last planned optmization here)
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// The dictionary only contains bytes that have been emitted, so we
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// can't add this byte until we've emitted it?
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if (DictionaryMatch(candidate_data, bytesInDictionary) < 0)
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{
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// Was there a dictionary match
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std::vector<unsigned char> prev_data = candidate_data;
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prev_data.pop_back();
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int MatchOffset = DictionaryMatch(prev_data, bytesInDictionary);
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if ((MatchOffset >= 0) && prev_data.size() > 3)
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{
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bytesInDictionary = AddDictionary(prev_data, bytesInDictionary);
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bytesEmitted += EmitReference(pDest + bytesEmitted, MatchOffset, prev_data);
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candidate_data[0] = candidate_data[ candidate_data.size() - 1 ];
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candidate_data.resize(1);
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bLastEmitIsLiteral = false;
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}
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else
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{
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// Add Dictionary
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bytesInDictionary = AddDictionary(candidate_data, bytesInDictionary);
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if (bLastEmitIsLiteral)
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{
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// If the last emit was a literal, I want to concatenate
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// this literal into the previous opcode, to save space
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bytesEmitted += ConcatLiteral(pDest + lastEmittedLiteralOffset, candidate_data);
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}
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else
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{
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lastEmittedLiteralOffset = bytesEmitted;
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bytesEmitted += EmitLiteral(pDest + bytesEmitted, candidate_data);
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}
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bLastEmitIsLiteral = true;
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}
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}
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}
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if (candidate_data.size() > 0)
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{
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int MatchOffset = DictionaryMatch(candidate_data, bytesInDictionary);
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if ((MatchOffset >=0) && candidate_data.size() > 2)
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{
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bytesInDictionary = AddDictionary(candidate_data, bytesInDictionary);
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bytesEmitted += EmitReference(pDest + bytesEmitted, MatchOffset, candidate_data);
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}
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else
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{
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// Add Dictionary
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bytesInDictionary = AddDictionary(candidate_data, bytesInDictionary);
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if (bLastEmitIsLiteral)
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{
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// If the last emit was a literal, I want to concatenate
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// this literal into the previous opcode, to save space
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bytesEmitted += ConcatLiteral(pDest + lastEmittedLiteralOffset, candidate_data);
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}
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else
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{
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bytesEmitted += EmitLiteral(pDest + bytesEmitted, candidate_data);
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}
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}
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}
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return bytesEmitted;
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}
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//------------------------------------------------------------------------------
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// Return new dictionarySize
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static int AddDictionary(const std::vector<unsigned char>&data, int dictionarySize)
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{
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int dataIndex = 0;
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while ((dictionarySize < DICTIONARY_SIZE) && (dataIndex < data.size()))
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{
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Dictionary[ dictionarySize++ ] = data[ dataIndex++ ];
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}
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return dictionarySize;
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}
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//------------------------------------------------------------------------------
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//
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// Return offset into dictionary where the string matches
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//
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// -1 means, no match
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//
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static int DictionaryMatch(const std::vector<unsigned char>& data, int dictionarySize)
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{
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if( (0 == dictionarySize ) ||
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(0 == data.size()) ||
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(data.size() > 16384) ) // 16384 is largest string copy we can encode
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{
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return -1;
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}
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// Check the end of the dictionary, to see if this data could be a
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// pattern "run" (where we can repeat a pattern for X many times for free
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// using the memcpy with overlapping source/dest buffers)
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// (This is a dictionary based pattern run/length)
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{
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// Check for pattern sizes, start small
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int max_pattern_size = dictionarySize;
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for (int pattern_size = 1; pattern_size <= max_pattern_size; ++pattern_size)
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{
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bool bMatch = true;
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int pattern_start = dictionarySize - pattern_size;
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for (int dataIndex = 0; dataIndex < data.size(); ++dataIndex)
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{
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if (data[ dataIndex ] == Dictionary[ pattern_start + (dataIndex % pattern_size) ])
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continue;
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bMatch = false;
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break;
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}
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if (bMatch)
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{
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// Return a RLE Style match result
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return pattern_start;
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}
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}
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}
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if (dictionarySize < data.size())
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{
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return -1;
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}
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int dictionaryOffset = 0;
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int result = -1;
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// Check the dictionary for a match, brute force
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for (int idx = 0; idx <= (dictionarySize-data.size()); ++idx)
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{
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bool bMatch = true;
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for (int dataIdx = 0; dataIdx < data.size(); ++dataIdx)
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{
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if (data[ dataIdx ] == Dictionary[ idx + dataIdx ])
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continue;
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bMatch = false;
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break;
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}
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if (bMatch)
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{
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result = idx;
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break;
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}
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}
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return result;
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}
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//------------------------------------------------------------------------------
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//
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// Emit a literal, that appends itself to an existing literal
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//
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static int ConcatLiteral(unsigned char *pDest, std::vector<unsigned char>& data)
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{
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// Return Size
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int outSize = (int)data.size();
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int opCode = pDest[0];
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opCode |= (int)(((pDest[1])&0x7F)<<8);
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int skip = opCode;
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opCode += outSize;
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// Opcode
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*pDest++ = (unsigned char)(opCode & 0xFF);
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*pDest++ = (unsigned char)((opCode >> 8) & 0x7F);
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pDest += skip;
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// Literal Data
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for (int idx = 0; idx < data.size(); ++idx)
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{
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*pDest++ = data[ idx ];
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}
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data.clear();
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return outSize;
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}
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//------------------------------------------------------------------------------
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static int EmitLiteral(unsigned char *pDest, std::vector<unsigned char>& data)
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{
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// Return Size
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int outSize = 2 + (int)data.size();
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// Opcode
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*pDest++ = (unsigned char)(data.size() & 0xFF);
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*pDest++ = (unsigned char)((data.size() >> 8) & 0x7F);
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// Literal Data
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for (int idx = 0; idx < data.size(); ++idx)
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{
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*pDest++ = data[ idx ];
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}
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data.clear();
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return outSize;
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}
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//------------------------------------------------------------------------------
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static int EmitReference(unsigned char *pDest, int dictionaryOffset, std::vector<unsigned char>& data)
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{
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// Return Size
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int outSize = 2 + 2;
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// Opcode
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*pDest++ = (unsigned char)(data.size() & 0xFF);
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*pDest++ = (unsigned char)((data.size() >> 8) & 0x7F) | 0x80;
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*pDest++ = (unsigned char)(dictionaryOffset & 0xFF);
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*pDest++ = (unsigned char)((dictionaryOffset>>8) & 0xFF);
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data.clear();
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return outSize;
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}
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//------------------------------------------------------------------------------
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//
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// Std C memcpy seems to be stopping the copy from happening, when I overlap
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// the buffer to get a pattern run copy (overlapped buffers)
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//
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static void my_memcpy(u8* pDest, u8* pSrc, int length)
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{
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while (length-- > 0)
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{
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*pDest++ = *pSrc++;
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}
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}
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//------------------------------------------------------------------------------
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//
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// Simple Decompress, for validation
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//
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void LZB_Decompress(unsigned char* pDest, unsigned char* pSource, int destSize)
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{
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int decompressedBytes = 0;
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while (decompressedBytes < destSize)
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{
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u16 opcode = *pSource++;
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opcode |= ((u16)(*pSource++))<<8;
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if (opcode & 0x8000)
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{
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// Dictionary
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opcode &= 0x7FFF;
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// Dictionary Copy from the output stream
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u16 offset = *pSource++;
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offset |= ((u16)(*pSource++))<<8;
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my_memcpy(&pDest[ decompressedBytes ], &pDest[ offset ], opcode);
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decompressedBytes += opcode;
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}
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else
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{
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// Literal Copy, from compressed stream
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memcpy(&pDest[ decompressedBytes ], pSource, opcode);
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decompressedBytes += opcode;
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pSource += opcode;
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}
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}
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}
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//------------------------------------------------------------------------------
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