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