430 lines
9.5 KiB
C++
430 lines
9.5 KiB
C++
//========= Copyright Valve Corporation, All rights reserved. ============//
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//
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// LZSS Codec. Designed for fast cheap gametime encoding/decoding. Compression results
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// are not aggresive as other alogrithms, but gets 2:1 on most arbitrary uncompressed data.
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//
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//=====================================================================================//
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#include "tier0/platform.h"
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#include "tier0/dbg.h"
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#include "tier0/vprof.h"
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#include "tier0/etwprof.h"
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#include "tier1/lzss.h"
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#include "tier1/utlbuffer.h"
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#define LZSS_LOOKSHIFT 4
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#define LZSS_LOOKAHEAD ( 1 << LZSS_LOOKSHIFT )
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// memdbgon must be the last include file in a .cpp file!!!
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#include "tier0/memdbgon.h"
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//-----------------------------------------------------------------------------
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// Returns true if buffer is compressed.
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//-----------------------------------------------------------------------------
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bool CLZSS::IsCompressed( const unsigned char *pInput )
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{
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lzss_header_t *pHeader = (lzss_header_t *)pInput;
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if ( pHeader && pHeader->id == LZSS_ID )
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{
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return true;
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}
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// unrecognized
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return false;
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}
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//-----------------------------------------------------------------------------
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// Returns uncompressed size of compressed input buffer. Used for allocating output
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// buffer for decompression. Returns 0 if input buffer is not compressed.
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//-----------------------------------------------------------------------------
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unsigned int CLZSS::GetActualSize( const unsigned char *pInput )
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{
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lzss_header_t *pHeader = (lzss_header_t *)pInput;
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if ( pHeader && pHeader->id == LZSS_ID )
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{
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return LittleLong( pHeader->actualSize );
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}
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// unrecognized
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return 0;
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}
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void CLZSS::BuildHash( const unsigned char *pData )
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{
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lzss_list_t *pList;
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lzss_node_t *pTarget;
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int targetindex = (unsigned int)pData & ( m_nWindowSize - 1 );
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pTarget = &m_pHashTarget[targetindex];
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if ( pTarget->pData )
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{
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pList = &m_pHashTable[*pTarget->pData];
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if ( pTarget->pPrev )
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{
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pList->pEnd = pTarget->pPrev;
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pTarget->pPrev->pNext = 0;
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}
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else
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{
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pList->pEnd = 0;
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pList->pStart = 0;
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}
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}
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pList = &m_pHashTable[*pData];
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pTarget->pData = pData;
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pTarget->pPrev = 0;
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pTarget->pNext = pList->pStart;
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if ( pList->pStart )
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{
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pList->pStart->pPrev = pTarget;
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}
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else
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{
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pList->pEnd = pTarget;
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}
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pList->pStart = pTarget;
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}
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unsigned char *CLZSS::CompressNoAlloc( const unsigned char *pInput, int inputLength, unsigned char *pOutputBuf, unsigned int *pOutputSize )
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{
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if ( inputLength <= sizeof( lzss_header_t ) + 8 )
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{
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return NULL;
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}
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VPROF( "CLZSS::CompressNoAlloc" );
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ETWMark1I("CompressNoAlloc", inputLength );
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// create the compression work buffers, small enough (~64K) for stack
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m_pHashTable = (lzss_list_t *)stackalloc( 256 * sizeof( lzss_list_t ) );
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memset( m_pHashTable, 0, 256 * sizeof( lzss_list_t ) );
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m_pHashTarget = (lzss_node_t *)stackalloc( m_nWindowSize * sizeof( lzss_node_t ) );
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memset( m_pHashTarget, 0, m_nWindowSize * sizeof( lzss_node_t ) );
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// allocate the output buffer, compressed buffer is expected to be less, caller will free
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unsigned char *pStart = pOutputBuf;
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// prevent compression failure (inflation), leave enough to allow dribble eof bytes
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unsigned char *pEnd = pStart + inputLength - sizeof ( lzss_header_t ) - 8;
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// set the header
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lzss_header_t *pHeader = (lzss_header_t *)pStart;
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pHeader->id = LZSS_ID;
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pHeader->actualSize = LittleLong( inputLength );
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unsigned char *pOutput = pStart + sizeof (lzss_header_t);
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const unsigned char *pLookAhead = pInput;
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const unsigned char *pWindow = pInput;
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const unsigned char *pEncodedPosition = NULL;
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unsigned char *pCmdByte = NULL;
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int putCmdByte = 0;
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while ( inputLength > 0 )
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{
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pWindow = pLookAhead - m_nWindowSize;
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if ( pWindow < pInput )
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{
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pWindow = pInput;
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}
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if ( !putCmdByte )
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{
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pCmdByte = pOutput++;
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*pCmdByte = 0;
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}
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putCmdByte = ( putCmdByte + 1 ) & 0x07;
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int encodedLength = 0;
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int lookAheadLength = inputLength < LZSS_LOOKAHEAD ? inputLength : LZSS_LOOKAHEAD;
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lzss_node_t *pHash = m_pHashTable[pLookAhead[0]].pStart;
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while ( pHash )
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{
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int matchLength = 0;
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int length = lookAheadLength;
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while ( length-- && pHash->pData[matchLength] == pLookAhead[matchLength] )
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{
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matchLength++;
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}
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if ( matchLength > encodedLength )
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{
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encodedLength = matchLength;
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pEncodedPosition = pHash->pData;
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}
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if ( matchLength == lookAheadLength )
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{
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break;
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}
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pHash = pHash->pNext;
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}
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if ( encodedLength >= 3 )
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{
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*pCmdByte = ( *pCmdByte >> 1 ) | 0x80;
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*pOutput++ = ( ( pLookAhead-pEncodedPosition-1 ) >> LZSS_LOOKSHIFT );
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*pOutput++ = ( ( pLookAhead-pEncodedPosition-1 ) << LZSS_LOOKSHIFT ) | ( encodedLength-1 );
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}
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else
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{
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encodedLength = 1;
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*pCmdByte = ( *pCmdByte >> 1 );
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*pOutput++ = *pLookAhead;
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}
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for ( int i=0; i<encodedLength; i++ )
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{
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BuildHash( pLookAhead++ );
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}
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inputLength -= encodedLength;
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if ( pOutput >= pEnd )
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{
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// compression is worse, abandon
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return NULL;
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}
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}
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if ( inputLength != 0 )
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{
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// unexpected failure
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Assert( 0 );
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return NULL;
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}
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if ( !putCmdByte )
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{
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pCmdByte = pOutput++;
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*pCmdByte = 0x01;
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}
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else
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{
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*pCmdByte = ( ( *pCmdByte >> 1 ) | 0x80 ) >> ( 7 - putCmdByte );
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}
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*pOutput++ = 0;
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*pOutput++ = 0;
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if ( pOutputSize )
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{
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*pOutputSize = pOutput - pStart;
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}
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return pStart;
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}
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//-----------------------------------------------------------------------------
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// Compress an input buffer. Caller must free output compressed buffer.
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// Returns NULL if compression failed (i.e. compression yielded worse results)
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//-----------------------------------------------------------------------------
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unsigned char* CLZSS::Compress( const unsigned char *pInput, int inputLength, unsigned int *pOutputSize )
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{
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unsigned char *pStart = (unsigned char *)malloc( inputLength );
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unsigned char *pFinal = CompressNoAlloc( pInput, inputLength, pStart, pOutputSize );
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if ( !pFinal )
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{
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free( pStart );
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return NULL;
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}
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return pStart;
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}
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/*
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// BUG BUG: This code is flaky, don't use until it's debugged!!!
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unsigned int CLZSS::Uncompress( unsigned char *pInput, CUtlBuffer &buf )
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{
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int cmdByte = 0;
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int getCmdByte = 0;
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unsigned int actualSize = GetActualSize( pInput );
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if ( !actualSize )
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{
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// unrecognized
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return 0;
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}
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unsigned char *pBase = ( unsigned char * )buf.Base();
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pInput += sizeof( lzss_header_t );
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while ( !buf.IsValid() )
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{
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if ( !getCmdByte )
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{
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cmdByte = *pInput++;
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}
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getCmdByte = ( getCmdByte + 1 ) & 0x07;
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if ( cmdByte & 0x01 )
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{
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int position = *pInput++ << LZSS_LOOKSHIFT;
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position |= ( *pInput >> LZSS_LOOKSHIFT );
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int count = ( *pInput++ & 0x0F ) + 1;
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if ( count == 1 )
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{
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break;
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}
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unsigned int pos = buf.TellPut();
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unsigned char *pSource = ( pBase + pos ) - position - 1;
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// BUGBUG:
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// This is failing!!!
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// buf.WriteBytes( pSource, count );
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// So have to iterate them manually
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for ( int i =0; i < count; ++i )
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{
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buf.PutUnsignedChar( *pSource++ );
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}
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}
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else
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{
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buf.PutUnsignedChar( *pInput++ );
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}
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cmdByte = cmdByte >> 1;
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}
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if ( buf.TellPut() != (int)actualSize )
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{
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// unexpected failure
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Assert( 0 );
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return 0;
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}
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return buf.TellPut();
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}
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*/
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unsigned int CLZSS::SafeUncompress( const unsigned char *pInput, unsigned char *pOutput, unsigned int unBufSize )
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{
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unsigned int totalBytes = 0;
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int cmdByte = 0;
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int getCmdByte = 0;
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unsigned int actualSize = GetActualSize( pInput );
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if ( !actualSize )
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{
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// unrecognized
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return 0;
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}
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if ( actualSize > unBufSize )
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{
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return 0;
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}
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pInput += sizeof( lzss_header_t );
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for ( ;; )
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{
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if ( !getCmdByte )
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{
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cmdByte = *pInput++;
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}
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getCmdByte = ( getCmdByte + 1 ) & 0x07;
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if ( cmdByte & 0x01 )
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{
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int position = *pInput++ << LZSS_LOOKSHIFT;
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position |= ( *pInput >> LZSS_LOOKSHIFT );
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int count = ( *pInput++ & 0x0F ) + 1;
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if ( count == 1 )
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{
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break;
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}
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unsigned char *pSource = pOutput - position - 1;
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if ( totalBytes + count > unBufSize )
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{
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return 0;
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}
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for ( int i=0; i<count; i++ )
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{
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*pOutput++ = *pSource++;
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}
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totalBytes += count;
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}
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else
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{
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if ( totalBytes + 1 > unBufSize )
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return 0;
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*pOutput++ = *pInput++;
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totalBytes++;
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}
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cmdByte = cmdByte >> 1;
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}
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if ( totalBytes != actualSize )
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{
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// unexpected failure
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Assert( 0 );
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return 0;
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}
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return totalBytes;
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}
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//-----------------------------------------------------------------------------
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// Uncompress a buffer, Returns the uncompressed size. Caller must provide an
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// adequate sized output buffer or memory corruption will occur.
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//-----------------------------------------------------------------------------
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unsigned int CLZSS::Uncompress( const unsigned char *pInput, unsigned char *pOutput )
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{
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unsigned int totalBytes = 0;
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int cmdByte = 0;
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int getCmdByte = 0;
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unsigned int actualSize = GetActualSize( pInput );
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if ( !actualSize )
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{
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// unrecognized
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return 0;
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}
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pInput += sizeof( lzss_header_t );
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for ( ;; )
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{
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if ( !getCmdByte )
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{
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cmdByte = *pInput++;
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}
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getCmdByte = ( getCmdByte + 1 ) & 0x07;
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if ( cmdByte & 0x01 )
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{
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int position = *pInput++ << LZSS_LOOKSHIFT;
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position |= ( *pInput >> LZSS_LOOKSHIFT );
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int count = ( *pInput++ & 0x0F ) + 1;
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if ( count == 1 )
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{
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break;
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}
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unsigned char *pSource = pOutput - position - 1;
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for ( int i=0; i<count; i++ )
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{
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*pOutput++ = *pSource++;
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}
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totalBytes += count;
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}
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else
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{
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*pOutput++ = *pInput++;
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totalBytes++;
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}
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cmdByte = cmdByte >> 1;
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}
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if ( totalBytes != actualSize )
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{
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// unexpected failure
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Assert( 0 );
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return 0;
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}
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return totalBytes;
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}
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