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/******************************************************************************
*
* Project: Raster Matrix Format
* Purpose: Implementation of the LZW compression algorithm as used in
* GIS "Panorama"/"Integratsia" raster files. Based on implementation
* of Kent Williams, but heavily modified over it. The key point
* in the initial implementation is a hashing algorithm.
* Author: Andrey Kiselev, dron@ak4719.spb.edu
*
******************************************************************************
* Copyright (c) 2007, Andrey Kiselev <dron@ak4719.spb.edu>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
******************************************************************************
* COPYRIGHT NOTICE FROM THE INITIAL IMPLEMENTATION:
*
* The programs LZWCOM and LZWUNC, both in binary executable and source forms,
* are in the public domain. No warranty is given or implied, and no
* liability will be assumed by the author.
*
* Everyone on earth is hereby given permission to use, copy, distribute,
* change, mangle, destroy or otherwise employ these programs, provided they
* hurt no one but themselves in the process.
*
* Kent Williams
* Norand Inc.
* 550 2nd St S.E.
* Cedar Rapids, Iowa 52401
* (319) 369-3131
****************************************************************************/
#include "cpl_conv.h"
#include "rmfdataset.h"
// Code marks that there is no predecessor in the string
constexpr GUInt32 NO_PRED = 0xFFFF;
// We are using 12-bit codes in this particular implementation
constexpr GUInt32 TABSIZE = 4096U;
constexpr GUInt32 STACKSIZE = TABSIZE;
constexpr GUInt32 NOT_FND = 0xFFFF;
/************************************************************************/
/* LZWStringTab */
/************************************************************************/
typedef struct
{
bool bUsed;
GUInt32 iNext; // hi bit is 'used' flag
GUInt32 iPredecessor; // 12 bit code
GByte iFollower;
} LZWStringTab;
/************************************************************************/
/* LZWUpdateTab() */
/************************************************************************/
CPL_NOSANITIZE_UNSIGNED_INT_OVERFLOW
static GUInt32 UnsanitizedMul(GUInt32 a, GUInt32 b)
{
return a * b;
}
static int UnsignedByteToSignedByte(GByte byVal)
{
return byVal >= 128 ? byVal - 256 : byVal;
}
static void LZWUpdateTab(LZWStringTab *poCodeTab, GUInt32 iPred, GByte bFollow)
{
/* -------------------------------------------------------------------- */
/* Hash uses the 'mid-square' algorithm. I.E. for a hash val of n bits */
/* hash = middle binary digits of (key * key). Upon collision, hash */
/* searches down linked list of keys that hashed to that key already. */
/* It will NOT notice if the table is full. This must be handled */
/* elsewhere */
/* -------------------------------------------------------------------- */
const int iFollow = UnsignedByteToSignedByte(bFollow);
GUInt32 nLocal = CPLUnsanitizedAdd<GUInt32>(iPred, iFollow) | 0x0800;
nLocal = (UnsanitizedMul(nLocal, nLocal) >> 6) &
0x0FFF; // middle 12 bits of result
// If string is not used
GUInt32 nNext = nLocal;
if (poCodeTab[nLocal].bUsed)
{
// If collision has occurred
while ((nNext = poCodeTab[nLocal].iNext) != 0)
nLocal = nNext;
// Search for free entry from nLocal + 101
nNext = (nLocal + 101) & 0x0FFF;
while (poCodeTab[nNext].bUsed)
{
if (++nNext >= TABSIZE)
nNext = 0;
}
// Put new tempnext into last element in collision list
poCodeTab[nLocal].iNext = nNext;
}
poCodeTab[nNext].bUsed = true;
poCodeTab[nNext].iNext = 0;
poCodeTab[nNext].iPredecessor = iPred;
poCodeTab[nNext].iFollower = bFollow;
}
/************************************************************************/
/* LZWCreateTab() */
/************************************************************************/
static LZWStringTab *LZWCreateTab()
{
// Allocate space for the new table and pre-fill it
LZWStringTab *poCodeTab =
(LZWStringTab *)CPLMalloc(TABSIZE * sizeof(LZWStringTab));
memset(poCodeTab, 0, TABSIZE * sizeof(LZWStringTab));
for (GUInt32 iCode = 0; iCode < 256; ++iCode)
LZWUpdateTab(poCodeTab, NO_PRED, static_cast<GByte>(iCode));
return poCodeTab;
}
/************************************************************************/
/* LZWFindIndex() */
/************************************************************************/
static GUInt32 LZWFindIndex(const LZWStringTab *poCodeTab, GUInt32 iPred,
GByte bFollow)
{
const int iFollow = UnsignedByteToSignedByte(bFollow);
GUInt32 nLocal = CPLUnsanitizedAdd<GUInt32>(iPred, iFollow) | 0x0800;
nLocal = (UnsanitizedMul(nLocal, nLocal) >> 6) &
0x0FFF; // middle 12 bits of result
do
{
CPLAssert(nLocal < TABSIZE);
if (poCodeTab[nLocal].iPredecessor == iPred &&
poCodeTab[nLocal].iFollower == bFollow)
{
return nLocal;
}
nLocal = poCodeTab[nLocal].iNext;
} while (nLocal > 0);
return NOT_FND;
}
/************************************************************************/
/* LZWPutCode() */
/************************************************************************/
static bool LZWPutCode(GUInt32 iCode, GUInt32 &iTmp, bool &bBitsleft,
GByte *&pabyCurrent, const GByte *const pabyOutEnd)
{
if (bBitsleft)
{
if (pabyCurrent >= pabyOutEnd)
{
return false;
}
*(pabyCurrent++) = static_cast<GByte>((iCode >> 4) & 0xFF);
iTmp = iCode & 0x000F;
bBitsleft = false;
}
else
{
if (pabyCurrent + 1 >= pabyOutEnd)
{
return false;
}
*(pabyCurrent++) =
static_cast<GByte>(((iTmp << 4) & 0xFF0) + ((iCode >> 8) & 0x00F));
*(pabyCurrent++) = static_cast<GByte>(iCode & 0xFF);
bBitsleft = true;
}
return true;
}
/************************************************************************/
/* LZWReadStream() */
/************************************************************************/
static size_t LZWReadStream(const GByte *pabyIn, GUInt32 nSizeIn,
GByte *pabyOut, GUInt32 nSizeOut,
LZWStringTab *poCodeTab)
{
GByte *const pabyOutBegin = pabyOut;
// The first code is always known
GUInt32 iCode = (*pabyIn++ << 4) & 0xFF0;
nSizeIn--;
iCode += (*pabyIn >> 4) & 0x00F;
GUInt32 iOldCode = iCode;
bool bBitsleft = true;
GByte iFinChar = poCodeTab[iCode].iFollower;
nSizeOut--;
*pabyOut++ = iFinChar;
GUInt32 nCount = TABSIZE - 256;
// Decompress the input buffer
while (nSizeIn > 0)
{
// Fetch 12-bit code from input stream
if (bBitsleft)
{
iCode = ((*pabyIn++ & 0x0F) << 8) & 0xF00;
nSizeIn--;
if (nSizeIn == 0)
break;
iCode += *pabyIn++;
nSizeIn--;
bBitsleft = FALSE;
}
else
{
iCode = (*pabyIn++ << 4) & 0xFF0;
nSizeIn--;
if (nSizeIn == 0)
break;
iCode += (*pabyIn >> 4) & 0x00F;
bBitsleft = TRUE;
}
const GUInt32 iInCode = iCode;
GByte bLastChar = 0; // TODO(schwehr): Why not nLastChar?
// Do we have unknown code?
bool bNewCode = false;
if (!poCodeTab[iCode].bUsed)
{
iCode = iOldCode;
bLastChar = iFinChar;
bNewCode = true;
}
GByte abyStack[STACKSIZE] = {};
GByte *pabyTail = abyStack + STACKSIZE;
GUInt32 nStackCount = 0;
while (poCodeTab[iCode].iPredecessor != NO_PRED)
{
// Stack overrun
if (nStackCount >= STACKSIZE)
return 0;
// Put the decoded character into stack
*(--pabyTail) = poCodeTab[iCode].iFollower;
nStackCount++;
iCode = poCodeTab[iCode].iPredecessor;
}
if (!nSizeOut)
return 0;
// The first character
iFinChar = poCodeTab[iCode].iFollower;
nSizeOut--;
*pabyOut++ = iFinChar;
// Output buffer overrun
if (nStackCount > nSizeOut)
return 0;
// Now copy the stack contents into output buffer. Our stack was
// filled in reverse order, so no need in character reordering
memcpy(pabyOut, pabyTail, nStackCount);
nSizeOut -= nStackCount;
pabyOut += nStackCount;
// If code isn't known
if (bNewCode)
{
// Output buffer overrun
if (!nSizeOut)
return 0;
iFinChar = bLastChar; // the follower char of last
*pabyOut++ = iFinChar;
nSizeOut--;
}
if (nCount > 0)
{
nCount--;
// Add code to the table
LZWUpdateTab(poCodeTab, iOldCode, iFinChar);
}
iOldCode = iInCode;
}
return static_cast<size_t>(pabyOut - pabyOutBegin);
}
/************************************************************************/
/* LZWDecompress() */
/************************************************************************/
size_t RMFDataset::LZWDecompress(const GByte *pabyIn, GUInt32 nSizeIn,
GByte *pabyOut, GUInt32 nSizeOut, GUInt32,
GUInt32)
{
if (pabyIn == nullptr || pabyOut == nullptr || nSizeIn < 2)
return 0;
LZWStringTab *poCodeTab = LZWCreateTab();
size_t nRet = LZWReadStream(pabyIn, nSizeIn, pabyOut, nSizeOut, poCodeTab);
CPLFree(poCodeTab);
return nRet;
}
/************************************************************************/
/* LZWWriteStream() */
/************************************************************************/
static size_t LZWWriteStream(const GByte *pabyIn, GUInt32 nSizeIn,
GByte *pabyOut, GUInt32 nSizeOut,
LZWStringTab *poCodeTab)
{
GUInt32 iCode;
iCode = LZWFindIndex(poCodeTab, NO_PRED, *pabyIn++);
nSizeIn--;
GUInt32 nCount = TABSIZE - 256;
GUInt32 iTmp = 0;
bool bBitsleft = true;
GByte *pabyCurrent = pabyOut;
GByte *pabyOutEnd = pabyOut + nSizeOut;
while (nSizeIn > 0)
{
const GByte bCurrentCode = *pabyIn++;
nSizeIn--;
GUInt32 iNextCode = LZWFindIndex(poCodeTab, iCode, bCurrentCode);
if (iNextCode != NOT_FND)
{
iCode = iNextCode;
continue;
}
if (!LZWPutCode(iCode, iTmp, bBitsleft, pabyCurrent, pabyOutEnd))
{
return 0;
}
if (nCount > 0)
{
nCount--;
LZWUpdateTab(poCodeTab, iCode, bCurrentCode);
}
iCode = LZWFindIndex(poCodeTab, NO_PRED, bCurrentCode);
}
if (!LZWPutCode(iCode, iTmp, bBitsleft, pabyCurrent, pabyOutEnd))
{
return 0;
}
if (!bBitsleft)
{
if (pabyCurrent >= pabyOutEnd)
{
return 0;
}
*(pabyCurrent++) = static_cast<GByte>((iTmp << 4) & 0xFF0);
}
return static_cast<size_t>(pabyCurrent - pabyOut);
}
/************************************************************************/
/* LZWCompress() */
/************************************************************************/
size_t RMFDataset::LZWCompress(const GByte *pabyIn, GUInt32 nSizeIn,
GByte *pabyOut, GUInt32 nSizeOut, GUInt32,
GUInt32, const RMFDataset *)
{
if (pabyIn == nullptr || pabyOut == nullptr || nSizeIn == 0)
return 0;
// Allocate space for the new table and pre-fill it
LZWStringTab *poCodeTab = LZWCreateTab();
size_t nWritten =
LZWWriteStream(pabyIn, nSizeIn, pabyOut, nSizeOut, poCodeTab);
CPLFree(poCodeTab);
return nWritten;
}
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