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// Copyright 2014 PDFium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
#ifndef _JBIG2_ARITHMETIC_DECODER_H_
#define _JBIG2_ARITHMETIC_DECODER_H_
#include "JBig2_Define.h"
#include "JBig2_BitStream.h"
#include "JBig2_ArithQe.h"
typedef struct {
unsigned int MPS;
unsigned int I;
} JBig2ArithCtx;
class CJBig2_ArithDecoder : public CJBig2_Object
{
public:
CJBig2_ArithDecoder(CJBig2_BitStream *pStream);
~CJBig2_ArithDecoder();
int DECODE(JBig2ArithCtx *pCX);
private:
void INITDEC();
void BYTEIN();
unsigned char B;
unsigned int C;
unsigned int A;
unsigned int CT;
CJBig2_BitStream *m_pStream;
};
inline CJBig2_ArithDecoder::CJBig2_ArithDecoder(CJBig2_BitStream *pStream)
{
m_pStream = pStream;
INITDEC();
}
inline CJBig2_ArithDecoder::~CJBig2_ArithDecoder()
{
}
inline void CJBig2_ArithDecoder::INITDEC()
{
B = m_pStream->getCurByte_arith();
C = (B ^ 0xff) << 16;;
BYTEIN();
C = C << 7;
CT = CT - 7;
A = 0x8000;
}
inline void CJBig2_ArithDecoder::BYTEIN()
{
unsigned char B1;
if(B == 0xff) {
B1 = m_pStream->getNextByte_arith();
if(B1 > 0x8f) {
CT = 8;
} else {
m_pStream->incByteIdx();
B = B1;
C = C + 0xfe00 - (B << 9);
CT = 7;
}
} else {
m_pStream->incByteIdx();
B = m_pStream->getCurByte_arith();
C = C + 0xff00 - (B << 8);
CT = 8;
}
}
inline int CJBig2_ArithDecoder::DECODE(JBig2ArithCtx *pCX)
{
int D;
const JBig2ArithQe * qe = &QeTable[pCX->I];
A = A - qe->Qe;
if((C >> 16) < A) {
if(A & 0x8000) {
D = pCX->MPS;
} else {
if(A < qe->Qe) {
D = 1 - pCX->MPS;
if(qe->nSwitch == 1) {
pCX->MPS = 1 - pCX->MPS;
}
pCX->I = qe->NLPS;
} else {
D = pCX->MPS;
pCX->I = qe->NMPS;
}
do {
if (CT == 0) {
BYTEIN();
}
A <<= 1;
C <<= 1;
CT--;
} while ((A & 0x8000) == 0);
}
} else {
C -= A << 16;
if(A < qe->Qe) {
A = qe->Qe;
D = pCX->MPS;
pCX->I = qe->NMPS;
} else {
A = qe->Qe;
D = 1 - pCX->MPS;
if(qe->nSwitch == 1) {
pCX->MPS = 1 - pCX->MPS;
}
pCX->I = qe->NLPS;
}
do {
if (CT == 0) {
BYTEIN();
}
A <<= 1;
C <<= 1;
CT--;
} while ((A & 0x8000) == 0);
}
return D;
}
#endif
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