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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"
struct JBig2ArithCtx {
unsigned int MPS;
unsigned int I;
};
class CJBig2_ArithDecoder {
public:
explicit 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) {
if (!pCX || pCX->I >= JBIG2_QE_NUM) {
return 0;
}
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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