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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
#include "JBig2_ArithDecoder.h"
#include "../../../include/fxcrt/fx_basic.h"
#include "JBig2_BitStream.h"
#include "JBig2_Define.h"
namespace {
struct JBig2ArithQe {
unsigned int Qe;
unsigned int NMPS;
unsigned int NLPS;
unsigned int nSwitch;
};
const JBig2ArithQe kQeTable[] = {
// Stupid hack to keep clang-format from reformatting this badly.
{0x5601, 1, 1, 1},
{0x3401, 2, 6, 0},
{0x1801, 3, 9, 0},
{0x0AC1, 4, 12, 0},
{0x0521, 5, 29, 0},
{0x0221, 38, 33, 0},
{0x5601, 7, 6, 1},
{0x5401, 8, 14, 0},
{0x4801, 9, 14, 0},
{0x3801, 10, 14, 0},
{0x3001, 11, 17, 0},
{0x2401, 12, 18, 0},
{0x1C01, 13, 20, 0},
{0x1601, 29, 21, 0},
{0x5601, 15, 14, 1},
{0x5401, 16, 14, 0},
{0x5101, 17, 15, 0},
{0x4801, 18, 16, 0},
{0x3801, 19, 17, 0},
{0x3401, 20, 18, 0},
{0x3001, 21, 19, 0},
{0x2801, 22, 19, 0},
{0x2401, 23, 20, 0},
{0x2201, 24, 21, 0},
{0x1C01, 25, 22, 0},
{0x1801, 26, 23, 0},
{0x1601, 27, 24, 0},
{0x1401, 28, 25, 0},
{0x1201, 29, 26, 0},
{0x1101, 30, 27, 0},
{0x0AC1, 31, 28, 0},
{0x09C1, 32, 29, 0},
{0x08A1, 33, 30, 0},
{0x0521, 34, 31, 0},
{0x0441, 35, 32, 0},
{0x02A1, 36, 33, 0},
{0x0221, 37, 34, 0},
{0x0141, 38, 35, 0},
{0x0111, 39, 36, 0},
{0x0085, 40, 37, 0},
{0x0049, 41, 38, 0},
{0x0025, 42, 39, 0},
{0x0015, 43, 40, 0},
{0x0009, 44, 41, 0},
{0x0005, 45, 42, 0},
{0x0001, 45, 43, 0},
{0x5601, 46, 46, 0}};
} // namespace
CJBig2_ArithDecoder::CJBig2_ArithDecoder(CJBig2_BitStream* pStream) {
m_pStream = pStream;
INITDEC();
}
CJBig2_ArithDecoder::~CJBig2_ArithDecoder() {
}
int CJBig2_ArithDecoder::DECODE(JBig2ArithCtx* pCX) {
if (!pCX || pCX->I >= FX_ArraySize(kQeTable)) {
return 0;
}
int D;
const JBig2ArithQe* qe = &kQeTable[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;
}
void CJBig2_ArithDecoder::INITDEC() {
B = m_pStream->getCurByte_arith();
C = (B ^ 0xff) << 16;
BYTEIN();
C = C << 7;
CT = CT - 7;
A = 0x8000;
}
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;
}
}
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