1// Copyright 2014 PDFium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
6
7#ifndef _JBIG2_ARITHMETIC_DECODER_H_
8#define _JBIG2_ARITHMETIC_DECODER_H_
9#include "JBig2_Define.h"
10#include "JBig2_BitStream.h"
11#include "JBig2_ArithQe.h"
12typedef struct {
13    unsigned int MPS;
14    unsigned int I;
15} JBig2ArithCtx;
16class CJBig2_ArithDecoder : public CJBig2_Object
17{
18public:
19
20    CJBig2_ArithDecoder(CJBig2_BitStream *pStream);
21
22    ~CJBig2_ArithDecoder();
23
24    int DECODE(JBig2ArithCtx *pCX);
25private:
26
27    void INITDEC();
28
29    void BYTEIN();
30    unsigned char B;
31    unsigned int C;
32    unsigned int A;
33    unsigned int CT;
34    CJBig2_BitStream *m_pStream;
35};
36inline CJBig2_ArithDecoder::CJBig2_ArithDecoder(CJBig2_BitStream *pStream)
37{
38    m_pStream = pStream;
39    INITDEC();
40}
41inline CJBig2_ArithDecoder::~CJBig2_ArithDecoder()
42{
43}
44inline void CJBig2_ArithDecoder::INITDEC()
45{
46    B = m_pStream->getCurByte_arith();
47    C = (B ^ 0xff) << 16;;
48    BYTEIN();
49    C = C << 7;
50    CT = CT - 7;
51    A = 0x8000;
52}
53inline void CJBig2_ArithDecoder::BYTEIN()
54{
55    unsigned char B1;
56    if(B == 0xff) {
57        B1 = m_pStream->getNextByte_arith();
58        if(B1 > 0x8f) {
59            CT = 8;
60        } else {
61            m_pStream->incByteIdx();
62            B = B1;
63            C = C + 0xfe00 - (B << 9);
64            CT = 7;
65        }
66    } else {
67        m_pStream->incByteIdx();
68        B = m_pStream->getCurByte_arith();
69        C = C + 0xff00 - (B << 8);
70        CT = 8;
71    }
72}
73inline int CJBig2_ArithDecoder::DECODE(JBig2ArithCtx *pCX)
74{
75    if (!pCX || pCX->I >= JBIG2_QE_NUM) {
76        return 0;
77    }
78
79    int D;
80    const JBig2ArithQe * qe = &QeTable[pCX->I];
81    A = A - qe->Qe;
82    if((C >> 16) < A) {
83        if(A & 0x8000) {
84            D = pCX->MPS;
85        } else {
86            if(A < qe->Qe) {
87                D = 1 - pCX->MPS;
88                if(qe->nSwitch == 1) {
89                    pCX->MPS = 1 - pCX->MPS;
90                }
91                pCX->I = qe->NLPS;
92            } else {
93                D = pCX->MPS;
94                pCX->I = qe->NMPS;
95            }
96            do {
97                if (CT == 0) {
98                    BYTEIN();
99                }
100                A <<= 1;
101                C <<= 1;
102                CT--;
103            } while ((A & 0x8000) == 0);
104        }
105    } else {
106        C -= A << 16;
107        if(A < qe->Qe) {
108            A = qe->Qe;
109            D = pCX->MPS;
110            pCX->I = qe->NMPS;
111        } else {
112            A = qe->Qe;
113            D = 1 - pCX->MPS;
114            if(qe->nSwitch == 1) {
115                pCX->MPS = 1 - pCX->MPS;
116            }
117            pCX->I = qe->NLPS;
118        }
119        do {
120            if (CT == 0) {
121                BYTEIN();
122            }
123            A <<= 1;
124            C <<= 1;
125            CT--;
126        } while ((A & 0x8000) == 0);
127    }
128    return D;
129}
130#endif
131