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1 // Copyright 2014 PDFium Authors. All rights reserved. | 1 // Copyright 2014 PDFium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com | 5 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com |
6 | 6 |
7 #ifndef _JBIG2_ARITHMETIC_DECODER_H_ | 7 #ifndef CORE_SRC_FXCODEC_JBIG2_JBIG2_ARITHDECODER_H_ |
8 #define _JBIG2_ARITHMETIC_DECODER_H_ | 8 #define CORE_SRC_FXCODEC_JBIG2_JBIG2_ARITHDECODER_H_ |
9 #include "JBig2_Define.h" | 9 |
10 #include "JBig2_BitStream.h" | 10 class CJBig2_BitStream; |
11 #include "JBig2_ArithQe.h" | |
12 | 11 |
13 struct JBig2ArithCtx { | 12 struct JBig2ArithCtx { |
14 unsigned int MPS; | 13 unsigned int MPS; |
15 unsigned int I; | 14 unsigned int I; |
16 }; | 15 }; |
17 | 16 |
18 class CJBig2_ArithDecoder { | 17 class CJBig2_ArithDecoder { |
19 public: | 18 public: |
20 explicit CJBig2_ArithDecoder(CJBig2_BitStream* pStream); | 19 explicit CJBig2_ArithDecoder(CJBig2_BitStream* pStream); |
21 | 20 |
22 ~CJBig2_ArithDecoder(); | 21 ~CJBig2_ArithDecoder(); |
23 | 22 |
24 int DECODE(JBig2ArithCtx* pCX); | 23 int DECODE(JBig2ArithCtx* pCX); |
25 | 24 |
26 private: | 25 private: |
27 void INITDEC(); | 26 void INITDEC(); |
28 void BYTEIN(); | 27 void BYTEIN(); |
29 | 28 |
30 unsigned char B; | 29 unsigned char B; |
31 unsigned int C; | 30 unsigned int C; |
32 unsigned int A; | 31 unsigned int A; |
33 unsigned int CT; | 32 unsigned int CT; |
34 CJBig2_BitStream* m_pStream; | 33 CJBig2_BitStream* m_pStream; |
35 }; | 34 }; |
36 | 35 |
37 inline CJBig2_ArithDecoder::CJBig2_ArithDecoder(CJBig2_BitStream* pStream) { | 36 #endif // CORE_SRC_FXCODEC_JBIG2_JBIG2_ARITHDECODER_H_ |
38 m_pStream = pStream; | |
39 INITDEC(); | |
40 } | |
41 inline CJBig2_ArithDecoder::~CJBig2_ArithDecoder() {} | |
42 inline void CJBig2_ArithDecoder::INITDEC() { | |
43 B = m_pStream->getCurByte_arith(); | |
44 C = (B ^ 0xff) << 16; | |
45 ; | |
46 BYTEIN(); | |
47 C = C << 7; | |
48 CT = CT - 7; | |
49 A = 0x8000; | |
50 } | |
51 inline void CJBig2_ArithDecoder::BYTEIN() { | |
52 unsigned char B1; | |
53 if (B == 0xff) { | |
54 B1 = m_pStream->getNextByte_arith(); | |
55 if (B1 > 0x8f) { | |
56 CT = 8; | |
57 } else { | |
58 m_pStream->incByteIdx(); | |
59 B = B1; | |
60 C = C + 0xfe00 - (B << 9); | |
61 CT = 7; | |
62 } | |
63 } else { | |
64 m_pStream->incByteIdx(); | |
65 B = m_pStream->getCurByte_arith(); | |
66 C = C + 0xff00 - (B << 8); | |
67 CT = 8; | |
68 } | |
69 } | |
70 inline int CJBig2_ArithDecoder::DECODE(JBig2ArithCtx* pCX) { | |
71 if (!pCX || pCX->I >= JBIG2_QE_NUM) { | |
72 return 0; | |
73 } | |
74 | |
75 int D; | |
76 const JBig2ArithQe* qe = &QeTable[pCX->I]; | |
77 A = A - qe->Qe; | |
78 if ((C >> 16) < A) { | |
79 if (A & 0x8000) { | |
80 D = pCX->MPS; | |
81 } else { | |
82 if (A < qe->Qe) { | |
83 D = 1 - pCX->MPS; | |
84 if (qe->nSwitch == 1) { | |
85 pCX->MPS = 1 - pCX->MPS; | |
86 } | |
87 pCX->I = qe->NLPS; | |
88 } else { | |
89 D = pCX->MPS; | |
90 pCX->I = qe->NMPS; | |
91 } | |
92 do { | |
93 if (CT == 0) { | |
94 BYTEIN(); | |
95 } | |
96 A <<= 1; | |
97 C <<= 1; | |
98 CT--; | |
99 } while ((A & 0x8000) == 0); | |
100 } | |
101 } else { | |
102 C -= A << 16; | |
103 if (A < qe->Qe) { | |
104 A = qe->Qe; | |
105 D = pCX->MPS; | |
106 pCX->I = qe->NMPS; | |
107 } else { | |
108 A = qe->Qe; | |
109 D = 1 - pCX->MPS; | |
110 if (qe->nSwitch == 1) { | |
111 pCX->MPS = 1 - pCX->MPS; | |
112 } | |
113 pCX->I = qe->NLPS; | |
114 } | |
115 do { | |
116 if (CT == 0) { | |
117 BYTEIN(); | |
118 } | |
119 A <<= 1; | |
120 C <<= 1; | |
121 CT--; | |
122 } while ((A & 0x8000) == 0); | |
123 } | |
124 return D; | |
125 } | |
126 #endif | |
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