1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
// 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_ArithIntDecoder.h"
#include "core/include/fxcrt/fx_basic.h"
namespace {
int ShiftOr(int val, int bitwise_or_val) {
return (val << 1) | bitwise_or_val;
}
const struct ArithIntDecodeData {
int nNeedBits;
int nValue;
} g_ArithIntDecodeData[] = {
{2, 0},
{4, 4},
{6, 20},
{8, 84},
{12, 340},
{32, 4436},
};
size_t RecursiveDecode(CJBig2_ArithDecoder* decoder,
std::vector<JBig2ArithCtx>* context,
int* prev,
size_t depth) {
static const size_t kDepthEnd = FX_ArraySize(g_ArithIntDecodeData) - 1;
if (depth == kDepthEnd)
return kDepthEnd;
JBig2ArithCtx* pCX = &(*context)[*prev];
int D = decoder->DECODE(pCX);
*prev = ShiftOr(*prev, D);
if (!D)
return depth;
return RecursiveDecode(decoder, context, prev, depth + 1);
}
} // namespace
CJBig2_ArithIntDecoder::CJBig2_ArithIntDecoder() {
m_IAx.resize(512);
}
CJBig2_ArithIntDecoder::~CJBig2_ArithIntDecoder() {
}
bool CJBig2_ArithIntDecoder::decode(CJBig2_ArithDecoder* pArithDecoder,
int* nResult) {
int PREV = 1;
const int S = pArithDecoder->DECODE(&m_IAx[PREV]);
PREV = ShiftOr(PREV, S);
const size_t nDecodeDataIndex =
RecursiveDecode(pArithDecoder, &m_IAx, &PREV, 0);
int nTemp = 0;
for (int i = 0; i < g_ArithIntDecodeData[nDecodeDataIndex].nNeedBits; ++i) {
int D = pArithDecoder->DECODE(&m_IAx[PREV]);
PREV = ShiftOr(PREV, D);
if (PREV >= 256)
PREV = (PREV & 511) | 256;
nTemp = ShiftOr(nTemp, D);
}
int nValue = g_ArithIntDecodeData[nDecodeDataIndex].nValue;
nValue += nTemp;
if (S == 1 && nValue > 0)
nValue = -nValue;
*nResult = nValue;
return S != 1 || nValue != 0;
}
CJBig2_ArithIaidDecoder::CJBig2_ArithIaidDecoder(unsigned char SBSYMCODELENA)
: SBSYMCODELEN(SBSYMCODELENA) {
m_IAID.resize(1 << SBSYMCODELEN);
}
CJBig2_ArithIaidDecoder::~CJBig2_ArithIaidDecoder() {
}
void CJBig2_ArithIaidDecoder::decode(CJBig2_ArithDecoder* pArithDecoder,
FX_DWORD* nResult) {
int PREV = 1;
for (unsigned char i = 0; i < SBSYMCODELEN; ++i) {
JBig2ArithCtx* pCX = &m_IAID[PREV];
int D = pArithDecoder->DECODE(pCX);
PREV = ShiftOr(PREV, D);
}
*nResult = PREV - (1 << SBSYMCODELEN);
}
|
