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ef416fc2 | 1 | //======================================================================== |
2 | // | |
3 | // JArithmeticDecoder.h | |
4 | // | |
5 | // Arithmetic decoder used by the JBIG2 and JPEG2000 decoders. | |
6 | // | |
7 | // Copyright 2002-2004 Glyph & Cog, LLC | |
8 | // | |
9 | //======================================================================== | |
10 | ||
11 | #ifndef JARITHMETICDECODER_H | |
12 | #define JARITHMETICDECODER_H | |
13 | ||
14 | #include <config.h> | |
15 | ||
16 | #ifdef USE_GCC_PRAGMAS | |
17 | #pragma interface | |
18 | #endif | |
19 | ||
20 | #include "gtypes.h" | |
21 | ||
22 | class Stream; | |
23 | ||
24 | //------------------------------------------------------------------------ | |
25 | // JArithmeticDecoderStats | |
26 | //------------------------------------------------------------------------ | |
27 | ||
28 | class JArithmeticDecoderStats { | |
29 | public: | |
30 | ||
31 | JArithmeticDecoderStats(int contextSizeA); | |
32 | ~JArithmeticDecoderStats(); | |
33 | JArithmeticDecoderStats *copy(); | |
34 | void reset(); | |
35 | int getContextSize() { return contextSize; } | |
36 | void copyFrom(JArithmeticDecoderStats *stats); | |
37 | void setEntry(Guint cx, int i, int mps); | |
38 | ||
39 | private: | |
40 | ||
41 | Guchar *cxTab; // cxTab[cx] = (i[cx] << 1) + mps[cx] | |
42 | int contextSize; | |
43 | ||
44 | friend class JArithmeticDecoder; | |
45 | }; | |
46 | ||
47 | //------------------------------------------------------------------------ | |
48 | // JArithmeticDecoder | |
49 | //------------------------------------------------------------------------ | |
50 | ||
51 | class JArithmeticDecoder { | |
52 | public: | |
53 | ||
54 | JArithmeticDecoder(); | |
55 | ~JArithmeticDecoder(); | |
56 | ||
57 | void setStream(Stream *strA) | |
58 | { str = strA; dataLen = 0; limitStream = gFalse; } | |
59 | void setStream(Stream *strA, int dataLenA) | |
60 | { str = strA; dataLen = dataLenA; limitStream = gTrue; } | |
61 | ||
62 | // Start decoding on a new stream. This fills the byte buffers and | |
63 | // runs INITDEC. | |
64 | void start(); | |
65 | ||
66 | // Restart decoding on an interrupted stream. This refills the | |
67 | // buffers if needed, but does not run INITDEC. (This is used in | |
68 | // JPEG 2000 streams when codeblock data is split across multiple | |
69 | // packets/layers.) | |
70 | void restart(int dataLenA); | |
71 | ||
72 | // Read any leftover data in the stream. | |
73 | void cleanup(); | |
74 | ||
75 | // Decode one bit. | |
76 | int decodeBit(Guint context, JArithmeticDecoderStats *stats); | |
77 | ||
78 | // Decode eight bits. | |
79 | int decodeByte(Guint context, JArithmeticDecoderStats *stats); | |
80 | ||
81 | // Returns false for OOB, otherwise sets *<x> and returns true. | |
82 | GBool decodeInt(int *x, JArithmeticDecoderStats *stats); | |
83 | ||
84 | Guint decodeIAID(Guint codeLen, | |
85 | JArithmeticDecoderStats *stats); | |
86 | ||
87 | private: | |
88 | ||
89 | Guint readByte(); | |
90 | int decodeIntBit(JArithmeticDecoderStats *stats); | |
91 | void byteIn(); | |
92 | ||
93 | static Guint qeTab[47]; | |
94 | static int nmpsTab[47]; | |
95 | static int nlpsTab[47]; | |
96 | static int switchTab[47]; | |
97 | ||
98 | Guint buf0, buf1; | |
99 | Guint c, a; | |
100 | int ct; | |
101 | ||
102 | Guint prev; // for the integer decoder | |
103 | ||
104 | Stream *str; | |
105 | int dataLen; | |
106 | GBool limitStream; | |
107 | }; | |
108 | ||
109 | #endif |