ZenLib
BitStream_LE.h
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1 /* Copyright (c) MediaArea.net SARL. All Rights Reserved.
2  *
3  * Use of this source code is governed by a zlib-style license that can
4  * be found in the License.txt file in the root of the source tree.
5  */
6 
7 //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
8 //
9 // Read a stream bit per bit, Little Endian version (rarely used!!!)
10 // Can read up to 32 bits at once
11 //
12 //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
13 
14 //---------------------------------------------------------------------------
15 #ifndef ZenBitStream_LEH
16 #define ZenBitStream_LEH
17 //---------------------------------------------------------------------------
18 
19 //---------------------------------------------------------------------------
20 #include "ZenLib/BitStream.h"
21 //---------------------------------------------------------------------------
22 
23 namespace ZenLib
24 {
25 
26 class BitStream_LE : public BitStream
27 {
28 public:
30  endbyte(0),
31  endbit(0),
32  buffer(NULL),
33  ptr(NULL),
34  ptr_BeforeLastCall(NULL),
35  storage(0) {
36  };
37 
38  BitStream_LE (const int8u* Buffer_, size_t Size_) : BitStream(Buffer_, Size_),
39  ptr_BeforeLastCall(NULL) {
40  Attach(Buffer_, Size_);
41  };
42 
43  void Attach(const int8u* Buffer_, size_t Size_)
44  {
45  endbyte=0;
46  endbit=0;
47  buffer=Buffer_;
48  ptr=Buffer_;
49  storage=(long)Size_;
50  };
51 
52  int32u Get (size_t HowMany)
53  {
54  ptr_BeforeLastCall=ptr;
55 
56  long ret;
57  static const int32u Mask[33]={
58  0x00000000,
59  0x00000001, 0x00000003, 0x00000007, 0x0000000f,
60  0x0000001f, 0x0000003f, 0x0000007f, 0x000000ff,
61  0x000001ff, 0x000003ff, 0x000007ff, 0x00000fff,
62  0x00001fff, 0x00003fff, 0x00007fff, 0x0000ffff,
63  0x0001ffff, 0x0003ffff, 0x0007ffff, 0x000fffff,
64  0x001fffff, 0x003fffff, 0x007fffff, 0x00ffffff,
65  0x01ffffff, 0x03ffffff, 0x07ffffff, 0x0fffffff,
66  0x1fffffff, 0x3fffffff, 0x7fffffff, 0xffffffff,
67  };
68  unsigned long m=Mask[HowMany];
69 
70  HowMany+=endbit;
71 
72  if(endbyte+4>=storage){
73  ret=-1L;
74  if(endbyte*8+(long)HowMany>storage*8){
75  Attach(NULL, 0);
76  goto overflow;
77  }
78  }
79 
80  ret=ptr[0]>>endbit;
81  if(HowMany>8){
82  ret|=ptr[1]<<(8-endbit);
83  if(HowMany>16){
84  ret|=ptr[2]<<(16-endbit);
85  if(HowMany>24){
86  ret|=ptr[3]<<(24-endbit);
87  if(HowMany>32 && endbit){
88  ret|=ptr[4]<<(32-endbit);
89  }
90  }
91  }
92  }
93  ret&=m;
94 
95  ptr+=HowMany/8;
96  endbyte+=(long)HowMany/8;
97  endbit=(long)HowMany&7;
98 
99  overflow:
100 
101  return(ret);
102  };
103 
104  void Skip(size_t bits)
105  {
106  Get(bits);
107  }
108 
109  int32u Remain () //How many bits remain?
110  {
111  return storage*8-(endbyte*8+endbit);
112  };
113 
114  void Byte_Align()
115  {
116  if (endbit)
117  Get(endbit);
118  };
119 
120  size_t Offset_Get()
121  {
122  return ptr-buffer;
123  };
124 
125  size_t BitOffset_Get()
126  {
127  return endbit;
128  };
129 
131  {
132  return ptr_BeforeLastCall-buffer;
133  };
134 
135 private :
136  long endbyte;
137  int endbit;
138 
139  const unsigned char *buffer;
140  const unsigned char *ptr;
141  const unsigned char *ptr_BeforeLastCall;
142  long storage;
143 };
144 
145 } //namespace ZenLib
146 #endif
void Byte_Align()
Definition: BitStream_LE.h:114
int32u Remain()
Definition: BitStream_LE.h:109
void Skip(size_t bits)
Definition: BitStream_LE.h:104
BitStream_LE()
Definition: BitStream_LE.h:29
Definition: BitStream.h:30
size_t Offset_Get()
Definition: BitStream_LE.h:120
#define NULL
Definition: HTTPClientWrapper.h:98
Definition: BitStream.h:23
int32u Get(size_t HowMany)
Definition: BitStream_LE.h:52
size_t BitOffset_Get()
Definition: BitStream_LE.h:125
BitStream_LE(const int8u *Buffer_, size_t Size_)
Definition: BitStream_LE.h:38
size_t OffsetBeforeLastCall_Get()
Definition: BitStream_LE.h:130
void Attach(const int8u *Buffer_, size_t Size_)
Definition: BitStream_LE.h:43
Definition: BitStream_LE.h:26