1 /*
2 Copyright 2015 Esri
3
4 Licensed under the Apache License, Version 2.0 (the "License");
5 you may not use this file except in compliance with the License.
6 You may obtain a copy of the License at
7
8 http://www.apache.org/licenses/LICENSE-2.0
9
10 Unless required by applicable law or agreed to in writing, software
11 distributed under the License is distributed on an "AS IS" BASIS,
12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 See the License for the specific language governing permissions and
14 limitations under the License.
15
16 A local copy of the license and additional notices are located with the
17 source distribution at:
18
19 http://github.com/Esri/lerc/
20
21 Contributors: Thomas Maurer
22 */
23
24 #ifndef BITSTUFFER2_H
25 #define BITSTUFFER2_H
26
27 #include <vector>
28 #include <cstring>
29 #include <utility>
30 #include "Defines.h"
31
32 NAMESPACE_LERC_START
33
34 /** Bit stuffer, for writing unsigned int arrays compressed lossless
35 *
36 */
37
38 class BitStuffer2
39 {
40 public:
BitStuffer2()41 BitStuffer2() {}
~BitStuffer2()42 virtual ~BitStuffer2() {}
43
44 // dst buffer is already allocated. byte ptr is moved like a file pointer.
45 bool EncodeSimple(Byte** ppByte, const std::vector<unsigned int>& dataVec, int lerc2Version) const;
46 bool EncodeLut(Byte** ppByte, const std::vector<std::pair<unsigned int, unsigned int> >& sortedDataVec, int lerc2Version) const;
47 bool Decode(const Byte** ppByte, size_t& nBytesRemaining, std::vector<unsigned int>& dataVec, size_t maxElementCount, int lerc2Version) const;
48
49 static unsigned int ComputeNumBytesNeededSimple(unsigned int numElem, unsigned int maxElem);
50 static unsigned int ComputeNumBytesNeededLut(const std::vector<std::pair<unsigned int, unsigned int> >& sortedDataVec, bool& doLut);
51
52 private:
53 mutable std::vector<unsigned int> m_tmpLutVec, m_tmpIndexVec, m_tmpBitStuffVec;
54
55 static void BitStuff_Before_Lerc2v3(Byte** ppByte, const std::vector<unsigned int>& dataVec, int numBits);
56 static bool BitUnStuff_Before_Lerc2v3(const Byte** ppByte, size_t& nBytesRemaining, std::vector<unsigned int>& dataVec, unsigned int numElements, int numBits);
57 void BitStuff(Byte** ppByte, const std::vector<unsigned int>& dataVec, int numBits) const;
58 bool BitUnStuff(const Byte** ppByte, size_t& nBytesRemaining, std::vector<unsigned int>& dataVec, unsigned int numElements, int numBits) const;
59
60 static bool EncodeUInt(Byte** ppByte, unsigned int k, int numBytes); // numBytes = 1, 2, or 4
61 static bool DecodeUInt(const Byte** ppByte, size_t& nBytesRemaining, unsigned int& k, int numBytes);
NumBytesUInt(unsigned int k)62 static int NumBytesUInt(unsigned int k) { return (k < 256) ? 1 : (k < (1 << 16)) ? 2 : 4; }
63 static unsigned int NumTailBytesNotNeeded(unsigned int numElem, int numBits);
64 };
65
66 // -------------------------------------------------------------------------- ;
67
ComputeNumBytesNeededSimple(unsigned int numElem,unsigned int maxElem)68 inline unsigned int BitStuffer2::ComputeNumBytesNeededSimple(unsigned int numElem, unsigned int maxElem)
69 {
70 int numBits = 0;
71 while ((numBits < 32) && (maxElem >> numBits))
72 numBits++;
73 return 1 + NumBytesUInt(numElem) + ((numElem * numBits + 7) >> 3);
74 }
75
76 // -------------------------------------------------------------------------- ;
77
EncodeUInt(Byte ** ppByte,unsigned int k,int numBytes)78 inline bool BitStuffer2::EncodeUInt(Byte** ppByte, unsigned int k, int numBytes)
79 {
80 Byte* ptr = *ppByte;
81
82 if (numBytes == 1)
83 *ptr = (Byte)k;
84 else if (numBytes == 2)
85 {
86 unsigned short kShort = (unsigned short)k;
87 memcpy(ptr, &kShort, sizeof(unsigned short));
88 }
89 else if (numBytes == 4)
90 memcpy(ptr, &k, sizeof(unsigned int));
91 else
92 return false;
93
94 *ppByte += numBytes;
95 return true;
96 }
97
98 // -------------------------------------------------------------------------- ;
99
DecodeUInt(const Byte ** ppByte,size_t & nBytesRemaining,unsigned int & k,int numBytes)100 inline bool BitStuffer2::DecodeUInt(const Byte** ppByte, size_t& nBytesRemaining, unsigned int& k, int numBytes)
101 {
102 if (nBytesRemaining < (size_t)numBytes)
103 return false;
104
105 const Byte* ptr = *ppByte;
106
107 if (numBytes == 1)
108 k = *ptr;
109 else if (numBytes == 2)
110 {
111 unsigned short s;
112 memcpy(&s, ptr, sizeof(unsigned short));
113 k = s;
114 }
115 else if (numBytes == 4)
116 memcpy(&k, ptr, sizeof(unsigned int));
117 else
118 return false;
119
120 *ppByte += numBytes;
121 nBytesRemaining -= numBytes;
122 return true;
123 }
124
125 // -------------------------------------------------------------------------- ;
126
NumTailBytesNotNeeded(unsigned int numElem,int numBits)127 inline unsigned int BitStuffer2::NumTailBytesNotNeeded(unsigned int numElem, int numBits)
128 {
129 int numBitsTail = ((unsigned long long)numElem * numBits) & 31;
130 int numBytesTail = (numBitsTail + 7) >> 3;
131 return (numBytesTail > 0) ? 4 - numBytesTail : 0;
132 }
133
134 // -------------------------------------------------------------------------- ;
135
136 NAMESPACE_LERC_END
137 #endif
138