LSSTApplications  20.0.0
LSSTDataManagementBasePackage
codec.h
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1 /*
2  * LSST Data Management System
3  * Copyright 2016 AURA/LSST.
4  *
5  * This product includes software developed by the
6  * LSST Project (http://www.lsst.org/).
7  *
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21  */
22 
23 #ifndef LSST_SPHGEOM_CODEC_H_
24 #define LSST_SPHGEOM_CODEC_H_
25 
29 
30 #include <vector>
31 
32 
33 namespace lsst {
34 namespace sphgeom {
35 
38 inline void encodeDouble(double item, std::vector<uint8_t> & buffer) {
39 #if defined(__x86_64__)
40  // x86-64 is little endian.
41  auto ptr = reinterpret_cast<uint8_t const *>(&item);
42  buffer.insert(buffer.end(), ptr, ptr + 8);
43 #else
44  union { uint64_t u; double d };
45  d = item;
46  buffer.push_back(static_cast<uint8_t>(value));
47  buffer.push_back(static_cast<uint8_t>(value >> 8));
48  buffer.push_back(static_cast<uint8_t>(value >> 16));
49  buffer.push_back(static_cast<uint8_t>(value >> 24));
50  buffer.push_back(static_cast<uint8_t>(value >> 32));
51  buffer.push_back(static_cast<uint8_t>(value >> 40));
52  buffer.push_back(static_cast<uint8_t>(value >> 48));
53  buffer.push_back(static_cast<uint8_t>(value >> 56));
54 #endif
55 }
56 
59 inline double decodeDouble(uint8_t const * buffer) {
60 #if defined(__x86_64__)
61  // x86-64 is little endian and supports unaligned loads.
62  return *reinterpret_cast<double const *>(buffer);
63 #else
64  union { uint64_t u; double d };
65  u = static_cast<uint64_t>(buffer[0]) +
66  (static_cast<uint64_t>(buffer[1]) << 8) +
67  (static_cast<uint64_t>(buffer[2]) << 16) +
68  (static_cast<uint64_t>(buffer[3]) << 24) +
69  (static_cast<uint64_t>(buffer[4]) << 32) +
70  (static_cast<uint64_t>(buffer[5]) << 40) +
71  (static_cast<uint64_t>(buffer[6]) << 48) +
72  (static_cast<uint64_t>(buffer[7]) << 56);
73  return d;
74 #endif
75 }
76 
77 }} // namespace lsst::sphgeom
78 
79 #endif // LSST_SPHGEOM_CODEC_H_
std::vector
STL class.
std::vector::push_back
T push_back(T... args)
ptr
uint64_t * ptr
Definition: RangeSet.cc:88
lsst
A base class for image defects.
Definition: imageAlgorithm.dox:1
lsst::sphgeom::decodeDouble
double decodeDouble(uint8_t const *buffer)
decode extracts an IEEE double from the 8 byte little-endian byte sequence in buffer.
Definition: codec.h:59
std::vector::insert
T insert(T... args)
std::vector::end
T end(T... args)
lsst::sphgeom::encodeDouble
void encodeDouble(double item, std::vector< uint8_t > &buffer)
encode appends an IEEE double in little-endian byte order to the end of buffer.
Definition: codec.h:38