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LSST Data Management Base Package
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codec.h
Go to the documentation of this file.
1/*
2 * This file is part of sphgeom.
3 *
4 * Developed for the LSST Data Management System.
5 * This product includes software developed by the LSST Project
6 * (http://www.lsst.org).
7 * See the COPYRIGHT file at the top-level directory of this distribution
8 * for details of code ownership.
9 *
10 * This software is dual licensed under the GNU General Public License and also
11 * under a 3-clause BSD license. Recipients may choose which of these licenses
12 * to use; please see the files gpl-3.0.txt and/or bsd_license.txt,
13 * respectively. If you choose the GPL option then the following text applies
14 * (but note that there is still no warranty even if you opt for BSD instead):
15 *
16 * This program is free software: you can redistribute it and/or modify
17 * it under the terms of the GNU General Public License as published by
18 * the Free Software Foundation, either version 3 of the License, or
19 * (at your option) any later version.
20 *
21 * This program is distributed in the hope that it will be useful,
22 * but WITHOUT ANY WARRANTY; without even the implied warranty of
23 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24 * GNU General Public License for more details.
25 *
26 * You should have received a copy of the GNU General Public License
27 * along with this program. If not, see <http://www.gnu.org/licenses/>.
28 */
29
30#ifndef LSST_SPHGEOM_CODEC_H_
31#define LSST_SPHGEOM_CODEC_H_
32
33// Optimized path requires little endian arch and support for unaligned loads.
34#if defined(__x86_64__) or \
35 (defined(__aarch64__) and \
36 (defined(__LITTLE_ENDIAN__) or \
37 (defined(__BYTE_ORDER__) and __BYTE_ORDER__ == 1234)))
38#define OPTIMIZED_LITTLE_ENDIAN
39#endif
40
41#ifdef NO_OPTIMIZED_PATHS
42#undef OPTIMIZED_LITTLE_ENDIAN
43#endif
44
48
49#include <vector>
50#include <cstdint>
51
52namespace lsst {
53namespace sphgeom {
54
57inline void encodeDouble(double item, std::vector<std::uint8_t> & buffer) {
58#ifdef OPTIMIZED_LITTLE_ENDIAN
59 auto ptr = reinterpret_cast<std::uint8_t const *>(&item);
60 buffer.insert(buffer.end(), ptr, ptr + 8);
61#else
62 union { std::uint64_t u; double d; };
63 d = item;
64 buffer.push_back(static_cast<std::uint8_t>(u));
65 buffer.push_back(static_cast<std::uint8_t>(u >> 8));
66 buffer.push_back(static_cast<std::uint8_t>(u >> 16));
67 buffer.push_back(static_cast<std::uint8_t>(u >> 24));
68 buffer.push_back(static_cast<std::uint8_t>(u >> 32));
69 buffer.push_back(static_cast<std::uint8_t>(u >> 40));
70 buffer.push_back(static_cast<std::uint8_t>(u >> 48));
71 buffer.push_back(static_cast<std::uint8_t>(u >> 56));
72#endif
73}
74
77inline double decodeDouble(std::uint8_t const * buffer) {
78#ifdef OPTIMIZED_LITTLE_ENDIAN
79 return *reinterpret_cast<double const *>(buffer);
80#else
81 union { std::uint64_t u; double d; };
82 u = static_cast<std::uint64_t>(buffer[0]) +
83 (static_cast<std::uint64_t>(buffer[1]) << 8) +
84 (static_cast<std::uint64_t>(buffer[2]) << 16) +
85 (static_cast<std::uint64_t>(buffer[3]) << 24) +
86 (static_cast<std::uint64_t>(buffer[4]) << 32) +
87 (static_cast<std::uint64_t>(buffer[5]) << 40) +
88 (static_cast<std::uint64_t>(buffer[6]) << 48) +
89 (static_cast<std::uint64_t>(buffer[7]) << 56);
90 return d;
91#endif
92}
93
97#ifdef OPTIMIZED_LITTLE_ENDIAN
98 auto ptr = reinterpret_cast<std::uint8_t const *>(&item);
99 buffer.insert(buffer.end(), ptr, ptr + 8);
100#else
101 union { std::uint64_t u; double d; };
102 d = item;
103 buffer.push_back(static_cast<std::uint8_t>(u));
104 buffer.push_back(static_cast<std::uint8_t>(u >> 8));
105 buffer.push_back(static_cast<std::uint8_t>(u >> 16));
106 buffer.push_back(static_cast<std::uint8_t>(u >> 24));
107 buffer.push_back(static_cast<std::uint8_t>(u >> 32));
108 buffer.push_back(static_cast<std::uint8_t>(u >> 40));
109 buffer.push_back(static_cast<std::uint8_t>(u >> 48));
110 buffer.push_back(static_cast<std::uint8_t>(u >> 56));
111#endif
112}
113
116inline std::uint64_t decodeU64(std::uint8_t const * buffer) {
117#ifdef OPTIMIZED_LITTLE_ENDIAN
118 return *reinterpret_cast<std::uint64_t const *>(buffer);
119#else
120 std::uint64_t u = static_cast<std::uint64_t>(buffer[0]) +
121 (static_cast<std::uint64_t>(buffer[1]) << 8) +
122 (static_cast<std::uint64_t>(buffer[2]) << 16) +
123 (static_cast<std::uint64_t>(buffer[3]) << 24) +
124 (static_cast<std::uint64_t>(buffer[4]) << 32) +
125 (static_cast<std::uint64_t>(buffer[5]) << 40) +
126 (static_cast<std::uint64_t>(buffer[6]) << 48) +
127 (static_cast<std::uint64_t>(buffer[7]) << 56);
128 return u;
129#endif
130}
131
132}} // namespace lsst::sphgeom
133
134#endif // LSST_SPHGEOM_CODEC_H_
T end(T... args)
T insert(T... args)
double decodeDouble(std::uint8_t const *buffer)
decodeDouble extracts an IEEE double from the 8 byte little-endian byte sequence in buffer.
Definition codec.h:77
void encodeDouble(double item, std::vector< std::uint8_t > &buffer)
encodeDouble appends an IEEE double in little-endian byte order to the end of buffer.
Definition codec.h:57
std::uint64_t decodeU64(std::uint8_t const *buffer)
decodeU64 extracts an uint64 from the 8 byte little-endian byte sequence in buffer.
Definition codec.h:116
void encodeU64(std::uint64_t item, std::vector< std::uint8_t > &buffer)
encodeU64 appends an uint64 in little-endian byte order to the end of buffer.
Definition codec.h:96
T push_back(T... args)