LSSTApplications  18.1.0
LSSTDataManagementBasePackage
hashCombine.h
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22 #ifndef LSST_UTILS_HASH_COMBINE_H
23 #define LSST_UTILS_HASH_COMBINE_H
24 
25 #include <functional>
26 
27 namespace lsst {
28 namespace utils {
29 
35 inline std::size_t hashCombine(std::size_t seed) noexcept { return seed; }
36 
59 // This implementation is provided by Matteo Italia, https://stackoverflow.com/a/38140932/834250
60 // Algorithm described at https://stackoverflow.com/a/27952689
61 // WARNING: should not be inline or constexpr; it can cause instantiation-order problems with std::hash<T>
62 template <typename T, typename... Rest>
63 std::size_t hashCombine(std::size_t seed, const T& value, Rest... rest) noexcept {
64  std::hash<T> hasher;
65  seed ^= hasher(value) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
66  return hashCombine(seed, rest...);
67 }
68 
90 // Note: not an overload of hashCombine to avoid ambiguity with hashCombine(size_t, T1, T2)
91 // WARNING: should not be inline or constexpr; it can cause instantiation-order problems with std::hash<T>
92 template <typename InputIterator>
93 std::size_t hashIterable(std::size_t seed, InputIterator begin, InputIterator end) noexcept {
94  std::size_t result = 0;
95  for (; begin != end; ++begin) {
96  result = hashCombine(result, *begin);
97  }
98  return result;
99 }
100 
101 }} // namespace lsst::utils
102 
103 #endif
py::object result
Definition: schema.cc:418
A base class for image defects.
std::size_t hashIterable(std::size_t seed, InputIterator begin, InputIterator end) noexcept
Combine hashes in an iterable.
Definition: hashCombine.h:93
std::size_t hashCombine(std::size_t seed) noexcept
Combine hashes.
Definition: hashCombine.h:35
int end