adamdebreceni commented on code in PR #1340:
URL: https://github.com/apache/nifi-minifi-cpp/pull/1340#discussion_r907497990
##########
libminifi/include/utils/Id.h:
##########
@@ -132,3 +134,26 @@ class NonRepeatingStringGenerator {
};
} // namespace org::apache::nifi::minifi::utils
+
+namespace std {
+template<>
+struct hash<org::apache::nifi::minifi::utils::Identifier> {
+ size_t operator()(const org::apache::nifi::minifi::utils::Identifier& id)
const noexcept {
+ constexpr int slices =
sizeof(org::apache::nifi::minifi::utils::Identifier) / sizeof(size_t);
+ const auto combine = [](size_t& seed, size_t new_hash) {
+ // from the boost hash_combine docs
+ seed ^= new_hash + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+ };
+ const auto get_slice = [](const
org::apache::nifi::minifi::utils::Identifier& id, size_t idx) -> size_t {
+ size_t result{};
+ memcpy(&result, reinterpret_cast<const unsigned char*>(&id.data_) + idx
* sizeof(size_t), sizeof(size_t));
+ return result;
+ };
+ size_t hash = get_slice(id, 0);
+ for (size_t i = 1; i < slices; ++i) {
+ combine(hash, get_slice(id, i));
+ }
+ return hash;
Review Comment:
we could use `gsl::span` here, it would also verify convertibility
```suggestion
for (size_t slice : gsl::span(id.data_).as_span<const size_t>()) {
combine(hash, slice);
}
```
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