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/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
#pragma once
#include <cstdint>
#include <type_traits>
#include "antlr4-common.h"
namespace antlr4 {
namespace misc {
class ANTLR4CPP_PUBLIC MurmurHash final {
private:
static constexpr size_t DEFAULT_SEED = 0;
/// Initialize the hash using the default seed value.
/// Returns the intermediate hash value.
public:
static size_t initialize() { return initialize(DEFAULT_SEED); }
/// Initialize the hash using the specified seed.
static size_t initialize(size_t seed) { return seed; }
/// Update the intermediate hash value for the next input {@code value}.
/// <param name="hash"> the intermediate hash value </param>
/// <param name="value"> the value to add to the current hash </param>
/// Returns the updated intermediate hash value.
static size_t update(size_t hash, size_t value);
/**
* Update the intermediate hash value for the next input {@code value}.
*
* @param hash the intermediate hash value
* @param value the value to add to the current hash
* @return the updated intermediate hash value
*/
template <class T>
static size_t update(size_t hash, Ref<T> const& value) {
return update(hash, value != nullptr ? value->hashCode() : 0);
}
template <class T>
static size_t update(size_t hash, T *value) {
return update(hash, value != nullptr ? value->hashCode() : 0);
}
static size_t update(size_t hash, const void *data, size_t size);
template <typename T>
static size_t update(size_t hash, const T *data, size_t size) {
return update(hash, static_cast<const void*>(data), size * sizeof(std::remove_reference_t<T>));
}
/// <summary>
/// Apply the final computation steps to the intermediate value {@code hash}
/// to form the final result of the MurmurHash 3 hash function.
/// </summary>
/// <param name="hash"> the intermediate hash value </param>
/// <param name="entryCount"> the number of calls to update() before calling finish() </param>
/// <returns> the final hash result </returns>
static size_t finish(size_t hash, size_t entryCount);
/// Utility function to compute the hash code of an array using the MurmurHash3 algorithm.
///
/// @param <T> the array element type </param>
/// <param name="data"> the array data </param>
/// <param name="seed"> the seed for the MurmurHash algorithm </param>
/// <returns> the hash code of the data </returns>
template<typename T> // where T is C array type
static size_t hashCode(const std::vector<Ref<T>> &data, size_t seed = DEFAULT_SEED) {
size_t hash = initialize(seed);
for (auto &entry : data) {
hash = update(hash, entry);
}
return finish(hash, data.size());
}
static size_t hashCode(const void *data, size_t size, size_t seed = DEFAULT_SEED) {
size_t hash = initialize(seed);
hash = update(hash, data, size);
return finish(hash, size);
}
template <typename T>
static size_t hashCode(const T *data, size_t size, size_t seed = DEFAULT_SEED) {
return hashCode(static_cast<const void*>(data), size * sizeof(std::remove_reference_t<T>), seed);
}
private:
MurmurHash() = delete;
MurmurHash(const MurmurHash&) = delete;
MurmurHash& operator=(const MurmurHash&) = delete;
};
} // namespace atn
} // namespace antlr4
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