HashKey.h

//
//  HashKey.h
//  libraries/shared/src
//
//  Created by Andrew Meadows 2017.10.25
//  Copyright 2017 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//
 
#ifndef hifi_HashKey_h
#define hifi_HashKey_h
 
#include <cstddef>
#include <stdint.h>
 
#include <glm/glm.hpp>
 
 
// HashKey for use with btHashMap which requires a particular API for its keys.  In particular it
// requires its Key to implement these methods:
//
//      bool Key::equals()
//      int32_t Key::getHash()
//
// The important thing about the HashKey implementation is that while getHash() returns 32-bits,
// internally HashKey stores a 64-bit hash which is used for the equals() comparison.  This allows
// btHashMap to insert "dupe" 32-bit keys to different "values".
 
class HashKey {
public:
    class Hasher {
    public:
        Hasher() {}
        void hashUint64(uint64_t data);
        void hashFloat(float data);
        void hashVec3(const glm::vec3& data);
        uint64_t getHash64() const { return _hash; }
    private:
        uint64_t _hash { 0 };
        uint8_t _hashCount { 0 };
    };
 
    static float getNumQuantizedValuesPerMeter();
 
    HashKey() {}
    HashKey(uint64_t hash) : _hash(hash) {}
 
    // These two methods are required by btHashMap.
    bool equals(const HashKey& other) const { return _hash == other._hash; }
    int32_t getHash() const { return (int32_t)((uint32_t)_hash); }
 
    uint64_t getHash64() const { return _hash; }
private:
    uint64_t _hash { 0 };
};
 
#endif // hifi_HashKey_h