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/*
* Copyright 2016 Google Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef NB_HASH_H_
#define NB_HASH_H_
#include "nb/bit_cast.h"
#include "starboard/types.h"
namespace nb {
enum { kDefaultSeed = 0x12345789 };
// RuntimeHash32 is a 32 bit hash for data. The only guarantee is that this
// hash is persistent for the lifetime of the program. This hash function
// is not guaranteed to be consistent across platforms. The hash value should
// never be saved to disk.
// It's sufficient however, to use as an in-memory hashtable.
uint32_t RuntimeHash32(const char* data,
int length,
uint32_t prev_hash = kDefaultSeed);
// Convenience functor for hashing plain old data types like int/float etc and
// POD structs.
template <typename T>
struct PODHasher {
uint32_t operator()(const T& value) const {
return RuntimeHash32(reinterpret_cast<const char*>(&value), sizeof(value));
}
};
// Specialization so that all pointers are PODs.
template <typename T>
struct PODHasher<T*> {
uint32_t operator()(const void* ptr) const {
uintptr_t ptr_value = bit_cast<uintptr_t>(ptr);
PODHasher<uintptr_t> pod_hasher;
return pod_hasher(ptr_value);
}
};
} // namespace nb
#endif // NB_HASH_H_