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/*
* Copyright 2015 WebAssembly Community Group participants
*
* 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 wasm_support_hash_h
#define wasm_support_hash_h
#include <functional>
#include <stdint.h>
namespace wasm {
typedef uint32_t HashType;
inline HashType rehash(HashType x, HashType y) {
// see http://www.cse.yorku.ca/~oz/hash.html and
// https://stackoverflow.com/a/2595226/1176841
HashType hash = 5381;
while (x) {
hash = ((hash << 5) + hash) ^ (x & 0xff);
x >>= 8;
}
while (y) {
hash = ((hash << 5) + hash) ^ (y & 0xff);
y >>= 8;
}
return hash;
}
inline uint64_t rehash(uint64_t x, uint64_t y) {
auto ret = rehash(HashType(x), HashType(x >> 32));
ret = rehash(ret, HashType(y));
return rehash(ret, HashType(y >> 32));
}
} // namespace wasm
#endif // wasm_support_hash_h
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