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/*
* libfud
* Copyright 2025 Dominick Allen
*
* 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.
*/
#include "fud_hash.hpp"
namespace fud::detail {
size_t djb2(const utf8* data, size_t length)
{
/* Allegedly djb chose 5381 after testing showed fewer collisions and better avalanching: see
* https://stackoverflow.com/questions/10696223/reason-for-the-number-5381-in-the-djb-hash-function */
constexpr size_t hashInit = 5381;
constexpr size_t mulBy = 33;
size_t hash = hashInit;
if (data == nullptr) {
return hash;
}
for (size_t index = 0; index < length; ++index) {
hash = (hash * mulBy) ^ data[index];
}
return hash;
}
size_t DefaultHash<String>::operator()(const String& value, size_t seed) const
{
static_cast<void>(seed);
return djb2(value.data(), value.length());
}
size_t DefaultHash<StringView>::operator()(const StringView& value, size_t seed) const
{
static_cast<void>(seed);
return djb2(value.data(), value.length());
}
}
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