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/*
* Copyright 2024 The Android Open Source Project
*
* 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.
*/
#pragma once
#include <cinttypes>
#include <optional>
#include <string_view>
#include <ftl/details/hash.h>
namespace android::ftl {
// Non-cryptographic hash function (namely CityHash64) for strings with at most 64 characters.
// Unlike std::hash, which returns std::size_t and is only required to produce the same result
// for the same input within a single execution of a program, this hash is stable.
inline std::optional<std::uint64_t> stable_hash(std::string_view view) {
const auto length = view.length();
if (length <= 16) {
return details::hash_length_0_to_16(view.data(), length);
}
if (length <= 32) {
return details::hash_length_17_to_32(view.data(), length);
}
if (length <= 64) {
return details::hash_length_33_to_64(view.data(), length);
}
return {};
}
} // namespace android::ftl
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