35 lines
1.1 KiB
TypeScript
35 lines
1.1 KiB
TypeScript
// Copyright 2021 The Pigweed Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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/** This module defines the string to ID hash used in pw_rpc. */
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const HASH_CONSTANT = 65599;
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/**
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* Hash by 65599
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*
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* This is the same hash function that is used in Python pw_rpc. It is chosen
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* due to its simplicity.
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*/
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export function hash(input: string): number {
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let hashValue = input.length;
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let coefficient = HASH_CONSTANT;
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for (let i = 0; i < input.length; i++) {
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const ord = input.charCodeAt(i);
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hashValue = (hashValue + coefficient * ord) % 2 ** 32;
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coefficient = (coefficient * HASH_CONSTANT) % 2 ** 32;
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}
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return hashValue;
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}
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