1// Copyright 2021 The Pigweed Authors 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); you may not 4// use this file except in compliance with the License. You may obtain a copy of 5// the License at 6// 7// https://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 11// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 12// License for the specific language governing permissions and limitations under 13// the License. 14 15/** This module defines the string to ID hash used in pw_rpc. */ 16 17const HASH_CONSTANT = 65599; 18 19/** 20 * Hash by 65599 21 * 22 * This is the same hash function that is used in Python pw_rpc. It is chosen 23 * due to its simplicity. 24 */ 25export function hash(input: string): number { 26 let hashValue = input.length; 27 let coefficient = HASH_CONSTANT; 28 for (let i = 0; i < input.length; i++) { 29 const ord = input.charCodeAt(i); 30 hashValue = (hashValue + coefficient * ord) % 2 ** 32; 31 coefficient = (coefficient * HASH_CONSTANT) % 2 ** 32; 32 } 33 return hashValue; 34} 35