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Module

std/bytes/equals.ts

The Deno Standard Library
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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
/** * Check whether byte slices are equal to each other using 8-bit comparisons. * * @param a First array to check equality * @param b Second array to check equality * @returns `true` if the arrays are equal, `false` otherwise * * @private */function equalsNaive(a: Uint8Array, b: Uint8Array): boolean { for (let i = 0; i < b.length; i++) { if (a[i] !== b[i]) return false; } return true;}
/** Check whether byte slices are equal to each other using 32-bit comparisons. * * @param a First array to check equality. * @param b Second array to check equality. * @returns `true` if the arrays are equal, `false` otherwise. * * @private */function equals32Bit(a: Uint8Array, b: Uint8Array): boolean { const len = a.length; const compactOffset = 3 - ((a.byteOffset + 3) % 4); const compactLen = Math.floor((len - compactOffset) / 4); const compactA = new Uint32Array( a.buffer, a.byteOffset + compactOffset, compactLen, ); const compactB = new Uint32Array( b.buffer, b.byteOffset + compactOffset, compactLen, ); for (let i = 0; i < compactOffset; i++) { if (a[i] !== b[i]) return false; } for (let i = 0; i < compactA.length; i++) { if (compactA[i] !== compactB[i]) return false; } for (let i = compactOffset + compactLen * 4; i < len; i++) { if (a[i] !== b[i]) return false; } return true;}
/** * Byte length threshold for when to use 32-bit comparisons, based on * benchmarks. * * @see {@link https://github.com/denoland/deno_std/pull/4635} */const THRESHOLD_32_BIT = 160;
/** * Check whether byte slices are equal to each other. * * @param a First array to check equality. * @param b Second array to check equality. * @returns `true` if the arrays are equal, `false` otherwise. * * @example Basic usage * ```ts * import { equals } from "https://deno.land/std@$STD_VERSION/bytes/equals.ts"; * * const a = new Uint8Array([1, 2, 3]); * const b = new Uint8Array([1, 2, 3]); * const c = new Uint8Array([4, 5, 6]); * * equals(a, b); // true * equals(b, c); // false * ``` */export function equals(a: Uint8Array, b: Uint8Array): boolean { if (a.length !== b.length) { return false; } return a.length >= THRESHOLD_32_BIT && (a.byteOffset % 4) === (b.byteOffset % 4) ? equals32Bit(a, b) : equalsNaive(a, b);}