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std/bytes/index_of_needle.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.
/** * Returns the index of the first occurrence of the needle array in the source * array, or -1 if it is not present. * * A start index can be specified as the third argument that begins the search * at that given index. The start index defaults to the start of the array. * * The complexity of this function is `O(source.length * needle.length)`. * * @param source Source array to check. * @param needle Needle array to check for. * @param start Start index in the source array to begin the search. Defaults to * 0. * @returns Index of the first occurrence of the needle array in the source * array, or -1 if it is not present. * * @example Basic usage * ```ts * import { indexOfNeedle } from "https://deno.land/std@$STD_VERSION/bytes/index_of_needle.ts"; * * const source = new Uint8Array([0, 1, 2, 1, 2, 1, 2, 3]); * const needle = new Uint8Array([1, 2]); * const notNeedle = new Uint8Array([5, 0]); * * indexOfNeedle(source, needle); // 1 * indexOfNeedle(source, notNeedle); // -1 * ``` * * @example Start index * ```ts * import { indexOfNeedle } from "https://deno.land/std@$STD_VERSION/bytes/index_of_needle.ts"; * * const source = new Uint8Array([0, 1, 2, 1, 2, 1, 2, 3]); * const needle = new Uint8Array([1, 2]); * * indexOfNeedle(source, needle, 2); // 3 * indexOfNeedle(source, needle, 6); // -1 * ``` * Defining a start index will begin the search at the specified index in the * source array. */export function indexOfNeedle( source: Uint8Array, needle: Uint8Array, start = 0,): number { if (start >= source.length) { return -1; } if (start < 0) { start = Math.max(0, source.length + start); } const s = needle[0]; for (let i = start; i < source.length; i++) { if (source[i] !== s) continue; let matched = 1; let j = i + 1; while (matched < needle.length && source[j] === needle[j - i]) { matched++; j++; } if (matched === needle.length) { return i; } } return -1;}