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std/bytes/last_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 last 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 end of the array. * * The complexity of this function is O(source.length * needle.length). * * ```ts * import { lastIndexOfNeedle } from "https://deno.land/std@$STD_VERSION/bytes/last_index_of_needle.ts"; * const source = new Uint8Array([0, 1, 2, 1, 2, 1, 2, 3]); * const needle = new Uint8Array([1, 2]); * console.log(lastIndexOfNeedle(source, needle)); // 5 * console.log(lastIndexOfNeedle(source, needle, 4)); // 3 * ``` */export function lastIndexOfNeedle( source: Uint8Array, needle: Uint8Array, start: number = source.length - 1,): number { if (start < 0) { return -1; } if (start >= source.length) { start = source.length - 1; } const e = needle[needle.length - 1]; for (let i = start; i >= 0; i--) { if (source[i] !== e) continue; const pin = i; let matched = 1; let j = i; while (matched < needle.length) { j--; if (source[j] !== needle[needle.length - 1 - (pin - j)]) { break; } matched++; } if (matched === needle.length) { return pin - needle.length + 1; } } return -1;}