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The typos were found with the typos[1] spell checker. That spell checker will be incorporated into the CI in a followup PR. [1]: https://github.com/crate-ci/typos
50 lines
1.4 KiB
TypeScript
50 lines
1.4 KiB
TypeScript
// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
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// This module is browser compatible.
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/** Returns the index of the last occurrence of the needle array in the source
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* array, or -1 if it is not present.
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*
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* A start index can be specified as the third argument that begins the search
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* at that given index. The start index defaults to the end of the array.
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*
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* The complexity of this function is O(source.length * needle.length).
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*
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* ```ts
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* import { lastIndexOfNeedle } from "https://deno.land/std@$STD_VERSION/bytes/last_index_of_needle.ts";
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* const source = new Uint8Array([0, 1, 2, 1, 2, 1, 2, 3]);
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* const needle = new Uint8Array([1, 2]);
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* console.log(lastIndexOfNeedle(source, needle)); // 5
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* console.log(lastIndexOfNeedle(source, needle, 4)); // 3
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* ```
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*/
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export function lastIndexOfNeedle(
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source: Uint8Array,
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needle: Uint8Array,
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start = source.length - 1,
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): number {
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if (start < 0) {
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return -1;
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}
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if (start >= source.length) {
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start = source.length - 1;
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}
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const e = needle[needle.length - 1];
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for (let i = start; i >= 0; i--) {
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if (source[i] !== e) continue;
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const pin = i;
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let matched = 1;
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let j = i;
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while (matched < needle.length) {
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j--;
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if (source[j] !== needle[needle.length - 1 - (pin - j)]) {
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break;
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}
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matched++;
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}
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if (matched === needle.length) {
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return pin - needle.length + 1;
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}
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}
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return -1;
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}
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