Helper functions for working with Uint8Array byte slices.

Concatenate byte slices

concat concatenates an array of byte slices into a single slice.

import { concat } from "https://deno.land/std@0.224.0/bytes/concat.ts";

const a = new Uint8Array([0, 1, 2]);
const b = new Uint8Array([3, 4, 5]);
concat([a, b]); // Uint8Array(6) [ 0, 1, 2, 3, 4, 5 ]

Copy byte slices

copy copies bytes from the src array to the dst array and returns the number of bytes copied.

import { copy } from "https://deno.land/std@0.224.0/bytes/copy.ts";

const src = new Uint8Array([9, 8, 7]);
const dst = new Uint8Array([0, 1, 2, 3, 4, 5]);

copy(src, dst); // 3
dst; // Uint8Array(6) [9, 8, 7, 3, 4, 5]

Check if a byte slice ends with another byte slice

endsWith returns true if the suffix array appears at the end of the source array, false otherwise.

import { endsWith } from "https://deno.land/std@0.224.0/bytes/ends_with.ts";

const source = new Uint8Array([0, 1, 2, 1, 2, 1, 2, 3]);
const suffix = new Uint8Array([1, 2, 3]);

endsWith(source, suffix); // true

Check if two byte slices are equal

equals checks whether byte slices are equal to each other.

import { equals } from "https://deno.land/std@0.224.0/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

Check if a byte slice includes another byte slice

includesNeedle determines whether the source array contains the needle array.

import { includesNeedle } from "https://deno.land/std@0.224.0/bytes/includes_needle.ts";

const source = new Uint8Array([0, 1, 2, 1, 2, 1, 2, 3]);
const needle = new Uint8Array([1, 2]);

includesNeedle(source, needle); // true

Find the index of a byte slice in another byte slice

indexOfNeedle returns the index of the first occurrence of the needle array in the source array, or -1 if it is not present.

import { indexOfNeedle } from "https://deno.land/std@0.224.0/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

Find the last index of a byte slice in another byte slice

lastIndexOfNeedle returns the index of the last occurrence of the needle array in the source array, or -1 if it is not present.

import { lastIndexOfNeedle } from "https://deno.land/std@0.224.0/bytes/last_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]);

lastIndexOfNeedle(source, needle); // 5
lastIndexOfNeedle(source, notNeedle); // -1

Repeat a byte slice

repeat returns a new byte slice composed of count repetitions of the source array.

import { repeat } from "https://deno.land/std@0.224.0/bytes/repeat.ts";

const source = new Uint8Array([0, 1, 2]);

repeat(source, 3); // Uint8Array(9) [0, 1, 2, 0, 1, 2, 0, 1, 2]

repeat(source, 0); // Uint8Array(0) []

repeat(source, -1); // Throws `RangeError`

Check if a byte slice starts with another byte slice

startsWith returns true if the prefix array appears at the start of the source array, false otherwise.

import { startsWith } from "https://deno.land/std@0.224.0/bytes/starts_with.ts";

const source = new Uint8Array([0, 1, 2, 1, 2, 1, 2, 3]);
const prefix = new Uint8Array([0, 1, 2]);

startsWith(source, prefix); // true