happy-dom/src/base64/Base64.ts

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. It includes many web standards from WHATWG DOM and HTML.

import DOMException from '../exception/DOMException.js';
import DOMExceptionNameEnum from '../exception/DOMExceptionNameEnum.js';

const BASE64_CHARS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

/**
 * Base64 encoding and decoding.
 */
export default class Base64 {
	/**
	 * Creates a Base64-encoded ASCII string from a binary string (i.e., a string in which each character in the string is treated as a byte of binary data).
	 *
	 * @see https://developer.mozilla.org/en-US/docs/Web/API/btoa
	 * @param data Binay data.
	 * @returns Base64-encoded string.
	 */
	public static btoa(data: unknown): string {
		const str = (<string>data).toString();
		if (/[^\u0000-\u00ff]/.test(str)) {
			throw new DOMException(
				"Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.",
				DOMExceptionNameEnum.invalidCharacterError
			);
		}

		let t = '';
		let p = -6;
		let a = 0;
		let i = 0;
		let v = 0;
		let c;
		while (i < str.length || p > -6) {
			if (p < 0) {
				if (i < str.length) {
					c = str.charCodeAt(i++);
					v += 8;
				} else {
					c = 0;
				}
				a = ((a & 255) << 8) | (c & 255);
				p += 8;
			}
			t += BASE64_CHARS.charAt(v > 0 ? (a >> p) & 63 : 64);
			p -= 6;
			v -= 6;
		}
		return t;
	}

	/**
	 * Decodes a string of data which has been encoded using Base64 encoding.
	 *
	 * @see https://developer.mozilla.org/en-US/docs/Web/API/atob
	 * @see https://infra.spec.whatwg.org/#forgiving-base64-encode.
	 * @see Https://html.spec.whatwg.org/multipage/webappapis.html#btoa.
	 * @param data Binay string.
	 * @returns An ASCII string containing decoded data from encodedData.
	 */
	public static atob(data: unknown): string {
		const str = (<string>data).toString();

		if (/[^\u0000-\u00ff]/.test(str)) {
			throw new DOMException(
				"Failed to execute 'atob' on 'Window': The string to be decoded contains characters outside of the Latin1 range.",
				DOMExceptionNameEnum.invalidCharacterError
			);
		}

		if (/[^A-Za-z\d+/=]/.test(str) || str.length % 4 == 1) {
			throw new DOMException(
				"Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.",
				DOMExceptionNameEnum.invalidCharacterError
			);
		}

		let t = '';
		let p = -8;
		let a = 0;
		let c;
		let d;
		for (let i = 0; i < str.length; i++) {
			if ((c = BASE64_CHARS.indexOf(str.charAt(i))) < 0) {
				continue;
			}
			a = (a << 6) | (c & 63);
			if ((p += 6) >= 0) {
				d = (a >> p) & 255;
				if (c !== 64) {
					t += String.fromCharCode(d);
				}
				a &= 63;
				p -= 8;
			}
		}
		return t;
	}
}