astro/packages/integrations/image/src/utils/shorthash.ts

/**
 * shortdash - https://github.com/bibig/node-shorthash
 *
 * @license
 *
 * (The MIT License)
 *
 * Copyright (c) 2013 Bibig <bibig@me.com>
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

const dictionary = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXY';
const binary = dictionary.length;

// refer to: http://werxltd.com/wp/2010/05/13/javascript-implementation-of-javas-string-hashcode-method/
function bitwise(str: string) {
	let hash = 0;
	if (str.length === 0) return hash;
	for (let i = 0; i < str.length; i++) {
		const ch = str.charCodeAt(i);
		hash = (hash << 5) - hash + ch;
		hash = hash & hash; // Convert to 32bit integer
	}
	return hash;
}

export function shorthash(text: string) {
	let num: number;
	let result = '';

	let integer = bitwise(text);
	const sign = integer < 0 ? 'Z' : ''; // If it's negative, start with Z, which isn't in the dictionary

	integer = Math.abs(integer);

	while (integer >= binary) {
		num = integer % binary;
		integer = Math.floor(integer / binary);
		result = dictionary[num] + result;
	}

	if (integer > 0) {
		result = dictionary[integer] + result;
	}

	return sign + result;
}