Function decode

lib/punycode.js:208–293

(input)

 * @returns {String} The resulting string of Unicode symbols.
 */
const decode = function(input) {
	// Don't use UCS-2.
	const output = [];
	const inputLength = input.length;
	let i = 0;
	let n = initialN;
	let bias = initialBias;

	// Handle the basic code points: let `basic` be the number of input code
	// points before the last delimiter, or `0` if there is none, then copy
	// the first basic code points to the output.

	let basic = input.lastIndexOf(delimiter);
	if (basic < 0) {
		basic = 0;
	}

	for (let j = 0; j < basic; ++j) {
		// if it's not a basic code point
		if (input.charCodeAt(j) >= 0x80) {
			error('not-basic');
		}
		output.push(input.charCodeAt(j));
	}

	// Main decoding loop: start just after the last delimiter if any basic code
	// points were copied; start at the beginning otherwise.

	for (let index = basic > 0 ? basic + 1 : 0; index < inputLength; /* no final expression */) {

		// `index` is the index of the next character to be consumed.
		// Decode a generalized variable-length integer into `delta`,
		// which gets added to `i`. The overflow checking is easier
		// if we increase `i` as we go, then subtract off its starting
		// value at the end to obtain `delta`.
		const oldi = i;
		for (let w = 1, k = base; /* no condition */; k += base) {

			if (index >= inputLength) {
				error('invalid-input');
			}

			const digit = basicToDigit(input.charCodeAt(index++));

			if (digit >= base) {
				error('invalid-input');
			}
			if (digit > floor((maxInt - i) / w)) {
				error('overflow');
			}

			i += digit * w;
			const t = k <= bias ? tMin : (k >= bias + tMax ? tMax : k - bias);

			if (digit < t) {
				break;
			}