Requests_IDNAEncoder::punycode_encode()

	public static function punycode_encode($input) {
		$output = '';
		// let n = initial_n
		$n = self::BOOTSTRAP_INITIAL_N;
		// let delta = 0
		$delta = 0;
		// let bias = initial_bias
		$bias = self::BOOTSTRAP_INITIAL_BIAS;
		// let h = b = the number of basic code points in the input
		$h = 0;
		$b = 0; // see loop
		// copy them to the output in order
		$codepoints = self::utf8_to_codepoints($input);
		$extended   = array();

		foreach ($codepoints as $char) {
			if ($char < 128) {
				// Character is valid ASCII
				// TODO: this should also check if it's valid for a URL
				$output .= chr($char);
				$h++;
			}
			// Check if the character is non-ASCII, but below initial n
			// This never occurs for Punycode, so ignore in coverage
			// @codeCoverageIgnoreStart
			elseif ($char < $n) {
				throw new Requests_Exception('Invalid character', 'idna.character_outside_domain', $char);
			}
			// @codeCoverageIgnoreEnd
			else {
				$extended[$char] = true;
			}
		}
		$extended = array_keys($extended);
		sort($extended);
		$b = $h;
		// [copy them] followed by a delimiter if b > 0
		if (strlen($output) > 0) {
			$output .= '-';
		}
		// {if the input contains a non-basic code point < n then fail}
		// while h < length(input) do begin
		$codepointcount = count($codepoints);
		while ($h < $codepointcount) {
			// let m = the minimum code point >= n in the input
			$m = array_shift($extended);
			//printf('next code point to insert is %s' . PHP_EOL, dechex($m));
			// let delta = delta + (m - n) * (h + 1), fail on overflow
			$delta += ($m - $n) * ($h + 1);
			// let n = m
			$n = $m;
			// for each code point c in the input (in order) do begin
			for ($num = 0; $num < $codepointcount; $num++) {
				$c = $codepoints[$num];
				// if c < n then increment delta, fail on overflow
				if ($c < $n) {
					$delta++;
				}
				// if c == n then begin
				elseif ($c === $n) {
					// let q = delta
					$q = $delta;
					// for k = base to infinity in steps of base do begin
					for ($k = self::BOOTSTRAP_BASE; ; $k += self::BOOTSTRAP_BASE) {
						// let t = tmin if k <= bias {+ tmin}, or
						//     tmax if k >= bias + tmax, or k - bias otherwise
						if ($k <= ($bias + self::BOOTSTRAP_TMIN)) {
							$t = self::BOOTSTRAP_TMIN;
						}
						elseif ($k >= ($bias + self::BOOTSTRAP_TMAX)) {
							$t = self::BOOTSTRAP_TMAX;
						}
						else {
							$t = $k - $bias;
						}
						// if q < t then break
						if ($q < $t) {
							break;
						}
						// output the code point for digit t + ((q - t) mod (base - t))
						$digit   = $t + (($q - $t) % (self::BOOTSTRAP_BASE - $t));
						$output .= self::digit_to_char($digit);
						// let q = (q - t) div (base - t)
						$q = floor(($q - $t) / (self::BOOTSTRAP_BASE - $t));
					} // end
					// output the code point for digit q
					$output .= self::digit_to_char($q);
					// let bias = adapt(delta, h + 1, test h equals b?)
					$bias = self::adapt($delta, $h + 1, $h === $b);
					// let delta = 0
					$delta = 0;
					// increment h
					$h++;
				} // end
			} // end
			// increment delta and n
			$delta++;
			$n++;
		} // end

		return $output;
	}