wtf-8.js #1

/*! https://mths.be/wtf8 v1.0.0 by @mathias */
;(function(root) {

	// Detect free variables `exports`
	var freeExports = typeof exports == 'object' && exports;

	// Detect free variable `module`
	var freeModule = typeof module == 'object' && module &&
		module.exports == freeExports && module;

	// Detect free variable `global`, from Node.js or Browserified code,
	// and use it as `root`
	var freeGlobal = typeof global == 'object' && global;
	if (freeGlobal.global === freeGlobal || freeGlobal.window === freeGlobal) {
		root = freeGlobal;
	}

	/*--------------------------------------------------------------------------*/

	var stringFromCharCode = String.fromCharCode;

	// Taken from https://mths.be/punycode
	function ucs2decode(string) {
		var output = [];
		var counter = 0;
		var length = string.length;
		var value;
		var extra;
		while (counter < length) {
			value = string.charCodeAt(counter++);
			if (value >= 0xD800 && value <= 0xDBFF && counter < length) {
				// high surrogate, and there is a next character
				extra = string.charCodeAt(counter++);
				if ((extra & 0xFC00) == 0xDC00) { // low surrogate
					output.push(((value & 0x3FF) << 10) + (extra & 0x3FF) + 0x10000);
				} else {
					// unmatched surrogate; only append this code unit, in case the next
					// code unit is the high surrogate of a surrogate pair
					output.push(value);
					counter--;
				}
			} else {
				output.push(value);
			}
		}
		return output;
	}

	// Taken from https://mths.be/punycode
	function ucs2encode(array) {
		var length = array.length;
		var index = -1;
		var value;
		var output = '';
		while (++index < length) {
			value = array[index];
			if (value > 0xFFFF) {
				value -= 0x10000;
				output += stringFromCharCode(value >>> 10 & 0x3FF | 0xD800);
				value = 0xDC00 | value & 0x3FF;
			}
			output += stringFromCharCode(value);
		}
		return output;
	}

	/*--------------------------------------------------------------------------*/

	function createByte(codePoint, shift) {
		return stringFromCharCode(((codePoint >> shift) & 0x3F) | 0x80);
	}

	function encodeCodePoint(codePoint) {
		if ((codePoint & 0xFFFFFF80) == 0) { // 1-byte sequence
			return stringFromCharCode(codePoint);
		}
		var symbol = '';
		if ((codePoint & 0xFFFFF800) == 0) { // 2-byte sequence
			symbol = stringFromCharCode(((codePoint >> 6) & 0x1F) | 0xC0);
		}
		else if ((codePoint & 0xFFFF0000) == 0) { // 3-byte sequence
			symbol = stringFromCharCode(((codePoint >> 12) & 0x0F) | 0xE0);
			symbol += createByte(codePoint, 6);
		}
		else if ((codePoint & 0xFFE00000) == 0) { // 4-byte sequence
			symbol = stringFromCharCode(((codePoint >> 18) & 0x07) | 0xF0);
			symbol += createByte(codePoint, 12);
			symbol += createByte(codePoint, 6);
		}
		symbol += stringFromCharCode((codePoint & 0x3F) | 0x80);
		return symbol;
	}

	function wtf8encode(string) {
		var codePoints = ucs2decode(string);
		var length = codePoints.length;
		var index = -1;
		var codePoint;
		var byteString = '';
		while (++index < length) {
			codePoint = codePoints[index];
			byteString += encodeCodePoint(codePoint);
		}
		return byteString;
	}

	/*--------------------------------------------------------------------------*/

	function readContinuationByte() {
		if (byteIndex >= byteCount) {
			throw Error('Invalid byte index');
		}

		var continuationByte = byteArray[byteIndex] & 0xFF;
		byteIndex++;

		if ((continuationByte & 0xC0) == 0x80) {
			return continuationByte & 0x3F;
		}

		// If we end up here, it’s not a continuation byte.
		throw Error('Invalid continuation byte');
	}

	function decodeSymbol() {
		var byte1;
		var byte2;
		var byte3;
		var byte4;
		var codePoint;

		if (byteIndex > byteCount) {
			throw Error('Invalid byte index');
		}

		if (byteIndex == byteCount) {
			return false;
		}

		// Read the first byte.
		byte1 = byteArray[byteIndex] & 0xFF;
		byteIndex++;

		// 1-byte sequence (no continuation bytes)
		if ((byte1 & 0x80) == 0) {
			return byte1;
		}

		// 2-byte sequence
		if ((byte1 & 0xE0) == 0xC0) {
			var byte2 = readContinuationByte();
			codePoint = ((byte1 & 0x1F) << 6) | byte2;
			if (codePoint >= 0x80) {
				return codePoint;
			} else {
				throw Error('Invalid continuation byte');
			}
		}

		// 3-byte sequence (may include unpaired surrogates)
		if ((byte1 & 0xF0) == 0xE0) {
			byte2 = readContinuationByte();
			byte3 = readContinuationByte();
			codePoint = ((byte1 & 0x0F) << 12) | (byte2 << 6) | byte3;
			if (codePoint >= 0x0800) {
				return codePoint;
			} else {
				throw Error('Invalid continuation byte');
			}
		}

		// 4-byte sequence
		if ((byte1 & 0xF8) == 0xF0) {
			byte2 = readContinuationByte();
			byte3 = readContinuationByte();
			byte4 = readContinuationByte();
			codePoint = ((byte1 & 0x0F) << 0x12) | (byte2 << 0x0C) |
				(byte3 << 0x06) | byte4;
			if (codePoint >= 0x010000 && codePoint <= 0x10FFFF) {
				return codePoint;
			}
		}

		throw Error('Invalid WTF-8 detected');
	}

	var byteArray;
	var byteCount;
	var byteIndex;
	function wtf8decode(byteString) {
		byteArray = ucs2decode(byteString);
		byteCount = byteArray.length;
		byteIndex = 0;
		var codePoints = [];
		var tmp;
		while ((tmp = decodeSymbol()) !== false) {
			codePoints.push(tmp);
		}
		return ucs2encode(codePoints);
	}

	/*--------------------------------------------------------------------------*/

	var wtf8 = {
		'version': '1.0.0',
		'encode': wtf8encode,
		'decode': wtf8decode
	};

	// Some AMD build optimizers, like r.js, check for specific condition patterns
	// like the following:
	if (
		typeof define == 'function' &&
		typeof define.amd == 'object' &&
		define.amd
	) {
		define(function() {
			return wtf8;
		});
	}	else if (freeExports && !freeExports.nodeType) {
		if (freeModule) { // in Node.js or RingoJS v0.8.0+
			freeModule.exports = wtf8;
		} else { // in Narwhal or RingoJS v0.7.0-
			var object = {};
			var hasOwnProperty = object.hasOwnProperty;
			for (var key in wtf8) {
				hasOwnProperty.call(wtf8, key) && (freeExports[key] = wtf8[key]);
			}
		}
	} else { // in Rhino or a web browser
		root.wtf8 = wtf8;
	}

}(this));