source: trip-planner-front/node_modules/engine.io/lib/parser-v3/utf8.js@ 6c1585f

/*! https://mths.be/utf8js v2.1.2 by @mathias */

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 checkScalarValue(codePoint, strict) {
        if (codePoint >= 0xD800 && codePoint <= 0xDFFF) {
                if (strict) {
                        throw Error(
                                'Lone surrogate U+' + codePoint.toString(16).toUpperCase() +
                                ' is not a scalar value'
                        );
                }
                return false;
        }
        return true;
}
/*--------------------------------------------------------------------------*/

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

function encodeCodePoint(codePoint, strict) {
        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
                if (!checkScalarValue(codePoint, strict)) {
                        codePoint = 0xFFFD;
                }
                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 utf8encode(string, opts) {
        opts = opts || {};
        var strict = false !== opts.strict;

        var codePoints = ucs2decode(string);
        var length = codePoints.length;
        var index = -1;
        var codePoint;
        var byteString = '';
        while (++index < length) {
                codePoint = codePoints[index];
                byteString += encodeCodePoint(codePoint, strict);
        }
        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(strict) {
        var byte1;
        var byte2;
        var byte3;
        var byte4;
        var codePoint;

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

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

        // Read 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) {
                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 checkScalarValue(codePoint, strict) ? codePoint : 0xFFFD;
                } else {
                        throw Error('Invalid continuation byte');
                }
        }

        // 4-byte sequence
        if ((byte1 & 0xF8) == 0xF0) {
                byte2 = readContinuationByte();
                byte3 = readContinuationByte();
                byte4 = readContinuationByte();
                codePoint = ((byte1 & 0x07) << 0x12) | (byte2 << 0x0C) |
                        (byte3 << 0x06) | byte4;
                if (codePoint >= 0x010000 && codePoint <= 0x10FFFF) {
                        return codePoint;
                }
        }

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

var byteArray;
var byteCount;
var byteIndex;
function utf8decode(byteString, opts) {
        opts = opts || {};
        var strict = false !== opts.strict;

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

module.exports = {
        version: '2.1.2',
        encode: utf8encode,
        decode: utf8decode
};