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function toUTF8Array(str) {
    var utf8 = [];
    for (var i=0; i < str.length; i++) {
        var charcode = str.charCodeAt(i);
        if (charcode < 0x80) utf8.push(charcode);
        else if (charcode < 0x800) {
            utf8.push(0xc0 | (charcode >> 6), 
                      0x80 | (charcode & 0x3f));
        }
        else if (charcode < 0xd800 || charcode >= 0xe000) {
            utf8.push(0xe0 | (charcode >> 12), 
                      0x80 | ((charcode>>6) & 0x3f), 
                      0x80 | (charcode & 0x3f));
        }
        // surrogate pair
        else {
            i++;
            charcode = ((charcode&0x3ff)<<10)|(str.charCodeAt(i)&0x3ff)
            utf8.push(0xf0 | (charcode >>18), 
                      0x80 | ((charcode>>12) & 0x3f), 
                      0x80 | ((charcode>>6) & 0x3f), 
                      0x80 | (charcode & 0x3f));
        }
    }
    return utf8;
}

function fromUTF8Array(data) { // array of bytes
    var str = '',
        i;

    for (i = 0; i < data.length; i++) {
        var value = data[i];

        if (value < 0x80) {
            str += String.fromCharCode(value);
        } else if (value > 0xBF && value < 0xE0) {
            str += String.fromCharCode((value & 0x1F) << 6 | data[i + 1] & 0x3F);
            i += 1;
        } else if (value > 0xDF && value < 0xF0) {
            str += String.fromCharCode((value & 0x0F) << 12 | (data[i + 1] & 0x3F) << 6 | data[i + 2] & 0x3F);
            i += 2;
        } else {
            // surrogate pair
            var charCode = ((value & 0x07) << 18 | (data[i + 1] & 0x3F) << 12 | (data[i + 2] & 0x3F) << 6 | data[i + 3] & 0x3F) - 0x010000;

            str += String.fromCharCode(charCode >> 10 | 0xD800, charCode & 0x03FF | 0xDC00); 
            i += 3;
        }
    }

    return str;
}