utils-html.js

/*****************************************************************************
*
*  This file is part of the MusicToy project. The project is
*  distributed at:
*  https://github.com/maximecb/MusicToy
*
*  Copyright (c) 2012, Maxime Chevalier-Boisvert. All rights reserved.
*
*  This software is licensed under the following license (Modified BSD
*  License):
*
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions are
*  met:
*   1. Redistributions of source code must retain the above copyright
*      notice, this list of conditions and the following disclaimer.
*   2. Redistributions in binary form must reproduce the above copyright
*      notice, this list of conditions and the following disclaimer in the
*      documentation and/or other materials provided with the distribution.
*   3. The name of the author may not be used to endorse or promote
*      products derived from this software without specific prior written
*      permission.
*
*  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
*  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
*  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
*  NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
*  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
*  NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
*  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
*  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
*  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
*  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*****************************************************************************/

/**
Find an element in the HTML DOM tree by its id
*/
function findElementById(id, elem)
{
    if (elem === undefined)
        elem = document

    for (k in elem.childNodes)
    {
        var child = elem.childNodes[k];

        if (child.attributes)
        {
            var childId = child.getAttribute('id');

            if (childId == id)
                return child;
        }

        var nestedElem = findElementById(id, child);

        if (nestedElem)
            return nestedElem;
    }

    return null;
}

/**
Escape a string for valid HTML formatting
*/
function escapeHTML(str)
{
    str = str.replace(/\n/g, '<br>');
    str = str.replace(/ /g, '&nbsp;');
    str = str.replace(/\t/g, '&nbsp;&nbsp;&nbsp;&nbsp;');

    return str;
}

/**
Encode an array of bytes into base64 string format
*/
function encodeBase64(data)
{
    assert (
        data instanceof Array,
        'invalid data array'
    );

    var str = '';

    function encodeChar(bits)
    {
        //console.log(bits);

        var ch;

        if (bits < 26)
            ch = String.fromCharCode(65 + bits);
        else if (bits < 52)
            ch = String.fromCharCode(97 + (bits - 26));
        else if (bits < 62)
            ch = String.fromCharCode(48 + (bits - 52));
        else if (bits === 62)
            ch = '+';
        else
            ch = '/';

        str += ch;
    }

    for (var i = 0; i < data.length; i += 3)
    {
        var numRem = data.length - i;

        // 3 bytes -> 4 base64 chars
        var b0 = data[i];
        var b1 = (numRem >= 2)? data[i+1]:0
        var b2 = (numRem >= 3)? data[i+2]:0

        var bits = (b0 << 16) + (b1 << 8) + b2;

        encodeChar((bits >> 18) & 0x3F);
        encodeChar((bits >> 12) & 0x3F);

        if (numRem >= 2)
        {
            encodeChar((bits >> 6) & 0x3F);

            if (numRem >= 3)
                encodeChar((bits >> 0) & 0x3F);
            else
                str += '=';
        }
        else
        {
            str += '==';
        }
    }

    return str;
}

// TODO
// TODO: decodeBase64(str)
// TODO