HuajiMidi/inc/shim/Base64binary.js

/**
 * @license -------------------------------------------------------------------
 *   module: Base64Binary
 *      src: http://blog.danguer.com/2011/10/24/base64-binary-decoding-in-javascript/
 *  license: Simplified BSD License
 * -------------------------------------------------------------------
 * Copyright 2011, Daniel Guerrero. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     - Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     - 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.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 DANIEL GUERRERO 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.
*/

var Base64Binary = {
	_keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",

	/* will return a  Uint8Array type */
	decodeArrayBuffer: function(input) {
		var bytes = Math.ceil( (3*input.length) / 4.0);
		var ab = new ArrayBuffer(bytes);
		this.decode(input, ab);

		return ab;
	},

	decode: function(input, arrayBuffer) {
		//get last chars to see if are valid
		var lkey1 = this._keyStr.indexOf(input.charAt(input.length-1));		 
		var lkey2 = this._keyStr.indexOf(input.charAt(input.length-1));		 

		var bytes = Math.ceil( (3*input.length) / 4.0);
		if (lkey1 == 64) bytes--; //padding chars, so skip
		if (lkey2 == 64) bytes--; //padding chars, so skip

		var uarray;
		var chr1, chr2, chr3;
		var enc1, enc2, enc3, enc4;
		var i = 0;
		var j = 0;

		if (arrayBuffer)
			uarray = new Uint8Array(arrayBuffer);
		else
			uarray = new Uint8Array(bytes);

		input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

		for (i=0; i<bytes; i+=3) {	
			//get the 3 octects in 4 ascii chars
			enc1 = this._keyStr.indexOf(input.charAt(j++));
			enc2 = this._keyStr.indexOf(input.charAt(j++));
			enc3 = this._keyStr.indexOf(input.charAt(j++));
			enc4 = this._keyStr.indexOf(input.charAt(j++));

			chr1 = (enc1 << 2) | (enc2 >> 4);
			chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
			chr3 = ((enc3 & 3) << 6) | enc4;

			uarray[i] = chr1;			
			if (enc3 != 64) uarray[i+1] = chr2;
			if (enc4 != 64) uarray[i+2] = chr3;
		}

		return uarray;	
	}
};