You might want to encode/decode strings in java but are unable to use conventional classes. This could be for example due to a restrictive environment like google web toolkit (gwt). In this case, you can use use these two methods:

private static String byte2str(byte[] utfarray) {
	StringBuilder sb = new StringBuilder();
	int i = 0;
	int c=0, c2=0, c3 = 0;

	while (i < utfarray.length) {

		c = (0xFF & utfarray[i]);

		if (c < 128) {
			sb.append((char)c);
			i++;
		} else if ((c > 191) && (c < 224)) {
			c2 =  (0xFF & utfarray[i + 1]);
			sb.append((char)(((c & 31) << 6) | (c2 & 63)));
			i += 2;
		} else {
			c2 =  (0xFF & utfarray[i + 1]);
			c3 =  (0xFF & utfarray[i + 2]);
			sb.append((char)(((c & 15) << 12)
					| ((c2 & 63) << 6) | (c3 & 63)));

			i += 3;
		}

	}

	return sb.toString();
}

private static byte[] str2byte(String string) {
	IndependentByteStream bos = new IndependentByteStream(string.length());
	for ( int n = 0; n < string.length(); n++) {

		char c = string.charAt(n);

		if (c < 128) {
			bos.write((byte) c);
		} else if ((c > 127) && (c < 2048)) {
			bos.write((byte) ((c >> 6) | 192));
			bos.write((byte) ((c & 63) | 128));
		} else {
			bos.write((byte) ((c >> 12) | 224));
			bos.write((byte) (((c >> 6) & 63) | 128));
			bos.write((byte) ((c & 63) | 128));
		}

	}

	return bos.toByteArray();
}

Using mumble and want to import your own CA certificate as trusted?

sudo cp /tmp/myCoolOwnCaCert.pem /etc/ssl/certs/

To deserialize a JSON array you can use an Overlay Type. However, those examples return objects instead of arrays. Here an example of how this is case is handled: JSON:

[{"age": 42, "name": "arthur"}, {"age": 23, "name": "adam"}]

public class PersonRecord extends JavaScriptObject{
	protected PersonRecord() {

	}
	public final native String getName() /*-{ return this.name; }-*/;
	public final native int getAge() /*-{ return this.age; }-*/;
}

public class Deserialize {
	public static final native JsArray<PersonRecord> deserialize(
			String json) /*-{
		return eval('(' + json + ')');
	}-*/;
}

dinosaurs, sorry :(

As it turns out, associative arrays can’t be used as a cheap hashSET surrogate. Consider the following source:

var hashset = {};
var obj1 = new Object();
obj1['foo'] = 42;
hashset[obj] = true;

for(key in hashset)
  alert(key.foo);

var _hashSetSufix = 0;

function HashSet() {
	this.data = {};
	this.counter = 0;
	this.objAttr = '_hashsetCounter_' + (_hashSetSufix++);
}

HashSet.prototype.add = function(obj) {
	obj[this.objAttr] = this.counter++;
	this.data[obj[this.objAttr]] = obj;
};

HashSet.prototype.contains = function(obj) {
	return this.objAttr in obj && obj[this.objAttr] in this.data;
};

HashSet.prototype.remove = function(obj) {
	delete this.data[obj[this.objAttr]];
	delete obj[this.objAttr];
};

// test

(function() {
	var hs = new HashSet();
	var obj1 = new Object();
	var obj2 = new Object();

	hs.add(obj1);

	if (!hs.contains(obj1) || hs.contains(obj2))
		alert("Hashset: selftest fail");

	hs.remove(obj1);
	if (hs.contains(obj1) || hs.contains(obj2))
		alert("Hashset: selftest fail2");
})();

1. Download ROM, place as .zip on sd card
2. Unlock bootloader: www.htcdev.com/bootloader/unlock-instructions/
3. Get in fastboot mode, boot cwm:

   ./fastboot boot /tmp/recovery-clockwork-5.0.2.0-saga.img

4. Wipe
5. Install zips
6. Reboot
7. If stuck at loading screen: flash boot.img by hand

   ./fastboot flash boot /tmp/boot.img

for(var i=0; i< view.length; ++i)
    str += String.fromCharCode(view[i]);

function convertFaster(view)
{
    var array = new Array(view.length);
    for(var i=0; i< view.length; ++i)
        array[i] = String.fromCharCode(view[i]);
    return array.join('');
}

var buffer = new ArrayBuffer(3)
var array = new Uint8Array(buffer);
var i=0;
array[i++] = 0x48;
array[i++] = 0x69;
array[i++] = 0x21;

var blobBuilder = new BlobBuilder();
blobBuilder.append(buffer);
buffer = null;
var blob = blobBuilder.getBlob();
var fileReader =new FileReader();
fileReader.onload = function (e) {
	//conversion done
};
fileReader.readAsBinaryString(blob);

To convert a binary string to a blob we can again use the BlobBuilder. Append also accept DOMStrings as argument.

Last but not least a nice performance comparison (ArrayBuffer to BinaryString): click me.

Some results with 5000000 bytes on a Core2Duo 6300:

• Firefox 9.0.1: 884ms vs 89ms
• Chromium 14.0.835.202: 1886ms vs 101ms

Conclusion: Speedup between 10x and 20x :)

I tried to benchmark an encryption function by passing an empty array to it:

var data = new Array(10* 1024* 1024);
var start = (new Date).getTime();
rc4.secureEncrypt([1, 2, 3, 4, 5, 6,7,8,9,0], data);
var diff = (new Date).getTime() - start;
alert("spent "+diff+" ms on encryption");

It was slow, but I didn’t know why. I gradually debugged the code and discovered, that 90% of the time was spent in that line:

plantext[i] = encrypted;

Why should accessing a simple array take that long? It’s an O(1) operation! Well, it turns out that the array is a sparse array. Since most of it will never be accessed, it’s simply empty (empty != 0) and is created on first access.
Just filling the array caused the function to be executed 3 to 4 times faster. The encryption itself turned out to be pretty fast, it was just a bad benchmark testing input.

var data = new Array(10* 1024* 1024);
for(var i=0; i < data.length; ++i) data[i]=42;
var start = (new Date).getTime();
rc4.secureEncrypt([1, 2, 3, 4, 5, 6,7,8,9,0], data);
var diff = (new Date).getTime() - start;
alert("spent "+diff+" ms on encryption");

!(wlan.fc.type_subtype == 0x1d) && !(wlan.sa == $MY_ADDRESS) && !(wlan.fc.type_subtype == 0x08) 0x1d = beacon 0x08 = ack

by maik

Searching for a simple function to convert javascript strings to byte arrays, I stumbled over this stackoverflow answer.

function stringToBytesFaster ( str ) { 
    var ch, st, re = [], j=0;
    for (var i = 0; i < str.length; i++ ) { 
        ch = str.charCodeAt(i);
        if(ch < 127)
        {
            re[j++] = ch & 0xFF;
        }
        else
        {
            st = [];    // clear stack
            do {
                st.push( ch & 0xFF );  // push byte to stack
                ch = ch >> 8;          // shift value down by 1 byte
            }
            while ( ch );
            // add stack contents to result
            // done because chars have "wrong" endianness
            st = st.reverse();
            for(var k=0;k<st.length; ++k)
                re[j++] = st[k];
        }
    }   
    // return an array of bytes
    return re; 
}

Example output on Firefox 8, core2duo and strlength = 10000:
Old: 2021ms
New: 4ms

Speedup factor:505.25