Develop Reference

Read Manufacturer data BLE device react-native-ble-plx

Hi I need to work with BLE integration using React-native.
I am using this package: https://polidea.github.io/react-native-ble-plx/
I have successfully searched a BLE device now I need to read it's manufacturer data and check for some values
issue: I am getting manufacturer data in string (Base64) format and I converted into byte array with following code.
convertStringToByteArray(str) {
String.prototype.encodeHex = function () {
var bytes = [];
for (var i = 0; i < this.length; ++i) {
bytes.push(this.charCodeAt(i));
}
return bytes;
};
var byteArray = str.encodeHex();
return byteArray
}
which results as below.
[xx, xx, xx, xx, xx, xx, xx, xx]
I am not sure how to go with it.
in Native iOS i get output in DATA format which is given by Apple itself. not sure how to handle in this
Requirement
I need to convert that subrange 2..<3 to Uint8 and check if Uint8 result contains some integeor
can anyone help me how I can parse such data ?

Using buffer js library, it can be achieved using the following snippet:
var Buffer = require('buffer/').Buffer
const strval = "base-64-encoded-string";
const buffer = new Buffer(strval, 'base64');
const bufStr = buffer.toString('hex'); //make sure to encode it as 'hex' and not 'string'

Found solution string was base64 ENCODED I have to decode string first then convert to byte array

decode windows 1256 to utf-8 in android

I have a string which is decoded by windows-1256 like this
A0C8E5CFC7CF2DC7DDDEE5ED
I want to encode that to UTF-8 in android.
I tried to encode like this
String input = "A0C8E5CFC7CF2DC7DDDEE5ED";
try {
String message = new String(input.getBytes(), "windows-1256");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
but I didn't see what expected expression.
I wrote some codes in C# for this purpose ,like this
int index = 0;
while (response[index] != 0x00)
result = result + Encoding.GetEncoding("windows-1256").GetString(response, index++, 1);
it works fine.
does anyone have any idea how to solve it?
Thanks in advance

First you convert your hex string into byte array. See this post.
Then, convert the byte array byte[] into UTF-8 using
String str = new String(byte[], "windows-1256");
UTF-8 is the native android encoding. Hope it helps.

NSNonLossyASCIIStringEncoding equivalent for Android

I got to port some chat code from iOS to Android. Before sending the chat message to the socket, the iOS code uses the NSNonLossyASCIIStringEncoding class as parameter of the NSString::dataUsingEncoding.
How would you do it in Android? Same question about the opposite decoding.
Without doing that, for instance, the line breaks disappear in the message received on the other mobile.
Code on iOS:
NSData *data1 = [myStringTosend dataUsingEncoding:NSNonLossyASCIIStringEncoding];
NSString *goodValue = [[[NSString alloc] initWithData:data1 encoding:NSUTF8StringEncoding] autorelease];
And decoding:
NSData *data = [[NSData alloc] initWithData:[response dataUsingEncoding:NSASCIIStringEncoding]];
So far (and not correct), encoding on the Android side:
OutputStream os = socket.getOutputStream();
os.write(request.getBytes("UTF-8"));
os.flush();
And decoding:
while ((bytesRead = is.read(buffer, 0, BUFFER_SIZE)) >= 0) {
if (bytesRead > 0) response.append(new String(buffer, 0, bytesRead, "UTF-8"));
if (bytesRead < BUFFER_SIZE) break;
}

#portforwardpodcast is absolutely correct that you should, if possible, avoid ASCII encoding your utf8 and instead set up your stack to handle/store utf8 directly. That said, if you don't have the ability to change the behavior, the following code may be helpful.
While there's no published explanation of how NSNonLossyASCIIStringEncoding works, based on its output it looks like:
Bytes in the extended ASCII range (decimal values 128 - 255) are escaped using an octal encoding (e.g. ñ with decimal value 241 -> \361)
Non-ASCII code points are escaped in two byte chunks using a hex encoding (e.g. 😥 which takes up 32 bits with decimal value 128549 -> \ud83d\ude25)
So to encode:
public static String encodeToNonLossyAscii(String original) {
Charset asciiCharset = Charset.forName("US-ASCII");
if (asciiCharset.newEncoder().canEncode(original)) {
return original;
}
StringBuffer stringBuffer = new StringBuffer();
for (int i = 0; i < original.length(); i++) {
char c = original.charAt(i);
if (c < 128) {
stringBuffer.append(c);
} else if (c < 256) {
String octal = Integer.toOctalString(c);
stringBuffer.append("\\");
stringBuffer.append(octal);
} else {
String hex = Integer.toHexString(c);
stringBuffer.append("\\u");
stringBuffer.append(hex);
}
}
return stringBuffer.toString();
}
And to decode (this can be made more efficient by parsing the two types of encodings in lock step, rather as two separate passes):
private static final Pattern UNICODE_HEX_PATTERN = Pattern.compile("\\\\u([0-9A-Fa-f]{4})");
private static final Pattern UNICODE_OCT_PATTERN = Pattern.compile("\\\\([0-7]{3})");
public static String decodeFromNonLossyAscii(String original) {
Matcher matcher = UNICODE_HEX_PATTERN.matcher(original);
StringBuffer charBuffer = new StringBuffer(original.length());
while (matcher.find()) {
String match = matcher.group(1);
char unicodeChar = (char) Integer.parseInt(match, 16);
matcher.appendReplacement(charBuffer, Character.toString(unicodeChar));
}
matcher.appendTail(charBuffer);
String parsedUnicode = charBuffer.toString();
matcher = UNICODE_OCT_PATTERN.matcher(parsedUnicode);
charBuffer = new StringBuffer(parsedUnicode.length());
while (matcher.find()) {
String match = matcher.group(1);
char unicodeChar = (char) Integer.parseInt(match, 8);
matcher.appendReplacement(charBuffer, Character.toString(unicodeChar));
}
matcher.appendTail(charBuffer);
return charBuffer.toString();
}

Don't use NSNonLossyASCIIStringEncoding, use utf-8 encoding. I just solved this problem myself on ios+android+java spring backend, and it took me around 4 full days to figure everything out. Android can't display emojis, but this gives me full character support in almost all (or all not sure) languages. Here are the articles that helped me:
Must Read: http://blog.manbolo.com/2012/10/29/supporting-new-emojis-on-ios-6 http://blog.manbolo.com/2011/12/12/supporting-ios-5-new-emoji-encoding
See the hex bytes of a string inside the DB: How can I see raw bytes stored in a MySQL column?
Details about how to setup MySQL: http://technovergence-en.blogspot.com/2012/03/mysql-from-utf8-to-utf8mb4.html
In depth FAQ of utf8- http://www.unicode.org/faq/utf_bom.html#utf8-4
Details about the difference from notation: \ud83d\udc7d and hex value in memory: 0xF09F91BD http://en.wikipedia.org/wiki/UTF-8#Description
Use this to copy and paste characters in to see real hex byte values (works for emojis): http://perishablepress.com/tools/utf8-hex/index.php
Get Spring to support utf8 in urls (for GET params) http://forum.springsource.org/showthread.php?93728-RequestParam-doesn-t-seem-to-be-decoded Get Parameter Encoding http://forum.springsource.org/showthread.php?112181-Unable-to-Override-the-Spring-MVC-URL-decoding-which-uses-default-quot-ISO-8859-1-quot

My answer code is equivalent to IOS NSNonLossyASCIIStringEncoding for Android.
In your gradle put below depandancy.
compile 'org.apache.commons:commons-lang3:3.4'
then Put method to your Utils Class Like this
public static String encode(String s)
{
return StringEscapeUtils.escapeJava(s);
}
public static String decode(String s)
{
return StringEscapeUtils.unescapeJava(s);
}
then Simply call this method where you want to encode string or decode String like this
//for encode
String stencode = Utils.encode("mystring");
//for decode
String stdecode = Utils.decode("mystring")

Android byte array to string to byte array

All I need is convert byte[] to String. Then do something with that string and convert back to byte[] array. But in this testing I'm just convert byte[] to string and convert back to byte[] and the result is different.
to convert byte[] to string by using this:
byte[] byteEntity = EntityUtils.toByteArray(entity);
String s = new String(byteEntity,"UTF-8");
Then i tried:
byte[] byteTest = s.getBytes("UTF-8");
Then i complared it:
if (byteEntity.equals(byteTest) Log.i("test","equal");
else Log.i("test","diff");
So the result is different.
I searched in stackoverflow about this but it doesn't match my case. The point is my data is .png picture so the string converted is unreadable. Thanks in advance.

Solved
Using something like this.
byte[] mByteEntity = EntityUtils.toByteArray(entity);
byte[] mByteDecrypted = clip_xor(mByteEntity,"your_key".getBytes());
baos.write(mByteDecrypted);
InputStream in = new ByteArrayInputStream(baos.toByteArray());
and this is function clip_xor
protected byte[] clip_xor(byte[] data, byte[] key) {
int num_key = key.length;
int num_data = data.length;
try {
if (num_key > 0) {
for (int i = 0, j = 0; i < num_data; i++, j = (j + 1)
% num_key) {
data[i] ^= key[j];
}
}
} catch (Exception ex) {
Log.i("error", ex.toString());
}
return data;
}
Hope this will useful for someone face same problem. Thanks you your all for helping me solve this.
Special thanks for P'krit_s

primitive arrays are actually Objects (that's why they have .equals method) but they do not implement the contract of equality (hashCode and equals) needed for comparison. You cannot also use == since according to docs, .getBytes will return a new instance byte[]. You should use Arrays.equals(byteEntity, byteTest) to test equality.

Have a look to the answer here.
In that case my target was transform a png image in a bytestream to display it in embedded browser (it was a particular case where browser did not show directly the png).
You may use the logic of that solution to convert png to byte and then to String.
Then reverse the order of operations to get back to the original file.

Android/PHP - Encryption and Decryption

I'm struggeling with code from this page: http://www.androidsnippets.com/encrypt-decrypt-between-android-and-php
I want to send data from a server to an Android application and vice versa, but it should be sent as an encrypted string. However, I manage to encrypt and decrypt the string in PHP. But on Android the application crashes with the following error message when decrypting:
java.lang.Exception: [decrypt] unable to parse ' as integer.
This error occours here in the for-loop:
public static byte[] hexToBytes(String str) {
if (str==null) {
return null;
} else if (str.length() < 2) {
return null;
} else {
int len = str.length() / 2;
byte[] buffer = new byte[len];
for (int i=0; i<len; i++) {
buffer[i] = (byte) Integer.parseInt(str.substring(i*2,i*2+2),16);
}
System.out.println("Buffer: " + buffer);
return buffer;
}
}
This is by the way the string that should be decrypted: f46d86e65fe31ed46920b20255dd8ea6

You're talking about encrypting and decrypting, but you're showing code which simply turns numeric bytes (such as 0x4F) into strings (such as "4F") -- which may be relevant to your transfer of data (if you cannot transfer binary format), but completely unrelated to encryption/decryption.
Since the Android code you have contains only a single Integer parse, have you examined the input you're giving it? str.substring(i*2,i*2+2) apparently contains data other than [0-9A-F] when the exception occurs. You should start by examining the string you've received and comparing it to what you sent, to make sure they agree and they only contain hexadecimal characters.
Edit -- passing the string "f46d86e65fe31ed46920b20255dd8ea6" through your hexToBytes() function works flawlessly. Your input is probably not what you think it is.