We Keep Coding

How to edit binary file in Android?

I want to create an app that can open binary file, read and edit it's content in decimal values, and then save it back to binary file.
This file that I want to open have multiple parameters written in 2 bytes. e.g. 00 06 00 50 01 AB = 6, 80, 427
So far I managed to open bin file, put all data from file into byte[].
Here is the code to open and read file:
String path = getFilesDir().getAbsolutePath();
File file = new File(path + "/file.bin");
int size = (int) file.length();
byte[] bytes = new byte[size];
FileInputStream fis = new FileInputStream(file);
try {
fis.read(bytes);
...
} finally {
fis.close();
}
Here is first attempt to convert byte[] into deciaml values:
for (int i = 0; i < size / 2; i = i + 2) {
intArray[i] = ((bytes[i] & 0xff) << 8) | (bytes[i + 1] & 0xff);
}
But in this code only every second value is correct. It's shows 6,0,80,0,1 and should be 6,80,1.
The second idea was to convert byte[] into String[] and then into e.g. int[] but It doesn't work as intended. In this fragment I didn't parse whole array, but only hexArray[4] which was 50 in hex and 80 in dec, but the result was 50.
for (int i = 0; i < size; i = i + 2) {
num1 = String.format("%02X", bytes[i] & 0xFF);
num2 = String.format("%02X", bytes[i + 1] & 0xFF);
String twoByte = num1 + num2;
hexArrayWithNull[i] = twoByte;
}
String[] hexArray = Arrays.stream(hexArrayWithNull).filter(Objects::nonNull).toArray(String[]::new);
num = String.format("%d", Integer.parseInt(hexArray[4]));
I'm quite stuck here and need some guidance. I must say also that I'm new in programming.
Thanks

You increment i in each iteration by 2 and you store in intArray[i]. So, you store in index [0] then index [2] then index [4] and so on. This explains the zeros at odd indices [1], [3], ...
Also, you must continue the loop until size, not size/2.
Here is the correct loop:
for (int i = 0; i < size; i = i + 2) {
intArray[i/2] = ((bytes[i] & 0xff) << 8) | (bytes[i + 1] & 0xff);
}
Here is the another possibility:
for (int i = 0; i < size/2; i = i + 1) {
intArray[i] = ((bytes[2*i] & 0xff) << 8) | (bytes[2*i + 1] & 0xff);
}
[EDIT]
The reverse operation would be:
for (int i = 0; i < size/2; i = i + 1) {
bytes[2*i] = (intArray[i] & 0xff00) / 256; //or >>8 instead of /256
bytes[2*i+1] = intArray[i] & 0xff;
}

Read /proc/net/tcp and get IP address from String

I'm reading proc/net/tcp file from filereader and parsing data from regex to get what need .
The example string from proc/net/tcp is :
0: 0401A8C0:D366 FFB79E23:01BB 01 00000000:00000000 00:00000000 00000000 11269 0 14392479 1 00000000 30 4 30 10 -1
So the local address : port is : 0401A8C0:D366 , i have tried convert hex to string via that method but it doesn't return valid data .... Can someone help how to read datas ?
It should give something like : 192.168.*.* .
To parse the ip address should get bytearray from this 0401A8C0 Little Endian String , but can't solve
The Hex to String method :
public String fromHex(String hex) throws UnsupportedEncodingException {
hex = hex.replaceAll("^(00)+", "");
byte[] bytes = new byte[hex.length() / 2];
for (int i = 0; i < hex.length(); i += 2) {
bytes[i / 2] = (byte) ((Character.digit(hex.charAt(i), 16) << 4) + Character.digit(hex.charAt(i + 1), 16));
}
return new String(bytes);
}

I have solved it by converting the string : 0401A8C0 to byte array :
public static byte[] hexStringToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
+ Character.digit(s.charAt(i+1), 16));
}
return data;
}
And than get IP address by :
InetAddress addresses = InetAddresses.fromLittleEndianByteArray(byte[]);

Issues With Sending Large Data Over Websockets With Chrome

I have been attempting to write a java HTTP server from scratch for my chat program that sends data over websockets and everything has been going well until I started trying to send large images with my program using google chrome. I discovered that when chrome is sending multiple frames of data to my server, it never sends the proper length of the data. The first frame is always fine, but all frames after the initial one send a number that is significantly smaller than the data that the frame contains. For example, it will send a frame saying that it contains 123 bytes of data, when it is really sending over 100 kilobytes. I have tested other browsers like firefox and safari (on my phone) and they don't seem to split up large data into frames like chrome does, so they don't have the same issue. Here are some screenshots of my results:
Initial frame:
enter image description here
Following frames (This is where it fails):
enter image description here
And here is my server side code that gets the data from an input stream and writes it to a file:
byte[] headerdata = new byte[12];
input.read(headerdata, 0, 2);
int frame = (headerdata[0] & 0b10000000) & 0xFF;
long length = (headerdata[1] & 0b01111111) & 0xFF;
System.out.format("Before: %d, Frame: %d%n", length, frame);
if(length == 127){
input.read(headerdata, 0, 12);
length = ((long)(headerdata[0] << 56) & 0xFFFFFFFFFFFFFFFFL | (long)(headerdata[1] << 48) & 0xFFFFFFFFFFFFFFL | (long)(headerdata[2] << 40) & 0xFFFFFFFFFFFFL | (long)(headerdata[3] << 32) & 0xFFFFFFFFFFL | (headerdata[4] << 24) & 0xFFFFFFFFL | (headerdata[5] << 16) & 0xFFFFFFL | (headerdata[6] << 8) & 0xFFFFL | headerdata[7] & 0xFFL)
} else if(length == 126){
input.read(headerdata, 6, 6);
length = ((headerdata[6] << 8) & 0xFFFF | headerdata[7] & 0xFF);
}else{
input.read(headerdata, 8, 4);
}
System.out.println("After: " + length);
int count;
int total = 0;
byte[] buffer = new byte[16384];
boolean done = false;
while(done == false){
count = input.read(buffer, 0, buffer.length);
//System.out.println(count);
for(int i = 0; i < count; i++){
buffer[i] = (byte)(buffer[i] ^ headerdata[(total & 3) + 8]);
total++;
}
fileoutput.write(buffer, 0, count);
System.out.format("Count: %d Left: %d%n", count, (length - total));
if(total >= length){
done = true;
}
}
if(frame == 128) break;
Any explanation as to why I might be failing to read the length of following frames would be greatly appreciated (I have a few suspicions of my own as well). Thank you for your time and efforts.

I found out that the buffer ends up overflowing, resulting in data being misread or lost, which is why I was getting the wrong length values from the frames. I fixed it by adding an if statement that checks to see if the number of bytes read are approaching the length value of that frame, and then only read what is left instead of the full buffer size to stop it from overflowing. Here is the code with the modification:
byte[] headerdata = new byte[12];
input.read(headerdata, 0, 2);
int frame = (headerdata[0] & 0b10000000) & 0xFF;
long length = (headerdata[1] & 0b01111111) & 0xFF;
System.out.format("Before: %d, Frame: %d%n", length, frame);
if(length == 127){
input.read(headerdata, 0, 12);
length = ((long)(headerdata[0] << 56) & 0xFFFFFFFFFFFFFFFFL | (long)(headerdata[1] << 48) & 0xFFFFFFFFFFFFFFL | (long)(headerdata[2] << 40) & 0xFFFFFFFFFFFFL | (long)(headerdata[3] << 32) & 0xFFFFFFFFFFL | (headerdata[4] << 24) & 0xFFFFFFFFL | (headerdata[5] << 16) & 0xFFFFFFL | (headerdata[6] << 8) & 0xFFFFL | headerdata[7] & 0xFFL);
}else if(length == 126){
input.read(headerdata, 6, 6);
length = ((headerdata[6] << 8) & 0xFFFF | headerdata[7] & 0xFF);
}else{
input.read(headerdata, 8, 4);
}
System.out.println("After: " + length);
int count;
int total = 0;
byte[] buffer = new byte[16384];
boolean done = false;
while(done == false){
if(length - total > buffer.length) count = input.read(buffer, 0, buffer.length);
else count = input.read(buffer, 0, (int) (length - total));
//System.out.println(count);
for(int i = 0; i < count; i++){
buffer[i] = (byte)(buffer[i] ^ headerdata[(total & 3) + 8]);
total++;
}
fileoutput.write(buffer, 0, count);
//System.out.format("Count: %d Left: %d%n", count, (length - total));
if(total >= length){
done = true;
}
}
if(frame == 128) break;
I also did some research on different ways to read byte streams from a socket and found that it would also be possible to use DataInputStream.readFully().

JAVA JDBC Driver PostgreSQL: Parse numbers encoded as BYTEA object

I have relation where for each record there is BYTEA column (UTF-8) encoding 3 numbers in the following order:
bytes 0-1: number 1
bytes 2-3: number 2
bytes 4-6: number 3
How can I parse the binary data to readable numbers?
Currently I have this and don't know how to continue:
Class.forName(dbDriver);
Connection connection = DriverManager.getConnection(dbUrl, dbUser, dbPass);
Statement st = connection.createStatement();
String query = "SELECT ...";
ResultSet rs = st.executeQuery(query);
while (rs.next()) {
byte[] data = rs.getBytes(1);
//TODO Parse
}
Thanks,

That depends on how the numbers are stored.
Are they binary?
Are they signed?
Are they big or little endian?
Assuming yes to the first two, you can use bit-manipulation, e.g.
// Little-endian
short num1 = (short) ((data[0] & 0xFF) | (data[1] & 0xFF) << 8);
// Big-endian
short num1 = (short) ((data[0] & 0xFF) << 8 | (data[1] & 0xFF));
But it's probably easier to use ByteBuffer:
ByteBuffer buf = ByteBuffer.wrap(data).order(ByteOrder.LITTLE_ENDIAN);
short num1 = buf.getShort();
short num2 = buf.getShort();
short num3 = buf.getShort();
ByteBuffer is BIG_ENDIAN by default.

Can you try this :
For String :
String tatto = "my tatto"; //for example
byte[] array = tatto.getBytes(); // Or any bytes
String s = new String(array);
System.out.println(s);
For byte[] :
byte[] data = new byte[]{ 1, 16, 84, 2, 101, 110, 83, 111};
long val = 0;
for (int i = 0; i < data.length; i++)
{
val = (val << 8) + (data[i] & 0xff);
}
System.out.println(val);

Content of (DataBufferUShort).getData()

I can't understand how to get RGBA values from a short[] that I get from bufferedImage.getRaster().dataBuffer.getData() if dataBuffer is an instance of DataBufferUShort.
How to convert these values (that can be even -30000) to 0..255? If dataBuffer is an instance of DataBufferByte I can simply make something like this:
result[i] = (array[i] < 0) ?
array[i] + 256 :
array[i];
But what should I do with DataBufferUShort? Some PNG images has this type instead of expecting DataBufferByte.
getType() returns TYPE_CUSTOM. Here is the image: http://i.stack.imgur.com/YwmkO.png

A DataBufferUShort can hold multiple types of samples, so you first need to determine what data you have. Here are the most common ones:
If the image data represents 16 bit gray samples, all you need to do scale each value down to get an 8 bit gray value. You can do that by shifting the values 8 bits to the right.
DataBufferUShort dataBuffer;
short[] data = dataBuffer.getData();
byte[] gray = new byte[data.length];
for (int i = 0; i < data.length; i++) {
gray[i] = (byte) ((data[i] & 0xff00) >> 8);
}
If the image data represents 16 bits per sample (A)RGB values, you can do just the same as above, you will just have 3 (or 4 if there's alpha) samples or array elements per pixel instead of one.
If the data represents 16 bits per sample ARGB (as seems to be the case with your sample), you can also convert to int packed ARGB samples, like this:
DataBufferUShort dataBuffer;
short[] data = dataBuffer.getData();
int[] argb = new byte[data.length / 4];
for (int i = 0; i < data.length; += 4) {
int a = (data[i ] & 0xff00) >> 8;
int r = (data[i + 1] & 0xff00) >> 8;
int g = (data[i + 2] & 0xff00) >> 8;
int b = (data[i + 3] & 0xff00) >> 8;
argb[i / 4] = a << 24 | r << 16 | g << 8 | b;
}
If the image data represents 15/16 bit RGB (like the TYPE_USHORT_555_RGB or TYPE_USHORT_565_RGB) you'll have to scale the RGB values up to the full 8 bit/sample range. Something like:
DataBufferUShort dataBuffer;
short[] data = dataBuffer.getData();
byte[] rgb = new byte[data.length * 3];
for (int i = 0; i < data.length; i++) {
int shortRGB = data[i] & 0xffff;
// Assuming 5 bit R, 5 bit G, 5 bit B, using the lower 15 bits
rgb[i * 3 + 0] = ((((shortRGB & 0x7C00) >> 10) + 1) * 8) - 1;
rgb[i * 3 + 1] = ((((shortRGB & 0x03E0) >> 5) + 1) * 8) - 1;
rgb[i * 3 + 2] = ((((shortRGB & 0x001F) ) + 1) * 8) - 1;
}
For 565 RGB or even 4444 ARGB (as used in some Android devices), the procedure is very similar.