We Keep Coding

Buffer to String

I send/receive data between Android and other device through the usb.
The code that I use for receive data:
StringBuilder stringBuilder = new StringBuilder();
int i = 0;
int s = buffer[0];
for (; i < s; i++) {
stringBuilder.append(String.valueOf((char)buffer[i]));
}
byte[] b = String.valueOf(stringBuilder).getBytes();
I receive fine all of bytes, except when the byte is bigger than 127. How to do?
I try to use:
stringBuilder2.append(String.valueOf((int)buffer[i] & 0xFF));
And work fine if I read String.valueOf(stringBuilder), but not when I create byte[]

If all the bytes you're receiving are in format ASCII, in your stringBuilder you already have the text of the String you need.
On the other side assuming that buffer[0] is the size of your buffer you could try something like this:
byte[] tmp = new byte[buffer[0]];
System.arraycopy(buffer, 1, tmp, 0, buffer[0]);
String result = new String(tmp);

convert byte array to string, string can't convert back after transfer

Code for the same:
public byte[] stringToBytesUTFCustom(String str) {
char[] buffer1 = str.toCharArray();
byte[] b = new byte[buffer1.length << 1];
for(int i = 0; i < buffer1.length; i++) {
int bpos = i << 1;
b[bpos] = (byte) ((buffer1[i]&0xFF00)>>8);
b[bpos + 1] = (byte) (buffer1[i]&0x00FF);
}
return b;
}
public String bytesToStringUTFCustom(byte[] bytes) {
char[] buffer = new char[bytes.length >> 1];
for(int i = 0; i < buffer.length; i++) {
int bpos = i << 1;
char c = (char)(((bytes[bpos]&0x00FF)<<8) + (bytes[bpos+1]&0x00FF));
buffer[i] = c;
}
String txt = String.valueOf(buffer);
//return new String(buffer);
return txt;
}
First, I implement a SMS encryption app (Client to Client) and then want to encode cipher(format "Byte[]") to string, Base64 it's work but can't send because more than 160 character.
I'm want to convert byte array to string ,when use function above it's work for same function, but when I use bytesToStringUTFCustom and then send this text(SMS) can't work.
Receiver cannot read a text to decode from.
Cipher is a result of bytesToStringUTFCustom function, so anyone can help me?
Thanks.

Did you know these:
String.getBytes(Charset encoding)
new String(byte[] byteArray, Charset encoding)
You can use Charset.forName(String) to get the Charset.
Charset UTF8 = Charset.forName("UTF-8");
byte[] bytes = str.getBytes(UTF8);
String reverted = new String(bytes, UTF8);

How to convert a binary representation of a string into byte in Java?

as the title says, how do I do it? Its easy to convert from string -> byte -> string binary, But how do I convert back? Below is a example.
The output is :
'f' to binary: 01100110
294984
I read somewhere that I could use the Integer.parseInt but clearly that is not the case :( Or am I doing something wrong?
Thanks,
:)
public class main{
public static void main(String[] args) {
String s = "f";
byte[] bytes = s.getBytes();
StringBuilder binary = new StringBuilder();
for (byte b : bytes)
{
int val = b;
for (int i = 0; i < 8; i++)
{
binary.append((val & 128) == 0 ? 0 : 1);
val <<= 1;
}
binary.append(' ');
}
System.out.println("'" + s + "' to binary: " + binary);
System.out.println(Integer.parseInt("01100110", 2));
}
}

You can use Byte.parseByte() with a radix of 2:
byte b = Byte.parseByte(str, 2);
Using your example:
System.out.println(Byte.parseByte("01100110", 2));
102

You can parse it to an integer in base 2, and convert to a byte array.
In your example you've got 16 bits you can also use short.
short a = Short.parseShort(b, 2);
ByteBuffer bytes = ByteBuffer.allocate(2).putShort(a);
byte[] array = bytes.array();
Just in case if you need it for a Very Big String.
String b = "0110100001101001";
byte[] bval = new BigInteger(b, 2).toByteArray();

I made like this, converted a string s -> byte[] and then used Integer.toBinaryString to get binaryStringRep. I converted bianryStringRep by using Byte.parseByte to get the bianryStringRep into byte and the String(newByte[]) to get the byte[] into a String! Hope it helps others then me aswell! ^^
public class main{
public static void main(String[] args) throws UnsupportedEncodingException {
String s = "foo";
byte[] bytes = s.getBytes();
byte[] newBytes = new byte[s.getBytes().length];
for(int i = 0; i < bytes.length; i++){
String binaryStringRep = String.format("%8s", Integer.toBinaryString(bytes[i] & 0xFF)).replace(' ', '0');
byte newByte = Byte.parseByte(binaryStringRep, 2);
newBytes[i] = newByte;
}
String str = new String(newBytes, "UTF-8");
System.out.println(str);
}
}

How to autoconvert hexcode to use it as byte[] in Java?

I have many hexcodes here and I want to get them into Java without appending 0x to every entity. Like:
0102FFAB and I have to do the following:
byte[] test = {0x01, 0x02, 0xFF, 0xAB};
And I have many hexcodes which are pretty long. Is there any way to make this automatically?

You could try and put the hex codes into a string and then iterate over the string, similar to this:
String input = "0102FFAB";
byte[] bytes = new byte[input.length() / 2];
for( int i = 0; i < input.length(); i+=2)
{
bytes[i/2] = Integer.decode( "0x" + input.substring( i, i + 2 ) ).byteValue();
}
Note that this requires even length strings and it is quite a quick and dirty solution. However, it should still get you started.

You can use BigInteger to load a long hex string.
public static void main(String[] args) {
String hex = "c33b2cfca154c3a3362acfbde34782af31afb606f6806313cc0df40928662edd3ef1d630ab1b75639154d71ed490a36e5f51f6c9d270c4062e8266ad1608bdc496a70f6696fa6e7cd7078c6674188e8a49ecba71fad049a3d483ccac45d27aedfbb31d82adb8135238b858143492b1cbda2e854e735909256365a270095fc";
byte[] bytes2 = hexToBytes(hex);
for(byte b: bytes2)
System.out.printf("%02x", b & 0xFF);
}
public static byte[] hexToBytes(String hex) {
// add a 10 to the start to avoid sign issues, or an odd number of characters.
BigInteger bi2 = new BigInteger("10" +hex, 16);
byte[] bytes2 = bi2.toByteArray();
byte[] bytes = new byte[bytes2.length-1];
System.arraycopy(bytes2, 1, bytes, 0, bytes.length);
return bytes;
}
prints
0c33b2cfca154c3a3362acfbde34782af31afb606f6806313cc0df40928662edd3ef1d630ab1b75639154d71ed490a36e5f51f6c9d270c4062e8266ad1608bdc496a70f6696fa6e7cd7078c6674188e8a49ecba71fad049a3d483ccac45d27aedfbb31d82adb8135238b858143492b1cbda2e854e735909256365a270095fc
note: it handles the possibility that there is one hex value short at the start.

Translate a byte sequence given an InputStream

In Java, is there a library anywhere that will, given a byte sequence (preferable expressed as hex), translate to another byte sequence given an InputStream? For example:
InputStream input = new FileInputStream(new File(...));
OutputStream output = new FileOutputStream(new File(...));
String fromHex = "C3BEAB";
String toHex = "EAF6"
MyMagicLibrary.translate(fromHex, toHex, input, output)
So if the input file (in hex looked like)
00 00 12 18 33 C3 BE AB 00 23 C3 BE AB 00
after translation, the result would be
00 00 12 18 33 EA F6 00 23 EA F6 00

Once I did something like this (for trivially patching exe-files) using regexes. I read the whole input into a byte[] and converted into String using latin1, then did the substitution and converted back. It wasn't efficient but it didn't matter at all. You don't need regexes, simple String.replace would do.
But in your case it can be done quite simply and very efficiently:
int count = 0;
while (true) {
int n = input.read();
if (n == (fromAsByteArray[count] & 255)) {
++count;
if (count==fromAsByteArray.length) { // match found
output.write(toAsByteArray);
count = 0;
}
} else { // mismatch
output.write(fromAsByteArray, 0, count); // flush matching chars so far
count = 0;
if (n == -1) break;
output.write(n);
}
}
}

If u mean that u want to use a class whch translate from hex and to hex
here's two methods I usualluy use, u can put them inside a class and reuse it any where u want
public static String toHex(byte buf[]) {
StringBuffer strbuf = new StringBuffer(buf.length * 2);
int i;
for (i = 0; i < buf.length; i++) {
if (((int) buf[i] & 0xff) < 0x10) {
strbuf.append("0");
}
strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
}
return strbuf.toString();
}
public static byte[] fromHexString(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;
}
Actually I don't understand each line in the code, but I usually reuse them.

Since your input can have spaces then you first need to scrub your input to remove the spaces. After reading a pair of characters just use Byte.parseByte(twoCharString, 16) then use String.format to convert back to a String.
Doing it byte by byte would most likely be VERY inefficient, though easy to test. Once you get the result you want, you can tweak it by reading and parsing a whole buffer and spitting out more than one resulting byte a time, maybe 16 "byte" characters per line for formatting. It is all up to you at that point.

One way to implement this is to use IOUtils and String replace method.
public static void translate(byte[] fromHex, byte[] toHex, InputStream input, OutputStream output) throws IOException {
IOUtils.write(translate(fromHex, toHex, IOUtils.toByteArray(input)), output);
}
public static byte[] translate(byte[] fromHex, byte[] toHex, byte[] inBytes) throws UnsupportedEncodingException {
String inputText = new String(inBytes, "ISO-8859-1");
String outputText = inputText.replace(new String(fromHex, "ISO-8859-1"), new String(toHex, "ISO-8859-1"));
return outputText.getBytes("ISO-8859-1");
}