Hello stackoverflow community,
I need to convert a byte array to a binary byte-array (yes, binary bytes). See this example:
byte[] source = new byte[] {0x0A, 0x00};
//shall be converted to this:
byte[] target = new byte[] {0x00, 0x00, 0x10, 0x10, 0x00, 0x00, 0x00, 0x00};
//this would be ok as well:
also[0] = new byte[] {0x00, 0x00, 0x10, 0x10};
also[1] = new byte[] {0x00, 0x00, 0x00, 0x00};
At the moment I'm solving this by using Integer.toBinaryString to get the binary string and hexStringToByteArray to convert the binary string to a byte array:
for(int o = 0; o < cPage.getCpData().length; o+=cPage.getWidth()) {
String fBinString = "";
for(int u = 0; u < cPage.getWidth(); u++) {
byte[] value = new byte[1];
raBa.read(value);
Byte part = new BigInteger(value).byteValue();
String binString = Integer.toBinaryString(0xFF & part);
fBinString+=("00000000" + binString).substring(binString.length());
}
cPage.addBinaryString(fBinString);
//binaryCodepage.add(fBinString);
testwidth = fBinString.length();
//System.out.println(fBinString);
}
//other class:
public byte[][] getBinaryAsByteArray() {
Object[] binary = getBinaryStrings().toArray();
byte[][] binAsHex = new byte[binary.length][getWidth()*8];
for(int i = 0; i < binary.length; i++) {
binAsHex[i] = ByteUtil.hexStringToByteArray(((String) binary[i]));
}
return binAsHex;
}
This works fine for small source byte-arrays but takes ages for large byte-arrays. Thats probably caused by the conversion to binary String and back. Any ideas how to improve this by not converting the source to a String?
I don't know what's the motivation to this strange conversion, but you could do something similar to the implementation of Integer.toBinaryString :
private static byte[] toFourBytes(byte i) {
byte[] buf = new byte[4];
int bytePos = 4;
do {
buf[--bytePos] = i & 0x3;
i >>>= 2;
} while (i != 0);
return buf;
}
This should convert (I haven't tested it) each byte to a 4 byte array, in which each byte contains 2 bits of the original byte.
EDIT:
I may have missed the exact requirement. If the two bits extracted from the input byte should be in positions 0 and 4 of the output byte, the code would change to :
private static byte[] toFourBytes(byte i) {
byte[] buf = new byte[4];
int bytePos = 4;
do {
byte temp = i & 0x1;
i >>>= 1;
buf[--bytePos] = ((i & 0x1) << 4) | temp;
i >>>= 1;
} while (i != 0);
return buf;
}
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