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Added get bits function for arrays

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This commit is contained in:
Ziver Koc 2016-04-15 17:13:36 +02:00
parent ccead35ee7
commit 542b242c41
2 changed files with 40 additions and 1 deletions
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28
src/zutil/ByteUtil.java
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@ -57,7 +57,18 @@ public class ByteUtil {
}
/**
* Creates a new sub byte from index and with a length
* Creates a new sub byte from index and with the given length length
*
* @param data is the byte data
* @param length is the length of bits to return, valid values 1-8
* @return a new byte containing a sub byte defined by the index and length
*/
public static byte getBits(byte data, int length){
return getBits(data, 0, length);
}
/**
* Creates a new sub byte from index and with the given length length
*
* @param data is the byte data
* @param index is the bit index, valid values 0-7
@ -69,6 +80,21 @@ public class ByteUtil {
return ret;
}
/**
* Creates a new sub byte array with only the given length of bits from the data array.
*
* @param data is the byte data array
* @param length is the length of bits to return
* @return a new byte array of te given length containing the given data.
*/
public static byte[] getBits(byte[] data, int length){
byte[] dest = new byte[(int) Math.ceil(length/8.0)];
System.arraycopy(data, 0, dest, 0, Math.min(data.length, dest.length));
if(length % 8 != 0)
dest[dest.length-1] = getBits(dest[dest.length-1], length % 8);
return dest;
}
/**
* Returns a byte bitmask
*

13
test/zutil/ByteUtilTest.java
View file

@ -26,6 +26,7 @@ package zutil;
import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
@ -45,4 +46,16 @@ public class ByteUtilTest {
assertEquals((byte)0xFF, ByteUtil.getShiftedBits((byte)0b1111_1111, 7, 8));
}
@Test
public void getBitsArray(){
assertArrayEquals(new byte[]{}, ByteUtil.getBits(new byte[]{0x00}, 0));
assertArrayEquals(new byte[]{0x00}, ByteUtil.getBits(new byte[]{}, 1));
assertArrayEquals(new byte[]{0x00,0x00,0x00,0x00}, ByteUtil.getBits(new byte[]{0x00}, 32));
assertArrayEquals(new byte[]{0x00}, ByteUtil.getBits(new byte[]{0x00,0x10}, 1));
assertArrayEquals(new byte[]{0x00}, ByteUtil.getBits(new byte[]{0x00,0x10}, 8));
assertArrayEquals(new byte[]{0x00,0x01}, ByteUtil.getBits(new byte[]{0x00,0x01}, 9));
assertArrayEquals(new byte[]{0x00,0x01}, ByteUtil.getBits(new byte[]{0x00,0x11}, 9));
}
}