Mega Code Archive
Byte value conversion
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//package edu.cmu.ri.createlab.util;
/**
*
* @author BILL
*/
final class ByteUtils {
public static int unsignedByteToInt(final byte b) {
return b & 0xff;
}
/**
* Converts a <code>short</code> which should be treated as unsigned to an
* <code>int</code> having a range of [0, 65535].
*/
public static int unsignedShortToInt(final short b) {
return b & 0xffff;
}
/**
* Converts the given two <code>bytes</code>s to a <code>short</code>.
*/
public static short bytesToShort(final byte highByte, final byte lowByte) {
final short high = (short) (highByte & 0xff);
final short low = (short) (lowByte & 0xff);
return (short) (high << 8 | low);
}
/**
* Converts the given <code>int</code> to an unsigned <code>byte</code> by
* ensuring it is within the range of [0, 255] using the following rules:
* <ul>
* <li>If the given <code>int</code> is already within the range [0, 255],
* then it is simply cast to a <code>byte</code> and returned.</li>
* <li>If the given <code>int</code> is negative, this method returns a
* <code>byte</code> of 0.</li>
* <li>If the given <code>int</code> is greater than 255, this method
* returns a <code>byte</code> of 255 (i.e. the value 255 cast to a byte).</li>
* </ul>
*/
public static byte intToUnsignedByte(final int i) {
if (i < 0) {
return 0;
} else if (i > 255) {
return (byte) 255;
}
return (byte) i;
}
/**
* <p>
* Converts the bytes specified by <code>offset</code> and
* <code>length</code> in the given array of bytes containing ASCII hex
* values to an array of bytes. For example, if the given array was created
* like this:
* </p>
* <blockquote>
* <code>final byte[] asciiHexBytes = new byte[]{48, 48, 48, 48, 51, 51, 48, 48, 48, 70, 48, 48, 48, 48, 50, 51, 48, 48, 48, 48, 48, 49, 70, 70};</code>
* </blockquote>
* <p>
* ...or, equivalently, like this...
* </p>
* <blockquote>
* <code>final byte[] asciiHexBytes = "000033000F000023000001FF".getBytes();</code>
* </blockquote>
* <p>
* ...then this method would convert the hex values (
* <code>00 00 33 00 0F 00 00 23 00 00 01 FF</code>) to bytes and return the
* a byte array equal to the following:
* </p>
* <blockquote>
* <code>final byte[] byteArray4 = new byte[]{0,0,51,0,15,0,0,35,0,0,1,-1}</code>
* </blockquote>
* <p>
* Returns <code>null</code> if the given array is <code>null</code> .
* </p>
*
* @throws IllegalArgumentException
* if the <code>length</code> is negative or odd
* @throws ArrayIndexOutOfBoundsException
* if the <code>offset</code> is negative or out of bounds, or
* if the sum of the <code>offset</code> and the
* <code>length</code> is greater than the length of the given
* array
*/
public static byte[] asciiHexBytesToByteArray(final byte[] asciiHexBytes,
final int offset, final int length) {
if (asciiHexBytes != null) {
if (offset < 0) {
throw new ArrayIndexOutOfBoundsException(
"Offset cannot be negative.");
}
if (offset >= asciiHexBytes.length) {
throw new ArrayIndexOutOfBoundsException(
"Offset is out of bounds.");
}
if (length < 0) {
throw new IllegalArgumentException("Length cannot be negative.");
}
if (length % 2 != 0) {
throw new IllegalArgumentException("Length must be even.");
}
if (offset + length > asciiHexBytes.length) {
throw new ArrayIndexOutOfBoundsException(
"Specified length is too long, not enough elements.");
}
// do the conversion (code based on
// http://mindprod.com/jgloss/hex.html)
final byte[] output = new byte[length / 2];
for (int i = offset, j = 0; i < offset + length; i += 2, j++) {
final int high = charToNibble((char) asciiHexBytes[i]);
final int low = charToNibble((char) asciiHexBytes[i + 1]);
output[j] = (byte) ((high << 4) | low);
}
return output;
}
return null;
}
/**
* <p>
* Converts the given array of bytes containing ASCII hex values to an array
* of bytes. For example, if the given array was created like this:
* </p>
* <blockquote>
* <code>final byte[] asciiHexBytes = new byte[]{48, 48, 48, 48, 51, 51, 48, 48, 48, 70, 48, 48, 48, 48, 50, 51, 48, 48, 48, 48, 48, 49, 70, 70};</code>
* </blockquote>
* <p>
* ...or, equivalently, like this...
* </p>
* <blockquote>
* <code>final byte[] asciiHexBytes = "000033000F000023000001FF".getBytes();</code>
* </blockquote>
* <p>
* ...then this method would convert the hex values (
* <code>00 00 33 00 0F 00 00 23 00 00 01 FF</code>) to bytes and return the
* a byte array equal to the following:
* </p>
* <blockquote>
* <code>final byte[] byteArray4 = new byte[]{0,0,51,0,15,0,0,35,0,0,1,-1}</code>
* </blockquote>
* <p>
* Returns <code>null</code> if the given array is <code>null</code> .
* </p>
*
* @throws IllegalArgumentException
* if the given array does not have an even number of bytes
*/
public static byte[] asciiHexBytesToByteArray(final byte[] asciiHexBytes) {
if (asciiHexBytes != null) {
return asciiHexBytesToByteArray(asciiHexBytes, 0,
asciiHexBytes.length);
}
return null;
}
/**
* Converts the given byte to a (zero-padded, if necessary) hex
* {@link String}.
*/
public static String byteToHexString(final byte b) {
final String s = Integer.toHexString(ByteUtils.unsignedByteToInt(b));
return (s.length() == 1) ? "0" + s : s;
}
private static final byte[] CORRESPONDING_NIBBLE = new byte['f' + 1];
static {
// only 0..9 A..F a..f have meaning. rest are errors.
for (int i = 0; i <= 'f'; i++) {
CORRESPONDING_NIBBLE[i] = -1;
}
for (int i = '0'; i <= '9'; i++) {
CORRESPONDING_NIBBLE[i] = (byte) (i - '0');
}
for (int i = 'A'; i <= 'F'; i++) {
CORRESPONDING_NIBBLE[i] = (byte) (i - 'A' + 10);
}
for (int i = 'a'; i <= 'f'; i++) {
CORRESPONDING_NIBBLE[i] = (byte) (i - 'a' + 10);
}
}
private static int charToNibble(final char c) {
if (c > 'f') {
throw new IllegalArgumentException("Invalid hex character: " + c);
}
final int nibble = CORRESPONDING_NIBBLE[c];
if (nibble < 0) {
throw new IllegalArgumentException("Invalid hex character: " + c);
}
return nibble;
}
private ByteUtils() {
// private to prevent instantiation
}
}
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