com.plenigo.sdk.internal.util.HexUtils Maven / Gradle / Ivy
package com.plenigo.sdk.internal.util;
/**
*
* Provides different helper methods for working with hex encoding and decoding.
*
*
* IMPORTANT: This class is part of the internal API, please do not use it, because it can
* be removed in future versions of the SDK or access to such elements could
* be changed from 'public' to 'default' or less.
*
*
* Thread safety: This class is thread safe and can be injected.
*
*/
public final class HexUtils {
/**
* This is the fill needed when
* shifting during hex encoding.
*/
private static final int FOUR_DIGIT_FILL = 4;
/**
* This TWO char binary is used to decode
* every byte.
*/
private static final int BINARY_TWO_CHAR = 0xFF;
/**
* This is the ending binary number range used during hex encoding.
*/
private static final int ENDING_HX = 0x0F;
/**
* This is the starting binary number range used during hex encoding.
*/
private static final int STARTING_HX = 0xF0;
/**
* The array used for hexing all the characters.
*/
private static final char[] DIGITS_LOWER = {'0', '1', '2', '3', '4', '5',
'6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
/**
* Default constructor.
*/
private HexUtils() {
}
/**
* This method decodes hexadecimal data
* that is being contained in a char array.
*
* @param hexedString String of hexed characters
*
* @return decoded data as a byte array
*/
public static byte[] decodeHex(String hexedString) {
final char[] data = hexedString.toCharArray();
final int len = data.length;
if ((len & 0x01) != 0) {
throw new IllegalArgumentException("Odd number of characters.");
}
final byte[] out = new byte[len >> 1];
// two characters form the hex value.
for (int i = 0, j = 0; j < len; i++) {
int f = toDigit(data[j], j) << FOUR_DIGIT_FILL;
j++;
f = f | toDigit(data[j], j);
j++;
out[i] = (byte) (f & BINARY_TWO_CHAR);
}
return out;
}
/**
* This method encodes a byte array into a
* hexed string.
*
* @param data The data to encode
*
* @return A Hexadecimal encoded string.
*/
public static String encodeHexString(final byte[] data) {
final int l = data.length;
StringBuilder out = new StringBuilder(l << 1);
// two characters form the hex value.
for (byte aData : data) {
out.append(DIGITS_LOWER[(STARTING_HX & aData)
>>> FOUR_DIGIT_FILL]);
out.append(DIGITS_LOWER[ENDING_HX & aData]);
}
return out.toString();
}
/**
* Converts a character into a hexadecimal number.
*
* @param ch The character to convert
* @param index The index of the character in the array.
*
* @return a Digit representing the hexadecimal character.
*/
private static int toDigit(final char ch, final int index) {
final int digit = Character.digit(ch, 16);
if (digit == -1) {
throw new IllegalArgumentException("Illegal hexadecimal character "
+ ch + " at index " + index);
}
return digit;
}
}