[HexUtils] Add a couple more methods (openhab#5164)

* [HexUtils] Add a couple of methods

Signed-off-by: Andrew Fiddian-Green <software@whitebear.ch>

Author: andrewfg

bundles/org.openhab.core/src/main/java/org/openhab/core/util/HexUtils.java

@@ -12,6 +12,7 @@
  */
 package org.openhab.core.util;
 
+import java.math.BigInteger;
 import java.nio.charset.StandardCharsets;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
@@ -123,6 +124,47 @@ public static byte[] hexToBytes(String hexString) {
         return hexToBytes(hexString, "(?<=\\G.{2})");
     }
 
+    /**
+     * Convert a white space delimited hex block to a byte array.
+     *
+     * @param hexBlock the hex block
+     * @return the byte array
+     * @throws IllegalArgumentException if a value is invalid
+     */
+    public static byte[] hexBlockToBytes(String hexBlock) throws IllegalArgumentException {
+        String plainHex = hexBlock.replaceAll("\\s+", "");
+        if (plainHex.length() % 2 != 0) {
+            throw new IllegalArgumentException("Hex string must have even length");
+        }
+        int length = plainHex.length();
+        byte[] result = new byte[length / 2];
+        for (int i = 0; i < length; i += 2) {
+            int hi = Character.digit(plainHex.charAt(i), 16);
+            int lo = Character.digit(plainHex.charAt(i + 1), 16);
+            if (hi == -1 || lo == -1) {
+                throw new IllegalArgumentException(
+                        "Invalid hex character: " + plainHex.charAt(i) + plainHex.charAt(i + 1));
+            }
+            result[i / 2] = (byte) ((hi << 4) + lo);
+        }
+        return result;
+    }
+
+    /**
+     * Convert a white space delimited hex block to a {@link BigInteger}.
+     *
+     * @param hexBlock the hex block
+     * @return the BigInteger value
+     * @throws IllegalArgumentException if a value is invalid
+     */
+    public static BigInteger hexBlockToBigInteger(String hexBlock) throws IllegalArgumentException {
+        String plainHex = hexBlock.replaceAll("\\s+", "");
+        if (plainHex.length() % 2 != 0) {
+            throw new IllegalArgumentException("Hex string must have even length");
+        }
+        return new BigInteger(plainHex, 16);
+    }
+
     public static byte hexToByte(byte high, byte low) {
         return (byte) ((unhex(high) << 4) | unhex(low));
     }

bundles/org.openhab.core/src/test/java/org/openhab/core/util/HexUtilsTest.java

@@ -14,6 +14,8 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 
+import java.math.BigInteger;
+
 import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.junit.jupiter.api.Test;
 
@@ -72,4 +74,24 @@ public void testEmptyByteArray() {
         final byte[] output = HexUtils.hexToBytes(str);
         assertArrayEquals(input, output);
     }
+
+    @Test
+    public void testHexBlockToBytes() {
+        final String input = """
+                0000 0000
+                    F00f
+                                """;
+        final byte[] output = HexUtils.hexBlockToBytes(input);
+        assertArrayEquals(new byte[] { 0, 0, 0, 0, (byte) 240, (byte) 15 }, output);
+    }
+
+    @Test
+    public void hexBlockToBigInteger() {
+        final String input = """
+                0000 0000
+                    F00f
+                                """;
+        final BigInteger output = HexUtils.hexBlockToBigInteger(input);
+        assertEquals(new BigInteger("61455"), output);
+    }
 }