chore: Added PointerAddress class to decode a pointer address

Author: satran004

address/src/main/java/com/bloxbean/cardano/client/address/PointerAddress.java

@@ -0,0 +1,84 @@
+package com.bloxbean.cardano.client.address;
+
+import com.bloxbean.cardano.client.exception.AddressRuntimeException;
+import com.bloxbean.cardano.client.util.Tuple;
+
+import java.util.Arrays;
+
+/**
+ * PointerAddress class represents Shelley Pointer address. This class is useful to decode Pointer address and get the Pointer
+ */
+public class PointerAddress extends Address {
+    private Pointer pointer;
+
+    public PointerAddress(String prefix, byte[] bytes) {
+        super(prefix, bytes);
+
+        if (getAddressType() != AddressType.Ptr)
+            throw new AddressRuntimeException("Invalid address type. Expected Pointer address type");
+
+        decodePointer();
+    }
+
+    public PointerAddress(String address) {
+        super(address);
+
+        if (getAddressType() != AddressType.Ptr)
+            throw new AddressRuntimeException("Invalid address type. Expected Pointer address type");
+
+        decodePointer();
+    }
+
+    public PointerAddress(byte[] addressBytes) {
+        super(addressBytes);
+
+        if (getAddressType() != AddressType.Ptr)
+            throw new AddressRuntimeException("Invalid address type. Expected Pointer address type");
+
+        decodePointer();
+    }
+
+    private void decodePointer() {
+        byte[] pointerBytes = getDelegationCredentialHash()
+                .orElseThrow(() -> new AddressRuntimeException("Delegation credential hash not found"));
+
+        int index = 0;
+        Tuple<Long, Integer> slot = variableNatDecode(pointerBytes);
+        index += slot._2;
+        Tuple<Long, Integer> txIndex = variableNatDecode(getSubBytes(pointerBytes, index));
+        index += txIndex._2;
+        Tuple<Long, Integer> certIndex = variableNatDecode(getSubBytes(pointerBytes, index));
+
+        pointer = new Pointer(slot._1, txIndex._1.intValue(), certIndex._1.intValue());
+    }
+
+    private Tuple<Long, Integer> variableNatDecode(byte[] raw) {
+        long output = 0;
+        int bytesRead = 0;
+
+        for (byte rbyte : raw) {
+            output = (output << 7) | (rbyte & 0x7F);
+            bytesRead++;
+
+            if ((rbyte & 0x80) == 0) {
+                return new Tuple<>(output, bytesRead);
+            }
+        }
+
+        throw new IllegalArgumentException("Invalid variable nat encoding. Unexpected bytes");
+    }
+
+    // Get subarray from startPosition to the end of the array
+    private byte[] getSubBytes(byte[] array, int startPosition) {
+        // Validate startPosition
+        if (startPosition < 0 || startPosition > array.length) {
+            throw new IllegalArgumentException("Invalid start position");
+        }
+
+        return Arrays.copyOfRange(array, startPosition, array.length);
+    }
+
+    public Pointer getPointer() {
+        return pointer;
+    }
+}

address/src/test/java/com/bloxbean/cardano/client/address/PointerAddressTest.java

@@ -0,0 +1,26 @@
+package com.bloxbean.cardano.client.address;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class PointerAddressTest {
+
+    @Test
+    void getPointer() {
+        PointerAddress pointerAddress = new PointerAddress("addr1gx2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzer5ph3wczvf2w8lunk");
+        assertEquals(new Pointer(24157, 177, 42), pointerAddress.getPointer());
+    }
+
+    @Test
+    void getPointer2() {
+        PointerAddress pointerAddress = new PointerAddress("addr_test1gz2fxv2umyhttkxyxp8x0dlpdt3k6cwng5pxj3jhsydzerspqgpsqe70et");
+        assertEquals(new Pointer(1, 2, 3), pointerAddress.getPointer());
+    }
+
+    @Test
+    void getPointer3() {
+        PointerAddress pointerAddress = new PointerAddress("addr128phkx6acpnf78fuvxn0mkew3l0fd058hzquvz7w36x4gtupnz75xxcrtw79hu");
+        assertEquals(new Pointer(2498243, 27, 3), pointerAddress.getPointer());
+    }
+}