few optimizations on pruning

ethereumj-core/src/main/java/org/ethereum/crypto/HashUtil.java

@@ -26,6 +26,7 @@
 import org.spongycastle.crypto.Digest;
 import org.spongycastle.crypto.digests.RIPEMD160Digest;
 import org.spongycastle.util.encoders.Hex;
+
 import java.math.BigInteger;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
@@ -35,13 +36,12 @@
 
 import static java.util.Arrays.copyOfRange;
 import static org.ethereum.util.ByteUtil.EMPTY_BYTE_ARRAY;
-import static org.ethereum.util.ByteUtil.bigIntegerToBytes;
-import static org.ethereum.util.ByteUtil.bytesToBigInteger;
 
 public class HashUtil {
 
     private static final Logger LOG = LoggerFactory.getLogger(HashUtil.class);
 
+    private static final String[] HEX = hexDictionnary();
     public static final byte[] EMPTY_DATA_HASH;
     public static final byte[] EMPTY_LIST_HASH;
     public static final byte[] EMPTY_TRIE_HASH;
@@ -63,8 +63,7 @@ public class HashUtil {
     }
 
     /**
-     * @param input
-     *            - data for hashing
+     * @param input - data for hashing
      * @return - sha256 hash of the data
      */
     public static byte[] sha256(byte[] input) {
@@ -105,13 +104,10 @@ public static byte[] sha3(byte[] input1, byte[] input2) {
 
     /**
      * hashing chunk of the data
-     * 
-     * @param input
-     *            - data for hash
-     * @param start
-     *            - start of hashing chunk
-     * @param length
-     *            - length of hashing chunk
+     *
+     * @param input  - data for hash
+     * @param start  - start of hashing chunk
+     * @param length - length of hashing chunk
      * @return - keccak hash of the chunk
      */
     public static byte[] sha3(byte[] input, int start, int length) {
@@ -139,8 +135,7 @@ public static byte[] sha512(byte[] input) {
     }
 
     /**
-     * @param data
-     *            - message to hash
+     * @param data - message to hash
      * @return - reipmd160 hash of the message
      */
     public static byte[] ripemd160(byte[] data) {
@@ -157,9 +152,8 @@ public static byte[] ripemd160(byte[] data) {
     /**
      * Calculates RIGTMOST160(SHA3(input)). This is used in address
      * calculations. *
-     * 
-     * @param input
-     *            - data
+     *
+     * @param input - data
      * @return - 20 right bytes of the hash keccak of the data
      */
     public static byte[] sha3omit12(byte[] input) {
@@ -170,10 +164,8 @@ public static byte[] sha3omit12(byte[] input) {
     /**
      * The way to calculate new address inside ethereum
      *
-     * @param addr
-     *            - creating address
-     * @param nonce
-     *            - nonce of creating address
+     * @param addr  - creating address
+     * @param nonce - nonce of creating address
      * @return new address
      */
     public static byte[] calcNewAddr(byte[] addr, byte[] nonce) {
@@ -189,8 +181,8 @@ public static byte[] calcNewAddr(byte[] addr, byte[] nonce) {
      * sha3(0xff ++ msg.sender ++ salt ++ sha3(init_code)))[12:]
      *
      * @param senderAddr - creating address
-     * @param initCode - contract init code
-     * @param salt - salt to make different result addresses
+     * @param initCode   - contract init code
+     * @param salt       - salt to make different result addresses
      * @return new address
      */
     public static byte[] calcSaltAddr(byte[] senderAddr, byte[] initCode, byte[] salt) {
@@ -209,11 +201,9 @@ public static byte[] calcSaltAddr(byte[] senderAddr, byte[] initCode, byte[] sal
     }
 
     /**
-     * @see #doubleDigest(byte[], int, int)
-     *
-     * @param input
-     *            -
+     * @param input -
      * @return -
+     * @see #doubleDigest(byte[], int, int)
      */
     public static byte[] doubleDigest(byte[] input) {
         return doubleDigest(input, 0, input.length);
@@ -224,12 +214,9 @@ public static byte[] doubleDigest(byte[] input) {
      * resulting hash again. This is standard procedure in Bitcoin. The
      * resulting hash is in big endian form.
      *
-     * @param input
-     *            -
-     * @param offset
-     *            -
-     * @param length
-     *            -
+     * @param input  -
+     * @param offset -
+     * @param length -
      * @return -
      */
     public static byte[] doubleDigest(byte[] input, int offset, int length) {
@@ -272,7 +259,18 @@ public static byte[] randomHash() {
         return randomHash;
     }
 
+
     public static String shortHash(byte[] hash) {
-        return Hex.toHexString(hash).substring(0, 6);
+        return HEX[hash[0] & 0xFF]
+                + HEX[hash[1] & 0xFF]
+                + HEX[hash[2] & 0xFF];
+    }
+
+    private static String[] hexDictionnary() {
+        String[] values = new String[0xff + 0x1];
+        for (int i = 0; i <= 0xff; i++) {
+            values[i] = String.format("%02x", i & 0xFF);
+        }
+        return values;
     }
 }