Merge pull request #197 from ligi/ligi/code_review/speed_improvements

speed improvements, simplification and add test-cases

ethereumj-core/src/main/java/org/ethereum/util/ByteUtil.java

@@ -83,7 +83,7 @@ public class ByteUtil {
         int length = a.length < b.length ? a.length : b.length;
         while (i < length) {
             if (a[i] != b[i])
-                break;
+                return i;
             i++;
         }
         return i;
@@ -122,12 +122,11 @@ public class ByteUtil {
      */
     public static byte[] calcPacketLength(byte[] msg) {
         int msgLen = msg.length;
-        byte[] len = {
+        return new byte[]{
                 (byte) ((msgLen >> 24) & 0xFF),
                 (byte) ((msgLen >> 16) & 0xFF),
                 (byte) ((msgLen >> 8) & 0xFF),
                 (byte) ((msgLen) & 0xFF)};
-        return len;
     }
 
     /**
@@ -254,15 +253,12 @@ public class ByteUtil {
     }
 
     public static int firstNonZeroByte(byte[] data) {
-        int firstNonZero = -1;
-        int i = 0;
-        for (; i < data.length; ++i) {
+        for (int i = 0; i < data.length; ++i) {
             if (data[i] != 0) {
-                firstNonZero = i;
-                break;
+                return i;
             }
         }
-        return firstNonZero;
+        return -1;
     }
 
     public static byte[] stripLeadingZeroes(byte[] data) {
@@ -270,24 +266,21 @@ public class ByteUtil {
         if (data == null)
             return null;
 
-        int firstNonZero = firstNonZeroByte(data);
-        int i = 0;
-        for (; i < data.length; ++i) {
-            if (data[i] != 0) {
-                firstNonZero = i;
-                break;
-            }
-        }
-        if (i == data.length)
-            return new byte[1];
-        if (firstNonZero == 0)
+        final int firstNonZero = firstNonZeroByte(data);
+        switch (firstNonZero) {
+            case -1:
+                return EMPTY_BYTE_ARRAY;
+
+            case 0:
                 return data;
 
+            default:
                 byte[] result = new byte[data.length - firstNonZero];
                 System.arraycopy(data, firstNonZero, result, 0, data.length - firstNonZero);
 
                 return result;
         }
+    }
 
     /**
      * increment byte array as a number until max is reached

ethereumj-core/src/main/java/org/ethereum/vm/DataWord.java

@@ -32,16 +32,17 @@ public class DataWord implements Comparable<DataWord> {
     }
 
     public DataWord(int num) {
-        ByteBuffer bInt = ByteBuffer.allocate(4).putInt(num);
-        ByteBuffer data = ByteBuffer.allocate(32);
-        System.arraycopy(bInt.array(), 0, data.array(), 28, 4);
-        this.data = data.array();
+        this(ByteBuffer.allocate(4).putInt(num));
     }
 
     public DataWord(long num) {
-        ByteBuffer bLong = ByteBuffer.allocate(8).putLong(num);
-        ByteBuffer data = ByteBuffer.allocate(32);
-        System.arraycopy(bLong.array(), 0, data.array(), 24, 8);
+        this(ByteBuffer.allocate(8).putLong(num));
+    }
+
+    private DataWord(ByteBuffer buffer) {
+        final ByteBuffer data = ByteBuffer.allocate(32);
+        final byte[] array = buffer.array();
+        System.arraycopy(array, 0, data.array(), 32 - array.length, array.length);
         this.data = data.array();
     }
 
@@ -55,7 +56,7 @@ public class DataWord implements Comparable<DataWord> {
         else if (data.length <= 32)
             System.arraycopy(data, 0, this.data, 32 - data.length, data.length);
         else
-            throw new RuntimeException("Data word can't exit 32 bytes: " + data);
+            throw new RuntimeException("Data word can't exceed 32 bytes: " + data);
     }
 
     public byte[] getData() {
@@ -107,11 +108,10 @@ public class DataWord implements Comparable<DataWord> {
     }
 
     public boolean isZero() {
-        byte result = 0;
         for (byte tmp : data) {
-            result |= tmp;
+            if (tmp != 0) return false;
         }
-        return result == 0;
+        return true;
     }
 
     // only in case of signed operation
@@ -282,9 +282,8 @@ public class DataWord implements Comparable<DataWord> {
 
         DataWord dataWord = (DataWord) o;
 
-        if (!java.util.Arrays.equals(data, dataWord.data)) return false;
+        return java.util.Arrays.equals(data, dataWord.data);
 
-        return true;
     }
 
     @Override

ethereumj-core/src/test/java/test/ethereum/util/ByteUtilTest.java

@@ -100,11 +100,21 @@ public class ByteUtilTest {
 
     @Test
     public void testStripLeadingZeroes() {
-        byte[] test1 = new byte[]{0x00, 0x01};
-        byte[] test2 = new byte[]{0x00, 0x00, 0x01};
-        byte[] expected = new byte[]{0x01};
-        assertArrayEquals(expected, ByteUtil.stripLeadingZeroes(test1));
-        assertArrayEquals(expected, ByteUtil.stripLeadingZeroes(test2));
+        byte[] test1 = null;
+        byte[] test2 = new byte[]{};
+        byte[] test3 = new byte[]{0x00};
+        byte[] test4 = new byte[]{0x00, 0x01};
+        byte[] test5 = new byte[]{0x00, 0x00, 0x01};
+        byte[] expected1 = null;
+        byte[] expected2 = new byte[]{};
+        byte[] expected3 = new byte[]{};
+        byte[] expected4 = new byte[]{0x01};
+        byte[] expected5 = new byte[]{0x01};
+        assertArrayEquals(expected1, ByteUtil.stripLeadingZeroes(test1));
+        assertArrayEquals(expected2, ByteUtil.stripLeadingZeroes(test2));
+        assertArrayEquals(expected3, ByteUtil.stripLeadingZeroes(test3));
+        assertArrayEquals(expected4, ByteUtil.stripLeadingZeroes(test4));
+        assertArrayEquals(expected5, ByteUtil.stripLeadingZeroes(test5));
     }
 
     @Test