Replace GasLedger with Gas enum class

ethereumj-core/src/main/java/org/ethereum/core/Block.java

@@ -9,6 +9,8 @@ import org.ethereum.util.RLPElement;
 import org.ethereum.util.RLPList;
 import org.spongycastle.util.BigIntegers;
 
+import edu.emory.mathcs.backport.java.util.Arrays;
+
 import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.List;
@@ -320,7 +322,7 @@ public class Block {
 	}
 	
 	public byte[] calcDifficulty() {
-		if (this.header.getParentHash() == null)
+		if (Arrays.equals(this.header.getParentHash(), Genesis.PARENT_HASH))
 			return Genesis.DIFFICULTY;
 		else {
 			Block parent = this.getParent();

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

@@ -0,0 +1,33 @@
+package org.ethereum.vm;
+
+/**
+ * The fundamental network cost unit. Paid for exclusively by Ether, which is converted 
+ * freely to and from Gas as required. Gas does not exist outside of the internal Ethereum 
+ * computation engine; its price is set by the Transaction and miners are free to 
+ * ignore Transactions whose Gas price is too low.
+ */
+public enum Gas {
+
+	G_STEP(1),
+	G_STOP(0),
+	G_SUICIDE(0),
+	G_SLOAD(20),
+	G_SHA3(20),
+	G_SSTORE(100),
+	G_BALANCE(20),
+	G_CREATE(100),
+	G_CALL(20),					 
+	G_MEMORY(1),
+	G_TXDATA(5),
+	G_TRANSACTION(500);
+			 
+	private int cost;
+	
+	private Gas(int value) {
+		this.cost = value;
+	}
+	
+	public int cost() {
+		return cost;
+	}
+}

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

@@ -1,41 +0,0 @@
-package org.ethereum.vm;
-
-import java.util.HashMap;
-
-/**
- * www.ethereumJ.com
- * User: Roman Mandeleil
- * Created on: 04/06/2014 23:58
- */
-
-public class GasLedger {
-
-/*  YP Appendix B.
-    Gstep 1 Default amount of gas to pay for execution cycle.
-    Gstop 0 Nothing paid for the STOP operation.
-    Gsuicide 0 Nothing paid for the SUICIDE operation.
-    Gsha3 20 Paid for a SHA3 operation.
-    Gsload 20 Paid for a SLOAD operation.
-    Gsstore 100 Paid for a normal SSTORE operation (doubled or waived sometimes).
-    Gbalance 20 Paid for a BALANCE operation.
-    Gcreate 100 Paid for a CREATE operation.
-    Gcall 20 Paid for a CALL operation.
-    Gmemory 1 Paid for every additional word when expanding memory.
-    Gtxdata 5 Paid for every byte of data or code for a transaction.
-    Gtransaction 500 Paid for every transaction.
- */
-
-
-    public static int G_STEP    = 1;
-    public static int G_STOP    = 0;
-    public static int G_SUICIDE = 0;
-    public static int G_SLOAD   = 20;
-    public static int G_SHA3    = 20;
-    public static int G_SSTORE  = 100;
-    public static int G_BALANCE = 20;
-    public static int G_CREATE  = 100;
-    public static int G_CALL    = 20;
-    public static int G_MEMORY  = 1;
-    public static int G_TXDATA  = 5;
-    public static int G_TRANSACTION = 500;
-}

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

@@ -8,6 +8,7 @@ import java.math.BigInteger;
 import java.nio.ByteBuffer;
 
 import static org.ethereum.vm.OpCode.PUSH1;
+import static org.ethereum.vm.Gas.*;
 
 /**
  * www.ethereumJ.com
@@ -34,23 +35,23 @@ public class VM {
 
             switch (OpCode.code(op)) {
                 case SHA3:
-                   program.spendGas( GasLedger.G_SHA3 );
+                   program.spendGas(G_SHA3.cost());
                 break;
                 case SLOAD:
-                    program.spendGas( GasLedger.G_SLOAD );
+                    program.spendGas(G_SLOAD.cost());
                 break;
                 case SSTORE:
                     // todo: calc gas in the execution
                     // todo: according to the size
                 break;
                 case BALANCE:
-                    program.spendGas( GasLedger.G_BALANCE );
+                    program.spendGas(G_BALANCE.cost());
                 break;
                 case CREATE:
-                    program.spendGas( GasLedger.G_CREATE );
+                    program.spendGas(G_CREATE.cost());
                 break;
                 case CALL:
-                    program.spendGas( GasLedger.G_CALL );
+                    program.spendGas(G_CALL.cost());
                 break;
                 case MSTORE8:
                 case MSTORE:
@@ -58,7 +59,7 @@ public class VM {
                     // todo: according to the size
                 break;
                 default:
-                    program.spendGas( GasLedger.G_STEP );
+                    program.spendGas( G_STEP.cost() );
                 break;
             }
 
@@ -472,11 +473,11 @@ public class VM {
                     DataWord oldValue =  program.storageLoad(addr);
                     program.storageSave(addr, value);
                     if (oldValue == null && !value.isZero()){
-                        program.spendGas(GasLedger.G_SSTORE * 2);
+                        program.spendGas(G_SSTORE.cost() * 2);
                     } else if (oldValue != null && value.isZero()){
-                        program.spendGas(GasLedger.G_SSTORE * 0);
+                        program.spendGas(G_SSTORE.cost() * 0);
                     } else
-                        program.spendGas(GasLedger.G_SSTORE);
+                        program.spendGas(G_SSTORE.cost());
 
                     program.step();
                 }
@@ -554,7 +555,7 @@ public class VM {
 
                 // memory gas calc
                 int newMemSize = program.getMemSize();
-                program.spendGas(GasLedger.G_MEMORY * (newMemSize - oldMemSize) /32);
+                program.spendGas(G_MEMORY.cost() * (newMemSize - oldMemSize) /32);
             }
             program.fullTrace();
         } catch (RuntimeException e) {

ethereumj-core/src/test/java/org/ethereum/core/BlockTest.java

@@ -1,5 +1,7 @@
 package org.ethereum.core;
 
+import java.math.BigInteger;
+
 import org.ethereum.net.message.BlocksMessage;
 import org.ethereum.net.message.StaticMessages;
 import org.ethereum.util.RLPList;
@@ -89,7 +91,10 @@ public class BlockTest {
     
     @Test
     public void testCalcDifficulty() {
-    	// Block.calcDifficulty()
+    	Block genesis = Genesis.getInstance();
+    	byte[] diffBytes = genesis.calcDifficulty();
+    	BigInteger difficulty = new BigInteger(1, diffBytes);
+    	System.out.println(difficulty.toString());
     	fail("Yet to be implemented.");
     }