From 5aeade32e2fda3a888e39fc471214559a4db0258 Mon Sep 17 00:00:00 2001
From: nicksavers <nicksavers@gmail.com>
Date: Thu, 6 Nov 2014 00:05:57 +0100
Subject: [PATCH] Add SIGNEXTEND op code

---
 .../main/java/org/ethereum/vm/DataWord.java   | 11 ++-
 .../src/main/java/org/ethereum/vm/VM.java     | 13 +++
 .../java/org/ethereum/vm/DataWordTest.java    | 82 +++++++++++++++++++
 3 files changed, 105 insertions(+), 1 deletion(-)

diff --git a/ethereumj-core/src/main/java/org/ethereum/vm/DataWord.java b/ethereumj-core/src/main/java/org/ethereum/vm/DataWord.java
index 517caa12..acceac26 100644
--- a/ethereumj-core/src/main/java/org/ethereum/vm/DataWord.java
+++ b/ethereumj-core/src/main/java/org/ethereum/vm/DataWord.java
@@ -278,7 +278,7 @@ public class DataWord implements Comparable<DataWord> {
 
         return true;
     }
-
+    
     @Override
     public int hashCode() {
         return java.util.Arrays.hashCode(data);
@@ -293,4 +293,13 @@ public class DataWord implements Comparable<DataWord> {
         // Convert result into -1, 0 or 1 as is the convention
         return (int) Math.signum(result);
     }
+
+	public void signExtend(byte k) {
+		if (k > 31)
+			throw new IndexOutOfBoundsException();
+		byte mask = this.sValue().testBit((k * 8) + 7) ? (byte) 0xff : 0;
+		for (int i = 31; i > k; i--) {
+			this.data[31 - i] = mask;
+		}
+	}
 }
\ No newline at end of file
diff --git a/ethereumj-core/src/main/java/org/ethereum/vm/VM.java b/ethereumj-core/src/main/java/org/ethereum/vm/VM.java
index f109c8b4..6389dc2b 100644
--- a/ethereumj-core/src/main/java/org/ethereum/vm/VM.java
+++ b/ethereumj-core/src/main/java/org/ethereum/vm/VM.java
@@ -280,6 +280,19 @@ public class VM {
                     program.stackPush(word1);
                     program.step();
                 }	break;
+                case SIGNEXTEND: {
+                    DataWord word1 = program.stackPop();
+                    BigInteger k = word1.value();
+
+                    if (k.compareTo(_32_) < 0) {
+                        DataWord word2 = program.stackPop();
+                        if (logger.isInfoEnabled())
+                            hint = word1 + "  " + word2.value();
+                        word2.signExtend(k.byteValue());
+                        program.stackPush(word2);
+                    }
+                    program.step();
+                }   break;
                 case NOT:{
                 	DataWord word1 = program.stackPop();
                     word1.bnot();
diff --git a/ethereumj-core/src/test/java/org/ethereum/vm/DataWordTest.java b/ethereumj-core/src/test/java/org/ethereum/vm/DataWordTest.java
index 0935cf06..5373a0b4 100644
--- a/ethereumj-core/src/test/java/org/ethereum/vm/DataWordTest.java
+++ b/ethereumj-core/src/test/java/org/ethereum/vm/DataWordTest.java
@@ -134,6 +134,88 @@ public class DataWordTest {
 		System.out.println(result2);
 	}
 	
+	@Test
+	public void testSignExtend1() {
+
+		DataWord x = new DataWord(Hex.decode("f2"));
+		byte k = 0;
+		String expected = "fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff2";
+
+		x.signExtend(k);
+		System.out.println(x.toString());
+		assertEquals(expected, x.toString());
+	}
+
+	@Test
+	public void testSignExtend2() {
+		DataWord x = new DataWord(Hex.decode("f2"));
+		byte k = 1;
+		String expected = "00000000000000000000000000000000000000000000000000000000000000f2";
+
+		x.signExtend(k);
+		System.out.println(x.toString());
+		assertEquals(expected, x.toString());
+	}
+
+	@Test
+	public void testSignExtend3() {
+
+		byte k = 1;
+		DataWord x = new DataWord(Hex.decode("0f00ab"));
+		String expected = "00000000000000000000000000000000000000000000000000000000000000ab";
+
+		x.signExtend(k);
+		System.out.println(x.toString());
+		assertEquals(expected, x.toString());
+	}
+
+	@Test
+	public void testSignExtend4() {
+
+		byte k = 1;
+		DataWord x = new DataWord(Hex.decode("ffff"));
+		String expected = "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";
+
+		x.signExtend(k);
+		System.out.println(x.toString());
+		assertEquals(expected, x.toString());
+	}
+
+	@Test
+	public void testSignExtend5() {
+
+		byte k = 3;
+		DataWord x = new DataWord(Hex.decode("ffffffff"));
+		String expected = "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";
+
+		x.signExtend(k);
+		System.out.println(x.toString());
+		assertEquals(expected, x.toString());
+	}
+
+	@Test
+	public void testSignExtend6() {
+
+		byte k = 3;
+		DataWord x = new DataWord(Hex.decode("ab02345678"));
+		String expected = "0000000000000000000000000000000000000000000000000000000002345678";
+
+		x.signExtend(k);
+		System.out.println(x.toString());
+		assertEquals(expected, x.toString());
+	}
+
+	@Test
+	public void testSignExtend7() {
+
+		byte k = 3;
+		DataWord x = new DataWord(Hex.decode("ab82345678"));
+		String expected = "ffffffffffffffffffffffffffffffffffffffffffffffffffffffff82345678";
+
+		x.signExtend(k);
+		System.out.println(x.toString());
+		assertEquals(expected, x.toString());
+	}
 	
 	public static BigInteger pow(BigInteger x, BigInteger y) {
 		if (y.compareTo(BigInteger.ZERO) < 0)