Fix Sha256Hash hashcode function.

Delete wallet deserialization unit test, as we now consciously are breaking serialization compatibility. Resolves issue 213.

core/src/main/java/com/google/bitcoin/core/Sha256Hash.java

@@ -31,42 +31,9 @@ import static com.google.common.base.Preconditions.checkArgument;
  * map. It also checks that the length is correct and provides a bit more type safety.
  */
 public class Sha256Hash implements Serializable {
-    private static final long serialVersionUID = 3778897922647016546L;
-
     private byte[] bytes;
-    private int hash = -1;
-
-    /**
-     * @see setHashcodeByteLength(int hashcodeByteLength)
-     */
-    private static int HASHCODE_BYTES_TO_CHECK = 5;
-    private static boolean HASHCODE_BYTES_TO_CHECK_CHANGED = false;
-
-
     public static final Sha256Hash ZERO_HASH = new Sha256Hash(new byte[32]);
 
-    /**
-     * Alters the number of bytes from the backing array to use when generating java hashCodes.
-     * <br/><br/>
-     * The default value of 5 gives approximately 1 trillion possible unique combinations.
-     * Given that an int hashcode only has 4 billion possible values it should be more than enough.
-     * <br/><br/>
-     * Changing this value after Sha256Hashes have been stored in hashed collections breaks the
-     * hashCode contract and will result in unpredictable behaviour.  If this
-     * needs to be set to a different value it should be done once and only once
-     * and before any calls to hashCode() are made on any instance of Sha256Hash instances.
-     * <br/>
-     *
-     * @param hashcodeByteLength the number of bytes in the hash to use for generating the hashcode.
-     * @throws IllegalStateException if called more than once.
-     */
-    public static void setHashcodeByteLength(int hashcodeByteLength) {
-        if (HASHCODE_BYTES_TO_CHECK_CHANGED)
-            throw new IllegalStateException("setHashcodeByteLength can only be called once and should be called before any instances of Sha256Hash are constructed");
-        HASHCODE_BYTES_TO_CHECK = hashcodeByteLength;
-        HASHCODE_BYTES_TO_CHECK_CHANGED = true;
-    }
-
     /**
      * Creates a Sha256Hash by wrapping the given byte array. It must be 32 bytes long.
      */
@@ -76,12 +43,6 @@ public class Sha256Hash implements Serializable {
 
     }
 
-    private Sha256Hash(byte[] bytes, int hash) {
-        checkArgument(bytes.length == 32);
-        this.bytes = bytes;
-        this.hash = hash;
-    }
-
     /**
      * Creates a Sha256Hash by decoding the given hex string. It must be 64 characters long.
      */
@@ -118,12 +79,8 @@ public class Sha256Hash implements Serializable {
      */
     @Override
     public int hashCode() {
-        if (hash == -1) {
-            hash = 1;
-            for (int i = 0; i < HASHCODE_BYTES_TO_CHECK; i++)
-                hash = 31 * hash + bytes[i];
-        }
-        return hash;
+        // Use the last 4 bytes, not the first 4 which are often zeros in Bitcoin.
+        return (bytes[31] & 0xFF) | ((bytes[30] & 0xFF) << 8) | ((bytes[29] & 0xFF) << 16) | ((bytes[28] & 0xFF) << 24);
     }
 
     @Override
@@ -143,6 +100,6 @@ public class Sha256Hash implements Serializable {
     }
 
     public Sha256Hash duplicate() {
-        return new Sha256Hash(bytes, hash);
+        return new Sha256Hash(bytes);
     }
 }

core/src/test/java/com/google/bitcoin/core/WalletTest.java

@@ -19,18 +19,13 @@ package com.google.bitcoin.core;
 import com.google.bitcoin.core.WalletTransaction.Pool;
 import com.google.bitcoin.store.BlockStore;
 import com.google.bitcoin.store.MemoryBlockStore;
-import com.google.bitcoin.store.WalletProtobufSerializer;
 import com.google.bitcoin.utils.BriefLogFormatter;
 import org.junit.Before;
 import org.junit.Test;
 
-import java.io.ByteArrayInputStream;
-import java.io.ByteArrayOutputStream;
-import java.io.InputStream;
 import java.math.BigInteger;
 import java.util.HashSet;
 import java.util.List;
-import java.util.Set;
 
 import static com.google.bitcoin.core.TestUtils.*;
 import static com.google.bitcoin.core.Utils.bitcoinValueToFriendlyString;
@@ -622,37 +617,6 @@ public class WalletTest {
         assertNull(tx1.appearsIn);
     }
 
-    @Test
-    public void oldWalletsDeserialize() throws Exception {
-        // Check that the Wallet class fills out tx confidences as best it can when loading old wallets. The new
-        // API provides a superset of the info that used to be available so it's impossible to do a complete
-        // migration but we can do some.
-        //
-        // TODO: This test does not check migration of dead or pending transactions.
-        InputStream stream = getClass().getResourceAsStream("old1.wallet");
-        wallet = Wallet.loadFromFileStream(stream);
-        Set<Transaction> transactions = wallet.getTransactions(true, true);
-        assertEquals(91, transactions.size());
-        Transaction tx = wallet.unspent.get(new Sha256Hash("5649c63ad55002ce2f39d1d4744996ebaccc1d15e0491c9e8d60eb3720dabebd"));
-        assertEquals(tx.getAppearsInHashes().iterator().next(), new Sha256Hash("00000000019380f5aef28393827737f55a1cf8abb51a36d46ab6f2db0a5b9cb8"));
-        assertEquals(TransactionConfidence.ConfidenceType.BUILDING, tx.getConfidence().getConfidenceType());
-        assertEquals(42814, tx.getConfidence().getAppearedAtChainHeight());
-
-        // Re-serialize the wallet. Make sure it's all still there.
-        ByteArrayOutputStream bios = new ByteArrayOutputStream();
-        wallet.saveToFileStream(bios);
-        wallet = Wallet.loadFromFileStream(new ByteArrayInputStream(bios.toByteArray()));
-        assertEquals(91, transactions.size());
-        tx = wallet.unspent.get(new Sha256Hash("5649c63ad55002ce2f39d1d4744996ebaccc1d15e0491c9e8d60eb3720dabebd"));
-        assertEquals(tx.getAppearsInHashes().iterator().next(), new Sha256Hash("00000000019380f5aef28393827737f55a1cf8abb51a36d46ab6f2db0a5b9cb8"));
-        assertEquals(TransactionConfidence.ConfidenceType.BUILDING, tx.getConfidence().getConfidenceType());
-        assertEquals(42814, tx.getConfidence().getAppearedAtChainHeight());
-
-        // Now check we can serialize old wallets to protocol buffers. Covers bug 134.
-        bios.reset();
-        new WalletProtobufSerializer().writeWallet(wallet, bios);
-    }
-
     @Test
     public void spendToSameWallet() throws Exception {
         // Test that a spend to the same wallet is dealt with correctly.