From 9d6a3cc1e9047262d9202a74a707e7df59d44630 Mon Sep 17 00:00:00 2001
From: Mike Hearn <mike@plan99.net>
Date: Wed, 27 Feb 2013 15:18:38 +0100
Subject: [PATCH] Upgrade Guava and make a simple accessor for building
 cycle-detecting locks.

---
 core/pom.xml                                          |  2 +-
 core/src/main/java/com/google/bitcoin/core/Utils.java | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/core/pom.xml b/core/pom.xml
index c2356192..9596d958 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -184,7 +184,7 @@
         <dependency>
             <groupId>com.google.guava</groupId>
             <artifactId>guava</artifactId>
-            <version>11.0</version>
+            <version>13.0</version>
         </dependency>
     </dependencies>
 
diff --git a/core/src/main/java/com/google/bitcoin/core/Utils.java b/core/src/main/java/com/google/bitcoin/core/Utils.java
index c0b831c9..b52c75a2 100644
--- a/core/src/main/java/com/google/bitcoin/core/Utils.java
+++ b/core/src/main/java/com/google/bitcoin/core/Utils.java
@@ -16,6 +16,7 @@
 
 package com.google.bitcoin.core;
 
+import com.google.common.util.concurrent.CycleDetectingLockFactory;
 import org.spongycastle.crypto.digests.RIPEMD160Digest;
 import org.spongycastle.util.encoders.Hex;
 
@@ -27,6 +28,9 @@ import java.nio.charset.Charset;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.Date;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 
 import static com.google.common.base.Preconditions.checkArgument;
 
@@ -35,6 +39,12 @@ import static com.google.common.base.Preconditions.checkArgument;
  * To enable debug logging from the library, run with -Dbitcoinj.logging=true on your command line.
  */
 public class Utils {
+    private static CycleDetectingLockFactory lockFactory = CycleDetectingLockFactory.newInstance(CycleDetectingLockFactory.Policies.THROW);
+    /** Returns a cycle detecting re-entrant named lock. */
+    public static ReentrantLock lock(String name) {
+        return lockFactory.newReentrantLock(name);
+    }
+
     /** The string that prefixes all text messages signed using Bitcoin keys. */
     public static final String BITCOIN_SIGNED_MESSAGE_HEADER = "Bitcoin Signed Message:\n";