From f6a6c6e577f34867c5f3c0235787bbe825f80e6b Mon Sep 17 00:00:00 2001
From: Hairong Kuang <hairong@apache.org>
Date: Thu, 28 Oct 2010 18:49:39 +0000
Subject: [PATCH] HADOOP-7009. MD5Hash provides a public factory method that
 creates an instance of MessageDigest. Contributed by Hairong Kuang.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1028427 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES.txt                                |  3 +++
 src/java/org/apache/hadoop/io/MD5Hash.java | 11 +++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 78f40c82e50..f2616e5db38 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -152,6 +152,9 @@ Trunk (unreleased changes)
 
     HADOOP-7010. Typo in FileSystem.java. (Jingguo Yao via eli)
 
+    HADOOP-7009. MD5Hash provides a public factory method that creates an
+    instance of thread local MessageDigest. (hairong)
+
   OPTIMIZATIONS
 
     HADOOP-6884. Add LOG.isDebugEnabled() guard for each LOG.debug(..).
diff --git a/src/java/org/apache/hadoop/io/MD5Hash.java b/src/java/org/apache/hadoop/io/MD5Hash.java
index 4e358fd9bb2..f19f8db12c9 100644
--- a/src/java/org/apache/hadoop/io/MD5Hash.java
+++ b/src/java/org/apache/hadoop/io/MD5Hash.java
@@ -94,11 +94,18 @@ public static MD5Hash digest(byte[] data) {
     return digest(data, 0, data.length);
   }
 
+  /**
+   * Create a thread local MD5 digester
+   */
+  public static MessageDigest getDigester() {
+    return DIGESTER_FACTORY.get();
+  }
+
   /** Construct a hash value for the content from the InputStream. */
   public static MD5Hash digest(InputStream in) throws IOException {
     final byte[] buffer = new byte[4*1024]; 
 
-    final MessageDigest digester = DIGESTER_FACTORY.get();
+    final MessageDigest digester = getDigester();
     for(int n; (n = in.read(buffer)) != -1; ) {
       digester.update(buffer, 0, n);
     }
@@ -109,7 +116,7 @@ public static MD5Hash digest(InputStream in) throws IOException {
   /** Construct a hash value for a byte array. */
   public static MD5Hash digest(byte[] data, int start, int len) {
     byte[] digest;
-    MessageDigest digester = DIGESTER_FACTORY.get();
+    MessageDigest digester = getDigester();
     digester.update(data, start, len);
     digest = digester.digest();
     return new MD5Hash(digest);