[PATCH 2/4] Rework tree/commit cache

[Robin Rosenberg <robin.rosenberg@dewire.com>]

We now use SoftRefernces to hold the value objects and reuse
the object id's as cache keys. Seems to work much better, i.e.
the gc only throws out stuff from the cache when memory is
tight, rather than at the first opportunity.

Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>
---

 .../src/org/spearce/jgit/lib/Repository.java       |   30 +++++++++++++++--------
 1 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/org.spearce.jgit/src/org/spearce/jgit/lib/Repository.java b/org.spearce.jgit/src/org/spearce/jgit/lib/Repository.java
index d3b2178..c7c47ae 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/lib/Repository.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/lib/Repository.java
@@ -23,6 +23,8 @@ import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.FileWriter;
 import java.io.IOException;
+import java.lang.ref.Reference;
+import java.lang.ref.SoftReference;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Map;
@@ -190,19 +192,24 @@ public class Repository {
 	}
 
 	public Commit mapCommit(final ObjectId id) throws IOException {
-		Commit ret = (Commit)commitCache.get(id);
-		if (ret != null)
-			return ret;
+//		System.out.println("commitcache.size="+commitCache.size());
+		Reference retr = (Reference)commitCache.get(id);
+		if (retr != null) {
+			Commit ret = (Commit)retr.get();
+			if (ret != null)
+				return ret;
+			System.out.println("Found a null id, size was "+commitCache.size());
+		}
 
 		final ObjectLoader or = openObject(id);
 		if (or == null)
 			return null;
 		final byte[] raw = or.getBytes();
 		if (Constants.TYPE_COMMIT.equals(or.getType())) {
-			ret = new Commit(this, id, raw);
+			Commit ret = new Commit(this, id, raw);
 			// The key must not be the referenced strongly
 			// by the value in WeakHashMaps
-			commitCache.put(new ObjectId(id.getBytes()), ret);
+			commitCache.put(id, new SoftReference(ret));
 			return ret;
 		}
 		throw new IncorrectObjectTypeException(id, Constants.TYPE_COMMIT);
@@ -214,17 +221,20 @@ public class Repository {
 	}
 
 	public Tree mapTree(final ObjectId id) throws IOException {
-		Tree ret = (Tree)treeCache.get(id);
-		if (ret != null)
-			return ret;
+		Reference wret = (Reference)treeCache.get(id);
+		if (wret != null) {
+			Tree ret = (Tree)wret.get();
+			if (ret != null)
+				return ret;
+		}
 
 		final ObjectLoader or = openObject(id);
 		if (or == null)
 			return null;
 		final byte[] raw = or.getBytes();
 		if (Constants.TYPE_TREE.equals(or.getType())) {
-			ret = new Tree(this, id, raw);
-			treeCache.put(new ObjectId(id.getBytes()), ret);
+			Tree ret = new Tree(this, id, raw);
+			treeCache.put(id, new SoftReference(ret));
 			return ret;
 		}
 		if (Constants.TYPE_COMMIT.equals(or.getType()))