[EGIT PATCH] Improve end-of-file detection in DirCache

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

When reading from an BufferInputStream attached to a
FileInputStream the available() method seems to return
the number of unread bytes in the buffer plus the unread
number of bytes in the file.

There is no guarantee for this behaviour so this quick fix
might not be as stable as we would wish.

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

---
  http://code.google.com/p/egit/issues/detail?id=66
---
 .../src/org/spearce/jgit/dircache/DirCache.java    |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCache.java b/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCache.java
index 8eb4022..657762e 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCache.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCache.java
@@ -45,7 +45,6 @@
 import java.io.IOException;
 import java.io.OutputStream;
 import java.nio.ByteBuffer;
-import java.nio.channels.FileChannel;
 import java.security.DigestOutputStream;
 import java.security.MessageDigest;
 import java.util.Comparator;
@@ -344,8 +343,6 @@ public void clear() {
 
 	private void readFrom(final FileInputStream inStream) throws IOException,
 			CorruptObjectException {
-		final FileChannel fd = inStream.getChannel();
-		final long sizeOnDisk = fd.size();
 		final BufferedInputStream in = new BufferedInputStream(inStream);
 
 		// Read the index header and verify we understand it.
@@ -369,9 +366,16 @@ private void readFrom(final FileInputStream inStream) throws IOException,
 			sortedEntries[i] = new DirCacheEntry(infos, i * INFO_LEN, in);
 		lastModified = liveFile.lastModified();
 
-		// After the file entries are index extensions.
-		//
-		while (fd.position() - in.available() < sizeOnDisk - 20) {
+		/*
+		 * InputStream.available() on file input streams seems to return the
+		 * rest of the file i.e. buffer size + unread file on disk. There is no
+		 * guarantee for this so we need to fix this or we may miss extensions
+		 * when reading the index in a few races cases.
+		 *
+		 * That is currently no disaster though.
+		 */
+		while (in.available() > 20) {
+			// After the file entries are index extensions.
 			NB.readFully(in, hdr, 0, 8);
 			switch (NB.decodeInt32(hdr, 0)) {
 			case EXT_TREE: {
-- 
1.6.2.2.446.gfbdc0