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From: Yann Simon <yann.simon.fr@gmail.com>
To: Robin Rosenberg <robin.rosenberg.lists@dewire.com>,
	"Shawn O. Pearce" <spearce@spearce.org>
Cc: git <git@vger.kernel.org>
Subject: [JGIT] Questions about binary right shifting
Date: Thu, 05 Feb 2009 15:37:37 +0100	[thread overview]
Message-ID: <498AF9B1.1060200@gmail.com> (raw)

Hi,

I can see in the code that the signed right shifting is used.
Could it be a problem? Or do we manipulate only positive numbers?

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..d70eca0 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCache.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCache.java
@@ -577,7 +577,7 @@ int findEntry(final byte[] p, final int pLen) {
 		int low = 0;
 		int high = entryCnt;
 		do {
-			int mid = (low + high) >> 1;
+			int mid = (low + high) >>> 1;
 			final int cmp = cmp(p, pLen, sortedEntries[mid]);
 			if (cmp < 0)
 				high = mid;

And could we used right shifting to optimize a division per 2?

diff --git a/org.spearce.jgit/src/org/spearce/jgit/lib/Tree.java b/org.spearce.jgit/src/org/spearce/jgit/lib/Tree.java
index 0ecd04d..ff9e666 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/lib/Tree.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/lib/Tree.java
@@ -136,7 +136,7 @@ private static final int binarySearch(final TreeEntry[] entries,
 		int high = entries.length;
 		int low = 0;
 		do {
-			final int mid = (low + high) / 2;
+			final int mid = (low + high) >>> 1;
 			final int cmp = compareNames(entries[mid].getNameUTF8(), nameUTF8,
 					nameStart, nameEnd, TreeEntry.lastChar(entries[mid]), nameUTF8last);
 			if (cmp < 0)

Yann

             reply	other threads:[~2009-02-05 14:39 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-02-05 14:37 Yann Simon [this message]
2009-02-05 15:21 ` [JGIT] Questions about binary right shifting Shawn O. Pearce
2009-02-05 20:32   ` Robin Rosenberg

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