[JGIT PATCH] Fix more computation of integer average overflows

Shawn O. Pearce· Apr 27, 2009, 23:14 UTC · lore

In 1d99aaab8e364c6ad722437e43c77fd54e13b071 Matthias Sohn pointed out that (low+high)/2 can overflow, so (low+high)>>>1 is a better choice when the result will be used as an array index.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---

 I guess we need this too then, eh?

 .../src/org/spearce/jgit/lib/PackIndexV1.java      |    2 +-
 .../src/org/spearce/jgit/lib/PackIndexV2.java      |    6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

Show changes to 2 files +4 −4

org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV1.java, org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV2.java

diff --git a/org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV1.java b/org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV1.java
index fdaa094..0ad29e1 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV1.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV1.java
@@ -129,7 +129,7 @@ long findOffset(final AnyObjectId objId) {
 		int high = data.length / (4 + Constants.OBJECT_ID_LENGTH);
 		int low = 0;
 		do {
-			final int mid = (low + high) / 2;
+			final int mid = (low + high) >>> 1;
 			final int pos = ((4 + Constants.OBJECT_ID_LENGTH) * mid) + 4;
 			final int cmp = objId.compareTo(data, pos);
 			if (cmp < 0)
diff --git a/org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV2.java b/org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV2.java
index eb56ed9..b539547 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV2.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/lib/PackIndexV2.java
@@ -108,7 +108,7 @@ PackIndexV2(final InputStream fd) throws IOException {
 
 			final int intNameLen = (int) nameLen;
 			final byte[] raw = new byte[intNameLen];
-			final int[] bin = new int[intNameLen >> 2];
+			final int[] bin = new int[intNameLen >>> 2];
 			NB.readFully(fd, raw, 0, raw.length);
 			for (int i = 0; i < bin.length; i++)
 				bin[i] = NB.decodeInt32(raw, i << 2);
@@ -212,12 +212,12 @@ boolean hasCRC32Support() {
 
 	private int binarySearchLevelTwo(final AnyObjectId objId, final int levelOne) {
 		final int[] data = names[levelOne];
-		int high = offset32[levelOne].length >> 2;
+		int high = offset32[levelOne].length >>> 2;
 		if (high == 0)
 			return -1;
 		int low = 0;
 		do {
-			final int mid = (low + high) >> 1;
+			final int mid = (low + high) >>> 1;
 			final int mid4 = mid << 2;
 			final int cmp;

-- 
1.6.3.rc1.205.g37f8

patchFix more computation of integer average overflows