Subject: [PATCH 2/2] sha1-lookup: fix handling of duplicates in sha1_pos()

From: René Scharfe <[email-masked]>
Date: Wed, 01 Oct 2014 11:43:21 +0200

If the first 18 bytes of the SHA1's of all entries are the same then
sha1_pos() dies and reports that the lower and upper limits of the
binary search were the same that this wasn't supposed to happen.  This
is wrong because the remaining two bytes could still differ.

Furthermore: It wouldn't be a problem if they actually were the same,
i.e. if all entries have the same SHA1.  The code already handles
duplicates just fine otherwise.  Simply remove the erroneous check.

Signed-off-by: Rene Scharfe <[email-masked]>
---
 sha1-lookup.c         |  2 --
 t/t0064-sha1-array.sh | 20 ++++++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/sha1-lookup.c b/sha1-lookup.c
index 2dd8515..5f06921 100644
--- a/sha1-lookup.c
+++ b/sha1-lookup.c
@@ -84,8 +84,6 @@ int sha1_pos(const unsigned char *sha1, void *table, size_t nr,
 				die("BUG: assertion failed in binary search");
 			}
 		}
-		if (18 <= ofs)
-			die("cannot happen -- lo and hi are identical");
 	}
 
 	do {
diff --git a/t/t0064-sha1-array.sh b/t/t0064-sha1-array.sh
index bd68789..3fcb8d8 100755
--- a/t/t0064-sha1-array.sh
+++ b/t/t0064-sha1-array.sh
@@ -61,4 +61,24 @@ test_expect_success 'lookup with duplicates' '
 	test "$n" -le 3
 '
 
+test_expect_success 'lookup with almost duplicate values' '
+	{
+		echo "append 5555555555555555555555555555555555555555" &&
+		echo "append 555555555555555555555555555555555555555f" &&
+		echo20 "lookup " 55
+	} | test-sha1-array >actual &&
+	n=$(cat actual) &&
+	test "$n" -eq 0
+'
+
+test_expect_success 'lookup with single duplicate value' '
+	{
+		echo20 "append " 55 55 &&
+		echo20 "lookup " 55
+	} | test-sha1-array >actual &&
+	n=$(cat actual) &&
+	test "$n" -ge 0 &&
+	test "$n" -le 1
+'
+
 test_done
-- 
2.1.2