[PATCH] Re-re-re-fix common tail optimization

From

Junio C Hamano <gitster@pobox.com>

Date

Dec 16, 2007, 21:49 UTC

Message-ID

<7v3au2joo2.fsf_-_@gitster.siamese.dyndns.org>

In-Reply-To

<20071216212104.GA32307@coredump.intra.peff.net>

Jeff King <peff@peff.net> writes:

> No, I think it's right as-is. We forget about the blocks during the
> recovery section of the code. IOW, we just keep reading forward until we
> find all of the context lines, or we run out of trimmed content. In the
> first case, we are fine (we restored the right number of context lines).
> In the latter case, we are also fine, because we end up trimming nothing
> (IOW, there _weren't_ enough context lines in the first place).

-- >8 --
Subject: [PATCH] Re-re-re-fix common tail optimization

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 t/t4024-diff-optimize-common.sh |   69 +++++++++++++++++++++++++++++++++++++++
 xdiff-interface.c               |    2 +-
 2 files changed, 70 insertions(+), 1 deletions(-)

diff --git a/t/t4024-diff-optimize-common.sh b/t/t4024-diff-optimize-common.sh
new file mode 100755
index 0000000..10405f1
--- /dev/null
+++ b/t/t4024-diff-optimize-common.sh
@@ -0,0 +1,69 @@
+#!/bin/sh
+
+test_description='common tail optimization'
+
+. ./test-lib.sh
+
+z=zzzzzzzz ;# 8
+z="$z$z$z$z$z$z$z$z" ;# 64
+z="$z$z$z$z$z$z$z$z" ;# 512
+z="$z$z$z$z" ;# 2048
+z2047=$(expr "$z" : '.\(.*\)') ; #2047
+
+test_expect_success setup '
+
+	echo "a$z2047" >file-a &&
+	echo "b" >file-b &&
+	echo "$z2047" >>file-b &&
+	echo "c$z2047" | tr -d "\012" >file-c &&
+	echo "d" >file-d &&
+	echo "$z2047" | tr -d "\012" >>file-d &&
+
+	git add file-a file-b file-c file-d &&
+
+	echo "A$z2047" >file-a &&
+	echo "B" >file-b &&
+	echo "$z2047" >>file-b &&
+	echo "C$z2047" | tr -d "\012" >file-c &&
+	echo "D" >file-d &&
+	echo "$z2047" | tr -d "\012" >>file-d
+
+'
+
+echo >expect <<\EOF
+diff --git a/file-a b/file-a
+--- a/file-a
++++ b/file-a
+@@ -1 +1 @@
+-aZ
++AZ
+diff --git a/file-b b/file-b
+--- a/file-b
++++ b/file-b
+@@ -1 +1 @@
+-b
++B
+diff --git a/file-c b/file-c
+--- a/file-c
++++ b/file-c
+@@ -1 +1 @@
+-cZ
+\ No newline at end of file
++CZ
+\ No newline at end of file
+diff --git a/file-d b/file-d
+--- a/file-d
++++ b/file-d
+@@ -1 +1 @@
+-d
++D
+EOF
+
+test_expect_success 'diff -U0' '
+
+	git diff -U0 | sed -e "/^index/d" -e "s/$z2047/Z/g" >actual &&
+	diff -u expect actual
+
+'
+
+test_done
diff --git a/xdiff-interface.c b/xdiff-interface.c
index 98b02ed..9ee877c 100644
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -121,7 +121,7 @@ static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx)
 		bp -= blk;
 	}
 
-	while (recovered < trimmed && ctx)
+	while (recovered < trimmed && 0 <= ctx)
 		if (ap[recovered++] == '\n')
 			ctx--;
 	a->size -= (trimmed - recovered);