[PATCH 2/1] test-lib-functions: add object size functions

["René Scharfe" <l.s.r@web.de>]

Add test_object_size and its helpers test_loose_object_size and
test_packed_object_size, which allow determining the size of a Git
object using only the low-level Git commands rev-parse and show-index.

Use it in t6300 to replace the bare-bones function test_object_file_size
as a motivating example.  There it provides the expected output of the
high-level Git command for-each-ref.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: René Scharfe <l.s.r@web.de>
---
So how about this?  I'm a bit nervous about all the rules about output
descriptors and error propagation and whatnot in the test library, but
this implementation seems simple enough and might be useful in more than
one test.  No idea how to add support for alternate object directories,
but I doubt we'll ever need it.
---
 t/t6300-for-each-ref.sh | 16 ++++++--------
 t/test-lib-functions.sh | 47 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 9 deletions(-)

diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index 843a7fe143..4687660f38 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -20,12 +20,6 @@ setdate_and_increment () {
     export GIT_COMMITTER_DATE GIT_AUTHOR_DATE
 }

-test_object_file_size () {
-	oid=$(git rev-parse "$1")
-	path=".git/objects/$(test_oid_to_path $oid)"
-	test_file_size "$path"
-}
-
 test_expect_success setup '
 	# setup .mailmap
 	cat >.mailmap <<-EOF &&
@@ -40,7 +34,11 @@ test_expect_success setup '
 	git branch -M main &&
 	setdate_and_increment &&
 	git tag -a -m "Tagging at $datestamp" testtag &&
+	testtag_oid=$(git rev-parse refs/tags/testtag) &&
+	testtag_disksize=$(test_object_size $testtag_oid) &&
 	git update-ref refs/remotes/origin/main main &&
+	commit_oid=$(git rev-parse refs/heads/main) &&
+	commit_disksize=$(test_object_size $commit_oid) &&
 	git remote add origin nowhere &&
 	git config branch.main.remote origin &&
 	git config branch.main.merge refs/heads/main &&
@@ -129,7 +127,7 @@ test_atom head push:strip=1 remotes/myfork/main
 test_atom head push:strip=-1 main
 test_atom head objecttype commit
 test_atom head objectsize $((131 + hexlen))
-test_atom head objectsize:disk $(test_object_file_size refs/heads/main)
+test_atom head objectsize:disk $commit_disksize
 test_atom head deltabase $ZERO_OID
 test_atom head objectname $(git rev-parse refs/heads/main)
 test_atom head objectname:short $(git rev-parse --short refs/heads/main)
@@ -203,8 +201,8 @@ test_atom tag upstream ''
 test_atom tag push ''
 test_atom tag objecttype tag
 test_atom tag objectsize $((114 + hexlen))
-test_atom tag objectsize:disk $(test_object_file_size refs/tags/testtag)
-test_atom tag '*objectsize:disk' $(test_object_file_size refs/heads/main)
+test_atom tag objectsize:disk $testtag_disksize
+test_atom tag '*objectsize:disk' $commit_disksize
 test_atom tag deltabase $ZERO_OID
 test_atom tag '*deltabase' $ZERO_OID
 test_atom tag objectname $(git rev-parse refs/tags/testtag)
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 9c3cf12b26..9b49645f77 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -1733,6 +1733,53 @@ test_oid_to_path () {
 	echo "${1%$basename}/$basename"
 }

+test_loose_object_size () {
+	test "$#" -ne 1 && BUG "1 param"
+	local path=$(test_oid_to_path "$1")
+	test_file_size "$(git rev-parse --git-path "objects/$path")" 2>&4
+}
+
+test_packed_object_size () {
+	test "$#" -ne 2 && BUG "2 params"
+	local oid=$1 idx=$2 packsize rawsz end
+
+	packsize=$(test_file_size "${idx%.idx}.pack")
+	rawsz=$(test_oid rawsz)
+	end=$(($packsize - $rawsz))
+
+	git show-index <"$idx" |
+	awk -v oid="$oid" -v end="$end" '
+		$2 == oid {start = $1}
+		{offsets[$1] = 1}
+		END {
+			if (!start || start >= end)
+				exit 1
+			for (o in offsets)
+				if (start < o && o < end)
+					end = o
+			print end - start
+		}
+	' && return 0
+
+	echo >&4 "error: '$oid' not found in '$idx'"
+	return 1
+}
+
+test_object_size () {
+	test "$#" -ne 1 && BUG "1 param"
+	local oid=$1
+
+	test_loose_object_size "$oid" 4>/dev/null && return 0
+
+	for idx in "$(git rev-parse --git-path objects/pack)"/pack-*.idx
+	do
+		test_packed_object_size "$oid" "$idx" 4>/dev/null && return 0
+	done
+
+	echo >&4 "error: '$oid' not found"
+	return 1
+}
+
 # Parse oids from git ls-files --staged output
 test_parse_ls_files_stage_oids () {
 	awk '{print $2}' -
--
2.43.0