From d1be60bbe8e23aa8a00c67bd73d2209421d65c13 Mon Sep 17 00:00:00 2001
From: Vladyslav Yeremeichuk <CVlad.2006@gmail.com>
Date: Mon, 21 Oct 2024 22:42:56 +0300
Subject: [PATCH] Add the ability to check if a mempack is empty

Implement git_mempack_empty, which returns 1 if the mempack is empty
and 0 otherwise.
---
 include/git2/sys/mempack.h          |  8 ++++++++
 src/libgit2/odb_mempack.c           | 11 +++++++++++
 tests/libgit2/odb/backend/mempack.c | 15 +++++++++++----
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/include/git2/sys/mempack.h b/include/git2/sys/mempack.h
index 96bd8a7e8..f8dedee82 100644
--- a/include/git2/sys/mempack.h
+++ b/include/git2/sys/mempack.h
@@ -101,6 +101,14 @@ GIT_EXTERN(int) git_mempack_dump(git_buf *pack, git_repository *repo, git_odb_ba
  */
 GIT_EXTERN(int) git_mempack_reset(git_odb_backend *backend);
 
+/**
+ * Checks if mempack is empty
+ *
+ * @param backend The mempack backend
+ * @return 1 if the repository is empty, 0 if it isn't
+ */
+GIT_EXTERN(int) git_mempack_empty(git_odb_backend *backend);
+
 GIT_END_DECL
 
 #endif
diff --git a/src/libgit2/odb_mempack.c b/src/libgit2/odb_mempack.c
index c6210cec6..732a30573 100644
--- a/src/libgit2/odb_mempack.c
+++ b/src/libgit2/odb_mempack.c
@@ -209,3 +209,14 @@ int git_mempack_new(git_odb_backend **out)
 	*out = (git_odb_backend *)db;
 	return 0;
 }
+
+int git_mempack_empty(git_odb_backend *_backend)
+{
+	struct memory_packer_db *db = (struct memory_packer_db *)_backend;
+	GIT_ASSERT_ARG(_backend);
+
+	if (git_odb_mempack_oidmap_size(&db->objects) || db->commits.size)
+		return 0;
+
+	return 1;
+}
diff --git a/tests/libgit2/odb/backend/mempack.c b/tests/libgit2/odb/backend/mempack.c
index c8a86a2ae..66450a6c5 100644
--- a/tests/libgit2/odb/backend/mempack.c
+++ b/tests/libgit2/odb/backend/mempack.c
@@ -8,14 +8,13 @@ static git_odb *_odb;
 static git_oid _oid;
 static git_odb_object *_obj;
 static git_repository *_repo;
+static git_odb_backend *_backend;
 
 void test_odb_backend_mempack__initialize(void)
 {
-	git_odb_backend *backend;
-
-	cl_git_pass(git_mempack_new(&backend));
+	cl_git_pass(git_mempack_new(&_backend));
 	cl_git_pass(git_odb__new(&_odb, NULL));
-	cl_git_pass(git_odb_add_backend(_odb, backend, 10));
+	cl_git_pass(git_odb_add_backend(_odb, _backend, 10));
 	cl_git_pass(git_repository__wrap_odb(&_repo, _odb, GIT_OID_SHA1));
 }
 
@@ -33,6 +32,14 @@ void test_odb_backend_mempack__write_succeeds(void)
 	cl_git_pass(git_odb_read(&_obj, _odb, &_oid));
 }
 
+void test_odb_backend_mempack_empty(void)
+{
+	const char *data = "data";
+	cl_assert_equal_sz(1, git_mempack_empty(_backend));
+	cl_git_pass(git_odb_write(&_oid, _odb, data, strlen(data) + 1, GIT_OBJECT_BLOB));
+	cl_assert_equal_sz(0, git_mempack_empty(_backend));
+}
+
 void test_odb_backend_mempack__read_of_missing_object_fails(void)
 {
 	cl_git_pass(git_oid__fromstr(&_oid, "f6ea0495187600e7b2288c8ac19c5886383a4633", GIT_OID_SHA1));