odb/source: make `close()` function pluggable

Introduce a new callback function in `struct odb_source` to make the
function pluggable.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 27 insertions, 4 deletions

diff --git a/odb.c b/odb.c
index 2cf6a53dc3..f7487eb0df 100644
--- a/odb.c
+++ b/odb.c
@@ -1062,10 +1062,8 @@ struct object_database *odb_new(struct repository *repo,
 void odb_close(struct object_database *o)
 {
 	struct odb_source *source;
-	for (source = o->sources; source; source = source->next) {
-		struct odb_source_files *files = odb_source_files_downcast(source);
-		packfile_store_close(files->packed);
-	}
+	for (source = o->sources; source; source = source->next)
+		odb_source_close(source);
 	close_commit_graph(o);
 }
 
diff --git a/odb/source-files.c b/odb/source-files.c
index d0f7ee072e..20a24f524a 100644
--- a/odb/source-files.c
+++ b/odb/source-files.c
@@ -28,6 +28,12 @@ static void odb_source_files_free(struct odb_source *source)
 	free(files);
 }
 
+static void odb_source_files_close(struct odb_source *source)
+{
+	struct odb_source_files *files = odb_source_files_downcast(source);
+	packfile_store_close(files->packed);
+}
+
 static void odb_source_files_reprepare(struct odb_source *source)
 {
 	struct odb_source_files *files = odb_source_files_downcast(source);
@@ -47,6 +53,7 @@ struct odb_source_files *odb_source_files_new(struct object_database *odb,
 	files->packed = packfile_store_new(&files->base);
 
 	files->base.free = odb_source_files_free;
+	files->base.close = odb_source_files_close;
 	files->base.reprepare = odb_source_files_reprepare;
 
 	/*
diff --git a/odb/source.h b/odb/source.h
index 09cca839fe..0e6c6abdb1 100644
--- a/odb/source.h
+++ b/odb/source.h
@@ -59,6 +59,14 @@ struct odb_source {
 	void (*free)(struct odb_source *source);
 
 	/*
+	 * This callback is expected to close any open resources, like for
+	 * example file descriptors or connections. The source is expected to
+	 * still be usable after it has been closed. Closed resources may need
+	 * to be reopened in that case.
+	 */
+	void (*close)(struct odb_source *source);
+
+	/*
 	 * This callback is expected to clear underlying caches of the object
 	 * database source. The function is called when the repository has for
 	 * example just been repacked so that new objects will become visible.
@@ -104,6 +112,16 @@ void odb_source_free(struct odb_source *source);
 void odb_source_release(struct odb_source *source);
 
 /*
+ * Close the object database source without releasing he underlying data. The
+ * source can still be used going forward, but it first needs to be reopened.
+ * This can be useful to reduce resource usage.
+ */
+static inline void odb_source_close(struct odb_source *source)
+{
+	source->close(source);
+}
+
+/*
  * Reprepare the object database source and clear any caches. Depending on the
  * backend used this may have the effect that concurrently-written objects
  * become visible.