[PATCH v5 03/27] refs: add a backend method structure with transaction functions

[David Turner <dturner@twopensource.com>]

From: Ronnie Sahlberg <sahlberg@google.com>

Add a ref structure for storage backend methods. Start by adding a
method pointer for the transaction commit function.

Add a function set_refs_backend to switch between storage
backends. The files based storage backend is the default.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: David Turner <dturner@twopensource.com>
---
 refs.c               | 40 ++++++++++++++++++++++++++++++++++++++++
 refs.h               |  7 +++++++
 refs/files-backend.c | 10 ++++++++--
 refs/refs-internal.h | 14 +++++++++++++-
 4 files changed, 68 insertions(+), 3 deletions(-)

diff --git a/refs.c b/refs.c
index c38311b..ac885cb 100644
--- a/refs.c
+++ b/refs.c
@@ -10,6 +10,39 @@
 #include "tag.h"
 
 /*
+ * We always have a files backend and it is the default.
+ */
+static struct ref_storage_be *the_refs_backend = &refs_be_files;
+/*
+ * List of all available backends
+ */
+static struct ref_storage_be *refs_backends = &refs_be_files;
+
+int set_ref_storage_backend(const char *name)
+{
+	struct ref_storage_be *be;
+
+	for (be = refs_backends; be; be = be->next)
+		if (!strcmp(be->name, name)) {
+			the_refs_backend = be;
+			return 0;
+		}
+	return 1;
+}
+
+int ref_storage_backend_exists(const char *name)
+{
+	struct ref_storage_be *be;
+
+	for (be = refs_backends; be; be = be->next)
+		if (!strcmp(be->name, name)) {
+			the_refs_backend = be;
+			return 1;
+		}
+	return 0;
+}
+
+/*
  * How to handle various characters in refnames:
  * 0: An acceptable character for refs
  * 1: End-of-component
@@ -1157,3 +1190,10 @@ int for_each_rawref(each_ref_fn fn, void *cb_data)
 	return do_for_each_ref(NULL, "", fn, 0,
 			       DO_FOR_EACH_INCLUDE_BROKEN, cb_data);
 }
+
+/* backend functions */
+int ref_transaction_commit(struct ref_transaction *transaction,
+			   struct strbuf *err)
+{
+	return the_refs_backend->transaction_commit(transaction, err);
+}
diff --git a/refs.h b/refs.h
index 3c3da29..5bc3fbc 100644
--- a/refs.h
+++ b/refs.h
@@ -508,4 +508,11 @@ extern int reflog_expire(const char *refname, const unsigned char *sha1,
 			 reflog_expiry_cleanup_fn cleanup_fn,
 			 void *policy_cb_data);
 
+/*
+ * Switch to an alternate ref storage backend.
+ */
+int set_ref_storage_backend(const char *name);
+
+int ref_storage_backend_exists(const char *name);
+
 #endif /* REFS_H */
diff --git a/refs/files-backend.c b/refs/files-backend.c
index fd664d6..caeb478 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -3066,8 +3066,8 @@ static int ref_update_reject_duplicates(struct string_list *refnames,
 	return 0;
 }
 
-int ref_transaction_commit(struct ref_transaction *transaction,
-			   struct strbuf *err)
+static int files_transaction_commit(struct ref_transaction *transaction,
+				    struct strbuf *err)
 {
 	int ret = 0, i;
 	int n = transaction->nr;
@@ -3453,3 +3453,9 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
 	unlock_ref(lock);
 	return -1;
 }
+
+struct ref_storage_be refs_be_files = {
+	NULL,
+	"files",
+	files_transaction_commit,
+};
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 92aae80..c240ca6 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -197,7 +197,6 @@ const char *find_descendant_ref(const char *dirname,
 
 int rename_ref_available(const char *oldname, const char *newname);
 
-
 /* Include broken references in a do_for_each_ref*() iteration: */
 #define DO_FOR_EACH_INCLUDE_BROKEN 0x01
 
@@ -206,4 +205,17 @@ int rename_ref_available(const char *oldname, const char *newname);
  */
 int do_for_each_ref(const char *submodule, const char *base,
 		    each_ref_fn fn, int trim, int flags, void *cb_data);
+
+/* refs backends */
+typedef int ref_transaction_commit_fn(struct ref_transaction *transaction,
+				      struct strbuf *err);
+
+struct ref_storage_be {
+	struct ref_storage_be *next;
+	const char *name;
+	ref_transaction_commit_fn *transaction_commit;
+};
+
+extern struct ref_storage_be refs_be_files;
+
 #endif /* REFS_REFS_INTERNAL_H */
-- 
2.4.2.767.g62658d5-twtrsrc