[PATCH 04/38] refs: add a backend method structure

[Michael Haggerty <mhagger@alum.mit.edu>]

From: Ronnie Sahlberg <sahlberg@google.com>

Add a `struct ref_storage_be` to represent types of reference stores. In
OO notation, this is the class, and will soon hold some class
methods (e.g., a factory to create new ref_store instances) and will
also serve as the vtable for ref_store instances of that type.

As yet, the backends cannot do anything.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c               | 19 +++++++++++++++++++
 refs.h               |  2 ++
 refs/files-backend.c |  5 +++++
 refs/refs-internal.h |  8 ++++++++
 4 files changed, 34 insertions(+)

diff --git a/refs.c b/refs.c
index 814cad3..f57a93e 100644
--- a/refs.c
+++ b/refs.c
@@ -10,6 +10,25 @@
 #include "tag.h"
 
 /*
+ * List of all available backends
+ */
+static struct ref_storage_be *refs_backends = &refs_be_files;
+
+static struct ref_storage_be *find_ref_storage_backend(const char *name)
+{
+	struct ref_storage_be *be;
+	for (be = refs_backends; be; be = be->next)
+		if (!strcmp(be->name, name))
+			return be;
+	return NULL;
+}
+
+int ref_storage_backend_exists(const char *name)
+{
+	return find_ref_storage_backend(name) != NULL;
+}
+
+/*
  * How to handle various characters in refnames:
  * 0: An acceptable character for refs
  * 1: End-of-component
diff --git a/refs.h b/refs.h
index 442c1a5..52ea93b 100644
--- a/refs.h
+++ b/refs.h
@@ -544,4 +544,6 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
 		  reflog_expiry_cleanup_fn cleanup_fn,
 		  void *policy_cb_data);
 
+int ref_storage_backend_exists(const char *name);
+
 #endif /* REFS_H */
diff --git a/refs/files-backend.c b/refs/files-backend.c
index b94aad2..bde6f0e 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -4066,3 +4066,8 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
 	unlock_ref(lock);
 	return -1;
 }
+
+struct ref_storage_be refs_be_files = {
+	NULL,
+	"files"
+};
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index d8a2606..4d88849 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -520,4 +520,12 @@ int do_for_each_ref_iterator(struct ref_iterator *iter,
 int read_raw_ref(const char *refname, unsigned char *sha1,
 		 struct strbuf *referent, unsigned int *type);
 
+/* refs backends */
+struct ref_storage_be {
+	struct ref_storage_be *next;
+	const char *name;
+};
+
+extern struct ref_storage_be refs_be_files;
+
 #endif /* REFS_REFS_INTERNAL_H */
-- 
2.8.1