refs: refactor logic to look up storage backends

In order to look up ref storage backends, we're currently using a linked
list of backends, where each backend is expected to set up its `next`
pointer to the next ref storage backend. This is kind of a weird setup
as backends need to be aware of other backends without much of a reason.

Refactor the code so that the array of backends is centrally defined in
"refs.c", where each backend is now identified by an integer constant.
Expose functions to translate from those integer constants to the name
and vice versa, which will be required by subsequent patches.

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

diff --git a/refs.c b/refs.c
index 16bfa21df75e6d6425674817e1e5eb847f1d16b7..dea3d5c9a083a0d42f0b676c0716df0d1a930c2b 100644 (file)
--- a/refs.c
+++ b/refs.c
@@ -33,17 +33,33 @@
 /*
  * List of all available backends
  */
-static struct ref_storage_be *refs_backends = &refs_be_files;
+static const struct ref_storage_be *refs_backends[] = {
+       [REF_STORAGE_FORMAT_FILES] = &refs_be_files,
+};
 
-static struct ref_storage_be *find_ref_storage_backend(const char *name)
+static const struct ref_storage_be *find_ref_storage_backend(unsigned int ref_storage_format)
 {
-       struct ref_storage_be *be;
-       for (be = refs_backends; be; be = be->next)
-               if (!strcmp(be->name, name))
-                       return be;
+       if (ref_storage_format < ARRAY_SIZE(refs_backends))
+               return refs_backends[ref_storage_format];
        return NULL;
 }
 
+unsigned int ref_storage_format_by_name(const char *name)
+{
+       for (unsigned int i = 0; i < ARRAY_SIZE(refs_backends); i++)
+               if (refs_backends[i] && !strcmp(refs_backends[i]->name, name))
+                       return i;
+       return REF_STORAGE_FORMAT_UNKNOWN;
+}
+
+const char *ref_storage_format_to_name(unsigned int ref_storage_format)
+{
+       const struct ref_storage_be *be = find_ref_storage_backend(ref_storage_format);
+       if (!be)
+               return "unknown";
+       return be->name;
+}
+
 /*
  * How to handle various characters in refnames:
  * 0: An acceptable character for refs
@@ -2029,12 +2045,12 @@ static struct ref_store *ref_store_init(struct repository *repo,
                                        const char *gitdir,
                                        unsigned int flags)
 {
-       const char *be_name = "files";
-       struct ref_storage_be *be = find_ref_storage_backend(be_name);
+       unsigned int format = REF_STORAGE_FORMAT_FILES;
+       const struct ref_storage_be *be = find_ref_storage_backend(format);
        struct ref_store *refs;
 
        if (!be)
-               BUG("reference backend %s is unknown", be_name);
+               BUG("reference backend is unknown");
 
        refs = be->init(repo, gitdir, flags);
        return refs;

diff --git a/refs.h b/refs.h
index 23211a5ea1cabbb0a35d091bf2b5dbbd87e28252..916b874ae3ee2d16c5368231e32d6fbb890d1a6d 100644 (file)
--- a/refs.h
+++ b/refs.h
@@ -11,6 +11,9 @@ struct string_list;
 struct string_list_item;
 struct worktree;
 
+unsigned int ref_storage_format_by_name(const char *name);
+const char *ref_storage_format_to_name(unsigned int ref_storage_format);
+
 /*
  * Resolve a reference, recursively following symbolic refererences.
  *

diff --git a/refs/debug.c b/refs/debug.c
index 83b7a0ba655a50e83430da8ad3d80885cc68bd99..b9775f2c37c7eb5e9de275fc3d6ad2125802eeef 100644 (file)
--- a/refs/debug.c
+++ b/refs/debug.c
@@ -426,7 +426,6 @@ static int debug_reflog_expire(struct ref_store *ref_store, const char *refname,
 }
 
 struct ref_storage_be refs_be_debug = {
-       .next = NULL,
        .name = "debug",
        .init = NULL,
        .init_db = debug_init_db,

diff --git a/refs/files-backend.c b/refs/files-backend.c
index ad8b1d143fc23bea8b6a26f2244ee2741ebd4842..43fd0ac760e9e9dad0a4e0b50d51f9115072e80e 100644 (file)
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -3241,7 +3241,6 @@ static int files_init_db(struct ref_store *ref_store, struct strbuf *err UNUSED)
 }
 
 struct ref_storage_be refs_be_files = {
-       .next = NULL,
        .name = "files",
        .init = files_ref_store_create,
        .init_db = files_init_db,

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index b9fa097a29ca6ac21e29102235b58ee716ec04d4..8d1090e284e6cb3bfa0b3130f3f63ce738c1f7f4 100644 (file)
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -1705,7 +1705,6 @@ static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_s
 }
 
 struct ref_storage_be refs_be_packed = {
-       .next = NULL,
        .name = "packed",
        .init = packed_ref_store_create,
        .init_db = packed_init_db,

diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 4af83bf9a5e4d400939dfb61af28995aef33d6cc..8e9f04cc670baeddd68b933ee41d11062b2fbe32 100644 (file)
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -663,7 +663,6 @@ typedef int read_symbolic_ref_fn(struct ref_store *ref_store, const char *refnam
                                 struct strbuf *referent);
 
 struct ref_storage_be {
-       struct ref_storage_be *next;
        const char *name;
        ref_store_init_fn *init;
        ref_init_db_fn *init_db;

diff --git a/repository.h b/repository.h
index 5f18486f6465c44b44abb2ded74bcdda14ba7bd9..ea4c488b819530b41e5aa7751d6191b90aa3d579 100644 (file)
--- a/repository.h
+++ b/repository.h
@@ -24,6 +24,9 @@ enum fetch_negotiation_setting {
        FETCH_NEGOTIATION_NOOP,
 };
 
+#define REF_STORAGE_FORMAT_UNKNOWN 0
+#define REF_STORAGE_FORMAT_FILES   1
+
 struct repo_settings {
        int initialized;