[GSoC][PATCH v8 7/9] files-backend: add unified interface for refs scanning

[shejialuo <shejialuo@gmail.com>]

For refs and reflogs, we need to scan its corresponding directories to
check every regular file or symbolic link which shares the same pattern.
Introduce a unified interface for scanning directories for
files-backend.

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: shejialuo <shejialuo@gmail.com>
---
 refs/files-backend.c | 77 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 76 insertions(+), 1 deletion(-)

diff --git a/refs/files-backend.c b/refs/files-backend.c
index d89eeda8ef..84acb58782 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -6,6 +6,7 @@
 #include "../gettext.h"
 #include "../hash.h"
 #include "../hex.h"
+#include "../fsck.h"
 #include "../refs.h"
 #include "refs-internal.h"
 #include "ref-cache.h"
@@ -3408,6 +3409,78 @@ static int files_ref_store_remove_on_disk(struct ref_store *ref_store,
 	return ret;
 }
 
+/*
+ * For refs and reflogs, they share a unified interface when scanning
+ * the whole directory. This function is used as the callback for each
+ * regular file or symlink in the directory.
+ */
+typedef int (*files_fsck_refs_fn)(struct fsck_options *o,
+				  const char *gitdir,
+				  const char *refs_check_dir,
+				  struct dir_iterator *iter);
+
+static int files_fsck_refs_dir(struct ref_store *ref_store,
+			       struct fsck_options *o,
+			       const char *refs_check_dir,
+			       files_fsck_refs_fn *fsck_refs_fns)
+{
+	const char *gitdir = ref_store->gitdir;
+	struct strbuf sb = STRBUF_INIT;
+	struct dir_iterator *iter;
+	int iter_status;
+	int ret = 0;
+
+	strbuf_addf(&sb, "%s/%s", gitdir, refs_check_dir);
+
+	iter = dir_iterator_begin(sb.buf, 0);
+
+	if (!iter) {
+		ret = error_errno("cannot open directory %s", sb.buf);
+		goto out;
+	}
+
+	while ((iter_status = dir_iterator_advance(iter)) == ITER_OK) {
+		if (S_ISDIR(iter->st.st_mode)) {
+			continue;
+		} else if (S_ISREG(iter->st.st_mode) ||
+			   S_ISLNK(iter->st.st_mode)) {
+			if (o->verbose_refs)
+				fprintf_ln(stderr, "Checking %s/%s",
+					   refs_check_dir, iter->relative_path);
+			for (size_t i = 0; fsck_refs_fns[i]; i++) {
+				if (fsck_refs_fns[i](o, gitdir, refs_check_dir, iter))
+					ret = -1;
+			}
+		} else {
+			ret = error(_("unexpected file type for '%s'"),
+				    iter->basename);
+		}
+	}
+
+	if (iter_status != ITER_DONE)
+		ret = error(_("failed to iterate over '%s'"), sb.buf);
+
+out:
+	strbuf_release(&sb);
+	return ret;
+}
+
+static int files_fsck_refs(struct ref_store *ref_store,
+			   struct fsck_options *o)
+{
+	int ret;
+	files_fsck_refs_fn fsck_refs_fns[]= {
+		NULL
+	};
+
+	if (o->verbose_refs)
+		fprintf_ln(stderr, "Checking references consistency");
+
+	ret = files_fsck_refs_dir(ref_store, o, "refs", fsck_refs_fns);
+
+	return ret;
+}
+
 static int files_fsck(struct ref_store *ref_store,
 		      struct fsck_options *o)
 {
@@ -3415,7 +3488,9 @@ static int files_fsck(struct ref_store *ref_store,
 	struct files_ref_store *refs =
 		files_downcast(ref_store, REF_STORE_READ, "fsck");
 
-	ret = refs->packed_ref_store->be->fsck(refs->packed_ref_store, o);
+	ret = refs->packed_ref_store->be->fsck(refs->packed_ref_store, o)
+	    | files_fsck_refs(ref_store, o);
+
 	return ret;
 }
 
-- 
2.45.2