reftable/stack: provide convenience functions to create iterators

There exist a bunch of call sites in the reftable backend that want to
create iterators for a reftable stack. This is rather convoluted right
now, where you always have to go via the merged table. And it is about
to become even more convoluted when we split up iterator initialization
and seeking in the next commit.

Introduce convenience functions that allow the caller to create an
iterator from a reftable stack directly without going through the merged
table. Adapt callers accordingly.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

refs/reftable-backend.c

@@ -15,7 +15,6 @@
 #include "../reftable/reftable-record.h"
 #include "../reftable/reftable-error.h"
 #include "../reftable/reftable-iterator.h"
-#include "../reftable/reftable-merged.h"
 #include "../setup.h"
 #include "../strmap.h"
 #include "parse.h"
@@ -462,7 +461,6 @@ static struct reftable_ref_iterator *ref_iterator_for_stack(struct reftable_ref_
 							    const char *prefix,
 							    int flags)
 {
-	struct reftable_merged_table *merged_table;
 	struct reftable_ref_iterator *iter;
 	int ret;
 
@@ -482,9 +480,8 @@ static struct reftable_ref_iterator *ref_iterator_for_stack(struct reftable_ref_
 	if (ret)
 		goto done;
 
-	merged_table = reftable_stack_merged_table(stack);
-
-	ret = reftable_merged_table_seek_ref(merged_table, &iter->iter, prefix);
+	reftable_stack_init_ref_iterator(stack, &iter->iter);
+	ret = reftable_iterator_seek_ref(&iter->iter, prefix);
 	if (ret)
 		goto done;
 
@@ -1015,8 +1012,6 @@ static int transaction_update_cmp(const void *a, const void *b)
 static int write_transaction_table(struct reftable_writer *writer, void *cb_data)
 {
 	struct write_transaction_table_arg *arg = cb_data;
-	struct reftable_merged_table *mt =
-		reftable_stack_merged_table(arg->stack);
 	uint64_t ts = reftable_stack_next_update_index(arg->stack);
 	struct reftable_log_record *logs = NULL;
 	struct ident_split committer_ident = {0};
@@ -1051,6 +1046,8 @@ static int write_transaction_table(struct reftable_writer *writer, void *cb_data
 			struct reftable_log_record log = {0};
 			struct reftable_iterator it = {0};
 
+			reftable_stack_init_log_iterator(arg->stack, &it);
+
 			/*
 			 * When deleting refs we also delete all reflog entries
 			 * with them. While it is not strictly required to
@@ -1060,7 +1057,7 @@ static int write_transaction_table(struct reftable_writer *writer, void *cb_data
 			 * Unfortunately, we have no better way than to delete
 			 * all reflog entries one by one.
 			 */
-			ret = reftable_merged_table_seek_log(mt, &it, u->refname);
+			ret = reftable_iterator_seek_log(&it, u->refname);
 			while (ret == 0) {
 				struct reftable_log_record *tombstone;
 
@@ -1354,7 +1351,6 @@ static int write_copy_table(struct reftable_writer *writer, void *cb_data)
 {
 	struct write_copy_arg *arg = cb_data;
 	uint64_t deletion_ts, creation_ts;
-	struct reftable_merged_table *mt = reftable_stack_merged_table(arg->stack);
 	struct reftable_ref_record old_ref = {0}, refs[2] = {0};
 	struct reftable_log_record old_log = {0}, *logs = NULL;
 	struct reftable_iterator it = {0};
@@ -1488,7 +1484,8 @@ static int write_copy_table(struct reftable_writer *writer, void *cb_data)
 	 * copy over all log entries from the old reflog. Last but not least,
 	 * when renaming we also have to delete all the old reflog entries.
 	 */
-	ret = reftable_merged_table_seek_log(mt, &it, arg->oldname);
+	reftable_stack_init_log_iterator(arg->stack, &it);
+	ret = reftable_iterator_seek_log(&it, arg->oldname);
 	if (ret < 0)
 		goto done;
 
@@ -1694,7 +1691,6 @@ static struct ref_iterator_vtable reftable_reflog_iterator_vtable = {
 static struct reftable_reflog_iterator *reflog_iterator_for_stack(struct reftable_ref_store *refs,
 								  struct reftable_stack *stack)
 {
-	struct reftable_merged_table *merged_table;
 	struct reftable_reflog_iterator *iter;
 	int ret;
 
@@ -1711,9 +1707,8 @@ static struct reftable_reflog_iterator *reflog_iterator_for_stack(struct reftabl
 	if (ret < 0)
 		goto done;
 
-	merged_table = reftable_stack_merged_table(stack);
-
-	ret = reftable_merged_table_seek_log(merged_table, &iter->iter, "");
+	reftable_stack_init_log_iterator(stack, &iter->iter);
+	ret = reftable_iterator_seek_log(&iter->iter, "");
 	if (ret < 0)
 		goto done;
 
@@ -1771,16 +1766,15 @@ static int reftable_be_for_each_reflog_ent_reverse(struct ref_store *ref_store,
 	struct reftable_ref_store *refs =
 		reftable_be_downcast(ref_store, REF_STORE_READ, "for_each_reflog_ent_reverse");
 	struct reftable_stack *stack = stack_for(refs, refname, &refname);
-	struct reftable_merged_table *mt = NULL;
 	struct reftable_log_record log = {0};
 	struct reftable_iterator it = {0};
 	int ret;
 
 	if (refs->err < 0)
 		return refs->err;
 
-	mt = reftable_stack_merged_table(stack);
-	ret = reftable_merged_table_seek_log(mt, &it, refname);
+	reftable_stack_init_log_iterator(stack, &it);
+	ret = reftable_iterator_seek_log(&it, refname);
 	while (!ret) {
 		ret = reftable_iterator_next_log(&it, &log);
 		if (ret < 0)
@@ -1808,7 +1802,6 @@ static int reftable_be_for_each_reflog_ent(struct ref_store *ref_store,
 	struct reftable_ref_store *refs =
 		reftable_be_downcast(ref_store, REF_STORE_READ, "for_each_reflog_ent");
 	struct reftable_stack *stack = stack_for(refs, refname, &refname);
-	struct reftable_merged_table *mt = NULL;
 	struct reftable_log_record *logs = NULL;
 	struct reftable_iterator it = {0};
 	size_t logs_alloc = 0, logs_nr = 0, i;
@@ -1817,8 +1810,8 @@ static int reftable_be_for_each_reflog_ent(struct ref_store *ref_store,
 	if (refs->err < 0)
 		return refs->err;
 
-	mt = reftable_stack_merged_table(stack);
-	ret = reftable_merged_table_seek_log(mt, &it, refname);
+	reftable_stack_init_log_iterator(stack, &it);
+	ret = reftable_iterator_seek_log(&it, refname);
 	while (!ret) {
 		struct reftable_log_record log = {0};
 
@@ -1855,7 +1848,6 @@ static int reftable_be_reflog_exists(struct ref_store *ref_store,
 	struct reftable_ref_store *refs =
 		reftable_be_downcast(ref_store, REF_STORE_READ, "reflog_exists");
 	struct reftable_stack *stack = stack_for(refs, refname, &refname);
-	struct reftable_merged_table *mt = reftable_stack_merged_table(stack);
 	struct reftable_log_record log = {0};
 	struct reftable_iterator it = {0};
 	int ret;
@@ -1868,7 +1860,8 @@ static int reftable_be_reflog_exists(struct ref_store *ref_store,
 	if (ret < 0)
 		goto done;
 
-	ret = reftable_merged_table_seek_log(mt, &it, refname);
+	reftable_stack_init_log_iterator(stack, &it);
+	ret = reftable_iterator_seek_log(&it, refname);
 	if (ret < 0)
 		goto done;
 
@@ -1966,21 +1959,21 @@ struct write_reflog_delete_arg {
 static int write_reflog_delete_table(struct reftable_writer *writer, void *cb_data)
 {
 	struct write_reflog_delete_arg *arg = cb_data;
-	struct reftable_merged_table *mt =
-		reftable_stack_merged_table(arg->stack);
 	struct reftable_log_record log = {0}, tombstone = {0};
 	struct reftable_iterator it = {0};
 	uint64_t ts = reftable_stack_next_update_index(arg->stack);
 	int ret;
 
 	reftable_writer_set_limits(writer, ts, ts);
 
+	reftable_stack_init_log_iterator(arg->stack, &it);
+
 	/*
 	 * In order to delete a table we need to delete all reflog entries one
 	 * by one. This is inefficient, but the reftable format does not have a
 	 * better marker right now.
 	 */
-	ret = reftable_merged_table_seek_log(mt, &it, arg->refname);
+	ret = reftable_iterator_seek_log(&it, arg->refname);
 	while (ret == 0) {
 		ret = reftable_iterator_next_log(&it, &log);
 		if (ret < 0)
@@ -2116,7 +2109,6 @@ static int reftable_be_reflog_expire(struct ref_store *ref_store,
 	struct reftable_ref_store *refs =
 		reftable_be_downcast(ref_store, REF_STORE_WRITE, "reflog_expire");
 	struct reftable_stack *stack = stack_for(refs, refname, &refname);
-	struct reftable_merged_table *mt = reftable_stack_merged_table(stack);
 	struct reftable_log_record *logs = NULL;
 	struct reftable_log_record *rewritten = NULL;
 	struct reftable_ref_record ref_record = {0};
@@ -2135,7 +2127,9 @@ static int reftable_be_reflog_expire(struct ref_store *ref_store,
 	if (ret < 0)
 		goto done;
 
-	ret = reftable_merged_table_seek_log(mt, &it, refname);
+	reftable_stack_init_log_iterator(stack, &it);
+
+	ret = reftable_iterator_seek_log(&it, refname);
 	if (ret < 0)
 		goto done;
 

reftable/merged.c

@@ -253,9 +253,9 @@ reftable_merged_table_min_update_index(struct reftable_merged_table *mt)
 	return mt->min;
 }
 
-static void merged_table_init_iter(struct reftable_merged_table *mt,
-				   struct reftable_iterator *it,
-				   uint8_t typ)
+void merged_table_init_iter(struct reftable_merged_table *mt,
+			    struct reftable_iterator *it,
+			    uint8_t typ)
 {
 	struct merged_iter *mi = reftable_malloc(sizeof(*mi));
 	merged_iter_init(mi, mt, typ);

reftable/merged.h

@@ -26,4 +26,10 @@ struct reftable_merged_table {
 
 void merged_table_release(struct reftable_merged_table *mt);
 
+struct reftable_iterator;
+
+void merged_table_init_iter(struct reftable_merged_table *mt,
+			    struct reftable_iterator *it,
+			    uint8_t typ);
+
 #endif

reftable/reftable-stack.h

@@ -66,6 +66,24 @@ int reftable_stack_add(struct reftable_stack *st,
 					  void *write_arg),
 		       void *write_arg);
 
+struct reftable_iterator;
+
+/*
+ * Initialize an iterator for the merged tables contained in the stack that can
+ * be used to iterate through refs. The iterator is valid until the next reload
+ * or write.
+ */
+void reftable_stack_init_ref_iterator(struct reftable_stack *st,
+				      struct reftable_iterator *it);
+
+/*
+ * Initialize an iterator for the merged tables contained in the stack that can
+ * be used to iterate through logs. The iterator is valid until the next reload
+ * or write.
+ */
+void reftable_stack_init_log_iterator(struct reftable_stack *st,
+				      struct reftable_iterator *it);
+
 /* returns the merged_table for seeking. This table is valid until the
  * next write or reload, and should not be closed or deleted.
  */

reftable/stack.c

@@ -10,6 +10,7 @@ license that can be found in the LICENSE file or at
 
 #include "../write-or-die.h"
 #include "system.h"
+#include "constants.h"
 #include "merged.h"
 #include "reader.h"
 #include "reftable-error.h"
@@ -130,6 +131,20 @@ int read_lines(const char *filename, char ***namesp)
 	return err;
 }
 
+void reftable_stack_init_ref_iterator(struct reftable_stack *st,
+				      struct reftable_iterator *it)
+{
+	merged_table_init_iter(reftable_stack_merged_table(st),
+			       it, BLOCK_TYPE_REF);
+}
+
+void reftable_stack_init_log_iterator(struct reftable_stack *st,
+				      struct reftable_iterator *it)
+{
+	merged_table_init_iter(reftable_stack_merged_table(st),
+			       it, BLOCK_TYPE_LOG);
+}
+
 struct reftable_merged_table *
 reftable_stack_merged_table(struct reftable_stack *st)
 {