8 files changed, 60 insertions, 75 deletions
diff --git a/reftable/merged.c b/reftable/merged.c
index 25d414ec41..2e72eab306 100644
--- a/reftable/merged.c
+++ b/reftable/merged.c
@@ -11,6 +11,7 @@ https://developers.google.com/open-source/licenses/bsd
 #include "constants.h"
 #include "iter.h"
 #include "pq.h"
+#include "reader.h"
 #include "record.h"
 #include "generic.h"
 #include "reftable-merged.h"
@@ -25,7 +26,7 @@ struct merged_subiter {
 struct merged_iter {
 	struct merged_subiter *subiters;
 	struct merged_iter_pqueue pq;
-	size_t stack_len;
+	size_t subiters_len;
 	int suppress_deletions;
 	ssize_t advance_index;
 };
@@ -38,12 +39,12 @@ static void merged_iter_init(struct merged_iter *mi,
 	mi->advance_index = -1;
 	mi->suppress_deletions = mt->suppress_deletions;
 
-	REFTABLE_CALLOC_ARRAY(mi->subiters, mt->stack_len);
-	for (size_t i = 0; i < mt->stack_len; i++) {
+	REFTABLE_CALLOC_ARRAY(mi->subiters, mt->readers_len);
+	for (size_t i = 0; i < mt->readers_len; i++) {
 		reftable_record_init(&mi->subiters[i].rec, typ);
-		table_init_iter(&mt->stack[i], &mi->subiters[i].iter, typ);
+		reader_init_iter(mt->readers[i], &mi->subiters[i].iter, typ);
 	}
-	mi->stack_len = mt->stack_len;
+	mi->subiters_len = mt->readers_len;
 }
 
 static void merged_iter_close(void *p)
@@ -51,7 +52,7 @@ static void merged_iter_close(void *p)
 	struct merged_iter *mi = p;
 
 	merged_iter_pqueue_release(&mi->pq);
-	for (size_t i = 0; i < mi->stack_len; i++) {
+	for (size_t i = 0; i < mi->subiters_len; i++) {
 		reftable_iterator_destroy(&mi->subiters[i].iter);
 		reftable_record_release(&mi->subiters[i].rec);
 	}
@@ -80,7 +81,7 @@ static int merged_iter_seek(struct merged_iter *mi, struct reftable_record *want
 
 	mi->advance_index = -1;
 
-	for (size_t i = 0; i < mi->stack_len; i++) {
+	for (size_t i = 0; i < mi->subiters_len; i++) {
 		err = iterator_seek(&mi->subiters[i].iter, want);
 		if (err < 0)
 			return err;
@@ -193,7 +194,7 @@ static void iterator_from_merged_iter(struct reftable_iterator *it,
 }
 
 int reftable_merged_table_new(struct reftable_merged_table **dest,
-			      struct reftable_table *stack, size_t n,
+			      struct reftable_reader **readers, size_t n,
 			      uint32_t hash_id)
 {
 	struct reftable_merged_table *m = NULL;
@@ -201,10 +202,10 @@ int reftable_merged_table_new(struct reftable_merged_table **dest,
 	uint64_t first_min = 0;
 
 	for (size_t i = 0; i < n; i++) {
-		uint64_t min = reftable_table_min_update_index(&stack[i]);
-		uint64_t max = reftable_table_max_update_index(&stack[i]);
+		uint64_t min = reftable_reader_min_update_index(readers[i]);
+		uint64_t max = reftable_reader_max_update_index(readers[i]);
 
-		if (reftable_table_hash_id(&stack[i]) != hash_id) {
+		if (reftable_reader_hash_id(readers[i]) != hash_id) {
 			return REFTABLE_FORMAT_ERROR;
 		}
 		if (i == 0 || min < first_min) {
@@ -216,8 +217,8 @@ int reftable_merged_table_new(struct reftable_merged_table **dest,
 	}
 
 	REFTABLE_CALLOC_ARRAY(m, 1);
-	m->stack = stack;
-	m->stack_len = n;
+	m->readers = readers;
+	m->readers_len = n;
 	m->min = first_min;
 	m->max = last_max;
 	m->hash_id = hash_id;
@@ -229,7 +230,6 @@ void reftable_merged_table_free(struct reftable_merged_table *mt)
 {
 	if (!mt)
 		return;
-	FREE_AND_NULL(mt->stack);
 	reftable_free(mt);
 }
 
diff --git a/reftable/merged.h b/reftable/merged.h
index 2efe571da6..de5fd33f01 100644
--- a/reftable/merged.h
+++ b/reftable/merged.h
@@ -12,8 +12,8 @@ https://developers.google.com/open-source/licenses/bsd
 #include "system.h"
 
 struct reftable_merged_table {
-	struct reftable_table *stack;
-	size_t stack_len;
+	struct reftable_reader **readers;
+	size_t readers_len;
 	uint32_t hash_id;
 
 	/* If unset, produce deletions. This is useful for compaction. For the
diff --git a/reftable/reader.c b/reftable/reader.c
index 29c99e2269..f7ae35da72 100644
--- a/reftable/reader.c
+++ b/reftable/reader.c
@@ -605,9 +605,9 @@ static void iterator_from_table_iter(struct reftable_iterator *it,
 	it->ops = &table_iter_vtable;
 }
 
-static void reader_init_iter(struct reftable_reader *r,
-			     struct reftable_iterator *it,
-			     uint8_t typ)
+void reader_init_iter(struct reftable_reader *r,
+		      struct reftable_iterator *it,
+		      uint8_t typ)
 {
 	struct reftable_reader_offsets *offs = reader_offsets_for(r, typ);
 
diff --git a/reftable/reader.h b/reftable/reader.h
index e869165f23..a2c204d523 100644
--- a/reftable/reader.h
+++ b/reftable/reader.h
@@ -57,6 +57,10 @@ int init_reader(struct reftable_reader *r, struct reftable_block_source *source,
 void reader_close(struct reftable_reader *r);
 const char *reader_name(struct reftable_reader *r);
 
+void reader_init_iter(struct reftable_reader *r,
+		      struct reftable_iterator *it,
+		      uint8_t typ);
+
 /* initialize a block reader to read from `r` */
 int reader_init_block_reader(struct reftable_reader *r, struct block_reader *br,
 			     uint64_t next_off, uint8_t want_typ);
diff --git a/reftable/reftable-merged.h b/reftable/reftable-merged.h
index 72762483b9..03c2619c0f 100644
--- a/reftable/reftable-merged.h
+++ b/reftable/reftable-merged.h
@@ -28,13 +28,14 @@ struct reftable_merged_table;
 
 /* A generic reftable; see below. */
 struct reftable_table;
+struct reftable_reader;
 
 /*
- * reftable_merged_table_new creates a new merged table. It takes ownership of
- * the stack array.
+ * reftable_merged_table_new creates a new merged table. The readers must be
+ * kept alive as long as the merged table is still in use.
  */
 int reftable_merged_table_new(struct reftable_merged_table **dest,
-			      struct reftable_table *stack, size_t n,
+			      struct reftable_reader **readers, size_t n,
 			      uint32_t hash_id);
 
 /* Initialize a merged table iterator for reading refs. */
diff --git a/reftable/stack.c b/reftable/stack.c
index 64c7fdf8c4..7f4e267ea9 100644
--- a/reftable/stack.c
+++ b/reftable/stack.c
@@ -225,13 +225,11 @@ static int reftable_stack_reload_once(struct reftable_stack *st,
 				      const char **names,
 				      int reuse_open)
 {
-	size_t cur_len = !st->merged ? 0 : st->merged->stack_len;
+	size_t cur_len = !st->merged ? 0 : st->merged->readers_len;
 	struct reftable_reader **cur = stack_copy_readers(st, cur_len);
 	size_t names_len = names_length(names);
 	struct reftable_reader **new_readers =
 		reftable_calloc(names_len, sizeof(*new_readers));
-	struct reftable_table *new_tables =
-		reftable_calloc(names_len, sizeof(*new_tables));
 	size_t new_readers_len = 0;
 	struct reftable_merged_table *new_merged = NULL;
 	struct strbuf table_path = STRBUF_INIT;
@@ -267,17 +265,15 @@ static int reftable_stack_reload_once(struct reftable_stack *st,
 		}
 
 		new_readers[new_readers_len] = rd;
-		reftable_table_from_reader(&new_tables[new_readers_len], rd);
 		new_readers_len++;
 	}
 
 	/* success! */
-	err = reftable_merged_table_new(&new_merged, new_tables,
+	err = reftable_merged_table_new(&new_merged, new_readers,
 					new_readers_len, st->opts.hash_id);
 	if (err < 0)
 		goto done;
 
-	new_tables = NULL;
 	st->readers_len = new_readers_len;
 	if (st->merged)
 		reftable_merged_table_free(st->merged);
@@ -309,7 +305,6 @@ done:
 		reftable_reader_free(new_readers[i]);
 	}
 	reftable_free(new_readers);
-	reftable_free(new_tables);
 	reftable_free(cur);
 	strbuf_release(&table_path);
 	return err;
@@ -520,7 +515,7 @@ static int stack_uptodate(struct reftable_stack *st)
 		}
 	}
 
-	if (names[st->merged->stack_len]) {
+	if (names[st->merged->readers_len]) {
 		err = 1;
 		goto done;
 	}
@@ -659,7 +654,7 @@ int reftable_addition_commit(struct reftable_addition *add)
 	if (add->new_tables_len == 0)
 		goto done;
 
-	for (i = 0; i < add->stack->merged->stack_len; i++) {
+	for (i = 0; i < add->stack->merged->readers_len; i++) {
 		strbuf_addstr(&table_list, add->stack->readers[i]->name);
 		strbuf_addstr(&table_list, "\n");
 	}
@@ -839,7 +834,7 @@ done:
 
 uint64_t reftable_stack_next_update_index(struct reftable_stack *st)
 {
-	int sz = st->merged->stack_len;
+	int sz = st->merged->readers_len;
 	if (sz > 0)
 		return reftable_reader_max_update_index(st->readers[sz - 1]) +
 		       1;
@@ -906,30 +901,23 @@ static int stack_write_compact(struct reftable_stack *st,
 			       size_t first, size_t last,
 			       struct reftable_log_expiry_config *config)
 {
-	size_t subtabs_len = last - first + 1;
-	struct reftable_table *subtabs = reftable_calloc(
-		last - first + 1, sizeof(*subtabs));
 	struct reftable_merged_table *mt = NULL;
 	struct reftable_iterator it = { NULL };
 	struct reftable_ref_record ref = { NULL };
 	struct reftable_log_record log = { NULL };
+	size_t subtabs_len = last - first + 1;
 	uint64_t entries = 0;
 	int err = 0;
 
-	for (size_t i = first, j = 0; i <= last; i++) {
-		struct reftable_reader *t = st->readers[i];
-		reftable_table_from_reader(&subtabs[j++], t);
-		st->stats.bytes += t->size;
-	}
+	for (size_t i = first; i <= last; i++)
+		st->stats.bytes += st->readers[i]->size;
 	reftable_writer_set_limits(wr, st->readers[first]->min_update_index,
 				   st->readers[last]->max_update_index);
 
-	err = reftable_merged_table_new(&mt, subtabs, subtabs_len,
+	err = reftable_merged_table_new(&mt, st->readers + first, subtabs_len,
 					st->opts.hash_id);
-	if (err < 0) {
-		reftable_free(subtabs);
+	if (err < 0)
 		goto done;
-	}
 
 	merged_table_init_iter(mt, &it, BLOCK_TYPE_REF);
 	err = reftable_iterator_seek_ref(&it, "");
@@ -1207,7 +1195,7 @@ static int stack_compact_range(struct reftable_stack *st,
 			 * have compacted them.
 			 */
 			for (size_t j = 1; j < last - first + 1; j++) {
-				const char *old = first + j < st->merged->stack_len ?
+				const char *old = first + j < st->merged->readers_len ?
 					st->readers[first + j]->name : NULL;
 				const char *new = names[i + j];
 
@@ -1248,10 +1236,10 @@ static int stack_compact_range(struct reftable_stack *st,
 		 * `fd_read_lines()` uses a `NULL` sentinel to indicate that
 		 * the array is at its end. As we use `free_names()` to free
 		 * the array, we need to include this sentinel value here and
-		 * thus have to allocate `stack_len + 1` many entries.
+		 * thus have to allocate `readers_len + 1` many entries.
 		 */
-		REFTABLE_CALLOC_ARRAY(names, st->merged->stack_len + 1);
-		for (size_t i = 0; i < st->merged->stack_len; i++)
+		REFTABLE_CALLOC_ARRAY(names, st->merged->readers_len + 1);
+		for (size_t i = 0; i < st->merged->readers_len; i++)
 			names[i] = xstrdup(st->readers[i]->name);
 		first_to_replace = first;
 		last_to_replace = last;
@@ -1358,7 +1346,7 @@ static int stack_compact_range_stats(struct reftable_stack *st,
 int reftable_stack_compact_all(struct reftable_stack *st,
 			       struct reftable_log_expiry_config *config)
 {
-	size_t last = st->merged->stack_len ? st->merged->stack_len - 1 : 0;
+	size_t last = st->merged->readers_len ? st->merged->readers_len - 1 : 0;
 	return stack_compact_range_stats(st, 0, last, config, 0);
 }
 
@@ -1449,9 +1437,9 @@ static uint64_t *stack_table_sizes_for_compaction(struct reftable_stack *st)
 	int overhead = header_size(version) - 1;
 	uint64_t *sizes;
 
-	REFTABLE_CALLOC_ARRAY(sizes, st->merged->stack_len);
+	REFTABLE_CALLOC_ARRAY(sizes, st->merged->readers_len);
 
-	for (size_t i = 0; i < st->merged->stack_len; i++)
+	for (size_t i = 0; i < st->merged->readers_len; i++)
 		sizes[i] = st->readers[i]->size - overhead;
 
 	return sizes;
@@ -1461,7 +1449,7 @@ int reftable_stack_auto_compact(struct reftable_stack *st)
 {
 	uint64_t *sizes = stack_table_sizes_for_compaction(st);
 	struct segment seg =
-		suggest_compaction_segment(sizes, st->merged->stack_len,
+		suggest_compaction_segment(sizes, st->merged->readers_len,
 					   st->opts.auto_compaction_factor);
 	reftable_free(sizes);
 	if (segment_size(&seg) > 0)
diff --git a/reftable/stack_test.c b/reftable/stack_test.c
index 8c36590ff0..dbca9eaf4a 100644
--- a/reftable/stack_test.c
+++ b/reftable/stack_test.c
@@ -347,9 +347,9 @@ static void test_reftable_stack_transaction_api_performs_auto_compaction(void)
 		 * all tables in the stack.
 		 */
 		if (i != n)
-			EXPECT(st->merged->stack_len == i + 1);
+			EXPECT(st->merged->readers_len == i + 1);
 		else
-			EXPECT(st->merged->stack_len == 1);
+			EXPECT(st->merged->readers_len == 1);
 	}
 
 	reftable_stack_destroy(st);
@@ -375,7 +375,7 @@ static void test_reftable_stack_auto_compaction_fails_gracefully(void)
 
 	err = reftable_stack_add(st, write_test_ref, &ref);
 	EXPECT_ERR(err);
-	EXPECT(st->merged->stack_len == 1);
+	EXPECT(st->merged->readers_len == 1);
 	EXPECT(st->stats.attempts == 0);
 	EXPECT(st->stats.failures == 0);
 
@@ -390,7 +390,7 @@ static void test_reftable_stack_auto_compaction_fails_gracefully(void)
 	ref.update_index = 2;
 	err = reftable_stack_add(st, write_test_ref, &ref);
 	EXPECT_ERR(err);
-	EXPECT(st->merged->stack_len == 2);
+	EXPECT(st->merged->readers_len == 2);
 	EXPECT(st->stats.attempts == 1);
 	EXPECT(st->stats.failures == 1);
 
@@ -881,7 +881,7 @@ static void test_reftable_stack_auto_compaction(void)
 
 		err = reftable_stack_auto_compact(st);
 		EXPECT_ERR(err);
-		EXPECT(i < 3 || st->merged->stack_len < 2 * fastlog2(i));
+		EXPECT(i < 3 || st->merged->readers_len < 2 * fastlog2(i));
 	}
 
 	EXPECT(reftable_stack_compaction_stats(st)->entries_written <
@@ -905,7 +905,7 @@ static void test_reftable_stack_auto_compaction_with_locked_tables(void)
 	EXPECT_ERR(err);
 
 	write_n_ref_tables(st, 5);
-	EXPECT(st->merged->stack_len == 5);
+	EXPECT(st->merged->readers_len == 5);
 
 	/*
 	 * Given that all tables we have written should be roughly the same
@@ -925,7 +925,7 @@ static void test_reftable_stack_auto_compaction_with_locked_tables(void)
 	err = reftable_stack_auto_compact(st);
 	EXPECT_ERR(err);
 	EXPECT(st->stats.failures == 0);
-	EXPECT(st->merged->stack_len == 4);
+	EXPECT(st->merged->readers_len == 4);
 
 	reftable_stack_destroy(st);
 	strbuf_release(&buf);
@@ -970,9 +970,9 @@ static void test_reftable_stack_add_performs_auto_compaction(void)
 		 * all tables in the stack.
 		 */
 		if (i != n)
-			EXPECT(st->merged->stack_len == i + 1);
+			EXPECT(st->merged->readers_len == i + 1);
 		else
-			EXPECT(st->merged->stack_len == 1);
+			EXPECT(st->merged->readers_len == 1);
 	}
 
 	reftable_stack_destroy(st);
@@ -994,7 +994,7 @@ static void test_reftable_stack_compaction_with_locked_tables(void)
 	EXPECT_ERR(err);
 
 	write_n_ref_tables(st, 3);
-	EXPECT(st->merged->stack_len == 3);
+	EXPECT(st->merged->readers_len == 3);
 
 	/* Lock one of the tables that we're about to compact. */
 	strbuf_reset(&buf);
@@ -1008,7 +1008,7 @@ static void test_reftable_stack_compaction_with_locked_tables(void)
 	err = reftable_stack_compact_all(st, NULL);
 	EXPECT(err == REFTABLE_LOCK_ERROR);
 	EXPECT(st->stats.failures == 1);
-	EXPECT(st->merged->stack_len == 3);
+	EXPECT(st->merged->readers_len == 3);
 
 	reftable_stack_destroy(st);
 	strbuf_release(&buf);
diff --git a/t/unit-tests/t-reftable-merged.c b/t/unit-tests/t-reftable-merged.c
index 210603e8c7..577b1a5be8 100644
--- a/t/unit-tests/t-reftable-merged.c
+++ b/t/unit-tests/t-reftable-merged.c
@@ -94,10 +94,8 @@ merged_table_from_records(struct reftable_ref_record **refs,
 			  struct strbuf *buf, const size_t n)
 {
 	struct reftable_merged_table *mt = NULL;
-	struct reftable_table *tabs;
 	int err;
 
-	REFTABLE_CALLOC_ARRAY(tabs, n);
 	REFTABLE_CALLOC_ARRAY(*readers, n);
 	REFTABLE_CALLOC_ARRAY(*source, n);
 
@@ -108,10 +106,9 @@ merged_table_from_records(struct reftable_ref_record **refs,
 		err = reftable_new_reader(&(*readers)[i], &(*source)[i],
 					  "name");
 		check(!err);
-		reftable_table_from_reader(&tabs[i], (*readers)[i]);
 	}
 
-	err = reftable_merged_table_new(&mt, tabs, n, GIT_SHA1_FORMAT_ID);
+	err = reftable_merged_table_new(&mt, *readers, n, GIT_SHA1_FORMAT_ID);
 	check(!err);
 	return mt;
 }
@@ -272,10 +269,8 @@ merged_table_from_log_records(struct reftable_log_record **logs,
 			      struct strbuf *buf, const size_t n)
 {
 	struct reftable_merged_table *mt = NULL;
-	struct reftable_table *tabs;
 	int err;
 
-	REFTABLE_CALLOC_ARRAY(tabs, n);
 	REFTABLE_CALLOC_ARRAY(*readers, n);
 	REFTABLE_CALLOC_ARRAY(*source, n);
 
@@ -286,10 +281,9 @@ merged_table_from_log_records(struct reftable_log_record **logs,
 		err = reftable_new_reader(&(*readers)[i], &(*source)[i],
 					  "name");
 		check(!err);
-		reftable_table_from_reader(&tabs[i], (*readers)[i]);
 	}
 
-	err = reftable_merged_table_new(&mt, tabs, n, GIT_SHA1_FORMAT_ID);
+	err = reftable_merged_table_new(&mt, *readers, n, GIT_SHA1_FORMAT_ID);
 	check(!err);
 	return mt;
 }
@@ -418,7 +412,6 @@ static void t_default_write_opts(void)
 	};
 	int err;
 	struct reftable_block_source source = { 0 };
-	struct reftable_table *tab = reftable_calloc(1, sizeof(*tab));
 	uint32_t hash_id;
 	struct reftable_reader *rd = NULL;
 	struct reftable_merged_table *merged = NULL;
@@ -440,10 +433,9 @@ static void t_default_write_opts(void)
 	hash_id = reftable_reader_hash_id(rd);
 	check_int(hash_id, ==, GIT_SHA1_FORMAT_ID);
 
-	reftable_table_from_reader(&tab[0], rd);
-	err = reftable_merged_table_new(&merged, tab, 1, GIT_SHA256_FORMAT_ID);
+	err = reftable_merged_table_new(&merged, &rd, 1, GIT_SHA256_FORMAT_ID);
 	check_int(err, ==, REFTABLE_FORMAT_ERROR);
-	err = reftable_merged_table_new(&merged, tab, 1, GIT_SHA1_FORMAT_ID);
+	err = reftable_merged_table_new(&merged, &rd, 1, GIT_SHA1_FORMAT_ID);
 	check(!err);
 
 	reftable_reader_free(rd);