[PATCH v3 3/4] box: introduce tuple_extra infrastructure

[Kirill Shcherbatov <kshcherbatov@tarantool.org>]

Introduced a new object tuple_extra: a memory allocation is
associated with given tuple and chunk_id. Extended tuple_format's
vtab with few new methods to manage tuple_extras lifecycle.
Supported tuple_extra for memtx engine: a memory
chunks are allocated with memtx's smalloc allocator.

Needed for #1260
---
 src/box/memtx_engine.c | 29 +++++++++++++++++++++++++++++
 src/box/tuple.c        |  8 ++++++++
 src/box/tuple.h        | 39 +++++++++++++++++++++++++++++++++++++++
 src/box/tuple_format.h | 15 +++++++++++++++
 src/box/vy_stmt.c      |  2 ++
 5 files changed, 93 insertions(+)

diff --git a/src/box/memtx_engine.c b/src/box/memtx_engine.c
index 428491c2d..49efcc192 100644
--- a/src/box/memtx_engine.c
+++ b/src/box/memtx_engine.c
@@ -1126,9 +1126,38 @@ memtx_tuple_delete(struct tuple_format *format, struct tuple *tuple)
 		smfree_delayed(&memtx->alloc, memtx_tuple, total);
 }
 
+void
+metmx_tuple_extra_delete(struct tuple_format *format,
+			 struct tuple_extra *tuple_extra)
+{
+	struct memtx_engine *memtx = (struct memtx_engine *)format->engine;
+	uint32_t sz = tuple_extra_sz(tuple_extra->data_sz);
+	smfree(&memtx->alloc, tuple_extra, sz);
+}
+
+struct tuple_extra *
+memtx_tuple_extra_new(struct tuple_format *format, struct tuple *tuple,
+		      uint32_t chunk_id, uint32_t data_sz)
+{
+	struct memtx_engine *memtx = (struct memtx_engine *)format->engine;
+	uint32_t sz = tuple_extra_sz(data_sz);
+	struct tuple_extra *tuple_extra =
+		(struct tuple_extra *) smalloc(&memtx->alloc, sz);
+	if (tuple == NULL) {
+		diag_set(OutOfMemory, sz, "smalloc", "tuple");
+		return NULL;
+	}
+	tuple_extra->tuple = tuple;
+	tuple_extra->chunk_id = chunk_id;
+	tuple_extra->data_sz = data_sz;
+	return tuple_extra;
+}
+
 struct tuple_format_vtab memtx_tuple_format_vtab = {
 	memtx_tuple_delete,
 	memtx_tuple_new,
+	metmx_tuple_extra_delete,
+	memtx_tuple_extra_new,
 };
 
 /**
diff --git a/src/box/tuple.c b/src/box/tuple.c
index c0e94d55b..ca0e5230a 100644
--- a/src/box/tuple.c
+++ b/src/box/tuple.c
@@ -67,6 +67,8 @@ runtime_tuple_new(struct tuple_format *format, const char *data, const char *end
 static struct tuple_format_vtab tuple_format_runtime_vtab = {
 	runtime_tuple_delete,
 	runtime_tuple_new,
+	NULL,
+	NULL,
 };
 
 static struct tuple *
@@ -785,3 +787,9 @@ mp_str(const char *data)
 		return "<failed to format message pack>";
 	return buf;
 }
+
+uint32_t
+tuple_extra_sz(uint32_t data_sz)
+{
+	return sizeof(struct tuple_extra) + data_sz;
+}
diff --git a/src/box/tuple.h b/src/box/tuple.h
index 99dfeb82d..70119292e 100644
--- a/src/box/tuple.h
+++ b/src/box/tuple.h
@@ -447,6 +447,45 @@ tuple_delete(struct tuple *tuple)
 	format->vtab.tuple_delete(format, tuple);
 }
 
+/** Tuple metadata hashtable entry. */
+struct tuple_extra {
+	/** Tuple pointer is used as a hash key. */
+	struct tuple *tuple;
+	/** An extention identifier. */
+	uint32_t chunk_id;
+	/** The payload size. Needed to perform memory release.*/
+	uint32_t data_sz;
+	/** Metadata object payload. */
+	char data[0];
+};
+
+/** Calculate the size of tuple_extra object by given data_sz. */
+uint32_t
+tuple_extra_sz(uint32_t data_sz);
+
+/**
+ * Allocate a new extra allocation for given tuple and
+ * unique chunk_id identifier.
+ */
+static inline struct tuple_extra *
+tuple_extra_new(struct tuple *tuple, uint32_t chunk_id, uint32_t data_sz)
+{
+	struct tuple_format *format = tuple_format(tuple);
+	return format->vtab.tuple_extra_new(format, tuple, chunk_id, data_sz);
+}
+
+/**
+ * Free allocated tuple extra for given tuple and unique
+ * chunk_id identifier.
+ */
+static inline void
+tuple_extra_delete(struct tuple_extra *tuple_extra)
+{
+	struct tuple_format *format =
+		tuple_format(tuple_extra->tuple);
+	format->vtab.tuple_extra_delete(format, tuple_extra);
+}
+
 /**
  * Check tuple data correspondence to space format.
  * Actually, checks everything that is checked by
diff --git a/src/box/tuple_format.h b/src/box/tuple_format.h
index e4f5f0018..ac4f8a702 100644
--- a/src/box/tuple_format.h
+++ b/src/box/tuple_format.h
@@ -64,6 +64,7 @@ enum { TUPLE_INDEX_BASE = 1 };
 enum { TUPLE_OFFSET_SLOT_NIL = INT32_MAX };
 
 struct tuple;
+struct tuple_extra;
 struct tuple_format;
 struct coll;
 
@@ -82,6 +83,20 @@ struct tuple_format_vtab {
 	struct tuple*
 	(*tuple_new)(struct tuple_format *format, const char *data,
 	             const char *end);
+	/**
+	 * Free allocated tuple extra for given tuple and unique
+	 * chunk_id identifier.
+	 */
+	void
+	(*tuple_extra_delete)(struct tuple_format *format,
+			      struct tuple_extra *tuple_extra);
+	/**
+	 * Allocate a new extra allocation for given tuple and
+	 * unique chunk_id identifier.
+	 */
+	struct tuple_extra *
+	(*tuple_extra_new)(struct tuple_format *format, struct tuple *tuple,
+			   uint32_t chunk_id, uint32_t data_sz);
 };
 
 /** Tuple field meta information for tuple_format. */
diff --git a/src/box/vy_stmt.c b/src/box/vy_stmt.c
index f936cd61f..6b09e5e53 100644
--- a/src/box/vy_stmt.c
+++ b/src/box/vy_stmt.c
@@ -118,6 +118,8 @@ vy_stmt_env_create(struct vy_stmt_env *env)
 {
 	env->tuple_format_vtab.tuple_new = vy_tuple_new;
 	env->tuple_format_vtab.tuple_delete = vy_tuple_delete;
+	env->tuple_format_vtab.tuple_extra_new = NULL;
+	env->tuple_format_vtab.tuple_extra_delete = NULL;
 	env->max_tuple_size = 1024 * 1024;
 	env->key_format = vy_stmt_format_new(env, NULL, 0, NULL, 0, 0, NULL);
 	if (env->key_format == NULL)
-- 
2.22.0