[Minor] Lua_tensor: Implement non-owning tensors (slices)

src/lua/lua_tensor.c

@@ -53,7 +53,7 @@ static luaL_reg rspamd_tensor_m[] = {
 };
 
 static struct rspamd_lua_tensor *
-lua_newtensor (lua_State *L, int ndims, const int *dim, bool zero_fill)
+lua_newtensor (lua_State *L, int ndims, const int *dim, bool zero_fill, bool own)
 {
 	struct rspamd_lua_tensor *res;
 
@@ -68,10 +68,16 @@ lua_newtensor (lua_State *L, int ndims, const int *dim, bool zero_fill)
 	}
 
 	/* To avoid allocating large stuff in Lua */
-	res->data = g_malloc (sizeof (rspamd_tensor_num_t) * res->size);
+	if (own) {
+		res->data = g_malloc (sizeof (rspamd_tensor_num_t) * res->size);
 
-	if (zero_fill) {
-		memset (res->data, 0, sizeof (rspamd_tensor_num_t) * res->size);
+		if (zero_fill) {
+			memset (res->data, 0, sizeof (rspamd_tensor_num_t) * res->size);
+		}
+	}
+	else {
+		/* Mark size negative to distinguish */
+		res->size = -(res->size);
 	}
 
 	rspamd_lua_setclass (L, TENSOR_CLASS, -1);
@@ -96,7 +102,7 @@ lua_tensor_new (lua_State *L)
 			dims[i] = lua_tointeger (L, i + 2);
 		}
 
-		(void)lua_newtensor (L, ndims, dims, true);
+		(void)lua_newtensor (L, ndims, dims, true, true);
 	}
 	else {
 		return luaL_error (L, "incorrect dimensions number: %d", ndims);
@@ -124,7 +130,7 @@ lua_tensor_fromtable (lua_State *L)
 			dims[1] = rspamd_lua_table_size (L, 1);
 
 			struct rspamd_lua_tensor *res = lua_newtensor (L, 2,
-					dims, false);
+					dims, false, true);
 
 			for (guint i = 0; i < dims[1]; i ++) {
 				lua_rawgeti (L, 1, i + 1);
@@ -179,7 +185,7 @@ lua_tensor_fromtable (lua_State *L)
 			dims[1] = ncols;
 
 			struct rspamd_lua_tensor *res = lua_newtensor (L, 2,
-					dims, false);
+					dims, false, true);
 
 			for (gint i = 0; i < nrows; i ++) {
 				lua_rawgeti (L, 1, i + 1);
@@ -219,7 +225,9 @@ lua_tensor_destroy (lua_State *L)
 	struct rspamd_lua_tensor *t = lua_check_tensor (L, 1);
 
 	if (t) {
-		g_free (t->data);
+		if (t->size > 0) {
+			g_free (t->data);
+		}
 	}
 
 	return 0;
@@ -234,19 +242,27 @@ static gint
 lua_tensor_save (lua_State *L)
 {
 	struct rspamd_lua_tensor *t = lua_check_tensor (L, 1);
+	gint size;
 
 	if (t) {
-		gsize sz = sizeof (gint) * 4 + t->size * sizeof (rspamd_tensor_num_t);
+		if (t->size > 0) {
+			size = t->size;
+		}
+		else {
+			size = -(t->size);
+		}
+
+		gsize sz = sizeof (gint) * 4 + size * sizeof (rspamd_tensor_num_t);
 		guchar *data;
 
 		struct rspamd_lua_text *out = lua_new_text (L, NULL, 0, TRUE);
 
 		data = g_malloc (sz);
 		memcpy (data, &t->ndims, sizeof (int));
-		memcpy (data + sizeof (int), &t->size, sizeof (int));
+		memcpy (data + sizeof (int), &size, sizeof (int));
 		memcpy (data + 2 * sizeof (int), t->dim, sizeof (int) * 2);
 		memcpy (data + 4 * sizeof (int), t->data,
-				t->size * sizeof (rspamd_tensor_num_t));
+				size * sizeof (rspamd_tensor_num_t));
 
 		out->start = (const gchar *)data;
 		out->len = sz;
@@ -324,11 +340,10 @@ lua_tensor_index (lua_State *L)
 
 
 				if (idx <= t->dim[0]) {
+					/* Non-owning tensor */
 					struct rspamd_lua_tensor *res =
-							lua_newtensor (L, 1, &dim, false);
-					for (gint i = 0; i < dim; i++) {
-						res->data[i] = t->data[(idx - 1) * t->dim[1] + i];
-					}
+							lua_newtensor (L, 1, &dim, false, false);
+					res->data = &t->data[(idx - 1) * t->dim[1]];
 				}
 				else {
 					lua_pushnil (L);

src/lua/lua_tensor.h

@@ -23,8 +23,8 @@ typedef float rspamd_tensor_num_t;
 struct rspamd_lua_tensor {
 	int ndims;
 	int size; /* overall size (product of dims) */
-	rspamd_tensor_num_t *data;
 	int dim[2];
+	rspamd_tensor_num_t *data;
 };
 
 struct rspamd_lua_tensor *lua_check_tensor (lua_State *L, int pos);