[PATCH v3 6/7] box: introduce field_map_builder class

[Vladimir Davydov]

On Tue, Apr 02, 2019 at 06:49:37PM +0300, Kirill Shcherbatov wrote:
> diff --git a/src/box/tuple_format.c b/src/box/tuple_format.c
> index 070897ec2..9a643b700 100644
> --- a/src/box/tuple_format.c
> +++ b/src/box/tuple_format.c
> @@ -769,27 +769,21 @@ tuple_format1_can_store_format2_tuples(struct tuple_format *format1,
>  
>  /** @sa declaration for details. */
>  int
> -tuple_field_map_create(struct tuple_format *format, const char *tuple,
> -		       bool validate, uint32_t **field_map,
> -		       uint32_t *field_map_size)
> +tuple_field_map_create(struct field_map_builder *builder,
> +		       struct tuple_format *format, const char *tuple,
> +		       bool validate)

The field map builder should be the last in the argument list as it is
an out parameter.

>  {
> +	struct region *region = &fiber()->gc;
>  	if (tuple_format_field_count(format) == 0) {
> -		*field_map = NULL;
> -		*field_map_size = 0;
> +		/* Nothing to initialize */
> +		if (field_map_builder_create(builder, 0, region) != 0)
> +			unreachable();

Nit: no need in this branching. You could create a builder with
format->field_map_size in both cases.

>  		return 0; /* Nothing to initialize */
>  	}
> -	struct region *region = &fiber()->gc;
> -	*field_map_size = format->field_map_size;
> -	*field_map = region_alloc(region, *field_map_size);
> -	if (*field_map == NULL) {
> -		diag_set(OutOfMemory, *field_map_size, "region_alloc",
> -			 "field_map");
> +	if (field_map_builder_create(builder, format->field_map_size,
> +				     region) != 0)
>  		return -1;
> -	}
> -	*field_map = (uint32_t *)((char *)*field_map + *field_map_size);
> -
>  	const char *pos = tuple;
> -	int rc = 0;
>  	/* Check to see if the tuple has a sufficient number of fields. */
>  	uint32_t field_count = mp_decode_array(&pos);
>  	if (validate && format->exact_field_count > 0 &&

> diff --git a/src/box/tuple_format.h b/src/box/tuple_format.h
> index bef1d0903..88f03d5eb 100644
> --- a/src/box/tuple_format.h
> +++ b/src/box/tuple_format.h
> @@ -36,6 +36,7 @@
>  #include "errinj.h"
>  #include "json/json.h"
>  #include "tuple_dictionary.h"
> +#include "field_map.h"
>  
>  #if defined(__cplusplus)
>  extern "C" {
> @@ -169,8 +170,9 @@ struct tuple_format {
>  	 */
>  	bool is_ephemeral;
>  	/**
> -	 * Size of field map of tuple in bytes.
> -	 * \sa struct tuple
> +	 * Size of minimal field map of tuple where each indexed
> +	 * field has own offset slot (in bytes).
> +	 * \sa struct field_map_builder
>  	 */

Minimal? What's that supposed to mean? Is it from the next patch?

Other than that, looks okay to me.