Re: [Tarantool-patches] [PATCH v2 09/10] iproto: refactor error encoding with mpstream

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Thanks for the patch!

> diff --git a/src/box/xrow.c b/src/box/xrow.c
> index 5e3cb0709..256dd4d91 100644
> --- a/src/box/xrow.c
> +++ b/src/box/xrow.c
> @@ -478,46 +475,77 @@ iproto_reply_vote(struct obuf *out, const struct ballot *ballot,
>  int
>  iproto_reply_error(struct obuf *out, const struct error *e, uint64_t sync,
>  		   uint32_t schema_version)
>  {
> -	uint32_t msg_len = strlen(e->errmsg);
> -	uint32_t errcode = box_error_code(e);
> -
> -	struct iproto_body_bin body = iproto_error_bin;
>  	char *header = (char *)obuf_alloc(out, IPROTO_HEADER_LEN);
>  	if (header == NULL)
>  		return -1;
>  
> +	bool is_error = false;
> +	struct mpstream stream;
> +	mpstream_init(&stream, out, obuf_reserve_cb, obuf_alloc_cb,
> +		      mpstream_error_handler, &is_error);
> +
> +	uint32_t used = obuf_size(out);
> +	mpstream_iproto_encode_error(&stream, e);
> +	mpstream_flush(&stream);
> +
> +	uint32_t errcode = box_error_code(e);
>  	iproto_header_encode(header, iproto_encode_error(errcode), sync,
> -			     schema_version, sizeof(body) + msg_len);
> -	body.v_data_len = mp_bswap_u32(msg_len);
> +			     schema_version, obuf_size(out) - used);
> +
>  	/* Malformed packet appears to be a lesser evil than abort. */
> -	return obuf_dup(out, &body, sizeof(body)) != sizeof(body) ||
> -	       obuf_dup(out, e->errmsg, msg_len) != msg_len ? -1 : 0;
> +	return is_error;

The function is supposed to return 0/-1. So better keep this
convention. You can declare is_error as 'int rc', and set it to
-1 in mpstream_error_handler(). Should be fine. Or make it

    return is_error ? -1 : 0;