[Tarantool-patches] [PATCH 3/3] box: introduce box_return_mp() public C function
Igor Munkin
imun at tarantool.org
Fri Apr 3 17:13:01 MSK 2020
Vlad,
Thanks for the patch! LGTM except the one nit.
On 08.03.20, Vladislav Shpilevoy wrote:
> Closes #4641
>
> @TarantoolBot document
> Title: box_return_mp() public C function
>
> Stored C functions could return a result only via
> `box_return_tuple()` function. That made users create a tuple
> every time they wanted to return something from a C function.
>
> Now public C API offers another way to return - `box_return_mp()`.
> It allows to return arbitrary MessagePack, not wrapped into a
> tuple object. This is simpler to use for small results like a
> number, boolean, or a short string. Besides, `box_return_mp()` is
> much faster than `box_return_tuple()`, especially for small
> MessagePack.
>
> Note, that it is faster only if an alternative is to create a
> tuple by yourself. If an already existing tuple was obtained from
> an iterator, and you want to return it, then of course it is
> faster to return via `box_return_tuple()`, than via extraction of
> tuple data, and calling `box_return_mp()`.
>
> Here is the function declaration from module.h:
> ```C
> /**
> * Return MessagePack from a stored C procedure. The MessagePack
> * is copied, so it is safe to free/reuse the passed arguments
> * after the call.
> * MessagePack is not validated, for the sake of speed. It is
> * expected to be a single encoded object. An attempt to encode
> * and return multiple objects without wrapping them into an
> * MP_ARRAY or MP_MAP is undefined behaviour.
> *
> * \param ctx An opaque structure passed to the stored C procedure
> * by Tarantool.
> * \param mp Begin of MessagePack.
> * \param mp_end End of MessagePack.
> * \retval -1 Error.
> * \retval 0 Success.
> */
> API_EXPORT int
> box_return_mp(box_function_ctx_t *ctx, const char *mp, const char *mp_end);
> ```
> ---
> extra/exports | 1 +
> src/box/box.cc | 6 ++++++
> src/box/box.h | 19 +++++++++++++++++++
> test/box/function1.c | 37 +++++++++++++++++++++++++++++++++++++
> test/box/function1.result | 31 +++++++++++++++++++++++++++++++
> test/box/function1.test.lua | 14 ++++++++++++++
> 6 files changed, 108 insertions(+)
>
<snipped>
> diff --git a/test/box/function1.result b/test/box/function1.result
> index b91d63c51..301f666ef 100644
> --- a/test/box/function1.result
> +++ b/test/box/function1.result
> @@ -791,6 +791,37 @@ box.schema.func.drop("function1.multireturn")
> ---
> ...
> --
> +-- gh-4641: box_return_mp() C API to return arbitrary MessagePack
> +-- from C functions.
> +--
> +name = 'function1.test_return_mp'
> +---
> +...
> +box.schema.func.create(name, {language = "C", exports = {'LUA'}})
> +---
> +...
> +box.func[name]:call()
> +---
> +- 1
> +- -1
> +- 18446744073709551615
> +- '123456789101112131415'
> +- [2]
> +...
> +box.schema.user.grant('guest', 'super')
> +---
> +...
Minor: I guess it worth to add a comment below referring the #4799 since
I was confused with the output below.
> +net:connect(box.cfg.listen):call(name)
> +---
> +- [1, -1, 18446744073709551615, '123456789101112131415', [2]]
> +...
> +box.schema.user.revoke('guest', 'super')
> +---
> +...
> +box.schema.func.drop(name)
> +---
> +...
> +--
> -- gh-4182: Introduce persistent Lua functions.
> --
> test_run:cmd("setopt delimiter ';'")
<snipped>
> --
> 2.21.1 (Apple Git-122.3)
>
--
Best regards,
IM
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