Tarantool development patches archive
 help / color / mirror / Atom feed
From: Vladislav Shpilevoy via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: imeevma@tarantool.org, tsafin@tarantool.org
Cc: tarantool-patches@dev.tarantool.org
Subject: Re: [Tarantool-patches] [PATCH v5 49/52] sql: introduce mem_get_str0() and mem_as_str0()
Date: Wed, 14 Apr 2021 01:06:09 +0200	[thread overview]
Message-ID: <57b42211-19a9-1629-5d91-bc2e729f7dee@tarantool.org> (raw)
In-Reply-To: <056987bba3f23e3298201d14728452f3033a166c.1618000037.git.imeevma@gmail.com>

Thanks for the discussion!

See 2 comments below.

1. With this getter it is less trivial than with the previous
ones.

I just realized, that we call mem_as_str() on function arguments.
What if a mem is passed to multiple functions, and one of them
changes it affecting the other functions? What if the same function
is called multiple times during a query? - the first execution
affects the argument for the next executions? Does not look right.
Am I missing something?

It seems that could be fixed not so hard.

If the value is already a 0-terminated string, we return it.
If it is a blob or not terminated string, we extended it, add 0,
and return. It does not really change the original value anyway.
Mem.n stays the same, and the first n bytes stay the same.
If it is a number, we can save its string representation to
Mem.z, which is not used for numbers.

Will it work?

> diff --git a/src/box/sql/mem.h b/src/box/sql/mem.h
> index e48e8788c..5848ae729 100644
> --- a/src/box/sql/mem.h
> +++ b/src/box/sql/mem.h
> @@ -568,6 +568,28 @@ mem_get_double(const struct Mem *mem, double *d);
>  int
>  mem_get_bool(const struct Mem *mem, bool *b);
>  
> +/**
> + * Return value for MEM of STRING type if MEM contains a NULL-terminated string.
> + * Otherwise convert value of the MEM to NULL-terminated string if possible and
> + * return converted value. Original MEM is not changed.
> + */
> +int
> +mem_get_str0(const struct Mem *mem, const char **s);
> +
> +/**
> + * Return value for MEM of STRING type if MEM contains NULL-terminated string.
> + * Otherwise convert MEM to MEM of string type that contains NULL-terminated
> + * string and return its value. Return NULL if conversion is impossible.
> + */
> +static inline const char *
> +mem_as_str0(struct Mem *mem)
> +{
> + const char *str;
> + if (mem_to_str0(mem) != 0 || mem_get_str0(mem, &str) != 0)

2. If mem_to_str0 succeeded, why can't you return mem->z right away?

> +   return NULL;
> + return str;
> +}

  reply	other threads:[~2021-04-13 23:06 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <cover.1618000036.git.imeevma@gmail.com>
2021-04-09 20:53 ` [Tarantool-patches] [PATCH v5 41/52] sql: introduce mem_to_number() Mergen Imeev via Tarantool-patches
2021-04-13 23:25   ` Mergen Imeev via Tarantool-patches
2021-04-09 20:53 ` [Tarantool-patches] [PATCH v5 42/52] sql: introduce mem_to_str() and mem_to_str0() Mergen Imeev via Tarantool-patches
2021-04-13 22:58   ` Vladislav Shpilevoy via Tarantool-patches
2021-04-13 23:41     ` Mergen Imeev via Tarantool-patches
2021-04-09 20:53 ` [Tarantool-patches] [PATCH v5 43/52] sql: introduce mem_cast_explicit() Mergen Imeev via Tarantool-patches
2021-04-13 22:59   ` Vladislav Shpilevoy via Tarantool-patches
2021-04-14  0:01     ` Mergen Imeev via Tarantool-patches
2021-04-09 20:53 ` [Tarantool-patches] [PATCH v5 44/52] sql: introduce mem_cast_implicit() Mergen Imeev via Tarantool-patches
2021-04-13 22:59   ` Vladislav Shpilevoy via Tarantool-patches
2021-04-14  0:05     ` Mergen Imeev via Tarantool-patches
2021-04-09 20:53 ` [Tarantool-patches] [PATCH v5 45/52] sql: introduce mem_get_int() Mergen Imeev via Tarantool-patches
2021-04-13 23:01   ` Vladislav Shpilevoy via Tarantool-patches
2021-04-14  0:28     ` Mergen Imeev via Tarantool-patches
2021-04-14  1:17       ` Mergen Imeev via Tarantool-patches
2021-04-09 21:08 ` [Tarantool-patches] [PATCH v5 46/52] sql: introduce mem_get_uint() Mergen Imeev via Tarantool-patches
2021-04-13 23:04   ` Vladislav Shpilevoy via Tarantool-patches
2021-04-14  0:39     ` Mergen Imeev via Tarantool-patches
2021-04-14  1:21       ` Mergen Imeev via Tarantool-patches
2021-04-09 21:08 ` [Tarantool-patches] [PATCH v5 47/52] sql: introduce mem_get_double() Mergen Imeev via Tarantool-patches
2021-04-13 23:04   ` Vladislav Shpilevoy via Tarantool-patches
2021-04-14  1:00     ` Mergen Imeev via Tarantool-patches
2021-04-15  0:17       ` Vladislav Shpilevoy via Tarantool-patches
2021-04-15  0:46         ` Mergen Imeev via Tarantool-patches
2021-04-09 21:08 ` [Tarantool-patches] [PATCH v5 48/52] sql: introduce mem_get_bool() Mergen Imeev via Tarantool-patches
2021-04-13 23:04   ` Vladislav Shpilevoy via Tarantool-patches
2021-04-14  1:29     ` Mergen Imeev via Tarantool-patches
2021-04-09 21:08 ` [Tarantool-patches] [PATCH v5 49/52] sql: introduce mem_get_str0() and mem_as_str0() Mergen Imeev via Tarantool-patches
2021-04-13 23:06   ` Vladislav Shpilevoy via Tarantool-patches [this message]
2021-04-14  1:43     ` Mergen Imeev via Tarantool-patches
2021-04-09 21:08 ` [Tarantool-patches] [PATCH v5 50/52] sql: introduce mem_get_bin() Mergen Imeev via Tarantool-patches
2021-04-09 21:08 ` [Tarantool-patches] [PATCH v5 51/52] sql: introduce mem_get_bytes_len() Mergen Imeev via Tarantool-patches
2021-04-13 23:06   ` Vladislav Shpilevoy via Tarantool-patches
2021-04-14  1:55     ` Mergen Imeev via Tarantool-patches
2021-04-15  0:21       ` Vladislav Shpilevoy via Tarantool-patches
2021-04-15  0:51         ` Mergen Imeev via Tarantool-patches
2021-04-09 21:08 ` [Tarantool-patches] [PATCH v5 52/52] sql: introduce mem_get_agg() Mergen Imeev via Tarantool-patches

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=57b42211-19a9-1629-5d91-bc2e729f7dee@tarantool.org \
    --to=tarantool-patches@dev.tarantool.org \
    --cc=imeevma@tarantool.org \
    --cc=tsafin@tarantool.org \
    --cc=v.shpilevoy@tarantool.org \
    --subject='Re: [Tarantool-patches] [PATCH v5 49/52] sql: introduce mem_get_str0() and mem_as_str0()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox