linux-kernel - Re: [PATCH v1]] lib/btree.c: optimise the code by previously getpos function

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Message-ID: <CAHp75VfX0u11mRieRAH=P_6xzbL2cKjbhKNopv-ia70duH1Cfg@mail.gmail.com>
Date:   Fri, 28 Apr 2017 19:40:34 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Leno Hou <lenohou@...il.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1]] lib/btree.c: optimise the code by previously getpos function

On Tue, Apr 11, 2017 at 9:53 AM, Leno Hou <lenohou@...il.com> wrote:
> This patch optimized the code by previously getpos function call.
> Therefore, It's takes the convenience to understand logic of code.

Besides what Christoph told you (I agree with him, writing test suites
/ modules is quite good exercise for newbies) my 2 cents for below
code that you may consider in the future as a technique of cleaning
up,

> +static int getpos(struct btree_geo *geo, unsigned long *node,
> +               unsigned long *key)
> +{

> +       int i;

unsigned int i;

> +
> +       for (i = 0; i < geo->no_pairs; i++) {
> +               if (keycmp(geo, node, i, key) <= 0)

> +                       break;

Here you return directly
return i;

> +       }

> +       return i;

And here is the best to return negative error code instead, like

return -ENOENT;

> +}

>         for ( ; height > 1; height--) {
> -               for (i = 0; i < geo->no_pairs; i++)
> -                       if (keycmp(geo, node, i, key) <= 0)
> -                               break;

> +               i = getpos(geo, node, key);
>                 if (i == geo->no_pairs)
>                         return NULL;

Taking above into consideration you may do

        i = getpos(geo, node, key);
        if (i < 0)
          return NULL;

Rationale behind that:
1) getpos() return value may be directly used whenever we need return
code to return;
2) you hide implementation details in your helper function
(geo->no_pairs dereference).

Though here both of them kinda minors you may use such technique in
the future for more complex code.

-- 
With Best Regards,
Andy Shevchenko