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Date: Thu, 17 Apr 2014 18:22:19 +0300
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To: =?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>
Cc: Leigh <leight@gmail.com>, "internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Negative string offsets
From: narf@devilix.net (Andrey Andreev)

Hi,

On Thu, Apr 17, 2014 at 6:07 PM, Johannes Schl=C3=BCter
<johannes@schlueters.de> wrote:
> On Thu, 2014-04-17 at 17:18 +0300, Andrey Andreev wrote:
>> For example, every time you need to check for a filename extension,
>> last segment of a path, etc. When I need that, I always endup with
>> substr(), strrchr() or explode(), end() ... both are suboptimal.
>
> I don't see where this helps in that case.
>
>         $sep =3D strrpos($filename, ".");
>         if ($sep !=3D=3D false) {
>             $ext =3D substr($filename, $sep + 1);
>         }
>
> is clear and concise, two fcalls, can be understood even after years and
> the new programmer easily.
>
> This is the most concise form I came up using this new offset:
>
>         $ext =3D '';
>         $pos =3D -1;
>         do {
>             $ext =3D $filename[$pos].$ext;
>         } while ($filename[--$pos] !=3D '.');
>
> While this form is bugged as it assumes that there is a . without
> checking. For checking I'd have to use strlen(), but if i call strlen()
> I can also initialize $pos accordingly and iterate from strlen() to 0.
> Also this form does more comparisons and way more allocations and is (in
> my opinion) way harder to understand.
>
> Maye I didn't see a simple form ...
>
> johannes

For most filename extensions:

    if ($filename[-4] =3D=3D=3D '.')
    {
        $ext =3D substr($filename, -3);
    }

Or, checking if a path has a slash at the end:

    if ($path[-1] =3D=3D=3D '/') { ... }

I'm talking strictly about validation here (and yes, the filename
example won't work with i.e. .jpeg, but would satisfy a large amount
of use cases), comparing stuff on the fly.

Cheers,
Andrey.