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Date: Wed, 19 Oct 2016 14:15:38 +0100
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Subject: Re: [PHP-DEV] Exploit fully packed array/hash property
From: ajf@ajf.me (Andrea Faulds)

Hi Benjamin,

These are interesting optimisations. I definitely see the usefulness of 
detecting packed arrays and short-circuiting: I've done that in my patch 
to fix object/array casting, in order to avoid wasting time checking for 
the existence of non-string keys, even if (object)[1, 2, 3] is probably 
quite a rare case.

Personally, having macros for this in the Zend API might bother me 
slightly, because it would make it easier to rely on what is essentially 
an implementation detail, and therefore perhaps slightly complicate 
future changes to the hashtable internals.

However, so long as they're only used as hints about the shape of the 
array, I guess this wouldn't be an issue. In any case, I don't know if 
my concern here is worth worrying about.

Two further thoughts. First, are these the best names for the macros? I 
don't know if the meaning of “fully packed array” would be clear without 
an explanatory comment. Second, do you know if any other PHP functions 
do a similar check to JSON's php_json_determine_array_type for whether 
an array is free of string keys and consecutively indexed? I wonder if 
that could be abtracted into a zend_hash.c function.

Thanks!
-- 
Andrea Faulds
https://ajf.me/