Re: CFMutableDictionary Capacity
Re: CFMutableDictionary Capacity
- Subject: Re: CFMutableDictionary Capacity
- From: Jean-Daniel Dupas <email@hidden>
- Date: Thu, 21 Jul 2011 01:52:26 +0200
Le 21 juil. 2011 à 01:48, Jean-Daniel Dupas a écrit :
>
> Le 21 juil. 2011 à 00:30, Jens Alfke a écrit :
>
>>
>> On Jul 20, 2011, at 2:34 PM, Andreas Grosam wrote:
>>
>>> According the doc, the parameter "capacity" in function CFDictionaryCreateMutable() sets the *maximum number* of key-value pairs which can be inserted into the container. That is, it's not an *initial* capacity.
>>
>> I think that was a mistake in the docs. The comment in CFDictionary.h in the 10.7 SDK says:
>>
>> @param capacity A hint about the number of values that will be held
>> by the CFDictionary. Pass 0 for no hint. The implementation may
>> ignore this hint, or may use it to optimize various
>> operations. A dictionary's actual capacity is only limited by
>> address space and available memory constraints). If this
>> parameter is negative, the behavior is undefined.
>>
>> Since CFDictionary and NSDictionary have the same implementation under the hood, I think the capacity will have the same effect at runtime whichever API you use.
>
>
> IIRC, the semantic of the capacity parameter changed in 10.5. Before 10.5, it specified the max capacity and trying to insert more elements was documented as an undefined behavior.
Just for the record, my previous comment is about the CoreFoundation API only. The Foundation API has always defined the capacity parameter as a hint.
-- Jean-Daniel
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