Re: Is there a way to efficiently access NSArray element contents?
Re: Is there a way to efficiently access NSArray element contents?
- Subject: Re: Is there a way to efficiently access NSArray element contents?
- From: Jean-Daniel Dupas <email@hidden>
- Date: Sun, 8 Jun 2008 21:56:45 +0200
Le 8 juin 08 à 20:51, Joan Lluch (casa) a écrit :
El 08/06/2008, a las 20:13, Brent Fulgham escribió:
I've been enjoying the NSArray/NSMutableArray classes as I work
with various user interface features for a program I'm working on
that interacts with a legacy C++ library.
I've recently begun considering how to efficiently display the
contents of a binary data stream. Currently I'm appending to an
NSMutableArray of NSNumber objects, which is great for allowing me
to bind to some UI elements in close to real time and has provided
a simple and functional mechanism for text numerical display.
Ideally, I'd like to be able to access a raw binary buffer of data
so I could for example bind it to something like an OpenGL vector
buffer for display. However, unlike an STL vector, I don't think
the NS[Mutable]Array provides any guarantees of memory
organization, nor any way to 'unbox' the NSNumber to deal with the
internal values.
For example, in the STL, I could make use of the fact that the
vector template guarantees the storage to be in contiguous memory
and accessible as raw double values through the address of the
first element of the vector. However, I don't think this is
possible via NSMutableArray and NSNumbers.
Is my only option to periodically sync a buffer of binary double
values by copying from the NSMutableArray on some periodic basis?
Thanks,
-Brent
Since each item contained in an NSArray is a pointer to an object,
you will not be able to retrieve them as raw data of different size
even if the pointers in the NSArray were contiguous (which I believe
they are)
Assumption are evil. The actual implementation uses a different memory
layout for very big arrays. In this special case objects in the array
are not in contiguous memory. Anyway this is an implementation details
and you should not make any assumption about it.
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