Re: Creating NSStrings without copying memory
Re: Creating NSStrings without copying memory
- Subject: Re: Creating NSStrings without copying memory
- From: Mike Abdullah <email@hidden>
- Date: Tue, 2 May 2017 22:42:03 +0200
Drop down to CFString. It has similar api to the NSData one you like.
Mike.
Sent from my iPhone
> On 2 May 2017, at 22:11, Jens Alfke <email@hidden> wrote:
>
> I’ve got a heap block containing many UTF-8 strings, and I’m looking for the cheapest way to create NSString objects from them, i.e. without copying all the characters.
>
> -initWithBytesNoCopy:length:freeWhenDone: would be perfect, except that the string bytes are not an individual malloc block (so I can’t use freeWhenDone:YES), and I shouldn’t leave the big heap block in memory longer than necessary (so I can’t use freeWhenDone:NO.)
>
> NSData has -initWithBytesNoCopy:length:deallocator:, which is exactly what I want: the callback block tells me when the object doesn’t need the original bytes anymore, so I can reference-count that heap block and free it when there are no clients left. But NSString doesn’t have this :(
>
> If I created an NSData from the bytes this way, and then used that object to initialize an NSString, would I get what I want? Or would the NSString initializer just copy the bytes from the NSData without retaining it? Has anyone experimented with this?
>
> —Jens
>
> PS: I’m aware of the tradeoffs of this technique, i.e. that a client holding on to one small NSString could inadvertently keep the large heap block around.
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