Re: NSData from dispatch_data_t?
Re: NSData from dispatch_data_t?
- Subject: Re: NSData from dispatch_data_t?
- From: Greg Parker <email@hidden>
- Date: Tue, 30 Oct 2018 19:49:21 -0700
> On Tue, Oct 30, 2018 at 7:26 PM Carl Hoefs <email@hidden>
> wrote:
>
> Is it possible to create an NSData object from a dispatch_data_t?
>
> I'm interfacing to a 3rd party library that returns only a dispatch_data_t
> object. Once upon a time you could simply cast that to (NSData *) and work
> with it that way, but Xcode now flags it as an error:
>
> dispatch_data_t data_t = BGRequestSidebandDL(channel);
> NSData *nsdata = data_t; // Incompatible pointer types initializing
> 'NSData *' with an
> expression
> of type 'dispatch_data_t' (aka 'NSObject<OS_dispatch_data> *')
You may use a dispatch_data_t as if it were an NSData (assuming you're on iOS 7
or macOS 10.9 or later). But you do need to cast it explicitly:
NSData *nsdata = (NSData *)data_t;
> On Oct 30, 2018, at 7:37 PM, Ryan Dignard <email@hidden>
> wrote:
>
> To get the size of the dispatch data you can call
> dispatch_data_get_size(dispatch_data_t) on it which would let you create an
> NSData object.
This may be inefficient. dispatch_data_t often uses a discontiguous
representation. Allocating an NSData this way is would need to copy the data.
(Of course, if the code using it as an NSData goes on to call -bytes instead of
-enumerateByteRangesUsingBlock: then it would be forced to copy into a
contiguous representation anyway.)
--
Greg Parker email@hidden <mailto:email@hidden> Runtime
Wrangler
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