[swift-users] How to get UnsafePointer or UnsafeMutablePointer from ContiguousArray?

[Jordan Rose]

withExtendedLifetime is the function you're looking for.

> On Feb 11, 2016, at 1:10 , Sergey Kuratov via swift-users <swift-users at swift.org> wrote:
> 
> I try to find _fixLifetime in standard library and finally can't :( But function exists in reality and I can call it.
> I also found some discussion about https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20151228/005017.html <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20151228/005017.html> 
> So as I can understand it's not fixed API to manage scoped life and probably will be changed in the future.
> 
> On Thu, Feb 11, 2016 at 5:38 PM, Dmitri Gribenko <gribozavr at gmail.com <mailto:gribozavr at gmail.com>> wrote:
> On Thu, Feb 11, 2016 at 12:19 AM, Dmitri Gribenko <gribozavr at gmail.com <mailto:gribozavr at gmail.com>> wrote:
> > On Thu, Feb 11, 2016 at 12:13 AM, Sergey Kuratov <ksubox.swift at gmail.com <mailto:ksubox.swift at gmail.com>> wrote:
> >>>> Can I define similar for my Swift classes ?
> >>
> >>>No.  What would be your use case?
> >>
> >> I also could have my Swift object with several members, but when send to
> >> native part would like to send address exactly one of members.
> >> Something like this:
> >>
> >> // Swift part
> >>
> >> class ABlock {
> >>
> >> var channels = 2
> >>
> >> var samplerate = 44100
> >>
> >> var  buffer : UnsafeMutablePointer<Int16>
> >>
> >> init() {
> >>
> >> buffer = UnsafeMutablePointer<Int16>.alloc(2048)
> >>
> >> }
> >>
> >> deinit {
> >>
> >> buffer.dealloc(2048)
> >>
> >> }
> >>
> >> }
> >>
> >>
> >> var block = ABlock
> >> generate(block) <- here I would like to send address of ABlock.buffer to
> >> native part
> >>
> >> // C part
> >> void generate(int16_t *buf) {
> >> ...
> >> }
> >
> > I'd recommend to write a Swift wrapper for your C code that accepts
> > the class instance, and calls the generate() function with appropriate
> > arguments.
> 
> Oh, and since your class stores an unsafe pointer (and not an array),
> you'd need to call _fixLifetime() on it after the your C function
> returns, to ensure that the class instance can't be deallocated before
> then.  Unless you have other requirements though, I'd recommend just
> storing an array though.  Then you wouldn't need to care about
> _fixLifetime().
> 
> Dmitri
> 
> --
> main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
> (j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr at gmail.com <mailto:gribozavr at gmail.com>>*/
> 
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