[swift-users] How to bridge between CoreFoundation and SwiftFoundation on Linux?

[Philippe Hausler]

I would suggest that the way to do it is to follow the NSString/NSNumber approach used in swift-corelibs-foundation where the structural size is equivalent.

the layout would roughly look like:


open class InputStream : Stream {
    typealias CFType = CFReadStream
    // This layout MUST be the same as CFReadStream so that they are bridgeable
    private var _base = _CFInfo(typeID: CFReadStreamGetTypeID())
    private var _flags: CFOptionFlags = 0
    private var _error: UnsafeMutableRawPointer? = nil
    private var _info: UnsafeMutableRawPointer? = nil
    private var _callBacks: UnsafeMutableRawPointer? = nil
#if os(OSX) || os(iOS)
    private var _lock = pthread_mutex_t()
#elseif os(Linux)
    private var _lock = Int32(0)
#endif
    private var _previousRunloopsAndModes: UnsafeMutableRawPointer? = nil
#if DEPLOYMENT_ENABLE_LIBDISPATCH
    private var _queue: UnsafeMutableRawPointer? = nil
#endif

    internal var _cfObject: CFType {
        return unsafeBitCast(self, to: CFType.self)
    }

    ...
}

This would ensure the memory size of the allocation of InputStream would be the same as CFReadStream. 

These two calls would then need to be un-commented in NSSwiftRuntime.swift

//    _CFRuntimeBridgeTypeToClass(CFReadStreamGetTypeID(), unsafeBitCast(InputStream.self, UnsafeRawPointer.self))
//    _CFRuntimeBridgeTypeToClass(CFWriteStreamGetTypeID(), unsafeBitCast(OutputStream.self, UnsafeRawPointer.self))

and __CFSwiftBridge would need entries for calling out to swift for subclassers.


> On Sep 21, 2016, at 1:03 PM, Bouke Haarsma via swift-users <swift-users at swift.org> wrote:
> 
> The one that comes with SwiftFoundation (https://github.com/apple/swift-corelibs-foundation/tree/master/CoreFoundation <https://github.com/apple/swift-corelibs-foundation/tree/master/CoreFoundation>).
> 
> I think it should be a bug that CFReadStream cannot be bridged to (NS)InputStream, as otherwise there’s no way to intertwine Sockets (CFSockets) with SwiftFoundation. As the implementation already uses a CFReadStream internally (https://github.com/apple/swift-corelibs-foundation/blob/d3872cb094124d5dd189839505ae73e2fa717cfd/Foundation/NSStream.swift#L122 <https://github.com/apple/swift-corelibs-foundation/blob/d3872cb094124d5dd189839505ae73e2fa717cfd/Foundation/NSStream.swift#L122>), it would be a matter of adding an initializer. However the value is private, so adding the initializer cannot be done from an extension.
> 
> —
> Bouke
> 
>> On 21 Sep 2016, at 21:22, Jens Alfke <jens at mooseyard.com <mailto:jens at mooseyard.com>> wrote:
>> 
>> 
>>> On Sep 20, 2016, at 9:38 PM, Bouke Haarsma via swift-users <swift-users at swift.org <mailto:swift-users at swift.org>> wrote:
>>> 
>>> When working with CoreFoundation objects (e.g. CFReadStream, CFWriteStream) it isn't immediately obvious to me how to bridge them to SwiftFoundation counterparts (InputStream / OutputStream).
>>> 
>>> The following works on OSX, but doesn't work on Linux;
>> 
>> What implementation of CF are you using on Linux? OpenStep?
>> 
>> The bridging between Swift and Obj-C Foundation classes is only implemented on Apple platforms. It’s not part of the open source release. The plan is to implement classes like InputStream in native Swift as part of the standard library; that work is in progress.
>> 
>> —Jens
> 
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