> On Jan 25, 2017, at 1:23 AM, Rien via swift-users <swift-users@swift.org>
> wrote:
>
> I have a case where a callback has the following signature:
>
> @convention(c) (_ ssl: OpaquePointer?, _ num: UnsafeMutablePointer<Int32>?, _
> arg: UnsafeMutableRawPointer?) -> Int32
>
> But to install this callback I have to use a c-function with this signature:
>
> SSL_CTX_callback_ctrl (OpaquePointer!, Int32, (() -> Void)! )
>
> Is it possible to cast the first function to the second? If so, how?
I think your best bet would be to write the shim closure yourself. Is `num` a
pointer to the value you're supposed to receive from SSL_CTX_callback_ctrl? Is
the `arg` really a function pointer? In that case, something like this might
work:
func callback(_ ssl: OpaquePointer?, _ num: UnsafeMutablePointer<Int32>?, _
arg: UnsafeMutableRawPointer?) -> Int32
let shimCallback: SSL_CTX_callback_ctrl = { ctx, cmd, fp in
var cmdNum = cmd
callback(ctx, &cmdNum, unsafeBitCast(fp, to: UnsafeMutableRawPointer?.self))
}
-Joe
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