withUnsafeMutablePointer for safe allocation interoperability

withUnsafeMutablePointerConstructing.swift

/**
 Helper function for efficiently initializing a value based on a pointer
 
 - Parameter type: the type of value the pointers value will be cast to
 - Parameter closure: block of code that will handle the pointer
 
 - Returns: tuple of (value the pointer was given, return type of closure)
 */
func withUnsafeMutablePointer<T, R>(ofType type: T.Type, _ closure: (UnsafeMutablePointer<T>) -> R) -> (T?, R) {
    let ptr = UnsafeMutablePointer<T>.allocate(capacity: 1)
    
    defer {
        // close out the pointer once this is done
        ptr.deallocate()
    }
    
    // pass pointer to closure
    let ret = closure(ptr)
    
    return (ptr.move(), ret)
}