Converting an UnsafePointer with length to a Swift Array type

Question

I\'m looking for the simplest ways to achieve reasonable C interoperability in Swift, and my current block is converting an UnsafePointer (which was

Answer 1

extension NSData {

    public func convertToBytes() -> [UInt8] {
        let count = self.length / sizeof(UInt8)
        var bytesArray = [UInt8](count: count, repeatedValue: 0)
        self.getBytes(&bytesArray, length:count * sizeof(UInt8))
        return bytesArray
    }
}

You can convert row data to byts (Uint8)

Copy Extension and use it..

Answer 2

You can simply initialize a Swift Array from an UnsafeBufferPointer:

func convert(length: Int, data: UnsafePointer<Int8>) -> [Int8] {

    let buffer = UnsafeBufferPointer(start: data, count: length);
    return Array(buffer)
}

This creates an array of the needed size and copies the data.

Or as a generic function:

func convert<T>(count: Int, data: UnsafePointer<T>) -> [T] {

    let buffer = UnsafeBufferPointer(start: data, count: count);
    return Array(buffer) 
}

where length is the number of items that the pointer points to.

If you have a UInt8 pointer but want to create an [T] array from the pointed-to data, then this is a possible solution:

// Swift 2:
func convert<T>(length: Int, data: UnsafePointer<UInt8>, _: T.Type) -> [T] {

    let buffer = UnsafeBufferPointer<T>(start: UnsafePointer(data), count: length/strideof(T));
    return Array(buffer) 
}

// Swift 3:
func convert<T>(length: Int, data: UnsafePointer<UInt8>, _: T.Type) -> [T] {
    let numItems = length/MemoryLayout<T>.stride
    let buffer = data.withMemoryRebound(to: T.self, capacity: numItems) {
        UnsafeBufferPointer(start: $0, count: numItems)
    }
    return Array(buffer) 
}

where length now is the number of bytes. Example:

let arr  = convert(12, data: ptr, Float.self)

would create an array of 3 Floats from the 12 bytes pointed to by ptr.