hotpaw2 hotpaw2 - 4 months ago 35
Swift Question

Creating an UnsafeMutablePointer<UnsafeMutablePointer<Float>> parameter in Swift 3

The Swift signature of the Accelerate framework

function includes parameter types of

How does one declare and create such types in Swift 3, and then fill these pointer arrays with references to several Swift arrays of type


When you need to pass multiple values for UnsafeMutablePointer<T> parameters, you need to declare a variable of type [T] (aka Array<T>) and pass it as an inout argument. In your case T is UnsafeMutablePointer<Float>.

So, if you want to start with [Float], you may need to write something like this:

let input: [Float] = [/*...*/]
var output: [Float] = Array(repeating: 0, count: outputTotalSize)
input.withUnsafeBufferPointer {inBuf in
    let inputPtr = inBuf.baseAddress!
    output.withUnsafeMutableBufferPointer {outBuf in
        let outputPtr = outBuf.baseAddress!
        var pInputs: [UnsafePointer<Float>] = [inputPtr,/*...*/]
        var pOutputs: [UnsafeMutablePointer<Float>] = [outputPtr/*...*/]
        vDSP_biquadm(setup, &pInputs, inStride, &pOutputs, outStride, length)