Swift数组与C的互操作性？

Question

如何在C数组中传递或复制数据,例如

float foo[1024];

在C和Swift函数之间使用固定大小的数组,例如声明的

let foo = Float[](count: 1024, repeatedValue: 0.0)

？

Answer 1

我认为这不容易.就像你不能使用C样式数组的参数一样NSArray.

Swift中的所有C数组都由UnsafePointer例如UnsafePointer<Float>.Swift并不真正知道数据是一个数组.如果要将它们转换为Swift数组,您将创建一个新对象并逐个复制项目.

let array: Array<Float> = [10.0, 50.0, 40.0]

// I am not sure if alloc(array.count) or alloc(array.count * sizeof(Float))
var cArray: UnsafePointer<Float> = UnsafePointer<Float>.alloc(array.count)
cArray.initializeFrom(array)

cArray.dealloc(array.count)

编辑

刚刚找到了更好的解决方案,这实际上可以避免复制.

let array: Array<Float> = [10.0, 50.0, 40.0]

// .withUnsafePointerToElements in Swift 2.x
array.withUnsafeBufferPointer() { (cArray: UnsafePointer<Float>) -> () in
    // do something with the C array
}

Answer 2

从Beta 5开始,可以使用pass和array以下示例将2个float数组传递给vDSP C函数:

let logLen = 10
let len = Int(pow(2.0, Double(logLen)))
let setup : COpaquePointer = vDSP_create_fftsetup(vDSP_Length(logLen), FFTRadix(kFFTRadix2))

var myRealArray = [Float](count: len, repeatedValue: 0.0)
var myImagArray = [Float](count: len, repeatedValue: 0.0)
var cplxData = DSPSplitComplex(realp: &myRealArray, imagp: &myImagArray)

vDSP_fft_zip(setup, &cplxData, 1, vDSP_Length(logLen),FFTDirection(kFFTDirection_Forward))

Answer 3

该withUnsafePointerToElements()方法已被删除,现在您可以使用withUnsafeBufferPointer()替代baseAddress方法,并使用块中的方法来实现这一点

let array: Array<Float> = [10.0, 50.0, 40.0]
array.withUnsafeBufferPointer { (cArray: UnsafePointer<Float>) -> () in
    cArray.baseAddress
}