Question

我正在使用C库，并且想使用Pointers作为参数来调用函数。它说我需要将Double转换为UnsafeMutablePointer<Double>。

这就是我走了多远：

class ViewController: UIViewController {

    var buffer1 = [Double]()
    var buffersize = [Int32]()
    var ar = UnsafeMutablePointer<Double>.allocate(capacity: 10)
    var ar2 = UnsafeMutablePointer<Double>.allocate(capacity: 2)

    override func viewDidLoad() {
        super.viewDidLoad()

        randomBuffer()
        print(buffer1)
        ar.deallocate()
        ar2.deallocate()
        let grade = ar.pointee
        let isevent = ar2.pointee

        print(grade, isevent)

        let pointer = app_ios_ersatzfunktion(buffer1, buffersize, ar, ar2)
        print(pointer)
    }
    func randomBuffer()
    {
        let randomDouble = Double.random(in: -1...2)
        if buffer1.count<200{ 
        buffer1.append(randomDouble) 
        }  
        else {
            buffer1.removeFirst()
            buffer1.append(randomDouble)
        }
    }

}

我的C代码是使用Matlab创建的，如下所示：

void app_ios_ersatzfunktion(const double buffer2_data[], const int buffer2_size
  [2], double *grade, double *event_found)
{
  double jerk;
  *grade = 0.0;
  *event_found = 0.0;

  jerk = (buffer2_data[buffer2_size[1] - 1] - buffer2_data[buffer2_size[1] - 2])
    / 0.01;

  if ((jerk >= 200.0) || (jerk <= -200.0)) {
    *event_found = 1.0;
    *grade = jerk / 50.0;
      }
}

Answer 1

您可以将Swift数组直接传递给C函数，这将传递元素存储的地址。对于“输出参数”，您必须使用&将变量作为“输入参数”传递：

let buffer2_data: [Double] = ...
let buffer2_size: [CInt] = ...

var grade: Double = 0
var event_found: Double = 0

app_ios_ersatzfunktion(buffer2_data, buffer2_size, &grade, &event_found)

print(grade, event_found)

我如何使用与C（库）交互的指针

1 个答案: