ios - 将 float 数组的数组转换为 UnsafeMutablePointer<UnsafeMutablePointer<Float>>

Question

我需要使用一个使用 UnsafeMutablePointer<UnsafeMutablePointer<Float>?>! 的函数作为参数。它是用 Objective-C++ 框架编写的，我通过桥接 header 访问它:

- (void) applyFilters: (float *) input_image input_params: (long *) input_params output_image : (float *) output_image output_params : (long *) output_params filter_id : (int) filter_id args : (float**) args

我在理解 args 参数的结构时遇到了一些困难，即 float** 。在 Swift 中，它要求 UnsafeMutablePointer<UnsafeMutablePointer<Float>> 类型的参数，我猜测它指向一个 float 组的数组。

applyFilters(input_image: UnsafeMutablePointer<Float>!UnsafeMutablePointer<Float>!, input_params: UnsafeMutablePointer<Int>!, output_image: UnsafeMutablePointer<Float>!, output_params: UnsafeMutablePointer<Int>!, filter_id: Int32, args: UnsafeMutablePointer<UnsafeMutablePointer<Float>?>!)

如果我创建一个 float 数组的数组，如何使用 UnsafeMutablePointer<UnsafeMutablePointer<Float>> 指向它所以我可以将它传递给 C++ 函数？

Answer 1

弄清楚如何做到这一点:

func arrayOfArrayExample() {

    let floatArray: [[Float]] = [
        [50.0, 23.0, 15.6],
        [24.0, 9.5, 12.7]
    ]

    let size1 = floatArray.count
    let size2 = floatArray[0].count

    var vectorBuf : UnsafeMutablePointer<Float>?
    let bufferOut = UnsafeMutablePointer< UnsafeMutablePointer<Float>?>.allocate(capacity: Int(size1))

    for i in 0..<size1 {
        vectorBuf = UnsafeMutablePointer<Float>.allocate(capacity: size2)
        for j in 0..<size2 {
            vectorBuf!.advanced(by: j).pointee = floatArray[i][j]
        }
        bufferOut.advanced(by: i).pointee = vectorBuf
    }

    defer {
        //deallocating memory
        for i in 0..<size1 {
            bufferOut.advanced(by: i).deallocate()
        }
    }
}

变量bufferOut返回 UnsafeMutablePointer<UnsafeMutablePointer<Float>>指向 Float 数组的数组的指针，随后释放内存。