withUnsafeMutableShapedBufferPointer(using:_:)

Declaration

mutating func withUnsafeMutableShapedBufferPointer<R>(using bufferLayout: MLShapedArrayBufferLayout, _ body: (inout UnsafeMutableBufferPointer<Scalar>, [Int], [Int]) throws -> R) rethrows -> R

Discussion

The storage contains the scalars according to buffer layout parameter. For example, the scalar at [x1, x2, ... xn] with strides [s1, s2, ... sn] is stored at ptr[x1 * s1 + x2 * s2 + ... + xn * sn]

Unlike withUnsafeMutableShapedBufferPointer(:), this function allows the caller to specify the buffer layout.

// Initialize the middle 2x2 of 4x4 shaped array using an external data that lays out
// scalars in last-major order.
let data: [Int32] = [1, 3,
                     2, 4]
var array = MLShapedArray<Int32>(repeating: 0, shape: [4, 4])
array[1...2, 1...2].withUnsafeMutableShapedBufferPointer(using: .lastMajorContiguous) { destinationPtr, _, _ in
    data.withUnsafeBufferPointer() { sourcePtr in
        destinationPtr.update(from: sourcePtr)
    }
}

// array.scalars == [0, 0, 0, 0,
//                   0, 1, 2, 0,
//                   0, 3, 4, 0,
//                   0, 0, 0, 0,])