---
title: "withUnsafeMutableShapedBufferPointer(using:_:)"
framework: coreml
role: symbol
role_heading: Instance Method
path: "coreml/mlshapedarrayslice/withunsafemutableshapedbufferpointer(using:_:)"
---

# withUnsafeMutableShapedBufferPointer(using:_:)

Calls the given closure with a pointer to the array’s mutable storage that has a specified buffer layout.

## Declaration

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

## Discussion

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,])