MemoryLayout

Overview

You can use MemoryLayout as a source of information about a type when allocating or binding memory using raw pointers. The following example declares a Point type with x and y coordinates and a Boolean isFilled property.

struct Point {
    let x: Double
    let y: Double
    let isFilled: Bool
}

The size, stride, and alignment of the Point type are accessible as static properties of MemoryLayout<Point>.

// MemoryLayout<Point>.size == 17
// MemoryLayout<Point>.stride == 24
// MemoryLayout<Point>.alignment == 8

Always use a multiple of a type’s stride instead of its size when allocating memory or accounting for the distance between instances in memory. This example allocates uninitialized raw memory with space for four instances of Point.

let count = 4
let pointPointer = UnsafeMutableRawPointer.allocate(
        byteCount: count * MemoryLayout<Point>.stride,
        alignment: MemoryLayout<Point>.alignment)