memory-layout.swift

import Foundation

func dumpMemory(_ p: UnsafeRawPointer, _ size: Int) {
    let addr = unsafeBitCast(p, to: UInt64.self)
    var p = p.bindMemory(to: UInt8.self, capacity: size)
    for i in 0..<size {
        if i % 8 == 0 {
            if i != 0 {
                print()
            }
            print(String(format: "[0x%016lx]", addr + UInt64(i)), terminator: "")
        }
        print(String(format: " %02x", p[i]), terminator: "")
    }
    print()
}

struct SA {
    var v1: UInt32 = 0xA1B1C1D1
    var v2: UInt32 = 0xA2B2C2D2
    var v3: UInt32 = 0xA3B3C3D3
    var v4: UInt32 = 0xA4B4C4D4
}

class CA {
    var v1: UInt32 = 0xA1B1C1D1
    var v2: UInt32 = 0xA2B2C2D2
    var v3: UInt32 = 0xA3B3C3D3
    var v4: UInt32 = 0xA4B4C4D4
}

func test1() {
    print("--test1 enter")

    var x = SA()
    let p = UnsafeRawPointer(UnsafeMutablePointer<SA>(&x))
    dumpMemory(p, MemoryLayout<SA>.size)

    print("--test1 exit")
}

func test2() {
    print("--test2 enter")

    var x = CA()
    let p = UnsafeRawPointer(UnsafeMutablePointer<CA>(&x))
    dumpMemory(p, MemoryLayout<CA>.size)

    print("--")
    
    let p2 = p.bindMemory(to: UnsafeRawPointer.self, capacity: 1).pointee
    dumpMemory(p2, 32)

    print("--")
    
    var x2 = x
    dumpMemory(p2, 32)

    print("--")

    weak var x3 = x
    dumpMemory(p2, 32)

    print("--test2 exit")
}

func test3() {
    print("--test3 enter")

    var x1: SA? = .some(SA())

    let px1 = UnsafeRawPointer(UnsafeMutablePointer<SA?>(&x1))
    dumpMemory(px1, MemoryLayout<SA?>.size)

    var x2: SA? = .none
    let px2 = UnsafeRawPointer(UnsafeMutablePointer<SA?>(&x2))
    dumpMemory(px2, MemoryLayout<SA?>.size)

    print("--test3 exit")
}

func test4() {
    print("--test4 enter")

    var x1: SA?? = .some(.some(SA()))
    let px1 = UnsafeRawPointer(UnsafeMutablePointer<SA??>(&x1))
    dumpMemory(px1, MemoryLayout<SA??>.size)

    var x2: SA?? = .some(.none)
    let px2 = UnsafeRawPointer(UnsafeMutablePointer<SA??>(&x2))
    dumpMemory(px2, MemoryLayout<SA??>.size)

    var x3: SA?? = .none
    let px3 = UnsafeRawPointer(UnsafeMutablePointer<SA??>(&x3))
    dumpMemory(px3, MemoryLayout<SA??>.size)

    print("--test4 exit")
}

func test5() {
    print("--test5 enter")

    var x1: CA? = .some(CA())
    let px1 = UnsafeRawPointer(UnsafeMutablePointer<CA?>(&x1))
    dumpMemory(px1, MemoryLayout<CA?>.size)

    let ppx1 = px1.bindMemory(to: UnsafeRawPointer.self, capacity: 1).pointee
    dumpMemory(ppx1, 32)

    var x2: CA? = .none
    let px2 = UnsafeRawPointer(UnsafeMutablePointer<CA?>(&x2))
    dumpMemory(px2, MemoryLayout<CA?>.size)

    print("--test5 exit")
}

func test6() {
    print("--test6 enter")

    var x1: CA?? = .some(.some(CA()))
    let px1 = UnsafeRawPointer(UnsafeMutablePointer<CA??>(&x1))
    dumpMemory(px1, MemoryLayout<CA??>.size)

    let ppx1 = px1.bindMemory(to: UnsafeRawPointer.self, capacity: 1).pointee
    dumpMemory(ppx1, 32)

    var x2: CA?? = .some(.none)
    let px2 = UnsafeRawPointer(UnsafeMutablePointer<CA??>(&x2))
    dumpMemory(px2, MemoryLayout<CA??>.size)

    var x3: CA?? = .none
    let px3 = UnsafeRawPointer(UnsafeMutablePointer<CA??>(&x3))
    dumpMemory(px3, MemoryLayout<CA??>.size)

    print("--test6 exit")
}

func test7() {
    print("--test7 enter")

    var x1: CA????? = .some(.some(.some(.some(.some(CA())))))
    let px1 = UnsafeRawPointer(UnsafeMutablePointer<CA?????>(&x1))
    dumpMemory(px1, MemoryLayout<CA?????>.size)
    let ppx1 = px1.bindMemory(to: UnsafeRawPointer.self, capacity: 1).pointee
    dumpMemory(ppx1, 32)

    var x2: CA????? = .some(.some(.some(.some(.none))))
    let px2 = UnsafeRawPointer(UnsafeMutablePointer<CA?????>(&x2))
    dumpMemory(px2, MemoryLayout<CA?????>.size)

    var x3: CA????? = .some(.some(.some(.none)))
    let px3 = UnsafeRawPointer(UnsafeMutablePointer<CA?????>(&x3))
    dumpMemory(px3, MemoryLayout<CA?????>.size)

    var x4: CA????? = .some(.some(.none))
    let px4 = UnsafeRawPointer(UnsafeMutablePointer<CA?????>(&x4))
    dumpMemory(px4, MemoryLayout<CA?????>.size)

    var x5: CA????? = .some(.none)
    let px5 = UnsafeRawPointer(UnsafeMutablePointer<CA?????>(&x5))
    dumpMemory(px5, MemoryLayout<CA?????>.size)

    var x6: CA????? = .none
    let px6 = UnsafeRawPointer(UnsafeMutablePointer<CA?????>(&x6))
    dumpMemory(px6, MemoryLayout<CA?????>.size) 

    print("--test7 exit")
}

test1()
test2()
test3()
test4()
test5()
test6()
test7()