Swift 中的 C 样式指针/数组转换？

Question

Is there any way I can cast an array of different integer sizes to another array type?

For example, in C, I can do:

unsigned char byteArray[] = { 0x1, 0x5, 0xF, 0x3, 0xA5, 0x3, 0x8, 0x8, 0xAB };
unsigned long long *largeArray = (unsigned long long *)(byteArray);

which would make largeArray equal to { 0x80803A5030F0501, 0x51B76EB7140024AB } .

Is there any similar thing in Swift? For example, something like:

let byteArray: [UInt8] = [0x1, 0x5, 0xF, 0x3, 0xA5, 0x3, 0x8, 0x8, 0xAB]
let largeArray = [UInt64](byteArray)

I know it is possible to do programmatically, I was just wondering if there's a built in method before I delve into making my own thing that will cast them.

Any help will be greatly appreciated!

Answer 1

Let's assume the byteArray had eight bytes in it. You could do:

let byteArray: [UInt8] = [0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7]

let value = byteArray.withUnsafeBytes { 
    $0.bindMemory(to: UInt64.self)[0].littleEndian    // or .bigEndian
}

Resulting in:

0x0706050403020100     // or 0x0001020304050607 if you use bigEndian

Or, if you had enough bytes for multiple UInt64 , you could do:

let longByteArray: [UInt8] = [
    0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7,
    0x8, 0x9, 0xa, 0xb, 0xc, 0xd, 0xe, 0xf
]

let values = longByteArray.withUnsafeBytes {
    $0.bindMemory(to: UInt64.self)
}.map {
    $0.littleEndian       // or .bigEndian
}

Resulting in

[0x0706050403020100, 0x0f0e0d0c0b0a0908] // or [0x0001020304050607, 0x08090a0b0c0d0e0f] if you use bigEndian