Swift 数据到 Int 数组

Question

我想以数字类型数组的形式访问数据中的原始字节以进行快速解析。我有很多数据要解析，所以我正在寻找效率。数据是短裤、整数、长裤和双打的混合。

下面的代码似乎可以运行并且速度很快，但是我收到了已弃用的警告：'withUnsafeBytes' 已弃用

我想不出将底层字节视为数字数组以便快速查找的更新方法。

    var data: Data = ...
            
    // create "virtual" arrays of different types to directly access bytes (without copying bytes)
    
    let ushortArray: [UInt16] = data.withUnsafeBytes {
        [UInt16](UnsafeBufferPointer(start: [=11=], count: data.count/2))
    }
    let intArray: [Int32] = data.withUnsafeBytes {
        [Int32](UnsafeBufferPointer(start: [=11=], count: data.count/4))
    }

    // Access data simply
    var i1: UInt16 = ushortArray[0]
    var i2: Int32 = intArray[1]

P.S。我不关心 big/little endian

Answer 1

如果您想将其作为数组加载，您需要使用 UnsafeRawBufferPointer bindMemory 方法来指定您想要的类型。您还可以扩展 ContiguousBytes 以创建通用方法并简化语法：

Note: if you are planing to get a subsequence of your data make sure to do NOT subscript the data to avoid misaligned errors. You need to use Data subdata method instead.

extension ContiguousBytes {
    func objects<T>() -> [T] { withUnsafeBytes { .init([=10=].bindMemory(to: T.self)) } }
    var uInt16Array: [UInt16] { objects() }
    var int32Array: [Int32] { objects() }
}

extension Array {
    var data: Data { withUnsafeBytes { .init([=11=]) } }
}

用法：

let uInt16Array: [UInt16] = [.min, 1, 2, 3, .max]  // [0, 1, 2, 3, 65535]
let int32Array: [Int32] = [.min, 1, 2, 3, .max]    // [-2147483648, 1, 2, 3, 2147483647]

let uInt16ArrayData = uInt16Array.data  // 10 bytes
let int32ArrayData = int32Array.data    // 20 bytes

let uInt16ArrayLoaded = uInt16ArrayData.uInt16Array  // [0, 1, 2, 3, 65535]
let int32ArrayLoaded = int32ArrayData.int32Array       // [-2147483648, 1, 2, 3, 2147483647]

// Access data simply
let i1 = uInt16ArrayLoaded[0]   //  UInt16 0
let i2 = int32ArrayLoaded[0]    // Int32 -2147483648
let i3 = uInt16ArrayLoaded[4]   //  UInt16 65535
let i4 = int32ArrayLoaded[4]    // Int32 2147483647

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