Swift:Java 相当于 [UInt8] 的 Arrays.copyOfRange

Question

我正在将 java 代码翻译成 swift，我想知道 Arrays.copyOfRange 的 swift 等价物是什么:

public static byte[] copyOfRange(byte[] original, int from, int to) 

对于我的示例，我想翻译下一行:

Arrays.copyOfRange(packet.value(), 2, packet.length())

谢谢

Answer 1

如果上限值大于数组长度，Java 的 copyOfRange 也会用零填充结果数组。此函数也可以处理这种情况。

这个函数可以做成通用的。它适用于符合 ExpressibleByIntegerLiteral 的任何类型，这是 0 填充所需的。

func copyOfRange<T>(arr: [T], from: Int, to: Int) -> [T]? where T: ExpressibleByIntegerLiteral {
    guard from >= 0 && from <= arr.count && from <= to else { return nil }

    var to = to
    var padding = 0

    if to > arr.count {
        padding = to - arr.count
        to = arr.count
    }

    return Array(arr[from..<to]) + [T](repeating: 0, count: padding)
}

---

示例:

let arr: [UInt8] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

if let result = copyOfRange(arr: arr, from: 0, to: 3) {
    print(result)  // [0, 1, 2]
}
if let result = copyOfRange(arr: arr, from: 7, to: 12) {
    print(result)  // [7, 8, 9, 0, 0]
}