在Swift中将有符号转换为无符号 [英] Converting signed to unsigned in Swift

问题描述

在C语言中，我可以用数字做些技巧:

In C, I am able to do a trick with numbers:

uint8_t value = 0
int delta = -1
uint8_t result = value + delta  /* result will be 0xFF */

在Swift中有没有办法做到这一点?请注意，相同的方法无效:

Is there a way of doing the same in Swift? Notice that the same approach doesn't work:

let value: UInt8 = 0
let delta: Int = -1
var result: UInt8 = value + delta  // Error, even typecasting in different ways... 

是否有一种方法可以让C的行为在Swift中进行减法运算?

Is there a way to get C's behaviour for substraction in Swift?

谢谢！

推荐答案

所有有符号和无符号整数类型都有一个bitPattern:构造函数， 它从具有相同符号的已签名(反之亦然)中创建一个未签名的数字 内存表示形式:

All signed and unsigned integer types have a bitPattern: constructor, which creates an unsigned number from a signed (or vice versa) with the same memory representation:

let delta: Int8 = -1
let result: UInt8 = UInt8(bitPattern: delta) // 0xFF = 255

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