Question

我使用SHA1在Apple Watch上散列用户数据，并且在运行j = ( UInt32((msg[i]<<24) | (msg[i+1]<<16) | (msg[i+2]<<8) | msg[i+3]) )函数时，出现以下错误：

Thread1：exc_breakpoint（code = exc_arm_breakpoint，subcode = 0xe7ffdefe）。这条特定的行给了我错误： class func SHA1Bytes(msg: [Int])->String{ func rotateLeft(number: UInt32, rotateBy: UInt32)->UInt32{ return ((number << rotateBy) | (number>>(32-rotateBy))) } func cvt_hex(value: UInt32)->String{ var str = "" for i:UInt32 in stride(from: 7, through: 0, by: -1){ let v: UInt32 = (value >> (i*4)&0x0f) str += String(v,radix: 16, uppercase: false) } return str } var W = [UInt32](repeating: 0, count: 80) var H0 = UInt32("67452301",radix: 16)! var H1 = UInt32("EFCDAB89",radix: 16)! var H2 = UInt32("98BADCFE",radix: 16)! var H3 = UInt32("10325476",radix: 16)! var H4 = UInt32("C3D2E1F0",radix: 16)! var wordArray = [UInt32]() for k in stride(from: 0, to: msg.count-3, by: 4) { let j = ( UInt32((msg[k]<<24) | (msg[k+1]<<16) | (msg[k+2]<<8) | msg[k+3]) ) wordArray.append(j) } ... return encoded.uppercased() }

这是从中提取上述行的代码段：

完全相同的代码在iOS Playground中运行完美，但在第一代Apple Watch上运行时崩溃。我已检查并且输入数组存在，我正在尝试访问它的现有元素，j=(UInt32) 2308511418, k=(Int)48, msg=([Int])56values的结果不应该溢出。代码失败并带有以下变量值：

[47] Int 217 [48] Int 137 [49] Int 153 [50] Int 22 [51] Int 186 [52] Int 163 [53] Int 41 [54] Int 208 [55] Int 104

这些是msg：

的值

modulus

Answer 1

第一代Apple Watch是一款32位设备，与64位设备相比，具有不同的溢出限制。

在32位器件上，Int类型为32位，您可能会转入符号位。

在游乐场中尝试以下操作：

UInt32(Int64(153) << 24) // Equivalent to your code

UInt32(Int32(153) << 24) // Simulates a 32-bit device and crashes.

UInt32(153) << 24         // A possible solution

Answer 2

我设法弄清楚即使UInt32溢出，模拟器也没有崩溃，但是，在这种情况下，32位Apple Watch会崩溃。解决方案是使用溢出运算符，该运算符仅用于加法，减法和乘法。因此，我将按位左移改变为乘法2 ^（要移位的位数）。这是正确的解决方案：UInt32(msg[k])&*UInt32(1<<24)

let j = (UInt32(msg[k])&*UInt32(1<<24))|UInt32(msg[k+1]&*(1<<16))|UInt32(msg[k+2]&*(1<<8))|UInt32(msg[k+3])

Apple Watch在位操作时崩溃，错误代码为Thread1：exc_breakpoint（code = exc_arm_breakpoint，subcode = 0xe7ffdefe）

2 个答案: