swift - 如何将 String 转换为 UnsafeMutablePointer<UInt8> ？ swift 3

Question

我试过了

 return areKeysConsistent(
     certificate as! UnsafeMutablePointer<UInt8>,
     certificate.lengthOfBytes(using: <#T##String.Encoding#>.utf8),
     privateKey as! UnsafeMutablePointer<UInt8>,
     privateKey.lengthOfBytes(using: <#T##String.Encoding#>.utf8),
     password as! UnsafeMutablePointer<UInt8>
 ) 

但是IDE说 -“字符串总是失败。

转换它的正确方法是什么？谢谢

Answer 1

这是您必须使用 C 语言而遇到一些复杂情况的地方。

这里主要关注的是您传递给该函数的指针的生命周期。我下面的代码使用指向 Swift 字符串缓冲区的指针。如果 areKeysConsistent 捕获这些指针供以后使用，这将是一个问题。 ARC 有可能取消分配 Swift 字符串，使那些存储的指针变成悬空指针。

func areKeysConsistent(
        _ cert: UnsafeMutablePointer<UInt8>, _ certLength: Int,
        _ key: UnsafeMutablePointer<UInt8>, _ keyLength: Int,
        _ pass: UnsafeMutablePointer<UInt8>, _ passLength: Int
    ) {
    print(cert, key, pass)
}

let certificate = "cert"
let privateKey = "key"
let password = "password"

var certificateCString = certificate.utf8CString
var privateKeyCString = privateKey.utf8CString
var passwordCString = password.utf8CString


certificateCString.withUnsafeMutableBytes { certUMRBP in
privateKeyCString.withUnsafeMutableBytes { pkUMRBP in
passwordCString.withUnsafeMutableBytes { passUMRBP in

    areKeysConsistent(
        certUMRBP.baseAddress!.bindMemory(to: UInt8.self, capacity: certUMRBP.count),
        certUMRBP.count,
        pkUMRBP.baseAddress!.bindMemory(to: UInt8.self, capacity: pkUMRBP.count),
        pkUMRBP.count,
        passUMRBP.baseAddress!.bindMemory(to: UInt8.self, capacity: passUMRBP.count),
        passUMRBP.count
    )
}
}
}