问题描述
我有一个需要在我的 Swift 代码中使用的 C 库和一个需要 32 字节长的 UnsafeMutablePointer<UInt8> 的函数来从现有的私钥 (crypto_sign_public_key) 生成公钥。这是我正在调用的 C 函数文档的链接：https://monocypher.org/manual/sign。我在 C 和指针方面没有太多经验，但我阅读了一些教程，并且有一些看起来很完美的东西。
除此之外，我想看看是否有比我更有经验的人能说出这段代码是否“安全”和/或是否会产生未定义的行为？
func generatePublicKey(from privateKey: [UInt8]) -> [UInt8] {
/// Create an empty pointer that is 32 bytes long. The resulting public key will be written to the memory the pointer is pointing to.
let publicKeyPointer = UnsafeMutablePointer<UInt8>.allocate(capacity: 32)
/// This is using the 25519 curve and the Blake2b hash method.
/// Sign the private key and in turn,create the public key.
crypto_sign_public_key(publicKeyPointer,privateKey)
/// Go over the 32 bytes of the pointer and save it's locations as a "buffer"
let buffer = UnsafeMutableBufferPointer(start: publicKeyPointer,count: 32)
/// copy the data being pointed to,into an actual array.
let publicKey = Array(buffer)
/// Deallocate the memory being used by the pointer.
publicKeyPointer.deallocate()
return publicKey
}
谢谢！
解决方法
您的代码没问题，因为 UInt8 是一个普通类型，因此不需要您在分配的内存上调用 initialize 或 deinitialize。
但是，您可以完全避免手动分配和释放，如下所示：
func makePublicKey(withPrivateKey privateKey: [UInt8]) -> [UInt8] {
var publicKey = [UInt8](repeating: 0,count: 32)
publicKey.withUnsafeMutableBufferPointer { buffer in
crypto_sign_public_key(buffer.baseAddress!,privateKey)
}
return publicKey
}