在不同的UnsafePointer< T>之间进行转换在迅速 [英] Casting between different UnsafePointer<T> in swift

问题描述

我正试图从swift中使用C-Api。作为一个例子，C-Api采用这种方式：

I am trying to use a C-Api from swift. As an example the C-Api goes this ways:

void doThingsOnRawData(const unsigned char* data);

Swift将其转换为：

Swift converts this to:

void doThingsOnRawData(UnsafePointer<UInt8>);

现在我想将数据从NSData传递给函数。 NSData.byte返回类型：

Now I want to pass the data from an NSData to the function. NSData.byte returns the type:

UnsafePointer<()>

1. 这是某种类型的void *类型吗？

1. Is this some kind of void* type?

至少swift不会接受它作为 UnsafePointer< UInt8> 。我该怎么办呢？

At least swift won't accept it as an UnsafePointer<UInt8>. What do I do to cast this?

推荐答案

struct UnsafePointer< T> 有一个构造函数

/// Convert from a UnsafePointer of a different type.
///
/// This is a fundamentally unsafe conversion.
init<U>(_ from: UnsafePointer<U>)

您可以使用这里

doThingsOnRawData(UnsafePointer<UInt8>(data.bytes))

您甚至可以省略泛型类型，因为它是从上下文中推断出来的：

You can even omit the generic type because it is inferred from the context:

doThingsOnRawData(UnsafePointer(data.bytes))

Swift 3的更新：从Xcode 8 beta 6开始，您不能再在不同的不安全指针之间直接转换
。

Update for Swift 3: As of Xcode 8 beta 6, you cannot convert directly between different unsafe pointers anymore.

对于数据： NSData ， data.bytes 是一个 UnsafeRawPointer ，可以将
转换为 UnsafePointer< UInt8> with assumeMemoryBound ：

For data: NSData, data.bytes is a UnsafeRawPointer which can be converted to UnsafePointer<UInt8> with assumingMemoryBound:

doThingsOnRawData(data.bytes.assumingMemoryBound(to: UInt8.self))

对于数据：数据它甚至更简单：

data.withUnsafeBytes { doThingsOnRawData($0) }

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