Question

我有一个来自C库的ptr，它指向一个Floats数组。它的类型是UnsafeMutablePointer。如何在Swift 3中创建一个本机[Float]数组？

这是我尝试的内容：

var reconstructedFloats = [Float](repeatElement(0, count: size))
reconstructedFloats.withUnsafeMutableBufferPointer {
  let reconstructedFloatsPtr = $0
  print(type(of:$0)) // "UnsafeMutableBufferPointer<Float>"
  cFloatArrayPtr?.withMemoryRebound(to: [Float].self, capacity: size) {
    UnsafeMutableRawPointer(reconstructedFloatsPtr.baseAddress!).storeBytes(of: $0.pointee, as: Float.self)
  }

UnsafeMutableRawPointer(reconstructedFloatsPtr.baseAddress!).storeBytes(of: (cFloatArrayPtr?.pointee)!, as: Float.self)
}

这似乎过于复杂，所以希望这是一种简单的方法，但即使这段代码也会产生编译错误：Type of expression is ambiguous without more context。

如果你想将它插入游乐场，这里有一个设计cFloatArrayPtr的完整样本：

// Let's contrive a C array ptr:
var size = 3
var someFloats: [Float] = [0.1, 0.2, 0.3]
var cFloatArrayPtr: UnsafeMutablePointer<Float>?

someFloats.withUnsafeMutableBufferPointer {
    cFloatArrayPtr = $0.baseAddress
}

print(type(of:cFloatArrayPtr!)) // "UnsafeMutablePointer<Float>"

var reconstructedFloats = [Float](repeatElement(0, count: size))
reconstructedFloats.withUnsafeMutableBufferPointer {
    let reconstructedFloatsPtr = $0
    print(type(of:$0))
    cFloatArrayPtr?.withMemoryRebound(to: [Float].self, capacity: size) {
        UnsafeMutableRawPointer(reconstructedFloatsPtr.baseAddress!).storeBytes(of: $0.pointee, as: Float.self)
    }

    UnsafeMutableRawPointer(reconstructedFloatsPtr.baseAddress!).storeBytes(of: (cFloatArrayPtr?.pointee)!, as: Float.self)
}

print(reconstructedFloats)

Answer 1

您可以从指针中制作UnsafeBufferPointer。 UnsafeBufferPointer是Sequence，因此您可以直接从中创建数组：

let buffer = UnsafeBufferPointer(start: cFloatArrayPtr, count: size)
var reconstructedFloats = Array(buffer)

当然，这会创建一个副本。

在Swift 3中将C数组ptr转换为本机数组

1 个答案: