xcode - Swift 3使用 'withUnsafeBufferPointer'从网络套接字读取- 'init'无法使用 'withMemoryRebound'

Question

我在Swift 2.3中有一个从网络套接字读取Int值的函数

open func readInt() -> Int32 {
    var intValueBuffer = [UInt8](repeating: 0, count: MemoryLayout<Int32>.size)
    self.stream!.read (&intValueBuffer, maxLength: MemoryLayout<Int32>.size)
    let intValue = intValueBuffer.withUnsafeBufferPointer({
        UnsafePointer<Int32>($0.baseAddress!).pointee
    })
    return Int32(bigEndian: intValue)
}

迁移到Swift 3之后，我遇到了这个错误。我还无法弄清楚实际需要更改的内容，我们将不胜感激

Answer 1

从UInt8指针到Int32指针的转换
必须使用withMemoryRebound()明确指定:

func readInt() -> Int32 {
    var intValueBuffer = [UInt8](repeating: 0, count: MemoryLayout<Int32>.size)
    self.stream!.read(&intValueBuffer, maxLength: MemoryLayout<Int32>.size)
    let intValue = intValueBuffer.withUnsafeBufferPointer({
        $0.baseAddress!.withMemoryRebound(to: Int32.self, capacity: 1) {
            $0.pointee
        }
    })
    return Int32(bigEndian: intValue)
}

或者，读入 Data对象而不是数组:

func readInt() -> Int32 {
    var intValueBuffer = Data(count: MemoryLayout<Int32>.size)
    intValueBuffer.withUnsafeMutableBytes {
        _ = self.stream!.read($0, maxLength: MemoryLayout<Int32>.size)
    }
    return Int32(bigEndian: intValueBuffer.withUnsafeBytes { $0.pointee })
}

或直接转换为整数变量:

func readInt() -> Int32 {
    var intValue: Int32 = 0
    withUnsafePointer(to: &intValue) {
        $0.withMemoryRebound(to: UInt8.self, capacity: MemoryLayout<Int32>.size) {
            _ = self.stream!.read($0, maxLength: MemoryLayout<Int32>.size)
        }
    }
    return Int32(bigEndian: intValue)
}

有关更多信息，请参见swift.org上的 UnsafeRawPointer Migration。

您可能还需要检查 read方法的返回值
这是实际读取的字节数；如果读取操作失败，则为-1。