Swift中的unsigned char

Question

在Obj-C中,此代码用于将NSData转换为unsigned char:

unsigned char *dataToSentToPrinter = (unsigned char *)malloc(commandSize);

在Swift中,unsigned char被称为CUnsignedChar,但是我如何在Swift中将NSData对象转换为CUnsignedChar？

Answer 1

这可能是你正在寻找的:

let commandsToPrint: NSData = ...

// Create char array with the required size:
var dataToSentToPrinter = [CUnsignedChar](count: commandsToPrint.length, repeatedValue: 0)

// Fill with bytes from NSData object:
commandsToPrint.getBytes(&dataToSentToPrinter, length: sizeofValue(dataToSentToPrinter))

更新:实际上你根本不需要复制数据(既不在Objective-C代码也不在Swift中).有一个指向数据的指针就足够了.所以你的代码看起来像这样(比较 Error("'()'与'UInt8'不相同")使用Swift中的write函数将NSData字节写入NSOutputStream以 解决类似的问题):

let dataToSentToPrinter = UnsafePointer<CUnsignedChar>(commandsToPrint.bytes)
let commandSize = commandsToPrint.length
var totalAmountWritten = 0

while totalAmountWritten < commandSize {
    let remaining = commandSize - totalAmountWritten
    let amountWritten = starPort.writePort(dataToSentToPrinter, totalAmountWritten, remaining)
    totalAmountWritten += amountWritten
    // ...
}