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
    // ...
}