Swift String to unsigned char [](CUnsignedChar)

Question

Hello i'm trying to use an old legacy C library that uses buffers (unsigned char []) to transform the data. The main issue here is that I couldn't find a way to transform a String to a CUnsignedChar and then be able to alloc that buffer to a UnsafeMutablePointer

Answer 1

If you want to convert a Swift string to an immutable C string to pass to a C function, try this:

let s: String = "hello, world!"
s.nulTerminatedUTF8.withUnsafeBufferPointer { p -> Void in
    puts(UnsafePointer<Int8>(p.baseAddress))
    Void()
}

You may need to use UnsafePointer<UInt8> if your function takes an unsigned char *.

Answer 2

I turn String to NSData first ,then turn NSData to CUnsignedChar array

if let data = str.dataUsingEncoding(NSUTF8StringEncoding){
        var rawData = [CUnsignedChar](count: data.length,repeatedValue: 0)
        data.getBytes(&rawData, length: data.length)

}