NSDataとCFDataの関係をメモ (Toll-Free Bridge)

Sample.swift

import Foundation

var data: NSData = NSData.init(bytes: "Hello, World!", length: 13)

withUnsafePointer(to: data) {
    print("value \(String(describing: data)) has address: \($0)")
}

var cfData: CFData = data
withUnsafePointer(to: cfData) {
    print("value \(String(describing: cfData)) has address: \($0)")
}

var ptr = data.bytes.assumingMemoryBound(to: UInt8.self)
var cfDataRef: CFTypeRef = CFDataCreate(kCFAllocatorDefault, ptr, 13)
withUnsafePointer(to: cfDataRef) {
    print("value \(String(describing: cfDataRef)) has address: \($0)")
}

/**
 * 自分の環境だと
 * str value {length = 13, bytes = 0x48656c6c6f2c20576f726c6421} has address: 0x00007ffeeaee9b10
 * str value {length = 13, bytes = 0x48656c6c6f2c20576f726c6421} has address: 0x00007ffeeaee9b10
 * str value {length = 13, bytes = 0x48656c6c6f2c20576f726c6421} has address: 0x00007ffeeaee9b10
 */
 

nsdata -> cfdata にキャストしても、メモリは同じアドレスを参照しているように見える