Swift NSData getBytes reversed - swift

Question

I made an app communicating with a device with Bluetooth Low Energy.
Basically, my app and this device have their own message syntax. They exchange data as bytes and each values in thoses data are reversed.
My problem is that after reversing back value, when I'm converting a 3 bytes value to an Int32, the NSData.getBytes function seems to reverse the value, so I have a wrong value. Example:
var value; // containing [ 0x01, 0xD3, 0x00 ]
value = value.reverse(); // Reverse back : [ 0x00, 0xD3, 0x01 ]
let numb = value.getUInt32(); // Numb will be 119552, instead of 54017...
I don't know if I'm clear enough on my problem, but here is my code. A function which reverse back data and then tries to convert data to int.
// Those functions are in an extension of NSData
func getRUInt32(range:NSRange) -> UInt32
{
var data = message.subdataWithRange(range); // Extract data from main message
data = data.reverse(); // Reverse back data
return data.getUInt32(); // Convert to UInt32
}
func getUInt32() -> UInt32
{
var value:Int32 = 0;
getBytes(&value, length: self.length);
return UInt32(value);
}
func reverse() -> NSData
{
let count:Int = length / sizeof(UInt8);
var array = [UInt8](count: count, repeatedValue: 0);
getBytes(&array, length: count * sizeof(UInt8));
var reversedArray = [UInt8](count: count, repeatedValue: 0);
for index in 0..<array.count
{
reversedArray[index] = array[array.count - index - 1];
}
return NSData(bytes: reversedArray, length: reversedArray.count);
}

Answer 1

You should have a look at the byte order utilities reference:
https://developer.apple.com/library/ios/documentation/CoreFoundation/Reference/CFByteOrderUtils/index.html#//apple_ref/c/func/CFConvertDoubleHostToSwapped
You identify the native format of the current platform using the
CFByteOrderGetCurrent function. Use functions such as
CFSwapInt32BigToHost and CFConvertFloat32HostToSwapped to convert
values between different byte order formats.