Acessing structs from Swift

Generally, defining a binary data format using C-struct seems to be a bad idea.

Please check how MSG_t is layout in the byte stream.

Format 1:

Code Block 
+--+--+--+--+--+--+--+--+--+--+--+--+--+--
| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|12|...
+--+--+--+--+--+--+--+--+--+--+--+--+--+--
|sig  |len  |type |data       |
+-----+-----+-----+-----------+

Or

Format 2:

Code Block 
+--+--+--+--+--+--+--+--+--+--+--+--+--+--
| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11|12|...
+--+--+--+--+--+--+--+--+--+--+--+--+--+--
|sig  |len  |type |     |data       |
+-----+-----+-----+-----+-----------+

Many compiles put two-byte padding after type, to align data to 32-bit boundary. But that depends on the compiler, CPU architecture or compiling flags.
But in communications, people do not like putting unused bytes.

---

You also need to care about endianness.

In communication within the same device, you can expect all multi-byte data have the same endianness, so you can program your code using CPU-endian.

But in TCP communications, the two nodes on the internet may have different CPU-endian. And there are many people who prefers big-endian for binary data format on the internet, as you know network order, even if the CPU is little-endian.

---

So, if you mean this as including cast myData.bytes onto a struct, it is a wrong approach.

The first thing you need is defining the binary data format without using C-struct, specifying endianness explicitly.
(Also specify paddings explicitly, if exists.)

In the example below I assume something like this:

Code Block 
offset|number of bytes|endianness   |field name
------+---------------|-------------|----------
    +0|              2|little endian|sig
    +2|              2|little endian|len
    +4|              2|little endian|type
    +6|              4|little endian|data
------+---------------|-------------|----------

With the data format like this, you can write some code as follows:

Code Block 
class DataReader {
    var data: Data
    var offset: Int = 0
    
    init(data: Data) {
        self.data = data
    }
    
    func readLittleEndian<T: FixedWidthInteger>()->T {
        var rawValue: T = 0
        _ = withUnsafeMutableBytes(of: &rawValue) {rawBufPtr in
            data.copyBytes(to: rawBufPtr, from: offset...)
        }
        offset += MemoryLayout<T>.size
        
        return T(littleEndian: rawValue)
    }
}
//Sample data
let data: Data? = Data([
    0x12, 0x34,
    0x56, 0x78,
    0x9A, 0xBC,
    0xDE, 0xF0, 0x12, 0x34])
if let myData = data {
    var myStruct = MSG_t()
    let reader = DataReader(data: myData)
    myStruct.sig = reader.readLittleEndian()
    myStruct.len = reader.readLittleEndian()
    myStruct.type = reader.readLittleEndian()
    myStruct.data = reader.readLittleEndian()
    
    print(String(format: "%04X", myStruct.sig))
    print(String(format: "%04X", myStruct.len))
    print(String(format: "%04X", myStruct.type))
    print(String(format: "%08X", myStruct.data))
    
    if myStruct.sig == CORRECT_MSG_SIG {
        // do soemthig with the message...
    }
}

(Assuming MSG_t is defined in C-style header and imported into Swift.)

So, instead of answering my question you just lecture me on data packing?
Nice!

hi! can you please help me? i am begging! I believe that AI is growing too fast for the privacy tools needed to follow the speed of its evolvment.
i have the iphone 17 plus max, but for the last two months i have been using it like i have a old nokia to try to stop this unathorized remote acess to my devices. however, it still not enough.
i need help guys!! they have changed the roots of my devices, removed any possibility of me getting any notifications, deleted many files, photos and even tried to blackmail me with some nudes, ehich i told them to go ahead and post my nudes. inreally dont care. i care about me being able to work!
using healthkit, homekit, facetime and more apps I have been a target of this "boy band" that was hited by my ex fiance to delete all the media i had on him that can prove how abusive he was. it has been two months, they have deleted all my files, photos, contacts, voicemal.
Someone using without any of my approval or even notificarion:
1- AI, siri to run commands
2- Camera ( to connect or control my device)
3- Shortcuts + Run shortcuts apps (to run removal tasks, monitoring to my mailbox, to find and genarate QR codes to acesss my Wifi and any VPN i may be using )
4- Facetime (to start a remote session, i never get a request but they are so bad as hacking that they leave signs and i can tell when they are online)
5- Assitive access (voice over, dictation and assitive guide)
6- Accessibility tools (voice, typing, dictating, camera, nearby connection )
7- playground (to find and remove the photos faster)
8-screen recording (to record and monitor my isntagram, facebook, photos activity) it would record and saved in a hidden folder that would be send to them.. they are just dumb, but i am
very sick, i cant fight them alone, please help me
9- satellite connection ( i have seem that they have saved my coordinates of my house to access) i am sick, so i stay home until i get this MS flare on control..
appclips, healthkit, mirror, , shareplay, nearby connection, copilot, chatgpt, muse, notes, inivation app, youtube app, paypal app, authenticators, word, theres so many apps they have used to try and accomplished connection to my devices.
theres morr things but i am very upset and sick ( i have MS and facing a huge flare right now)
thanks - please help figure out how to stop this boy band to access my devices please
much appreciated
please feel free to contact me at 647-995-3230 or via email viviane.presa@gmail.com
they do delete emails, messages, block phone calls, please re-send ig needed. please i need help
Yes! this is crazy, i have done a report to the police. best buy its investigating my notebook