Reading C ++ structures from socket to LISP

We have an application protocol defined as C ++ classes that are passed over the network. I want to connect to a server that is sending data in this format. I want to write a client in lisp (preferably sbcl) to communicate with this server. I would prefer it written in pure lisp instead of using CFFI to wrap C ++ dlls. The sampling frames would look something like this:

class Header
{
public:
    int MsgType;
    uint64_t Length;
}

class SampleMsg
{
public:
    Header MsgHeader;
    char Field1[256];
    bool Field2;
    double Field3;
    SomeOtherClass Field4;
}

      

        
        
        
      

    

I want to know how to map these structures in lisp so that they are binary compatible and how to read / write such structures. Is there an easier way than packing / unpacking each field in the structure?

For example, in C #, you can map a binary structure like this and read it directly from a byte array:

[StructLayout(LayoutKind.Sequential)]
public struct Header
{
    public int MsgType;
    public ulong Length;
}

[StructLayout(LayoutKind.Sequential)]
public struct SampleMsg
{
public:
    public Header MsgHeader;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
    public string Field1;
    public bool Field2;
    public double Field3;
    public SomeOtherClass Field4;
}

      

        
        
        
      

    

If a similar method is possible in lisp, that would be ideal. If not, I'm ready to do some plumbing while it's manageable.

EDIT:

Tried Svante's suggestion:

(ql:quickload "userial")
(in-package :sb-bsd-sockets)

(defun read-buffer (host port)
  (let ((socket (make-instance 'inet-socket :type :stream :protocol :tcp)))
    (socket-connect socket host port)
    (let ((buf (socket-receive socket nil 1024 :element-type '(unsigned-byte 8))))
      (socket-close socket)
      buf)))


(defstruct header
  msg-type
  length)


(userial:make-slot-serializer (:header header (make-header))
                  :int64 msg-type
                  :uint64 length)

(defvar *buffer*)
(defvar *b*)
(setq *buffer* (read-buffer #(10 1 2 75) 5003))
(setq *b* (make-array 2048 :element-type '(unsigned-byte 8) :fill-pointer 0 :adjustable t))
(map 'vector #'(lambda (x) (vector-push x *b*)) *buffer*)

(setf (fill-pointer *b*) 0)

      

        
        
        
      

    

At this point, *b*

it runs something like this: #(7 0 0 0 0 0 0 0 176 2 0 0 0 0 0 0 45 71 253 83 0 0 0 0 165 30 11 11 0 0 0 ...)

. The first 7 correspond to type msg, which should be 7. The length should be 688 (176 + 2 * 256).

Now I am (userial:with-buffer *b* (userial:unserialize :header))

. It gives me

#S(HEADER :MSG-TYPE 504403158265495552 :LENGTH 12682699500628738048)
#(7 0 0 0 0 0 0 0 176 2 0 0 0 0 0 0)

      

        
        
        
      

    

Sounds like an entiancy problem. How to fix it? I can't seem to find a way to deal with content inside a custom library.

EDIT2:

Finally ended up dropping the custom one and writing these (the following are practical common lisps):

(defun read-64 (buf)
  (let ((u 0))
    (setf (ldb (byte 8 56) u) (aref buf 7))
    (setf (ldb (byte 8 48) u) (aref buf 6))
    (setf (ldb (byte 8 40) u) (aref buf 5))
    (setf (ldb (byte 8 32) u) (aref buf 4))
    (setf (ldb (byte 8 24) u) (aref buf 3))
    (setf (ldb (byte 8 16) u) (aref buf 2))
    (setf (ldb (byte 8 8) u) (aref buf 1))
    (setf (ldb (byte 8 0) u) (aref buf 0))
    u))

(defun read-32 (buf)
   (let ((u 0))
    (setf (ldb (byte 8 24) u) (aref buf 3))
    (setf (ldb (byte 8 16) u) (aref buf 2))
    (setf (ldb (byte 8 8) u) (aref buf 1))
    (setf (ldb (byte 8 0) u) (aref buf 0))
    u))

(defun read-16 (buf)
  (let ((u 0))
    (setf (ldb (byte 8 8) u) (aref buf 1))
    (setf (ldb (byte 8 0) u) (aref buf 0))
    u))

      

        
        
        
      

    

Now I can write (read-uint64 (subseq *buffer* 8 16))

to get the msg length. Thanks for the help.