Beginning a Session

You may specify the number of outgoing message buffers and the size of these buffers and the number of incoming message buffers and the size of these buffers. If you do not specify the number and size of these buffers, two buffers of each type are created and each buffer is 16kb in size.

The size of a single outgoing buffer is the maximum size of any outgoing message. If the user creates a larger message than the buffer, the overflowing packets are placed in the next buffer. If the user fills all of the available buffers, a new buffer is created and the overflowing packets are placed in this new buffer.
Warning: It is possible to get into a runaway buffer creation condition causing the system to abort the program.

If the program is using the provided incoming message buffers, the size of a single incoming message buffer is the maximum size of an incoming message. Otherwise, if the program is supplying its own incoming message buffer, the size of the supplied incoming message buffer is the maximum size of an incoming message. The user should never overflow the incoming message buffer. If a message is received that is larger than the buffer, the user must only put the portion of the message into the incoming message buffer that will fit.

The session creates an outgoing message object and an incoming message object. It also creates several needed tables and buffers. You can create the session by using any of the C++ object creation methods.

Example: IG session object creation

// Simple Creation: CigiIGSession IGsession; // Specifying the number of buffers and their size: CigiIGSession IGsession( Number_of_input_buffers, Size_of_each_input_buffer_in_bytes); // or CigiIGSession IGsession( Number_of_output_buffers, Size_of_each_output_buffer_in_bytes); // Using pointers: CigiIGSession *IGsessionPnt; ... IGsessionPnt = new CigiIGSession; // Using pointers and specifying the number of buffers and their size: CigiIGSession *IGsessionPnt; ... IGsessionPnt = new CigiIGSession( Number_of_input_buffers, Size_of_each_input_buffer_in_bytes); // or IGsessionPnt = new CigiIGSession( Number_of_output_buffers, Size_of_each_output_buffer_in_bytes);

Example: Host session object creation

// Simple Creation: CigiHostSession HostSession; // Specifying the number of buffers and their size: CigiHostSession HostSession( Number_of_input_buffers, Size_of_each_input_buffer_in_bytes); // or CigiIGSession IGsession( Number_of_output_buffers, Size_of_each_output_buffer_in_bytes); // Using pointers: CigiHostSession *HostSessionPnt; ... HostSessionPnt = new CigiHostSession; // Using pointers and specifying the number of buffers and their size: CigiHostSession *HostSessionPnt; ... HostSessionPnt = new CigiHostSession( Number_of_input_buffers, Size_of_each_input_buffer_in_bytes); // or HostSessionPnt = new CigiHostSession( Number_of_output_buffers, Size_of_each_output_buffer_in_bytes);

The user must set the initial version of CIGI that the external interface is using and set whether the interface is synchronous or asynchronous. The default is for the session to be synchronous.

Example: Setting the version and synchronization mode

// Set up cigi external interface version Session.SetCigiVersion(CIGI_major_version_number,CIGI_minor_version_number); // Set as synchronous (true) or asynchronous (false) Session.SetSynchronous(true_or_false);

The user may also create an IO class derived from the CigiIO class. This class must provide the virtual Read and Write methods that handle the actual buffer output and input. The CigiIO methods Send and Receive, inherited by the user's IO class, handle most of the high level buffer management. The user creates and manages the user's IO object. A simple example of this is the class ExampleIO in the example code. If the user chooses not to create an IO class, the user must perform all the functions that Send, Receive, Read, and Write provide.