--Copyright:      Matra Datavision 1992,1993

-- File:          OSD_MailBox.cdl
-- Created:       Thu 19 March 1992
-- Author:        Stephan GARNAUD (ARM)
--                <sga@sparc4>



class MailBox from OSD
   
   ---Purpose: Establishes a mailbox with VMS-like-features and with
   --          asynchronous functions.
   --          The mail boxes are used to communicate asynchronously
   --          between processes.
   --          Basically MailBox facilities provide tools to communicate
   --          between a client process and a server process.
   --          The client process puts data/requests into the mail-box and
   --          the server process gets these data/requests. In this context 
   --          client and server must run on the same machine. 
   --  Warning: On VMS, you need TMPMBX privilege.

   uses  Function, SharedMemory, Error, AsciiString from TCollection
raises ConstructionError, NullObject, OSDError, ProgramError


is
  Create returns MailBox;
    ---Purpose: To be used with 'Open'.
    --          It just allocates room for 'myName'.
    --          This is for a client process.
    ---Level: Advanced

  Create (name : AsciiString ; Size : Integer ; Async_function : Function) 
    returns MailBox
    ---Purpose: Instantiates MailBox object with a name, size required
    --          and a function to read mail boxes asynchronously.
    --          Each process working with the same MailBox must use
    --          a common known access : the mail-box's name.
    --
    --          This is for a server process.
    --          Raises ConstructionError when the name is not composed by
    --          characters in range of ' ' .. '~'.
    --          Raises NullObject when Async_function is a null function 
    --          pointer
    --          Raises ProgramError when Size has a negative or null value. 
    ---Level: Advanced
   raises ConstructionError, NullObject, ProgramError;

  Build (me : in out) is static;
   ---Purpose: Builds (physically) <me> into system.
   --          <me> is created and ready to run.
   --          This can be seen as an asynchronous server.
   ---Level: Advanced

  Open (me: out ; name : AsciiString ; Size : Integer)
    ---Purpose: Opens mail box, and is ready to communicate with an 
    --          already created mailbox.
    --          Raises NullObject when the name is a null string.
    --          Raises ConstructionError when the name contains characters not
    --          in range of ' '...'~'.
    --          Raises ProgramError when the mail box has a null size.
    --          This can be seen as a client.
    ---Level: Advanced
   raises ConstructionError, NullObject, ProgramError is static;

  Delete (me: out)
    ---Purpose: Removes the mail box from system.
    --          This is used only by server process !
    --          Raises ProgramError when the mail box is already deleted.
    ---Level: Advanced
    raises ProgramError is static;

  Write (me : in out; Message : AsciiString ; Length : Integer)
    ---Purpose: Writes a message of specified length into mail box.
    --          <Message> is used as a buffer, not as a common string.
    --          So this can be not null terminated like a 'char *'.
    --          This is why <Length> is useful.
    --          Raises ProgramError when the length of the data is either
    --          negative or zero.
    --          
    ---Level: Advanced
    raises ProgramError is static;

  Failed (me) returns Boolean is static;
    ---Purpose: Returns TRUE if an error occurs
    ---Level: Advanced

  Reset (me : in out) is static;
    ---Purpose: Resets error counter to zero
    ---Level: Advanced
      
  Perror (me : in out)
    ---Purpose: Raises OSD_Error
    ---Level: Advanced
    raises OSDError is static;

 Error (me) returns Integer is static;
   ---Purpose: Returns error number if 'Failed' is TRUE.
   ---Level: Advanced

fields
  myId   : Integer;  -- Mail box Identification
  myName : AsciiString;   -- Name of mail box
  mySize : Integer;  -- Size of data area
  myFunc : Function; -- AST like function
  myError: Error;
end MailBox from OSD;