/* BEGIN INCLUDE FILE ... mseg_message.incl.pl1 */
/* Created:  April 1985 by G. Palter from ms_block_hdr.incl.pl1 and ms_block_trailer.incl.pl1 */

/* format: style3,linecom */

/* NOTE: This include file references components of the mseg_segment structure which is defined separately in
   mseg_segment.incl.pl1.  Programs which use this include file must also include mseg_segment.incl.pl1 to prevent
   compilation errors. */


/* Definition of the structure of a message stored in a message segment --

   When a message is added to a message segment, it is split into one or more fixed sized blocks.  These blocks are then
   allocated in the blocks space of the message segment.  (See mseg_message.incl.pl1 and mseg_message_.pl1 for more
   information).  Each block includes a header which records where the next block of the message, if any, resides and how
   many bits of data is actually recorded in the block.

   In addition, the first block allocated for a message always includes a message descriptor.  This descriptor includes
   various pieces of information about the message such as its total length, access class, author, etc. */


/* Definition of the header found in all message blocks */

declare	1 message_block_header
			aligned based (mb_ptr),
	  2 next_block	fixed binary (18) unaligned unsigned,
	  2 descriptor_present			/* ON => a descriptor is in the last 22 words of the block */
			bit (1) unaligned,
	  2 data_lth				/* ... in bits */
			fixed binary (17) unaligned unsigned;

declare	mb_ptr		pointer;


/* Definition of the descriptor for a message recorded in the first block of the message */

declare	1 message_descriptor
			aligned based (md_ptr),
	  2 sentinel	bit (36) aligned,		/* proves that this is a message descriptor */
	  2 message_chain,				/* the chronological chain of messages in the segment */
	    3 next_message	fixed binary (18) unaligned unsigned,
	    3 prev_message	fixed binary (18) unaligned unsigned,
	  2 sender_level	fixed binary (3) unaligned unsigned,
	  2 pad1		bit (5) unaligned,
	  2 prev_message_in_hash_chain
			fixed binary (18) unaligned unsigned,
	  2 pad2		bit (10) unaligned,
	  2 ms_id		bit (72) aligned,
	  2 ms_len	fixed binary (24) unaligned unsigned,
	  2 pad3		bit (12) unaligned,
	  2 sender_id	char (32) aligned,
	  2 sender_authorization
			bit (72) aligned,
	  2 ms_access_class bit (72) aligned,
	  2 sender_max_authorization
			bit (72) aligned,
	  2 sender_process_id
			bit (36) aligned,
	  2 sender_audit	bit (36) aligned;

declare	md_ptr		pointer;

declare	MESSAGE_DESCRIPTOR_SENTINEL
			bit (36) aligned static options (constant) initial ("777777777777"b3);


/* Definition of the first block allocated for a message in a message segment */

declare	1 first_message_block
			aligned based (mb_ptr),
	  2 header	aligned like message_block_header,
	  2 data_space,
	    3 data	bit (0 refer (first_message_block.data_lth)) unaligned,
	    3 pad		bit (36
			* (mseg_segment.block_size - currentsize (message_block_header)
			- currentsize (message_descriptor)) - first_message_block.data_lth) unaligned,
	  2 descriptor	aligned like message_descriptor;


/* Definition of all but the first block allocated for a message in a message segment */

declare	1 other_message_block
			aligned based (mb_ptr),
	  2 header	aligned like message_block_header,
	  2 data_space,
	    3 data	bit (0 refer (other_message_block.data_lth)) unaligned,
	    3 pad		bit (36 * (mseg_segment.block_size - currentsize (message_block_header))
			- other_message_block.data_lth) unaligned;

/* END INCLUDE FILE ... mseg_message.incl.pl1 */


*/
                                          -----------------------------------------------------------


Historical Background

This edition of the Multics software materials and documentation is provided and donated
to Massachusetts Institute of Technology by Group Bull including Bull HN Information Systems Inc. 
as a contribution to computer science knowledge.  
This donation is made also to give evidence of the common contributions of Massachusetts Institute of Technology,
Bell Laboratories, General Electric, Honeywell Information Systems Inc., Honeywell Bull Inc., Groupe Bull
and Bull HN Information Systems Inc. to the development of this operating system. 
Multics development was initiated by Massachusetts Institute of Technology Project MAC (1963-1970),
renamed the MIT Laboratory for Computer Science and Artificial Intelligence in the mid 1970s, under the leadership
of Professor Fernando Jose Corbato. Users consider that Multics provided the best software architecture for 
managing computer hardware properly and for executing programs. Many subsequent operating systems 
incorporated Multics principles.
Multics was distributed in 1975 to 2000 by Group Bull in Europe , and in the U.S. by Bull HN Information Systems Inc., 
as successor in interest by change in name only to Honeywell Bull Inc. and Honeywell Information Systems Inc. .

                                          -----------------------------------------------------------

Permission to use, copy, modify, and distribute these programs and their documentation for any purpose and without
fee is hereby granted,provided that the below copyright notice and historical background appear in all copies
and that both the copyright notice and historical background and this permission notice appear in supporting
documentation, and that the names of MIT, HIS, Bull or Bull HN not be used in advertising or publicity pertaining
to distribution of the programs without specific prior written permission.
    Copyright 1972 by Massachusetts Institute of Technology and Honeywell Information Systems Inc.
    Copyright 2006 by Bull HN Information Systems Inc.
    Copyright 2006 by Bull SAS
    All Rights Reserved

*/