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msg.h

by Paul McJones last modified 2007-02-02 09:30

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/* @(#) msg.h 1.4 1/27/86 17:47:08 */
/*ident	"@(#)cfront:incl/sys/msg.h	1.4"*/
// ***** <sys/types.h and <sys/ipc.h> must be included.

/*
**	IPC Message Facility.
*/

/*
**	Implementation Constants.
*/

#define	PMSG	(PZERO + 2)	/* message facility sleep priority */

/*
**	Permission Definitions.
*/

#define	MSG_R	0400	/* read permission */
#define	MSG_W	0200	/* write permission */

/*
**	ipc_perm Mode Definitions.
*/

#define	MSG_RWAIT	01000	/* a reader is waiting for a message */
#define	MSG_WWAIT	02000	/* a writer is waiting to send */

/*
**	Message Operation Flags.
*/

#define	MSG_NOERROR	010000	/* no error if big message */

/*
**	Structure Definitions.
*/

/*
**	There is one msg queue id data structure for each q in the system.
*/

struct msqid_ds {
	struct ipc_perm	msg_perm;	/* operation permission struct */
	struct msg	*msg_first;	/* ptr to first message on q */
	struct msg	*msg_last;	/* ptr to last message on q */
	ushort		msg_cbytes;	/* current # bytes on q */
	ushort		msg_qnum;	/* # of messages on q */
	ushort		msg_qbytes;	/* max # of bytes on q */
	ushort		msg_lspid;	/* pid of last msgsnd */
	ushort		msg_lrpid;	/* pid of last msgrcv */
	time_t		msg_stime;	/* last msgsnd time */
	time_t		msg_rtime;	/* last msgrcv time */
	time_t		msg_ctime;	/* last change time */
};

/*
**	There is one msg structure for each message that may be in the system.
*/

struct msg {
	struct msg	*msg_next;	/* ptr to next message on q */
	long		msg_type;	/* message type */
	short		msg_ts;		/* message text size */
	short		msg_spot;	/* message text map address */
};

/*
**	User message buffer template for msgsnd and msgrecv system calls.
*/

struct msgbuf {
	long	mtype;		/* message type */
	char	mtext[1];	/* message text */
};

/*
**	Message information structure.
*/

struct msginfo {
	int	msgmap,	/* # of entries in msg map */
		msgmax,	/* max message size */
		msgmnb,	/* max # bytes on queue */
		msgmni,	/* # of message queue identifiers */
		msgssz,	/* msg segment size (should be word size multiple) */
		msgtql;	/* # of system message headers */
	ushort	msgseg;	/* # of msg segments (MUST BE < 32768) */
};

extern int msgctl (int, int, msqid_ds*),
           msgget (key_t, int),
           msgrcv (int, msgbuf*, int, long, int),
           msgsnd (int, const msgbuf*, int, int);
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