#ifndef _LINUX_MSG_H
  #define _LINUX_MSG_H
  
  #include <linux/ipc.h>

  
  /* ipcs ctl commands */
  #define MSG_STAT 11
  #define MSG_INFO 12
  
  /* msgrcv options */
  #define MSG_NOERROR     010000  /* no error if message is too big */
  #define MSG_EXCEPT      020000  /* recv any msg except of specified type.*/
  
  /* Obsolete, used only for backwards compatibility and libc5 compiles */
  struct msqid_ds {
  	struct ipc_perm msg_perm;
  	struct msg *msg_first;		/* first message on queue,unused  */
  	struct msg *msg_last;		/* last message in queue,unused */
  	__kernel_time_t msg_stime;	/* last msgsnd time */
  	__kernel_time_t msg_rtime;	/* last msgrcv time */
  	__kernel_time_t msg_ctime;	/* last change time */
  	unsigned long  msg_lcbytes;	/* Reuse junk fields for 32 bit */
  	unsigned long  msg_lqbytes;	/* ditto */
  	unsigned short msg_cbytes;	/* current number of bytes on queue */
  	unsigned short msg_qnum;	/* number of messages in queue */
  	unsigned short msg_qbytes;	/* max number of bytes on queue */
  	__kernel_ipc_pid_t msg_lspid;	/* pid of last msgsnd */
  	__kernel_ipc_pid_t msg_lrpid;	/* last receive pid */
  };
  
  /* Include the definition of msqid64_ds */
  #include <asm/msgbuf.h>
  
  /* message buffer for msgsnd and msgrcv calls */
  struct msgbuf {
  	long mtype;         /* type of message */
  	char mtext[1];      /* message text */
  };
  
  /* buffer for msgctl calls IPC_INFO, MSG_INFO */
  struct msginfo {
  	int msgpool;
  	int msgmap; 
  	int msgmax; 
  	int msgmnb; 
  	int msgmni; 
  	int msgssz; 
  	int msgtql; 
  	unsigned short  msgseg; 
  };

  /*
   * Scaling factor to compute msgmni:
   * the memory dedicated to msg queues (msgmni * msgmnb) should occupy
   * at most 1/MSG_MEM_SCALE of the lowmem (see the formula in ipc/msg.c):
   * up to 8MB       : msgmni = 16 (MSGMNI)
   * 4 GB            : msgmni = 8K
   * more than 16 GB : msgmni = 32K (IPCMNI)
   */
  #define MSG_MEM_SCALE 32

  #define MSGMNI    16   /* <= IPCMNI */     /* max # of msg queue identifiers */
  #define MSGMAX  8192   /* <= INT_MAX */   /* max size of message (bytes) */
  #define MSGMNB 16384   /* <= INT_MAX */   /* default max size of a message queue */
  
  /* unused */

  #define MSGPOOL (MSGMNI * MSGMNB / 1024) /* size in kbytes of message pool */

  #define MSGTQL  MSGMNB            /* number of system message headers */
  #define MSGMAP  MSGMNB            /* number of entries in message map */
  #define MSGSSZ  16                /* message segment size */

  #define __MSGSEG ((MSGPOOL * 1024) / MSGSSZ) /* max no. of segments */

  #define MSGSEG (__MSGSEG <= 0xffff ? __MSGSEG : 0xffff)
  
  #ifdef __KERNEL__

  #include <linux/list.h>

  
  /* one msg_msg structure for each message */
  struct msg_msg {
  	struct list_head m_list; 
  	long  m_type;          
  	int m_ts;           /* message text size */
  	struct msg_msgseg* next;
  	void *security;
  	/* the actual message follows immediately */
  };
  
  /* one msq_queue structure for each present queue on the system */
  struct msg_queue {
  	struct kern_ipc_perm q_perm;
  	time_t q_stime;			/* last msgsnd time */
  	time_t q_rtime;			/* last msgrcv time */
  	time_t q_ctime;			/* last change time */
  	unsigned long q_cbytes;		/* current number of bytes on queue */
  	unsigned long q_qnum;		/* number of messages in queue */
  	unsigned long q_qbytes;		/* max number of bytes on queue */
  	pid_t q_lspid;			/* pid of last msgsnd */
  	pid_t q_lrpid;			/* last receive pid */
  
  	struct list_head q_messages;
  	struct list_head q_receivers;
  	struct list_head q_senders;
  };

  /* Helper routines for sys_msgsnd and sys_msgrcv */
  extern long do_msgsnd(int msqid, long mtype, void __user *mtext,
  			size_t msgsz, int msgflg);
  extern long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
  			size_t msgsz, long msgtyp, int msgflg);

  #endif /* __KERNEL__ */
  
  #endif /* _LINUX_MSG_H */