mblktail(9f) [sunos man page]

MBLKHEAD(9F)						   Kernel Functions for Drivers 					      MBLKHEAD(9F)

NAME

       MBLKHEAD, MBLKIN, MBLKL, MBLKSIZE, MBLKTAIL - Message block utility macros

SYNOPSIS

       #include <sys/stream.h>
       #include <sys/strsun.h>

       int MBLKHEAD(mblk_t *mp);

       int MBLKTAIL(mblk_t *mp);

       int MBLKSIZE(mblk_t *mp);

       int MBLKL(mblk_t *mp);

       int MBLKIN(mblk_t *mp, int offset, int len);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

PARAMETERS

       mp	       Message to be examined.

       offset	       Offset from mp->b_rptr from which to start examining.

       len	       Number of bytes to examine.

DESCRIPTION

       The  MBLKHEAD()	macro  calculates  the	number	of  bytes  between the first byte and the first unread byte of the message block, that is:
       mp->b_rptr - mp->b_datap->db_base.

       The MBLKTAIL() macro calculates the number of bytes between the first unwritten byte and the last byte  of  the	message  block,  that  is:
       mp->b_datap->db_lim - mp->b_wptr.

       The MBLKSIZE() macros calculates the total size of the message block, that is: mp->b_datap->db_lim - mp->b_datap->db_base.

       The MBLKL() macro calculates the length of the message block, that is: mp->b_wptr - mp->b_rptr.

       The MBLKIN() macro checks whether the byte range specified by offset and len resides entirely within the message block.

RETURN VALUES

       The  MBLKHEAD(),  MBLKTAIL(),  MBLKL() and MBLKSIZE() functions all return the appropriate byte count, as specified above. MBLKIN() returns
       non-zero if the check succeeds, or zero if it fails.

CONTEXT

       These functions can be called from user, kernel or interrupt context.

NOTES

       These macros may evaluate any of their arguments more than once. This precludes passing arguments with side effects.

       These macros assume the message itself is well formed, that is: mp->b_datap->db_base <= mp->b_rptr <= mp->b_wptr <= mp->b_datap->db_lim.

SEE ALSO

       msgb(9S)

       STREAMS Programming Guide

SunOS 5.10							    9 June 2004 						      MBLKHEAD(9F)

msgb(4) 						     Kernel Interfaces Manual							   msgb(4)

NAME

       msgb - Defines a STREAMS message block

SYNOPSIS

       #include  <sys/stream.h>  struct  msgb  {       struct msgb *b_next;	 struct msgb *b_prev;	   struct msgb *b_cont;      unsigned char
       *b_rptr;      unsigned char *b_wptr;	 struct datab *b_datap;      MSG_KERNEL_FIELDS };

PARAMETERS

       b_next	 A pointer to the next message on the queue.

       b_prev	 A pointer to the previous message on the queue.

       b_cont	 A pointer to the next message block in the message.

       b_rptr	 A pointer to the first unread data byte in the buffer.

       b_wptr	 A pointer to the first unwritten data byte in the buffer.

       b_datap	 A pointer to the datab structure (data block) that contains the data for the message.

       MSG_KERNEL_FIELDS
		 Additional fields that are visible within the kernel.	The fields included and their contents depend on the kernel configuration.

DESCRIPTION

       The msgb structure defines a message block.  A message block carries data or information in a stream.  A STREAMS message consists  of  mes-
       sage blocks linked through b_cont.  Each message block points to a data block descriptor, which in turn points to a data buffer.

       The msgb structure is typedefed as mblk_t.  The associated data block is stored in a datab structure, which is typedefed as dblk_t.

       The datab structure is defined (in sys/stream.h) as:

       struct datab {
	       struct datab *  db_freep;
	       unsigned char * db_base;
	       unsigned char * db_lim;
	       unsigned char   db_ref;
	       unsigned char   db_type;
	       unsigned char   db_class;
	       unsigned char   db_pad[1]; };

       The datab fields are defined as follows:

	      db_freep	Used internally by the STREAMS memory allocator.

	      db_base	The first byte of the buffer.

	      db_lim	The last byte of the buffer, plus one.

	      db_ref	The number of message blocks ( struct msgb) that reference this data block.

	      db_type	The message type.

	      db_class	Used internally.

	      db_pade	Padding.

       Messages are typed according to the value in the db_type field in the associated datab structure.  Some possible type values are:

	      M_DATA	The message contains ordinary data.

	      M_PROTO	The message contains internal control information and data.

       As  part  of  its support for STREAMS, Tru64 UNIX provides the following interfaces for exchanging messages betweens STREAMS modules on the
       one hand and sockets and network protocols on the other: mbuf_to_mblk() - Converts an mbuf chain to an mblk chain mblk_to_mbuf() - Converts
       an mblk chain to an mbuf chain delim off

																	   msgb(4)