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)