Manual Pages for UNIX Operating System command usage for man MBLKHEAD

Kernel Functions for Drivers                         MBLKHEAD(9F)



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

SYNOPSIS
     #include 
     #include 



     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 examin-
               ing.


     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  mes-
     sage  block,  that  is:  mp->b_datap->db_lim  - mp->b_datap-



SunOS 5.11          Last change: 9 June 2004                    1






Kernel Functions for Drivers                         MBLKHEAD(9F)



     >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 5.11          Last change: 9 June 2004                    2