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 ALSOmsgb(9S)
STREAMS Programming Guide
SunOS 5.10 9 June 2004 MBLKHEAD(9F)
