rmvb

- remove a message block from a message

Synopsis

#include <sys/stream.h>

mblk_t *rmvb(mblk_t *mp, mblk_t *bp);

Interface Level

Architecture independent level 1 (DDI/DKI).

Parameters

mp

Message from which a block is to be removed. mblk_t is an instance of the msgb(9S) structure.

bp

Message block to be removed.

Description

The rmvb() function removes a message block (bp) from a message (mp), and returns a pointer to the altered message. The message block is not freed, merely removed from the message. It is the module or driver's responsibility to free the message block.

Return Values

If successful, a pointer to the message (minus the removed block) is returned. The pointer is NULL if bp was the only block of the message before rmvb() was called. If the designated message block (bp) does not exist, -1 is returned.

Context

The rmvb() function can be called from user, interrupt, or kernel context.

Examples

This routine removes all zero-length M_DATA message blocks from the given message. For each message block in the message, save the next message block (line 10). If the current message block is of type M_DATA and has no data in its buffer (line 11), then remove it from the message (line 12) and free it (line 13). In either case, continue with the next message block in the message (line 16).

1  void
 2  xxclean(mp)
 3      mblk_t *mp;
 4  {
 5           mblk_t *tmp;
 6           mblk_t *nmp;
 7
 8           tmp = mp;
 9           while (tmp) {
10                   nmp = tmp->b_cont;
11                   if ((tmp->b_datap->db_type == M_DATA) &&
                         (tmp->b_rptr == tmp->b_wptr)) {
12                       (void) rmvb(mp, tmp);
13                       freeb(tmp);
14                   }
15                   tmp = nmp;
16           }
17  }

See Also

freeb(9F), msgb(9S)

Writing Device Drivers

STREAMS Programming Guide