copyb(9F) Kernel Functions for Drivers copyb(9F)NAMEcopyb - copy a message block
SYNOPSIS
#include <sys/stream.h>
mblk_t *copyb(mblk_t *bp);
INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI).
PARAMETERS
bp Pointer to the message block from which data is copied.
DESCRIPTION
The copyb() function allocates a new message block, and copies into it
the data from the block that bp denotes. The new block will be at least
as large as the block being copied. copyb() uses the b_rptr and b_wptr
members of bp to determine how many bytes to copy.
RETURN VALUES
If successful, copyb() returns a pointer to the newly allocated message
block containing the copied data. Otherwise, it returns a NULL pointer.
CONTEXT
The copyb() function can be called from user, interrupt, or kernel con‐
text.
EXAMPLES
Example 1: Using copyb
For each message in the list, test to see if the downstream queue is
full with the canputnext(9F) function (line 21). If it is not full, use
copyb to copy a header message block, and dupmsg(9F) to duplicate the
data to be retransmitted. If either operation fails, reschedule a time‐
out at the next valid interval.
Update the new header block with the correct destination address (line
34), link the message to it (line 35), and send it downstream (line
36). At the end of the list, reschedule this routine.
1 struct retrans {
2 mblk_t *r_mp;
3 int r_address;
4 queue_t *r_outq;
5 struct retrans *r_next;
6 };
7
8 struct protoheader {
...
9 int h_address;
...
10 };
11
12 mblk_t *header;
13
14 void
15 retransmit(struct retrans *ret)
16 {
17 mblk_t *bp, *mp;
18 struct protoheader *php;
19
20 while (ret) {
21 if (!canputnext(ret->r_outq)) { /* no room */
22 ret = ret->r_next;
23 continue;
24 }
25 bp = copyb(header); /* copy header msg. block */
26 if (bp == NULL)
27 break;
28 mp = dupmsg(ret->r_mp); /* duplicate data */
29 if (mp == NULL) { /* if unsuccessful */
30 freeb(bp); /* free the block */
31 break;
32 }
33 php = (struct protoheader *)bp->b_rptr;
34 php->h_address = ret->r_address; /* new header */
35 bp->bp_cont = mp; /* link the message */
36 putnext(ret->r_outq, bp); /* send downstream */
37 ret = ret->r_next;
38 }
39 /* reschedule */
40 (void) timeout(retransmit, (caddr_t)ret, RETRANS_TIME);
41 }
SEE ALSOallocb(9F), canputnext(9F), dupmsg(9F)
Writing Device Drivers
STREAMS Programming Guide
SunOS 5.10 16 Jan 2006 copyb(9F)