copymsg(9F) Kernel Functions for Drivers copymsg(9F)NAMEcopymsg - copy a message
SYNOPSIS
#include <sys/stream.h>
mblk_t *copymsg(mblk_t *mp);
INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI).
PARAMETERS
mp Pointer to the message to be copied.
DESCRIPTION
The copymsg() function forms a new message by allocating new message
blocks, and copying the contents of the message referred to by mp
(using the copyb(9F) function). It returns a pointer to the new mes‐
sage.
RETURN VALUES
If the copy is successful, copymsg() returns a pointer to the new mes‐
sage. Otherwise, it returns a NULL pointer.
CONTEXT
The copymsg() function can be called from user, interrupt, or kernel
context.
EXAMPLES
Example 1: : Using copymsg
The routine lctouc() converts all the lowercase ASCII characters in the
message to uppercase. If the reference count is greater than one (line
8), then the message is shared, and must be copied before changing the
contents of the data buffer. If the call to the copymsg() function
fails (line 9), return NULL (line 10), otherwise, free the original
message (line 11). If the reference count was equal to 1, the message
can be modified. For each character (line 16) in each message block
(line 15), if it is a lowercase letter, convert it to an uppercase let‐
ter (line 18). A pointer to the converted message is returned (line
21).
1 mblk_t *lctouc(mp)
2 mblk_t *mp;
3 {
4 mblk_t *cmp;
5 mblk_t *tmp;
6 unsigned char *cp;
7
8 if (mp->b_datap->db_ref > 1) {
9 if ((cmp = copymsg(mp)) == NULL)
10 return (NULL);
11 freemsg(mp);
12 } else {
13 cmp = mp;
14 }
15 for (tmp = cmp; tmp; tmp = tmp->b_cont) {
16 for (cp = tmp->b_rptr; cp < tmp->b_wptr; cp++) {
17 if ((*cp <= 'z') && (*cp >= 'a'))
18 *cp -= 0x20;
19 }
20 }
21 return(cmp);
22 }
SEE ALSOallocb(9F), copyb(9F), msgb(9S)
Writing Device Drivers
STREAMS Programming Guide
SunOS 5.10 16 Jan 2006 copymsg(9F)
