copymsg(9F) Kernel Functions for Drivers copymsg(9F)
NAME
copymsg - 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
copymsg() 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 message.
RETURN VALUES
If the copy is successful, copymsg() returns a pointer to the new message. Otherwise, it returns a NULL pointer.
CONTEXT
copymsg() can be called from user or interrupt 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 upper-
case letter (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 ALSO
allocb(9F), copyb(9F), msgb(9S)
Writing Device Drivers
STREAMS Programming Guide
SunOS 5.10 27 Jun 1995 copymsg(9F)
