Tribblix: manual page: copymsg.9f

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

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
message.

RETURN VALUES

If the copy is successful, copymsg() returns a pointer to the new
message. 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 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 }