copymsg(D3)copymsg(D3)NAMEcopymsg - copy a message
SYNOPSIS
#include <sys/stream.h>
#include <sys/ddi.h>
mblk_t *copymsg(mblk_t *mp);
Arguments
mp Pointer to the message to be copied.
DESCRIPTIONcopymsg forms a new message by allocating new message blocks, copies the
contents of the message referred to by mp (using the copyb(D3) function),
and returns a pointer to the new message.
Return Values
On success, copymsg returns a pointer to the new message. On failure, it
returns a NULL pointer.
USAGE
Level
Base or Interrupt.
Synchronization Constraints
Does not sleep.
Driver-defined basic locks, read/write locks, and sleep locks may be held
across calls to this function.
Examples
The routine lctouc converts all the lower case ASCII characters in the
message to upper case. 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 copymsg fails (line 9), we
return NULL (line 10). Otherwise, we free the original message (line
11). If the reference count was equal to one, the message can be
modified. For each character (line 16) in each message block (line 15),
if it is a lower case letter, we convert it to an upper case letter (line
18). When done, we return a pointer to the converted message (line 21).
1 mblk_t *lctouc(mp)
2 mblk_t *mp;
3 {
4 mblk_t *cmp;
5 mblk_t *tmp;
6 uchar_t *cp;
7
8 if (mp->b_datap->db_ref > 1) {
9 if ((cmp = copymsg(mp)) == NULL)
10 return(NULL);
11 freemsg(mp);
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copymsg(D3)copymsg(D3)
12 } else {
13 cmp = mp;
14 }
15 for (tmp = cmp; tmp; tmp = tmp->b_next) {
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 }
REFERENCESallocb(D3), copyb(D3), msgb(D4)
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