copymsg(9f) - osol9

1copymsg(9F)              Kernel Functions for Drivers              copymsg(9F)
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NAME

6       copymsg - copy a message
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SYNOPSIS

9       #include <sys/stream.h>
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13       mblk_t *copymsg(mblk_t *mp);
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INTERFACE LEVEL

17       Architecture independent level 1 (DDI/DKI).
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PARAMETERS

20       mp    Pointer to the message to be copied.
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DESCRIPTION

24       The  copymsg()  function  forms a new message by allocating new message
25       blocks, and copying the contents of  the  message  referred  to  by  mp
26       (using  the  copyb(9F)  function). It returns a pointer to the new mes‐
27       sage.
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RETURN VALUES

30       If the copy is successful, copymsg() returns a pointer to the new  mes‐
31       sage. Otherwise, it returns a NULL pointer.
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CONTEXT

34       The  copymsg()  function  can be called from user, interrupt, or kernel
35       context.
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EXAMPLES

38       Example 1 : Using copymsg
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41       The routine lctouc() converts all the lowercase ASCII characters in the
42       message  to uppercase. If the reference count is greater than one (line
43       8), then the message is shared, and must be copied before changing  the
44       contents  of  the  data  buffer.  If the call to the copymsg() function
45       fails (line 9), return NULL (line 10),  otherwise,  free  the  original
46       message  (line  11). If the reference count was equal to 1, the message
47       can be modified. For each character (line 16)  in  each  message  block
48       (line 15), if it is a lowercase letter, convert it to an uppercase let‐
49       ter (line 18). A pointer to the converted  message  is  returned  (line
50       21).
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54          1 mblk_t *lctouc(mp)
55          2    mblk_t *mp;
56          3 {
57          4    mblk_t *cmp;
58          5    mblk_t *tmp;
59          6    unsigned char *cp;
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61          8    if (mp->b_datap->db_ref > 1) {
62          9            if ((cmp = copymsg(mp)) == NULL)
63         10                     return (NULL);
64         11            freemsg(mp);
65         12    } else {
66         13            cmp = mp;
67         14    }
68         15    for (tmp = cmp; tmp; tmp = tmp->b_cont) {
69         16            for (cp = tmp->b_rptr; cp < tmp->b_wptr; cp++) {
70         17                    if ((*cp <= 'z') && (*cp >= 'a'))
71         18                             *cp -= 0x20;
72         19            }
73         20    }
74         21    return(cmp);
75         22 }
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