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  char-
     acters  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 mes-
     sage (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 }

SEE ALSO

     allocb(9F), copyb(9F), msgb(9S)

     Writing Device Drivers

      STREAMS Programming Guide