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'\" te
.\" Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
.TH copyb 9F "16 Jan 2006" "Oracle Solaris 11.4" "Kernel Functions"
.SH NAME
copyb \- copy a message block
.SH SYNOPSIS

.LP
.nf
#include <sys/stream.h>

\fBmblk_t *\fR\fBcopyb\fR(\fBmblk_t *\fR\fIbp\fR);
.fi
.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 1 (DDI/DKI).
.SH PARAMETERS
.sp
.ne 2
.mk
.na
\fB\fIbp\fR\fR
.ad
.RS 6n
.rt
Pointer to the message block from which data is copied.
.RE

.SH DESCRIPTION
.sp
.LP
The \fBcopyb()\fR function allocates a new message block, and copies into it the data from the block that \fIbp\fR denotes. The new block will be at least as large as the block being copied. \fBcopyb()\fR uses the \fBb_rptr\fR and \fBb_wptr\fR members of \fIbp\fR to determine how many bytes to copy.
.SH RETURN VALUES
.sp
.LP
If successful, \fBcopyb()\fR returns a pointer to the newly allocated message block containing the copied data. Otherwise, it returns a \fINULL\fR pointer.
.SH CONTEXT
.sp
.LP
The \fBcopyb()\fR function can be called from user, interrupt, or kernel context.
.SH EXAMPLES
.LP
\fBExample 1\fR 
Using copyb

.sp
.LP
For each message in the list, test to see if the downstream queue is full with the \fBcanputnext\fR(9F) function (line 21). If it is not full, use \fBcopyb\fR to copy a header message block, and \fBdupmsg\fR(9F) to duplicate the data to be retransmitted. If either operation fails, reschedule a timeout at the next valid interval.

.sp
.LP
Update the new header block with the correct destination address (line 34), link the message to it (line 35), and send it downstream (line 36). At the end of the list, reschedule this routine.

.sp
.in +2
.nf
 1  struct retrans {
 2        mblk_t             *r_mp;
 3        int                r_address;
 4        queue_t            *r_outq;
 5        struct retrans     *r_next;
 6  };
 7  
 8  struct protoheader {
       ...
 9     int                    h_address;
       ...
10  };
11
12  mblk_t *header;
13
14  void
15  retransmit(struct retrans *ret)
16  {
17       mblk_t *bp, *mp;
18       struct protoheader *php;
19
20       while (ret) {
21         if (!canputnext(ret->r_outq)) {   /* no room */
22                ret = ret->r_next;
23                continue;
24         }
25         bp = copyb(header);               /* copy header msg. block */
26         if (bp == NULL)
27               break;
28         mp = dupmsg(ret->r_mp);           /* duplicate data */
29         if (mp == NULL) {                 /* if unsuccessful */
30              freeb(bp);                   /* free the block */
31              break;
32         }
33         php = (struct protoheader *)bp->b_rptr;
34         php->h_address = ret->r_address;   /* new header */
35         bp->bp_cont = mp;                  /* link the message */
36         putnext(ret->r_outq, bp);          /* send downstream */
37         ret = ret->r_next;
38       }
39       /* reschedule */
40       (void) timeout(retransmit, (caddr_t)ret, RETRANS_TIME);
41  }
.fi
.in -2
.sp

.SH SEE ALSO
.sp
.LP
\fBallocb\fR(9F), \fBcanputnext\fR(9F), \fBdupmsg\fR(9F)
.sp
.LP
\fIWriting Device Drivers in Oracle Solaris 11.4\fR
.sp
.LP
\fISTREAMS Programming Guide\fR