dupb(D3)dupb(D3)NAMEdupb - duplicate a message block
SYNOPSIS
#include <sys/stream.h>
#include <sys/ddi.h>
mblk_t *dupb(mblk_t *bp);
Arguments
bp Pointer to the message block to be duplicated.
DESCRIPTIONdupb creates a new message block structure that references the same data
block that is referenced by bp. Unlike copyb(D3), dupb does not copy the
information in the data block, but creates a new structure to point to
it.
Return Values
On success, dupb returns a pointer to the new message block. On failure,
it returns a NULL pointer.
USAGE
The following figure shows how the db_ref field of the data block
structure has been changed from 1 to 2, reflecting the increase in the
number of references to the data block. The new message block contains
the same information as the first. Note that b_rptr and b_wptr are
copied from bp, and that db_ref is incremented.
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nbp=dupb(bp);
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Before
After
db_base
db_ref (2)
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db_base
db_ref (1)
bp
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b_datap
b_rptr
b_wptr
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b_datap
b_rptr
b_wptr
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b_datap
b_rptr
b_wptr
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nbp
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bp
Level
Base or Interrupt.
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dupb(D3)dupb(D3)
Synchronization Constraints
Does not sleep.
Driver-defined basic locks, read/write locks, and sleep locks may be held
across calls to this function.
REFERENCEScopyb(D3), dupmsg(D3), datab(D4), msgb(D4)
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