datab

, dblk

- STREAMS message data structure

Synopsis

#include <sys/stream.h>

Interface Level

Architecture independent level 1 (DDI/DKI).

Description

The datab structure describes the data of a STREAMS message. The actual data contained in a STREAMS message is stored in a data buffer pointed to by this structure. A msgb (message block) structure includes a field that points to a datab structure.

Because a data block can have more than one message block pointing to it at one time, the db_ref member keeps track of a data block's references, preventing it from being deallocated until all message blocks are finished with it.

Structure Members

unsigned char     *db_base;     /* first byte of buffer */
unsigned char     *db_lim;      /* last byte (+1) of buffer */
unsigned char      db_ref;      /* # of message pointers to this data */
unsigned char      db_type;     /* message type */

A datab structure is defined as type dblk_t.

See Also

free_rtn(9S), msgb(9S)

Writing Device Drivers

STREAMS Programming Guide