NAME

datab - 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.

A data block can have more than one message block pointing to it at one time, so 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 * /
unsigned char   db_refmin;     /* data block reference count * /
unsigned int    db_size;       /* size of the data block * /
char            filler[8];      /* padding the structure * /
long            db_reserved;   /* reserved for future use * /

A datab structure is defined as type dblk_t.

SEE ALSO

free_rtn(9S), msgb (9S)

Writing Device Drivers

STREAMS Programmer's Guide