User guide

7: Host/ICP Interface
DC 900-1338I 121
7.2.1 System Buffer Header
As mentioned previously, every buffer of every queue element must begin with a system
buffer header. The following structure defines the format of the system buffer header:
struct SBH_TYPE
{
struct SBH_TYPE *sb_nxte; /* next element */
struct SBH_TYPE *sb_pree; /* previous element */
struct SBH_TYPE *sb_thse; /* this element */
struct SBH_TYPE *sb_nxtb; /* next buffer */
unsigned short sb_pid; /* partition ID */
unsigned short sb_dlen; /* data length */
unsigned short sb_disp; /* disposition flag */
unsigned short sb_dmod; /* disposition modifier */
};
The header fields, as used by the system, are described below:
Next Element This field is used only by the operating system, and only in the
first buffer of a queue element. While the element is attached to
a singly- or doubly-linked queue, this field contains the address
of the next element on the queue.
Previous Element This field is used only by the operating system, and only in the
first buffer of a queue element. While the element is attached to
a doubly-linked queue, this field contains the address of the
previous element on the queue.
This Element This field is used only by the operating system, and only in the
first buffer of the queue element, as a consistency check when
the element is posted to or removed from a queue. This field
contains the address of the buffer itself (that is, the address of
the queue element).