OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual

Information Architecture and Data Structures
OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual—522223-001
2-7
Descriptor Lists
A zero-length or empty bit string consists of a string length of 1 and a string element of
1 octet, containing all zeros.
Descriptor Lists
To provide values for the attributes of an object, you pass an array of attribute
descriptors called a descriptor list. The list might include values for single-valued
attributes and multivalued attributes.
Figure 2-4 shows the descriptor list of an object in the input queue. If you reserve the
object, you can examine it to determine what types of attributes are present. The
GPI_OM_EXAMINE_ procedure returns to the descriptor-list buffer one descriptor for
each attribute you request. An attribute position indicates the position of the attribute
in the object, regardless of how many values a previous attribute might have. The first
attribute is at attribute position 0. A value position indicates the position of a value of a
specific attribute. The first value is at value position 0.
Figure 2-3. Bit-String Structure
Note. This bit-string representation follows the rules specified by the BER for indicating the
number of unused bits in the last octet, but the GPI does not require encoding of the BER type
and value.
String Element
(Octets)
Indicates 5
unused bits
in last octet.
Bits: 0 1 2 3 4 5 6 7
Attribute Descriptor
Attribute
Type
Attribute
Syntax
Attribute
Value
IM-T-IMAGES
OM-S-BIT-STRING
String
Length
=
8
Octets
Pointer
to
String Element
All bits used.
All bits used.
All bits used.
All bits used.
All bits used.
All bits used.
0 0 0 0 0 1 0 1
Unused
o
Attribute
Type
Attribute
Syntax
Attribute
Value
203VST .VSD