OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual

Information Architecture and Data Structures
OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual—522223-001
2-6
Attribute Descriptor Structure
Attribute Descriptor Structure
Figure 2-2 illustrates the data structure of descriptors for each type of syntax. The
OM-S-xxx-STRING structure applies to all of the syntaxes for strings. (In the actual
DDL name, the type of string replaces xxx: for example, OM-S-BIT-STRING.) A
string value is a 32-bit length field and a 32-bit address of the string data. A value of
syntax OM-S-OBJECT is a 32-bit field, which is ignored, followed by a 32-bit object
identifier (Z-OBJ-ID). For the maximum length allowed for values of a particular
syntax, see Section 3, Object Classes and Attribute Types
.
Bit-String Structure
Figure 2-3 shows the structure of an attribute descriptor and string element for a value of
OM-S-BIT-STRING syntax. The bits of a bit string are represented as a sequence of
octets. The length of the string includes all octets. The first octet stores the number of
unused bits in the last octet. The first bit of actual data in the bit string is at bit 0 of the
second octet and the trailing bits fill the octet to bit 7. Additional bits continue in
successive octets from bit 0 to 7 until the final octet, which can be partially filled as
indicated in the first octet. (On Compaq NonStop™ systems, bit 0 is the most
significant bit, and bit 7 is the least significant bit.)
Figure 2-2. Attribute Descriptor Structure
Type
(Example)
Syntax
OM-S-
Value
16 Bits
16 Bits
32 Bits 32 Bits
MH-T-A3-WIDTH
Integer 1 or 0
OM-TRUE or OM-FALSE
-——
-——
BOOLEAN
MH-T-ACTION
Integer Value of
Enumeration Constant
-—— -——
ENUMERATION
INTEGER
MH-T-
CONTENT-TYPE
Integer Value
-—— -——
Object Identifier
Z-OBJ-ID
PaddingOBJECTMH-T-NAME
String Length
Pointer to String
Element
xxx-STRING
IM-T-TEXT
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