ESD Extended Attributes

In the ESD record for each external symbol, there is a pair of 4 byte fields located at offsets 28 and 32 for the Extended Attribute ESDID and offset, respectively. These two items locate the place in the object where the descriptive information about the symbol is found. The ESDID identifies the element. The offset is calculated with respect to the beginning of the element identified by the ESDID. The element must reside in the same section as the ESD record specifying the extended attribute information.

Extended Attribute information is represented using the following data structures:

Table 1. Extended attribute information data structures
Field	Length/Type	Meaning
Text length	Unsigned 32-bit integer	The length of the full attribute text including this field.
Extended attributes architecture level	Unsigned 16-bit integer	The level of definition for this extended attribute data structure.
Number of attribute entries	Unsigned 16-bit integer	The number of extended attribute data elements for this ESD or RLD item

Only architecture level 1 is currently supported.

Following the extended attributes header are one or more 8-byte data element descriptors. Each such descriptor is a structure of the following form:

Table 2. Data element descriptor data structures
Field	Length/Type	Meaning
Attribute type	Unsigned 16-bit integer	The type of attribute information.
Offset to data element	Unsigned 16-bit integer	The offset from the origin of the extended attributes header to the first byte of the data element associated with this descriptor.
Data element length	Unsigned 16-bit integer	The length in bytes of the data element associated with this descriptor.
Reserved	2 bytes	Reserved.

These data element descriptors are immediately followed by the data elements.

The following attribute codes are currently supported:

Table 3. Supported extended attribute type codes
Type Code	Attribute Assignment
0	Not defined; reserved.
1	XPLINK call descriptor for referenced function.
2–65535	Reserved.

IBM products currently place the attribute information in an initial load class named C_EXTNATTR.