Compaq AAR04BCTE Declaration Section, Index Definitions Section, Enumeration Definitions Section

Creating a Subagent Using the eSNMP API

3.3 Creating a MIB Source File

1. Declaration Section

The first section of the subtree_TBL.H file is a declaration of the subtree structure. The subtree is automatically initialized by code in the subtree_TBL.C file. A pointer to this structure is passed to the esnmp_register routine to register a subtree with the master agent. All access to the object table for this subtree is through this pointer. The declaration has the following form:

extern SUBTREE subtree_subtree;

2. Index Definitions Section

The second section of the subtree_TBL.H file contains index definitions for each MIB variable in the subtree of the form:

#define I_mib-variable nnn

These values are unique for each MIB variable in a subtree and are the index into the object table for this MIB variable. These values are also generally used to differentiate between variables that are implemented in the same method routine so they can be used in a switch operation.

3. Enumeration Definitions Section

The third section of the subtree_TBL.H file contains enumeration definitions for those integer MIB variables that are defined with enumerated values, as follows:

#define D_mib-variable_enumeration-name value

These definitions are useful because they describe the value that enumerated integer MIB variables may take on. For example:

/* enumerations for gameEntry group */
#define D_gameStatus_complete		1
#define	D_gameStatus_underway	2
#define	D_gameStatus_delete	3

4. MIB Group Data Structure Definitions Section

The fourth section of the subtree_TBL.H file contains data structure definitions of the following form:

typedef structxxx {

type mib-variable;

.

.

.

char mib-variable_mark;

.

.

.

} mib-group_type

The MIB compiler generates one of these data structures for each MIB group in the subtree. Each structure definition contains a field representing each MIB variable in the group. In addition to the MIB variable fields, the structure includes a 1-byte mib-variable-markfield for each variable. You can use these for maintaining status of a MIB variable. For example, the following is the group structure for the chess MIB:

3–8Creating a Subagent Using the eSNMP API