Network Monitor BLOBs

The Network Monitor binary large object (BLOB) is a generic data structure that contains configuration and location information of network interface cards (NICs). Use BLOBs to represent NICs and to filter entries in a list of NICs. BLOBS can also contain application-specific data without affecting the other data that they hold. BLOB implementation is opaque to all levels that must access BLOBs with BLOB APIs.

BLOB Structure

A BLOB can be considered as a hierarchical tree used to designate strings. This tree has three layers: Owner, Category, and Tag. Owner is a string that indicates, in general, who reads an entry. The Category is also a string, which designates a general functional grouping of tags under the owner. The Tag is the actual name of the entry.

The structural characteristics of BLOBs include:

• BLOB helpers within one process are protected from one another by a mutex built into each BLOB.
• Each BLOB has an internal version number so that the helpers can handle both present and future BLOB forms. Version conflicts may occur if you send a BLOB to another computer via a remote procedure call.
• The BLOB itself is a pointer to a void. Be aware that applications should allocate BLOBs with the const modifier to avoid altering the contents.
• Each of the designators, as well as their values, are strings. Be aware that the strings returned by GetString functions are actually pointers into the BLOB and should not be changed. For this reason, these strings must be specified as const char**pX* to keep applications from accidentally changing them.

In general, all parameters with the const designator encourage the caller to refrain from changing the values rather than prohibit the helper functions from changing them. In fact, the helper functions will usually change those values.