Linux Mac OSX Windows 
 mozIStorageFunction is to be implemented by storage consumers that
 wish to receive callbacks during the request execution.

 SQL can apply functions to values from tables. Examples of
 such functions are MIN(a1,a2) or SQRT(num). Many functions are
 implemented in SQL engine.

 This interface allows consumers to implement their own,
 problem-specific functions.
 These functions can be called from triggers, too.
[scriptable, uuid(9ff02465-21cb-49f3-b975-7d5b38ceec73)]
interface mozIStorageFunction : nsISupports

Methods

 onFunctionCall is called when execution of a custom
 function should occur.
 
 @param aNumArguments         The number of arguments
 @param aFunctionArguments    The arguments passed in to the function

 @returns any value as Variant type.
nsIVariant onFunctionCall(in mozIStorageValueArray aFunctionArguments)