nsISimpleEnumerator in Firefox 3.0

 Used to enumerate over elements defined by its implementor.
 Although hasMoreElements() can be called independently of getNext(),
 getNext() must be pre-ceeded by a call to hasMoreElements(). There is
 no way to "reset" an enumerator, once you obtain one.

 @status FROZEN
 @version 1.0

[scriptable, uuid(d1899240-f9d2-11d2-bdd6-000064657374)]

Methods

 Called to retrieve the next element in the enumerator. The "next"
 element is the first element upon the first call. Must be
 pre-ceeded by a call to hasMoreElements() which returns PR_TRUE.
 This method is generally called within a loop to iterate over
 the elements in the enumerator.

 @see hasMoreElements()
 @return NS_OK if the call succeeded in returning a non-null
               value through the out parameter.
         NS_ERROR_FAILURE if there are no more elements
                          to enumerate.
 @return the next element in the enumeration.

nsISupports getNext()

 Called to determine whether or not the enumerator has
 any elements that can be returned via getNext(). This method
 is generally used to determine whether or not to initiate or
 continue iteration over the enumerator, though it can be
 called without subsequent getNext() calls. Does not affect
 internal state of enumerator.

 @see getNext()
 @return PR_TRUE if there are remaining elements in the enumerator.
         PR_FALSE if there are no more elements in the enumerator.

boolean hasMoreElements()