Hash tables - how to look up values?

[Thorsten Jolitz]

Hi List, 
I would need a function that does the opposite of 

,--------------------
| (gethash key table)
`--------------------

i.e. something like 

,-------------------
| (getkey val table)
`-------------------

that returns the corresponding key of a known (string) value in a hash
table (similar to 'rassoc' for alists). 

I could not find such a function - does it exist already?

-- 
cheers,
Thorsten