-- RefTab.Mesa - definitions for REF table abstraction
-- last change: Bill Paxton - August 19, 1982 9:24 am
-- last change: Warren Teitelman - August 31, 1982 2:20 pm
-- last change: Paul Rovner - May 13, 1983 10:39 am

<<Last Edited by: Sweet, February 4, 1985 1:03:00 pm PST>>

DIRECTORY
PrincOps USING [ControlLink];

RefTab: CEDAR DEFINITIONS = BEGIN

  Ref: TYPE = REF RefTabRep;
  RefTabRep: TYPE;

  Key: TYPE = RECORD [
    link: PrincOps.ControlLink, fill: CARDINAL _ 0];
  Val: TYPE = REF LONG CARDINAL;

  Create: PROC [mod: CARDINAL _ 17] RETURNS [Ref];
    -- creates new table with suggested hash size

  GetSize: PROC [x: Ref] RETURNS [CARDINAL];
    -- returns number of key-value pairs in table

  Fetch: PROC [x: Ref, key: Key] RETURNS [found: BOOLEAN, val: Val];
    -- looks up key in table, returns associated value (if any)
    -- if found is TRUE, val is value associated with given key
    -- if found is FALSE, val is NIL

  Replace: PROC [x: Ref, key: Key, val: Val] RETURNS [BOOLEAN];
    -- returns TRUE after overwriting old value for existing key-value pair
    -- if no previous value for key, returns FALSE without inserting new pair
  
  Store: PROC [x: Ref, key: Key, val: Val] RETURNS [BOOLEAN];
    -- returns TRUE after inserting new pair
    -- returns FALSE after overwriting old value for existing key-value pair

  Insert: PROC [x: Ref, key: Key, val: Val] RETURNS [BOOLEAN];
    -- returns TRUE after inserted new pair
    -- if previous value existed for key, returns FALSE without changing value

  Delete: PROC [x: Ref, key: Key] RETURNS [BOOLEAN];
    -- deletes key-value pair associated with given key
    -- returns TRUE if deletion actually occurred, FALSE if no such key

  Pairs: PROC [x: Ref, action: EachPairAction] RETURNS [BOOLEAN];
    -- enumerates pairs currently in symbol table in unspecified order
    -- pairs inserted/deleted during enumeration may or may not be seen
    -- applies action to each pair until action returns TRUE or no more pairs
    -- returns TRUE if some action returns TRUE
  EachPairAction: TYPE = PROC [key: Key, val: Val] RETURNS [quit: BOOLEAN];

  END.