-- RefTab.Mesa - definitions for REF table abstraction
-- last change: Bill Paxton - 8-Feb-82 10:06:02

RefTab: DEFINITIONS = BEGIN

  Ref: TYPE = REF RefTabRep;
  RefTabRep: TYPE;

  Key: TYPE = REF;
  Val: TYPE = REF;

  Create: PROC [mod: CARDINAL _ 17, zone: ZONE _ NIL] RETURNS [Ref];
    -- creates new table with suggested hash size
    -- if zone is NIL, will do allocates from system zone

  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

  Store: PROC [x: Ref, key: Key, val: Val] RETURNS [BOOLEAN];
    -- stores new key-value pair, overwriting previous value for given key
    -- returns TRUE if new value, FALSE if previous value overwritten

  Insert: PROC [x: Ref, key: Key, val: Val] RETURNS [BOOLEAN];
    -- inserts new key-value pair, except if previous value for given key
    -- returns TRUE if inserted, FALSE if previous value for key

  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.