ClosedObjectHashTable

AddEntryAndData AdjustTableSize ChangeEntryData Clear EntryDataAt FindEntryWithData Init

LookUpEntry LookUpObject OptimalSize Reinsert RemoveEntryAt SafeReplaceHashTableEntries SetEntryDataAt

Attributes

Full NumDeletedEntries NumEntries Stride

Fields

instance ClosedObjectHashTable tag;
     numEntries: 0;
numDeletedEntries: 0;
end instance;

Define Class ClosedObjectHashTable;
    inherits from FixedList;
    
    field numEntries: Unsigned, getter;
        // number of all occupied entries, including deleted ones
    field numDeletedEntries: Unsigned, getter;
        // of all the entries used, nuber of deleted ones
        
    attribute Full: Boolean, readOnly, safe;
    attribute NumEntries: Unsigned, safe, readOnly;
    attribute NumDeletedEntries: Unsigned, safe, readOnly;

    overrides Init;
    overrides Stride;
    
    overrides Clear;
        // nuke everything

    // hash table public calls
    operation LookUpObject(object: Object): Signed;
    operation AddEntryAndData(object: Object; data: Signed): Signed;
    operation RemoveEntryAt(index: Signed);
    operation EntryDataAt(index: Signed): Signed;
    operation SetEntryDataAt(index: Signed; data: Signed);

    operation AdjustTableSize(newSize: Unsigned; nearThis: Object): ClosedObjectHashTable;
        // If a table is too full or contains too many deleted entries, this is called
        // to create a new fresh copy of the table with only non-empty copies.
        // The caller has to delete the original hash table, after the new one is 
        // safely referenced; this is to make the adjusting emergency shutdown proof.

    operation ChangeEntryData(oldData: Unsigned; newData: Unsigned);
        // used by the StringDictionary's compaction routine

    // hash table private calls
    operation OptimalSize(): Unsigned;
        // returns the size of table it thinks would be optimal for the
        // data it's containing
    operation LookUpEntry(key: Unsigned; newEntry: Boolean): Signed;
        // used for looking for existing and/or empty entries
    operation Reinsert(entry: ReadOnlyPointer);
        // used by AdjustTableSize to copy an entry from an old table to a new one

    operation FindEntryWithData(data: Signed): Signed;
    
    operation SafeReplaceHashTableEntries(other: ClosedObjectHashTable);
        // Used when we rehashed by making a new hash table in another
        // volume to copy the entries back in a reset-proof way.
end class;