source: branches/streams/abcl/src/org/armedbear/lisp/CharHashMap.java

package org.armedbear.lisp;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class CharHashMap<T> {

  final public T[] constants;
  final public T NULL;
  final static int CACHE_SIZE = 256; 
  final HashMap<Character, T> backing;

        @SuppressWarnings("unchecked")
  public CharHashMap(Class componentType, T def) {
    NULL = def;
    constants = (T[]) Array.newInstance(componentType, CACHE_SIZE);
    Arrays.fill(constants, NULL);
    backing = new HashMap<Character, T>();
  }
  
  @Override
  public Object clone() {
    CharHashMap<T> n = new CharHashMap<T>(constants.getClass().getComponentType(),NULL);
    System.arraycopy(constants,0, n.constants,0,CACHE_SIZE);
    n.backing.putAll(backing);
    return n;
  }
  
  public T get(char key) {
    if (key<CACHE_SIZE) return constants[key];
    T value = backing.get(key);
    return (value==null) ? NULL:value;
  }

  public void clear() {
    Arrays.fill(constants,NULL);
    backing.clear();
  }

  public T put(char key, T value) {
    if (key<CACHE_SIZE) {
      T old = constants[key];
      constants[key] = value;
      return old;
    }
    else return backing.put(key, value);
  }

  public Iterator<Character> getCharIterator() {
    return new Iterator<Character>() {      
      final Iterator<Character> carIt =  backing.keySet().iterator();
      int charNum = -1;
      public boolean hasNext() {
        if ( charNum<CACHE_SIZE) return true;
        return carIt.hasNext();
      }
      public Character next() {
        if ( charNum<CACHE_SIZE) return (char)++charNum;
        return carIt.next();
      }
      public void remove() {
        throw new UnsupportedOperationException();      
      }
      
    };
  }
}