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/**
* Copyright (c) Rich Hickey. All rights reserved.
* The use and distribution terms for this software are covered by the
* Common Public License 1.0 (http://opensource.org/licenses/cpl.php)
* which can be found in the file CPL.TXT at the root of this distribution.
* By using this software in any fashion, you are agreeing to be bound by
* the terms of this license.
* You must not remove this notice, or any other, from this software.
**/
using System;
using System.Collections;
namespace clojure.lang
{
/**
* Simple implementation of persistent map on an array
* Note that instances of this class are constant values
* i.e. add/remove etc return new values
*
* Copies array on every change, so only appropriate for _very_small_ maps
*
* null keys and values are ok, but you won't be able to distinguish a null value via get - use contains/find
*/
public class PersistentArrayMap : Obj, IPersistentMap, IPersistentCollection {
internal readonly Object[] array;
public static PersistentArrayMap EMPTY = new PersistentArrayMap();
internal const int HASHTABLE_THRESHOLD = 42;
protected PersistentArrayMap(){
this.array = RT.EMPTY_ARRAY;
}
virtual internal PersistentArrayMap create(params Object[] init){
PersistentArrayMap ret = new PersistentArrayMap(init);
ret._meta = _meta;
return ret;
}
virtual internal IPersistentMap createHT(Object[] init){
PersistentHashtableMap ret = new PersistentHashtableMap(init);
ret._meta = _meta;
return ret;
}
public override Obj withMeta(IPersistentMap meta)
{
Obj ret = (Obj)MemberwiseClone();
ret._meta = meta;
return ret;
}
/**
* This ctor captures/aliases the passed array, so do not modify later
* @param init {key1,val1,key2,val2,...}
*/
public PersistentArrayMap(params Object[] init){
this.array = init;
}
public int count() {
return array.Length/2;
}
public bool contains(Object key){
return indexOf(key) >= 0;
}
public IMapEntry find(Object key) {
int i = indexOf(key);
if(i >= 0)
return new Iter(array,i);
return null;
}
public IPersistentMap add(Object key, Object val) {
int i = indexOf(key);
Object[] newArray;
if(i >= 0)
{
throw new Exception("Key already present");
}
else //didn't have key, grow
{
if (array.Length > HASHTABLE_THRESHOLD)
return createHT(array).add(key, val);
newArray = new Object[array.Length + 2];
if(array.Length > 0)
Array.Copy(array,0,newArray,2,array.Length);
newArray[0] = key;
newArray[1] = val;
}
return create(newArray);
}
public IPersistentMap put(Object key, Object val) {
int i = indexOf(key);
Object[] newArray;
if(i >= 0) //already have key, same-sized replacement
{
if(array[i+1] == val) //no change, no op
return this;
newArray = (Object[])array.Clone();
newArray[i+1] = val;
}
else //didn't have key, grow
{
if (array.Length > HASHTABLE_THRESHOLD)
return createHT(array).put(key, val);
newArray = new Object[array.Length + 2];
if(array.Length > 0)
Array.Copy(array,0,newArray,2,array.Length);
newArray[0] = key;
newArray[1] = val;
}
return create(newArray);
}
public IPersistentMap remove(Object key) {
int i = indexOf(key);
if(i >= 0) //have key, will remove
{
int newlen = array.Length - 2;
if (newlen == 0)
return empty();
Object[] newArray = new Object[newlen];
for(int s=0,d=0;s<array.Length;s += 2)
{
if(!equalKey(array[s],key)) //skip removal key
{
newArray[d] = array[s];
newArray[d+1] = array[s+1];
d += 2;
}
}
return create(newArray);
}
//don't have key, no op
return this;
}
virtual public IPersistentMap empty() {
if(_meta == null)
return EMPTY;
PersistentArrayMap ret = new PersistentArrayMap();
ret._meta = _meta;
return ret;
}
public Object get(Object key) {
int i = indexOf(key);
if(i >= 0)
return array[i + 1];
return null;
}
public int capacity() {
return count();
}
int indexOf(Object key){
for(int i=0;i<array.Length;i+=2)
{
if(equalKey(array[i],key))
return i;
}
return -1;
}
internal virtual bool equalKey(Object k1,Object k2){
if(k1 == null)
return k2 == null;
return k1.Equals(k2);
}
public IEnumerator GetEnumerator() {
return new Iter(array);
}
public ISeq seq() {
if(array.Length > 0)
return new Seq(array,0);
return null;
}
internal class Seq : ISeq, IMapEntry{
readonly Object[] array;
readonly int i;
internal Seq(Object[] array, int i){
this.array = array;
this.i = i;
}
public Object key() {
return array[i];
}
public Object val() {
return array[i+1];
}
public Object first() {
return this;
}
public ISeq rest() {
if(i+2 < array.Length)
return new Seq(array, i + 2);
return null;
}
}
internal class Iter : IEnumerator,IMapEntry{
Object[] array;
int i;
//for iterator
internal Iter(Object[] array): this(array,-2)
{
}
//for find
internal Iter(Object[] array, int i){
this.array = array;
this.i = i;
}
public Object key() {
return array[i];
}
public Object val() {
return array[i+1];
}
#region IEnumerator Members
public object Current
{
get {return this;}
}
public bool MoveNext()
{
i += 2;
return i < array.Length - 2;
}
public void Reset()
{
throw new Exception("The method or operation is not implemented.");
}
#endregion
}
}
}
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