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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.
**/
/* rich Jun 2, 2006 */
using System;
using System.Threading;
using System.Collections;
namespace org.clojure.runtime
{
/**
* Hybrid range/BitArray, multi-thread-safe
*
* See Cohen for basic idea
*/
public class PersistentArray : IEnumerable{
#region IEnumerable Members
public IEnumerator GetEnumerator()
{
return new ValIter(this);
}
#endregion
internal class Master{
internal readonly Entry[] array;
internal readonly Object defaultVal;
internal int rev;
internal Master(int size, Object defaultVal)
{
this.array = new Entry[size];
this.defaultVal = defaultVal;
this.rev = 0;
}
}
internal class Entry
{
internal readonly int rev;
internal readonly Object val;
internal readonly Entry rest;
internal Entry(int rev, Object val, Entry rest)
{
this.rev = rev;
this.val = val;
this.rest = rest;
}
}
internal class ValIter : IEnumerator
{
internal PersistentArray p;
internal int i;
internal ValIter(PersistentArray p)
{
this.p = p;
this.i = -1;
}
#region IEnumerator Members
public object Current
{
get { return p.get(i); }
}
public bool MoveNext()
{
++i;
return i < p.length();
}
public void Reset()
{
throw new Exception("The method or operation is not implemented.");
}
#endregion
}
internal readonly Master master;
internal readonly int rev;
internal readonly int baseline;
internal readonly BitArray history;
public PersistentArray(int size,Object defaultVal){
this.master = new Master(size, defaultVal);
this.rev = 0;
this.baseline = 0;
this.history = null;
}
internal PersistentArray(Master master, int rev, int baseline, BitArray history)
{
this.master = master;
this.rev = rev;
this.baseline = baseline;
this.history = history;
}
public PersistentArray(int size)
: this(size, null)
{
}
public int length(){
return master.array.Length;
}
public Object get(int i){
for(Entry e = (Entry) master.array[i];e != null;e = e.rest)
{
if(e.rev <= rev)
{
if(e.rev >= baseline
|| (history != null && e.rev < history.Length && history.Get(e.rev)))
return e.val;
}
}
return master.defaultVal;
}
public PersistentArray set(int i,Object val) {
PersistentArray ret = getSetArray();
ret.doSet(i, val);
return ret;
}
void doSet(int i, Object val){
Entry oldEntry, newEntry;
lock(master.array)
{
oldEntry = (Entry) master.array[i];
newEntry = new Entry(rev, val, oldEntry);
master.array[i] = newEntry;
}
}
PersistentArray getSetArray(){
int nextRev;
int nextBaseline;
BitArray nextHistory;
//is this a sequential update?
if(Interlocked.CompareExchange(ref master.rev,rev + 1,rev) == rev)
{
nextRev = rev + 1;
nextBaseline = baseline;
nextHistory = history;
}
else //gap
{
nextRev = Interlocked.Increment(ref master.rev);
nextBaseline = nextRev;
if(history != null)
{
nextHistory = (BitArray) history.Clone();
nextHistory.Length = rev+1;
}
else
nextHistory = new BitArray(rev+1);
for(int i=baseline;i<=rev;i++)
nextHistory.Set(i,true);
}
return new PersistentArray(master, nextRev, nextBaseline, nextHistory);
}
//*
[STAThread]
static public void Main(String[] args){
if(args.Length != 3)
{
Console.Error.WriteLine("Usage: PersistentArray size writes reads");
return;
}
int size = Int32.Parse(args[0]);
int writes = Int32.Parse(args[1]);
int reads = Int32.Parse(args[2]);
ArrayList v = new ArrayList(size);
//v.setSize(size);
PersistentArray p = new PersistentArray(size);
for(int i = 0; i < size; i++)
{
v.Add(0);
p = p.set(i, 0);
}
Random rand;
rand = new Random(42);
long tv = 0;
Console.WriteLine("ArrayList");
for(int i = 0; i < writes; i++)
{
v[rand.Next(size)] = i;
}
for(int i = 0; i < reads; i++)
{
tv += (int)v[rand.Next(size)];
}
Console.WriteLine("PersistentArray");
rand = new Random(42);
long tp = 0;
for(int i = 0; i < writes; i++)
{
p = p.set(rand.Next(size), i);
//dummy set to force perverse branching
p.set(i%size, i);
}
for(int i = 0; i < reads; i++)
{
tp += (int)p.get(rand.Next(size));
}
Console.WriteLine("Done: " + tv + ", " + tp);
}
//*/
}
}
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