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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 May 30, 2006 */
using System;
using System.Threading;
using System.Collections.Generic;
namespace org.clojure.runtime
{
public class Transaction{
public const int COMMITTED = 0;
public const int WORKING = 1;
static readonly Object lockObj = new Object();
volatile static int nextSeq = 1;
static int getNextSeq(){
lock (lockObj)
{
return nextSeq++;
}
}
public class Info{
internal int seq;
internal int status;
internal Info(int seq,int status){
this.seq = seq;
this.status = status;
}
}
Info info;
int startSeq;
Dictionary<TRef,Object> sets;
Dictionary<TRef,ISeq> commutates;
static public Object runInTransaction(ThreadLocalData tld,IFn fn) {
if(tld.transaction != null)
return fn.invoke(tld);
tld.transaction = new Transaction();
try{
return tld.transaction.run(tld, fn);
}
finally{
tld.transaction = null;
}
}
static public TRef tref(ThreadLocalData tld, Object val) {
Transaction trans = tld.getTransaction();
TRef tref = new TRef();
trans.set(tref, val);
return tref;
}
static public Object get(ThreadLocalData tld, TRef tref) {
return tld.getTransaction().get(tref);
}
static public Object set(ThreadLocalData tld, TRef tref, Object val) {
return tld.getTransaction().set(tref,val);
}
static public void touch(ThreadLocalData tld, TRef tref) {
tld.getTransaction().touch(tref);
}
static public void commutate(ThreadLocalData tld, TRef tref, IFn fn) {
tld.getTransaction().commutate(tref, fn);
}
Object run(ThreadLocalData tld, IFn fn) {
bool done = false;
Object ret = null;
List<TRef> locks = null;
List<TRef> locked = null;
while(!done){
try
{
ret = fn.invoke(tld);
if(locks == null && (sets != null || commutates != null))
locks = new List<TRef>();
if(sets != null)
locks.AddRange(sets.Keys);
if(commutates != null)
locks.AddRange(commutates.Keys);
if(locks != null)
{
if(locked == null)
locked = new List<TRef>(locks.Count);
//lock in order, to avoid deadlocks
locks.Sort();
foreach(TRef tref in locks)
{
//will block here
Monitor.Enter(tref);
locked.Add(tref);
if(sets.ContainsKey(tref))
{
//try again if the thing we are trying to set has changed since we started
TVal curr = getCurrent(tref);
if(curr != null && curr.tinfo.seq > startSeq)
goto loop;
}
}
}
//at this point all write targets are locked
//turn commutates into sets
foreach(KeyValuePair<TRef, ISeq> e in commutates)
{
TRef tref = e.Key;
//note this will npe if tref has never been set, as designed
Object val = getCurrent(tref).val;
for(ISeq c = e.Value;c!=null;c = c.rest())
{
IFn f = (IFn) c.first();
val = f.invoke(tld, val);
}
sets[tref] = val;
}
//set the new vals
foreach(KeyValuePair<TRef, Object> entry in sets)
{
TRef tref = entry.Key;
tref.push(entry.Value, info);
}
//atomic commit
lock(lockObj){
info.seq = getNextSeq();
info.status = COMMITTED;
}
done = true;
loop:
;
}
finally{
if(locked != null)
{
foreach(TRef tref in locked)
{
Monitor.Exit(tref);
}
locked.Clear();
}
reset();
if(locks != null)
locks.Clear();
}
}
return ret;
}
private void reset(){
if(sets != null)
sets.Clear();
if(commutates != null)
commutates.Clear();
}
Transaction(){
lock(lockObj){
int seq = getNextSeq();
this.info = new Info(seq, WORKING);
this.startSeq = seq;
}
}
Object get(TRef tref) {
if(sets != null && sets.ContainsKey(tref))
return sets[tref];
for(TVal ver = tref;ver != null;ver = ver.prior)
{
//note this will npe if tref has never been set, as designed
if(ver.tinfo.status == COMMITTED && ver.tinfo.seq <= startSeq)
return ver.val;
}
throw new Exception("Version not found");
}
static TVal getCurrent(TRef tref) {
for(TVal ver = tref;ver != null;ver = ver.prior)
{
if(ver.tinfo != null && ver.tinfo.status == COMMITTED)
return ver;
}
//this return only if no value was ever successfully set
return null;
}
Object set(TRef tref, Object val) {
if(sets == null)
sets = new Dictionary<TRef,Object>();
if(commutates != null && commutates.ContainsKey(tref))
throw new Exception("Can't commutate and set a TRef in the same transaction");
sets[tref] =val;
return val;
}
void touch(TRef tref) {
set(tref, get(tref));
}
void commutate(TRef tref, IFn fn) {
if(commutates == null)
commutates = new Dictionary<TRef,ISeq>();
if(sets != null && sets.ContainsKey(tref))
throw new Exception("Can't commutate and set a TRef in the same transaction");
commutates[tref] = RT.cons(fn, commutates[tref]);
}
}
}
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