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/*******************************************************************************
* Copyright (c) 2013 Dennis Wagelaar.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Dennis Wagelaar - initial API and
* implementation and/or initial documentation
*******************************************************************************/
package org.eclipse.m2m.atl.emftvm.util;
import java.lang.ref.SoftReference;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Queue;
import org.eclipse.m2m.atl.emftvm.EmftvmFactory;
import org.eclipse.m2m.atl.emftvm.ExecEnv;
import org.eclipse.m2m.atl.emftvm.Metamodel;
/**
* Pool of reusable {@link ExecEnv}s.
*
* @author <a href="dwagelaar@gmail.com">Dennis Wagelaar</a>
*/
public class ExecEnvPool {
private final Map<String, Metamodel> metamodels = new LinkedHashMap<String, Metamodel>();
private ModuleResolverFactory moduleResolverFactory;
private final List<String> modules = new ArrayList<String>();
private boolean frozen;
private final Collection<SoftReference<ExecEnv>> pool = new LinkedList<SoftReference<ExecEnv>>();
private final Queue<SoftReference<ExecEnv>> freePool = new LinkedList<SoftReference<ExecEnv>>();
/**
* Registers <code>metamodel</code> under <code>name</code>.
*
* @param name
* the name under which to register
* @param metamodel
* the metamodel to register
* @throws IllegalStateException
* if {@link #getExecEnv()} has already been called on this pool
*/
public synchronized void registerMetaModel(String name, Metamodel metamodel) {
if (isFrozen()) {
throw new IllegalStateException("Cannot register metamodels after calling getExecEnv()");
}
metamodels.put(name, metamodel);
}
/**
* Loads the module with the given <code>name</code> and its imports closure, and registers its contents for execution.
*
* @param name
* the module name
* @throws IllegalStateException
* if {@link #getExecEnv()} has already been called on this pool
*/
public synchronized void loadModule(String name) {
if (isFrozen()) {
throw new IllegalStateException("Cannot load modules after calling getExecEnv()");
}
modules.add(name);
}
/**
* Returns the first available {@link ExecEnv} instance from this pool. Creates a new instance if necessary.
*
* @return the first available {@link ExecEnv} instance from this pool
*/
public synchronized ExecEnv getExecEnv() {
final boolean validate = !isFrozen(); // Only validate bytecode for first time load
setFrozen(true);
final Queue<SoftReference<ExecEnv>> freePool = getFreePool();
ExecEnv execEnv = null;
while (!freePool.isEmpty() && execEnv == null) {
execEnv = freePool.poll().get();
}
if (execEnv == null) {
execEnv = EmftvmFactory.eINSTANCE.createExecEnv();
for (Entry<String, Metamodel> metamodel : getMetamodels().entrySet()) {
execEnv.registerMetaModel(metamodel.getKey(), metamodel.getValue());
}
final ModuleResolverFactory moduleResolverFactory = getModuleResolverFactory();
final List<String> modules = getModules();
if (!modules.isEmpty()) {
if (moduleResolverFactory == null) {
throw new IllegalStateException("No module resolver factory set");
}
final ModuleResolver moduleResolver = moduleResolverFactory.createModuleResolver();
for (String module : getModules()) {
execEnv.loadModule(moduleResolver, module, validate);
}
}
getPool().add(new SoftReference<ExecEnv>(execEnv));
}
return execEnv;
}
/**
* Returns <code>env</code> to this pool. <code>env</code> must have been created by this pool.
*
* @param env
* the {@link ExecEnv} to return to this pool
* @throws IllegalArgumentException
* if <code>env</code> was not created by this pool
*/
public synchronized void returnExecEnv(ExecEnv env) {
boolean found = false;
for (Iterator<SoftReference<ExecEnv>> it = getPool().iterator(); it.hasNext();) {
ExecEnv envEntry = it.next().get();
if (envEntry == null) {
it.remove();
} else {
found |= (env == envEntry);
// Keep running to remove all empty soft references
}
}
if (!found) {
throw new IllegalArgumentException(String.format("%s was not created by this pool", env));
}
boolean freeFound = false;
for (Iterator<SoftReference<ExecEnv>> it = getFreePool().iterator(); it.hasNext();) {
ExecEnv envEntry = it.next().get();
if (envEntry == null) {
it.remove();
} else {
freeFound |= (env == envEntry);
// Keep running to remove all empty soft references
}
}
if (!freeFound) {
env.clearModels();
getFreePool().offer(new SoftReference<ExecEnv>(env));
}
}
/**
* Returns whether this {@link ExecEnvPool} has been frozen, i.e. no new metamodels or modules can be loaded.
*
* @return whether this {@link ExecEnvPool} has been frozen, i.e. no new metamodels or modules can be loaded
*/
public synchronized boolean isFrozen() {
return frozen;
}
/**
* @param frozen
* the frozen to set
*/
protected void setFrozen(boolean frozen) {
this.frozen = frozen;
}
/**
* @return the metamodels
*/
protected Map<String, Metamodel> getMetamodels() {
return metamodels;
}
/**
* @return the moduleResolverFactory
*/
protected ModuleResolverFactory getModuleResolverFactory() {
return moduleResolverFactory;
}
/**
* Sets the {@link ModuleResolverFactory} to use for loading modules.
*
* @param moduleResolverFactory
* the moduleResolverFactory to set
* @throws IllegalStateException
* if {@link #getExecEnv()} has already been called on this pool
*/
public synchronized void setModuleResolverFactory(ModuleResolverFactory moduleResolverFactory) {
if (isFrozen()) {
throw new IllegalStateException("Cannot load modules after calling getExecEnv()");
}
this.moduleResolverFactory = moduleResolverFactory;
}
/**
* @return the modules
*/
protected List<String> getModules() {
return modules;
}
/**
* Returns the pool of all {@link ExecEnv} instances created by this {@link ExecEnvPool}.
*
* @return the pool
*/
protected Collection<SoftReference<ExecEnv>> getPool() {
return pool;
}
/**
* Returns the pool of all free {@link ExecEnv} instances. Subset of {@link #getPool()}.
*
* @return the freePool
*/
protected Queue<SoftReference<ExecEnv>> getFreePool() {
return freePool;
}
}
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