jdk8-mips64-public/langtools: src/share/classes/com/sun/tools/javac/util/Context.java@24a47c3062fe (annotated)

src/share/classes/com/sun/tools/javac/util/Context.java@24a47c3062fe (annotated)

src/share/classes/com/sun/tools/javac/util/Context.java

Thu, 02 Oct 2008 19:58:40 -0700

author: xdono
date: Thu, 02 Oct 2008 19:58:40 -0700
changeset 117: 24a47c3062fe
parent 104: 5e89c4ca637c
child 184: 905e151a185a
permissions: -rw-r--r--

6754988: Update copyright year
Summary: Update for files that have been modified starting July 2008
Reviewed-by: ohair, tbell

 /*
  * Copyright 2001-2008 Sun Microsystems, Inc.  All Rights Reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Sun designates this
  * particular file as subject to the "Classpath" exception as provided
  * by Sun in the LICENSE file that accompanied this code.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  */
 package com.sun.tools.javac.util;
 import java.util.*;
 /**
  * Support for an abstract context, modelled loosely after ThreadLocal
  * but using a user-provided context instead of the current thread.
  *
  * <p>Within the compiler, a single Context is used for each
  * invocation of the compiler.  The context is then used to ensure a
  * single copy of each compiler phase exists per compiler invocation.
  *
  * <p>The context can be used to assist in extending the compiler by
  * extending its components.  To do that, the extended component must
  * be registered before the base component.  We break initialization
  * cycles by (1) registering a factory for the component rather than
  * the component itself, and (2) a convention for a pattern of usage
  * in which each base component registers itself by calling an
  * instance method that is overridden in extended components.  A base
  * phase supporting extension would look something like this:
  *
  * <p><pre>
  * public class Phase {
  *     protected static final Context.Key<Phase> phaseKey =
  *         new Context.Key<Phase>();
  *
  *     public static Phase instance(Context context) {
  *         Phase instance = context.get(phaseKey);
  *         if (instance == null)
  *             // the phase has not been overridden
  *             instance = new Phase(context);
  *         return instance;
  *     }
  *
  *     protected Phase(Context context) {
  *         context.put(phaseKey, this);
  *         // other intitialization follows...
  *     }
  * }
  * </pre>
  *
  * <p>In the compiler, we simply use Phase.instance(context) to get
  * the reference to the phase.  But in extensions of the compiler, we
  * must register extensions of the phases to replace the base phase,
  * and this must be done before any reference to the phase is accessed
  * using Phase.instance().  An extended phase might be declared thus:
  *
  * <p><pre>
  * public class NewPhase extends Phase {
  *     protected NewPhase(Context context) {
  *         super(context);
  *     }
  *     public static void preRegister(final Context context) {
  *         context.put(phaseKey, new Context.Factory<Phase>() {
  *             public Phase make() {
  *                 return new NewPhase(context);
  *             }
  *         });
  *     }
  * }
  * </pre>
  *
  * <p>And is registered early in the extended compiler like this
  *
  * <p><pre>
  *     NewPhase.preRegister(context);
  * </pre>
  *
  *  <p><b>This is NOT part of any API supported by Sun Microsystems.  If
  *  you write code that depends on this, you do so at your own risk.
  *  This code and its internal interfaces are subject to change or
  *  deletion without notice.</b>
  */
 public class Context {
     /** The client creates an instance of this class for each key.
      */
     public static class Key<T> {
         // note: we inherit identity equality from Object.
     }
     /**
      * The client can register a factory for lazy creation of the
      * instance.
      */
     public static interface Factory<T> {
         T make();
     };
     /**
      * The underlying map storing the data.
      * We maintain the invariant that this table contains only
      * mappings of the form
      * Key<T> -> T or Key<T> -> Factory<T> */
     private Map<Key,Object> ht = new HashMap<Key,Object>();
     /** Set the factory for the key in this context. */
     public <T> void put(Key<T> key, Factory<T> fac) {
         checkState(ht);
         Object old = ht.put(key, fac);
         if (old != null)
             throw new AssertionError("duplicate context value");
     }
     /** Set the value for the key in this context. */
     public <T> void put(Key<T> key, T data) {
         if (data instanceof Factory)
             throw new AssertionError("T extends Context.Factory");
         checkState(ht);
         Object old = ht.put(key, data);
         if (old != null && !(old instanceof Factory) && old != data && data != null)
             throw new AssertionError("duplicate context value");
     }
     /** Get the value for the key in this context. */
     public <T> T get(Key<T> key) {
         checkState(ht);
         Object o = ht.get(key);
         if (o instanceof Factory) {
             Factory fac = (Factory)o;
             o = fac.make();
             if (o instanceof Factory)
                 throw new AssertionError("T extends Context.Factory");
             assert ht.get(key) == o;
         }
         /* The following cast can't fail unless there was
          * cheating elsewhere, because of the invariant on ht.
          * Since we found a key of type Key<T>, the value must
          * be of type T.
          */
         return Context.<T>uncheckedCast(o);
     }
     public Context() {}
     private Map<Class<?>, Key<?>> kt = new HashMap<Class<?>, Key<?>>();
     private <T> Key<T> key(Class<T> clss) {
         checkState(kt);
         Key<T> k = uncheckedCast(kt.get(clss));
         if (k == null) {
             k = new Key<T>();
             kt.put(clss, k);
         }
         return k;
     }
     public <T> T get(Class<T> clazz) {
         return get(key(clazz));
     }
     public <T> void put(Class<T> clazz, T data) {
         put(key(clazz), data);
     }
     public <T> void put(Class<T> clazz, Factory<T> fac) {
         put(key(clazz), fac);
     }
     /**
      * TODO: This method should be removed and Context should be made type safe.
      * This can be accomplished by using class literals as type tokens.
      */
     @SuppressWarnings("unchecked")
     private static <T> T uncheckedCast(Object o) {
         return (T)o;
     }
     public void dump() {
         for (Object value : ht.values())
             System.err.println(value == null ? null : value.getClass());
     }
     public void clear() {
         ht = null;
         kt = null;
     }
     private static void checkState(Map<?,?> t) {
         if (t == null)
             throw new IllegalStateException();
     }
 }

Mercurial > jdk8-mips64-public > langtools / annotate

src/share/classes/com/sun/tools/javac/util/Context.java@24a47c3062fe (annotated)

src/share/classes/com/sun/tools/javac/util/Context.java