| 1 | /* |
| 2 | * Copyright 2001-2006 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package com.sun.tools.javac.util; |
| 27 | |
| 28 | import com.sun.tools.javac.Main; |
| 29 | import java.util.*; |
| 30 | |
| 31 | /** |
| 32 | * Support for an abstract context, modelled loosely after ThreadLocal |
| 33 | * but using a user-provided context instead of the current thread. |
| 34 | * |
| 35 | * <p>Within the compiler, a single Context is used for each |
| 36 | * invocation of the compiler. The context is then used to ensure a |
| 37 | * single copy of each compiler phase exists per compiler invocation. |
| 38 | * |
| 39 | * <p>The context can be used to assist in extending the compiler by |
| 40 | * extending its components. To do that, the extended component must |
| 41 | * be registered before the base component. We break initialization |
| 42 | * cycles by (1) registering a factory for the component rather than |
| 43 | * the component itself, and (2) a convention for a pattern of usage |
| 44 | * in which each base component registers itself by calling an |
| 45 | * instance method that is overridden in extended components. A base |
| 46 | * phase supporting extension would look something like this: |
| 47 | * |
| 48 | * <p><pre> |
| 49 | * public class Phase { |
| 50 | * protected static final Context.Key<Phase> phaseKey = |
| 51 | * new Context.Key<Phase>(); |
| 52 | * |
| 53 | * public static Phase instance(Context context) { |
| 54 | * Phase instance = context.get(phaseKey); |
| 55 | * if (instance == null) |
| 56 | * // the phase has not been overridden |
| 57 | * instance = new Phase(context); |
| 58 | * return instance; |
| 59 | * } |
| 60 | * |
| 61 | * protected Phase(Context context) { |
| 62 | * context.put(phaseKey, this); |
| 63 | * // other intitialization follows... |
| 64 | * } |
| 65 | * } |
| 66 | * </pre> |
| 67 | * |
| 68 | * <p>In the compiler, we simply use Phase.instance(context) to get |
| 69 | * the reference to the phase. But in extensions of the compiler, we |
| 70 | * must register extensions of the phases to replace the base phase, |
| 71 | * and this must be done before any reference to the phase is accessed |
| 72 | * using Phase.instance(). An extended phase might be declared thus: |
| 73 | * |
| 74 | * <p><pre> |
| 75 | * public class NewPhase extends Phase { |
| 76 | * protected NewPhase(Context context) { |
| 77 | * super(context); |
| 78 | * } |
| 79 | * public static void preRegister(final Context context) { |
| 80 | * context.put(phaseKey, new Context.Factory<Phase>() { |
| 81 | * public Phase make() { |
| 82 | * return new NewPhase(context); |
| 83 | * } |
| 84 | * }); |
| 85 | * } |
| 86 | * } |
| 87 | * </pre> |
| 88 | * |
| 89 | * <p>And is registered early in the extended compiler like this |
| 90 | * |
| 91 | * <p><pre> |
| 92 | * NewPhase.preRegister(context); |
| 93 | * </pre> |
| 94 | * |
| 95 | * <p><b>This is NOT part of any API supported by Sun Microsystems. If |
| 96 | * you write code that depends on this, you do so at your own risk. |
| 97 | * This code and its internal interfaces are subject to change or |
| 98 | * deletion without notice.</b> |
| 99 | */ |
| 100 | public class Context { |
| 101 | /** The client creates an instance of this class for each key. |
| 102 | */ |
| 103 | public static class Key<T> { |
| 104 | // note: we inherit identity equality from Object. |
| 105 | } |
| 106 | |
| 107 | /** |
| 108 | * The client can register a factory for lazy creation of the |
| 109 | * instance. |
| 110 | */ |
| 111 | public static interface Factory<T> { |
| 112 | T make(); |
| 113 | }; |
| 114 | |
| 115 | /** |
| 116 | * The underlying map storing the data. |
| 117 | * We maintain the invariant that this table contains only |
| 118 | * mappings of the form |
| 119 | * Key<T> -> T or Key<T> -> Factory<T> */ |
| 120 | private Map<Key,Object> ht = new HashMap<Key,Object>(); |
| 121 | |
| 122 | /** Set the factory for the key in this context. */ |
| 123 | public <T> void put(Key<T> key, Factory<T> fac) { |
| 124 | checkState(ht); |
| 125 | Object old = ht.put(key, fac); |
| 126 | if (old != null) |
| 127 | throw new AssertionError("duplicate context value"); |
| 128 | } |
| 129 | |
| 130 | /** Set the value for the key in this context. */ |
| 131 | public <T> void put(Key<T> key, T data) { |
| 132 | if (data instanceof Factory) |
| 133 | throw new AssertionError("T extends Context.Factory"); |
| 134 | checkState(ht); |
| 135 | Object old = ht.put(key, data); |
| 136 | if (old != null && !(old instanceof Factory) && old != data && data != null) |
| 137 | throw new AssertionError("duplicate context value"); |
| 138 | } |
| 139 | |
| 140 | /** Get the value for the key in this context. */ |
| 141 | public <T> T get(Key<T> key) { |
| 142 | checkState(ht); |
| 143 | Object o = ht.get(key); |
| 144 | if (o instanceof Factory) { |
| 145 | Factory fac = (Factory)o; |
| 146 | o = fac.make(); |
| 147 | if (o instanceof Factory) |
| 148 | throw new AssertionError("T extends Context.Factory"); |
| 149 | assert ht.get(key) == o; |
| 150 | } |
| 151 | |
| 152 | /* The following cast can't fail unless there was |
| 153 | * cheating elsewhere, because of the invariant on ht. |
| 154 | * Since we found a key of type Key<T>, the value must |
| 155 | * be of type T. |
| 156 | */ |
| 157 | return Context.<T>uncheckedCast(o); |
| 158 | } |
| 159 | |
| 160 | public Context() {} |
| 161 | |
| 162 | private Map<Class<?>, Key<?>> kt = new HashMap<Class<?>, Key<?>>(); |
| 163 | |
| 164 | private <T> Key<T> key(Class<T> clss) { |
| 165 | checkState(kt); |
| 166 | Key<T> k = uncheckedCast(kt.get(clss)); |
| 167 | if (k == null) { |
| 168 | k = new Key<T>(); |
| 169 | kt.put(clss, k); |
| 170 | } |
| 171 | return k; |
| 172 | } |
| 173 | |
| 174 | public <T> T get(Class<T> clazz) { |
| 175 | return get(key(clazz)); |
| 176 | } |
| 177 | |
| 178 | public <T> void put(Class<T> clazz, T data) { |
| 179 | put(key(clazz), data); |
| 180 | } |
| 181 | public <T> void put(Class<T> clazz, Factory<T> fac) { |
| 182 | put(key(clazz), fac); |
| 183 | } |
| 184 | |
| 185 | /** |
| 186 | * TODO: This method should be removed and Context should be made type safe. |
| 187 | * This can be accomplished by using class literals as type tokens. |
| 188 | */ |
| 189 | @SuppressWarnings("unchecked") |
| 190 | private static <T> T uncheckedCast(Object o) { |
| 191 | return (T)o; |
| 192 | } |
| 193 | |
| 194 | public void dump() { |
| 195 | for (Object value : ht.values()) |
| 196 | System.err.println(value == null ? null : value.getClass()); |
| 197 | } |
| 198 | |
| 199 | public void clear() { |
| 200 | ht = null; |
| 201 | kt = null; |
| 202 | } |
| 203 | |
| 204 | private static void checkState(Map<?,?> t) { |
| 205 | if (t == null) |
| 206 | throw new IllegalStateException(); |
| 207 | } |
| 208 | } |