--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jvmci/com.oracle.jvmci.options/src/com/oracle/jvmci/options/OptionValue.java	Tue Jun 09 00:22:49 2015 +0200
@@ -0,0 +1,475 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. 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.
+ *
+ * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.jvmci.options;
+
+import java.io.*;
+import java.util.*;
+import java.util.Map.Entry;
+
+/**
+ * An option value.
+ */
+public class OptionValue<T> {
+    /**
+     * Temporarily changes the value for an option. The {@linkplain OptionValue#getValue() value} of
+     * {@code option} is set to {@code value} until {@link OverrideScope#close()} is called on the
+     * object returned by this method.
+     * <p>
+     * Since the returned object is {@link AutoCloseable} the try-with-resource construct can be
+     * used:
+     *
+     * <pre>
+     * try (OverrideScope s = OptionValue.override(myOption, myValue) {
+     *     // code that depends on myOption == myValue
+     * }
+     * </pre>
+     */
+    public static OverrideScope override(OptionValue<?> option, Object value) {
+        OverrideScope current = getOverrideScope();
+        if (current == null) {
+            if (!value.equals(option.getValue())) {
+                return new SingleOverrideScope(option, value);
+            }
+            Map<OptionValue<?>, Object> overrides = Collections.emptyMap();
+            return new MultipleOverridesScope(current, overrides);
+        }
+        return new MultipleOverridesScope(current, option, value);
+    }
+
+    /**
+     * Temporarily changes the values for a set of options. The {@linkplain OptionValue#getValue()
+     * value} of each {@code option} in {@code overrides} is set to the corresponding {@code value}
+     * in {@code overrides} until {@link OverrideScope#close()} is called on the object returned by
+     * this method.
+     * <p>
+     * Since the returned object is {@link AutoCloseable} the try-with-resource construct can be
+     * used:
+     *
+     * <pre>
+     * Map&lt;OptionValue, Object&gt; overrides = new HashMap&lt;&gt;();
+     * overrides.put(myOption1, myValue1);
+     * overrides.put(myOption2, myValue2);
+     * try (OverrideScope s = OptionValue.override(overrides) {
+     *     // code that depends on myOption == myValue
+     * }
+     * </pre>
+     */
+    public static OverrideScope override(Map<OptionValue<?>, Object> overrides) {
+        OverrideScope current = getOverrideScope();
+        if (current == null && overrides.size() == 1) {
+            Entry<OptionValue<?>, Object> single = overrides.entrySet().iterator().next();
+            OptionValue<?> option = single.getKey();
+            Object overrideValue = single.getValue();
+            if (!overrideValue.equals(option.getValue())) {
+                return new SingleOverrideScope(option, overrideValue);
+            }
+        }
+        return new MultipleOverridesScope(current, overrides);
+    }
+
+    /**
+     * Temporarily changes the values for a set of options. The {@linkplain OptionValue#getValue()
+     * value} of each {@code option} in {@code overrides} is set to the corresponding {@code value}
+     * in {@code overrides} until {@link OverrideScope#close()} is called on the object returned by
+     * this method.
+     * <p>
+     * Since the returned object is {@link AutoCloseable} the try-with-resource construct can be
+     * used:
+     *
+     * <pre>
+     * try (OverrideScope s = OptionValue.override(myOption1, myValue1, myOption2, myValue2) {
+     *     // code that depends on myOption == myValue
+     * }
+     * </pre>
+     *
+     * @param overrides overrides in the form {@code [option1, override1, option2, override2, ...]}
+     */
+    public static OverrideScope override(Object... overrides) {
+        OverrideScope current = getOverrideScope();
+        if (current == null && overrides.length == 2) {
+            OptionValue<?> option = (OptionValue<?>) overrides[0];
+            Object overrideValue = overrides[1];
+            if (!overrideValue.equals(option.getValue())) {
+                return new SingleOverrideScope(option, overrideValue);
+            }
+        }
+        Map<OptionValue<?>, Object> map = Collections.emptyMap();
+        for (int i = 0; i < overrides.length; i += 2) {
+            OptionValue<?> option = (OptionValue<?>) overrides[i];
+            Object overrideValue = overrides[i + 1];
+            if (!overrideValue.equals(option.getValue())) {
+                if (map.isEmpty()) {
+                    map = new HashMap<>();
+                }
+                map.put(option, overrideValue);
+            }
+        }
+        return new MultipleOverridesScope(current, map);
+    }
+
+    private static final ThreadLocal<OverrideScope> overrideScopeTL = new ThreadLocal<>();
+
+    protected static OverrideScope getOverrideScope() {
+        return overrideScopeTL.get();
+    }
+
+    protected static void setOverrideScope(OverrideScope overrideScope) {
+        overrideScopeTL.set(overrideScope);
+    }
+
+    private T defaultValue;
+
+    /**
+     * The raw option value.
+     */
+    protected T value;
+
+    private OptionDescriptor descriptor;
+
+    private long reads;
+    private OptionValue<?> next;
+    private static OptionValue<?> head;
+
+    private static final boolean ShowReadsHistogram = Boolean.getBoolean("jvmci.showOptionValueReadsHistogram");
+
+    private static void addToHistogram(OptionValue<?> option) {
+        if (ShowReadsHistogram) {
+            synchronized (OptionValue.class) {
+                option.next = head;
+                head = option;
+            }
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    public OptionValue(T value) {
+        this.defaultValue = value;
+        this.value = (T) DEFAULT;
+        addToHistogram(this);
+    }
+
+    private static final Object DEFAULT = "DEFAULT";
+    private static final Object UNINITIALIZED = "UNINITIALIZED";
+
+    /**
+     * Creates an uninitialized option value for a subclass that initializes itself
+     * {@link #defaultValue() lazily}.
+     */
+    @SuppressWarnings("unchecked")
+    protected OptionValue() {
+        this.defaultValue = (T) UNINITIALIZED;
+        this.value = (T) DEFAULT;
+        addToHistogram(this);
+    }
+
+    /**
+     * Lazy initialization of default value.
+     */
+    protected T defaultValue() {
+        throw new InternalError("Option without a default value value must override defaultValue()");
+    }
+
+    /**
+     * Sets the descriptor for this option.
+     */
+    public void setDescriptor(OptionDescriptor descriptor) {
+        this.descriptor = descriptor;
+    }
+
+    /**
+     * Returns the descriptor for this option, if it has been set by
+     * {@link #setDescriptor(OptionDescriptor)}.
+     */
+    public OptionDescriptor getDescriptor() {
+        return descriptor;
+    }
+
+    /**
+     * Gets the name of this option. The name for an option value with a null
+     * {@linkplain #setDescriptor(OptionDescriptor) descriptor} is the value of
+     * {@link Object#toString()}.
+     */
+    public String getName() {
+        return descriptor == null ? super.toString() : (descriptor.getDeclaringClass().getName() + "." + descriptor.getName());
+    }
+
+    @Override
+    public String toString() {
+        return getName() + "=" + getValue();
+    }
+
+    /**
+     * The initial value specified in source code. The returned value is not affected by calls to
+     * {@link #setValue(Object)} or registering {@link OverrideScope}s. Therefore, it is also not
+     * affected by options set on the command line.
+     */
+    public T getDefaultValue() {
+        if (defaultValue == UNINITIALIZED) {
+            defaultValue = defaultValue();
+        }
+        return defaultValue;
+    }
+
+    /**
+     * Returns true if the option has the same value that was set in the source code.
+     */
+    public boolean hasDefaultValue() {
+        getValue(); // ensure initialized
+        return value == DEFAULT || Objects.equals(value, getDefaultValue());
+    }
+
+    /**
+     * Gets the value of this option.
+     */
+    public T getValue() {
+        if (ShowReadsHistogram) {
+            reads++;
+        }
+        if (!(this instanceof StableOptionValue)) {
+            OverrideScope overrideScope = getOverrideScope();
+            if (overrideScope != null) {
+                T override = overrideScope.getOverride(this);
+                if (override != null) {
+                    return override;
+                }
+            }
+        }
+        if (value != DEFAULT) {
+            return value;
+        } else {
+            return getDefaultValue();
+        }
+    }
+
+    /**
+     * Gets the values of this option including overridden values.
+     *
+     * @param c the collection to which the values are added. If null, one is allocated.
+     * @return the collection to which the values were added in order from most overridden to
+     *         current value
+     */
+    @SuppressWarnings("unchecked")
+    public Collection<T> getValues(Collection<T> c) {
+        Collection<T> values = c == null ? new ArrayList<>() : c;
+        if (!(this instanceof StableOptionValue)) {
+            OverrideScope overrideScope = getOverrideScope();
+            if (overrideScope != null) {
+                overrideScope.getOverrides(this, (Collection<Object>) values);
+            }
+        }
+        if (value != DEFAULT) {
+            values.add(value);
+        } else {
+            values.add(getDefaultValue());
+        }
+        return values;
+    }
+
+    /**
+     * Sets the value of this option.
+     */
+    @SuppressWarnings("unchecked")
+    public void setValue(Object v) {
+        this.value = (T) v;
+    }
+
+    /**
+     * An object whose {@link #close()} method reverts the option value overriding initiated by
+     * {@link OptionValue#override(OptionValue, Object)} or {@link OptionValue#override(Map)}.
+     */
+    public abstract static class OverrideScope implements AutoCloseable {
+
+        private Map<DerivedOptionValue<?>, Object> derivedCache = null;
+
+        public <T> T getDerived(DerivedOptionValue<T> key) {
+            if (derivedCache == null) {
+                derivedCache = new HashMap<>();
+            }
+            @SuppressWarnings("unchecked")
+            T ret = (T) derivedCache.get(key);
+            if (ret == null) {
+                ret = key.createValue();
+                derivedCache.put(key, ret);
+            }
+            return ret;
+        }
+
+        abstract void addToInherited(Map<OptionValue<?>, Object> inherited);
+
+        abstract <T> T getOverride(OptionValue<T> option);
+
+        abstract void getOverrides(OptionValue<?> option, Collection<Object> c);
+
+        public abstract void close();
+    }
+
+    static class SingleOverrideScope extends OverrideScope {
+
+        private final OptionValue<?> option;
+        private final Object value;
+
+        public SingleOverrideScope(OptionValue<?> option, Object value) {
+            if (option instanceof StableOptionValue) {
+                throw new IllegalArgumentException("Cannot override stable option " + option);
+            }
+            this.option = option;
+            this.value = value;
+            setOverrideScope(this);
+        }
+
+        @Override
+        void addToInherited(Map<OptionValue<?>, Object> inherited) {
+            inherited.put(option, value);
+        }
+
+        @SuppressWarnings("unchecked")
+        @Override
+        <T> T getOverride(OptionValue<T> key) {
+            if (key == this.option) {
+                return (T) value;
+            }
+            return null;
+        }
+
+        @Override
+        void getOverrides(OptionValue<?> key, Collection<Object> c) {
+            if (key == this.option) {
+                c.add(value);
+            }
+        }
+
+        @Override
+        public void close() {
+            setOverrideScope(null);
+        }
+    }
+
+    static class MultipleOverridesScope extends OverrideScope {
+        final OverrideScope parent;
+        final Map<OptionValue<?>, Object> overrides;
+
+        public MultipleOverridesScope(OverrideScope parent, OptionValue<?> option, Object value) {
+            this.parent = parent;
+            this.overrides = new HashMap<>();
+            if (parent != null) {
+                parent.addToInherited(overrides);
+            }
+            if (option instanceof StableOptionValue) {
+                throw new IllegalArgumentException("Cannot override stable option " + option);
+            }
+            if (!value.equals(option.getValue())) {
+                this.overrides.put(option, value);
+            }
+            if (!overrides.isEmpty()) {
+                setOverrideScope(this);
+            }
+        }
+
+        MultipleOverridesScope(OverrideScope parent, Map<OptionValue<?>, Object> overrides) {
+            this.parent = parent;
+            if (overrides.isEmpty() && parent == null) {
+                this.overrides = Collections.emptyMap();
+                return;
+            }
+            this.overrides = new HashMap<>();
+            if (parent != null) {
+                parent.addToInherited(this.overrides);
+            }
+            for (Map.Entry<OptionValue<?>, Object> e : overrides.entrySet()) {
+                OptionValue<?> option = e.getKey();
+                if (option instanceof StableOptionValue) {
+                    throw new IllegalArgumentException("Cannot override stable option " + option);
+                }
+                if (!e.getValue().equals(option.getValue())) {
+                    this.overrides.put(option, e.getValue());
+                }
+            }
+            if (!this.overrides.isEmpty()) {
+                setOverrideScope(this);
+            }
+        }
+
+        @Override
+        void addToInherited(Map<OptionValue<?>, Object> inherited) {
+            if (parent != null) {
+                parent.addToInherited(inherited);
+            }
+            inherited.putAll(overrides);
+        }
+
+        @SuppressWarnings("unchecked")
+        @Override
+        <T> T getOverride(OptionValue<T> option) {
+            return (T) overrides.get(option);
+        }
+
+        @Override
+        void getOverrides(OptionValue<?> option, Collection<Object> c) {
+            Object v = overrides.get(option);
+            if (v != null) {
+                c.add(v);
+            }
+            if (parent != null) {
+                parent.getOverrides(option, c);
+            }
+        }
+
+        @Override
+        public void close() {
+            if (!overrides.isEmpty()) {
+                setOverrideScope(parent);
+            }
+        }
+    }
+
+    static {
+        if (ShowReadsHistogram) {
+            Runtime.getRuntime().addShutdownHook(new Thread() {
+                @Override
+                public void run() {
+                    ArrayList<OptionValue<?>> options = new ArrayList<>();
+                    for (OptionValue<?> option = head; option != null; option = option.next) {
+                        options.add(option);
+                    }
+                    Collections.sort(options, new Comparator<OptionValue<?>>() {
+
+                        public int compare(OptionValue<?> o1, OptionValue<?> o2) {
+                            if (o1.reads < o2.reads) {
+                                return -1;
+                            } else if (o1.reads > o2.reads) {
+                                return 1;
+                            } else {
+                                return o1.getName().compareTo(o2.getName());
+                            }
+                        }
+                    });
+                    PrintStream out = System.out;
+                    out.println("=== OptionValue reads histogram ===");
+                    for (OptionValue<?> option : options) {
+                        out.println(option.reads + "\t" + option);
+                    }
+                }
+            });
+        }
+    }
+}