--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/truffle/com.oracle.truffle.api/src/com/oracle/truffle/api/debug/Breakpoint.java	Sat Jul 18 18:03:36 2015 +0200
@@ -0,0 +1,219 @@
+/*
+ * Copyright (c) 2015, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle 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 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.truffle.api.debug;
+
+import com.oracle.truffle.api.instrument.*;
+import com.oracle.truffle.api.source.*;
+import java.io.IOException;
+
+public abstract class Breakpoint {
+
+    /**
+     * A general model of the states occupied by a breakpoint during its lifetime.
+     */
+    public enum State {
+
+        /**
+         * Not attached, enabled.
+         * <p>
+         * Created for a source location but not yet attached: perhaps just created and the source
+         * hasn't been loaded yet; perhaps source has been loaded, but the line location isn't
+         * probed so a breakpoint cannot be attached. Can be either enabled or disabled.
+         */
+        ENABLED_UNRESOLVED("Enabled/Unresolved"),
+
+        /**
+         * Not attached, disabled.
+         * <p>
+         * Created for a source location but not yet attached: perhaps just created and the source
+         * hasn't been loaded yet; perhaps source has been loaded, but the line location isn't
+         * probed so a breakpoint cannot be attached.
+         */
+        DISABLED_UNRESOLVED("Disabled/Unresolved"),
+
+        /**
+         * Attached, instrument enabled.
+         * <p>
+         * Is currently implemented by some {@link Instrument}, which is attached to a {@link Probe}
+         * at a specific node in the AST, and the breakpoint is enabled.
+         */
+        ENABLED("Enabled"),
+
+        /**
+         * Attached, instrument disabled.
+         * <p>
+         * Is currently implemented by some {@link Instrument}, which is attached to a {@link Probe}
+         * at a specific node in the AST, and the breakpoint is disabled.
+         */
+        DISABLED("Disabled"),
+
+        /**
+         * Not attached, instrument is permanently disabled.
+         */
+        DISPOSED("Disposed");
+
+        private final String name;
+
+        State(String name) {
+            this.name = name;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        @Override
+        public String toString() {
+            return name;
+        }
+
+    }
+
+    private final boolean isOneShot;
+
+    private int ignoreCount;
+
+    private int hitCount;
+
+    private State state;
+
+    Breakpoint(State state, int ignoreCount, boolean isOneShot) {
+        this.state = state;
+        this.isOneShot = isOneShot;
+        this.ignoreCount = ignoreCount;
+    }
+
+    /**
+     * Enables or disables this breakpoint's AST instrumentation. The breakpoint is enabled by
+     * default.
+     *
+     * @param enabled <code>true</code> to activate the instrumentation, <code>false</code> to
+     *            deactivate the instrumentation so that it has no effect.
+     */
+    public abstract void setEnabled(boolean enabled);
+
+    /**
+     * Is this breakpoint active?
+     */
+    public abstract boolean isEnabled();
+
+    /**
+     * Sets the condition on this breakpoint, {@code null} to make it unconditional.
+     *
+     * @param expr if non{@code -null}, a boolean expression, expressed in the guest language, to be
+     *            evaluated in the lexical context at the breakpoint location.
+     * @throws IOException if condition is invalid
+     * @throws UnsupportedOperationException if the breakpoint does not support conditions
+     */
+    public abstract void setCondition(String expr) throws IOException;
+
+    /**
+     * Gets the string, expressed in the Guest Language, that defines the current condition on this
+     * breakpoint; {@code null} if this breakpoint is currently unconditional.
+     */
+    public String getCondition() {
+        return null;
+    }
+
+    /**
+     * Does this breakpoint remove itself after first activation?
+     */
+    public final boolean isOneShot() {
+        return isOneShot;
+    }
+
+    /**
+     * Gets the number of hits left to be ignored before halting.
+     */
+    public final int getIgnoreCount() {
+        return ignoreCount;
+    }
+
+    /**
+     * Change the threshold for when this breakpoint should start causing a break. When both an
+     * ignore count and a {@linkplain #setCondition(String) condition} are specified, the condition
+     * is evaluated first: if {@code false} it is not considered to be a hit. In other words, the
+     * ignore count is for successful conditions only.
+     */
+    public final void setIgnoreCount(int ignoreCount) {
+        this.ignoreCount = ignoreCount;
+    }
+
+    /**
+     * Number of times this breakpoint has reached, with one exception; if the breakpoint has a
+     * condition that evaluates to {@code false}, it does not count as a hit.
+     */
+    public final int getHitCount() {
+        return hitCount;
+    }
+
+    /**
+     * Disables this breakpoint and removes any associated instrumentation; it becomes permanently
+     * inert.
+     */
+    public abstract void dispose();
+
+    /**
+     * Gets a human-sensible description of this breakpoint's location in a {@link Source}.
+     */
+    public abstract String getLocationDescription();
+
+    public final State getState() {
+        return state;
+    }
+
+    final void assertState(State s) {
+        assert state == s;
+    }
+
+    final void setState(State state) {
+        this.state = state;
+    }
+
+    /**
+     * Assumes that all conditions for causing the break have been satisfied, so increments the
+     * <em>hit count</em>. Then checks if the <em>ignore count</em> has been exceeded, and if so
+     * returns {@code true}. If not, it still counts as a <em>hit</em> but should be ignored.
+     *
+     * @return whether to proceed
+     */
+    final boolean incrHitCountCheckIgnore() {
+        return ++hitCount > ignoreCount;
+    }
+
+    @Override
+    public String toString() {
+        final StringBuilder sb = new StringBuilder(getClass().getSimpleName());
+        sb.append(" state=");
+        sb.append(getState() == null ? "<none>" : getState().getName());
+        if (isOneShot()) {
+            sb.append(", " + "One-Shot");
+        }
+        if (getCondition() != null) {
+            sb.append(", condition=\"" + getCondition() + "\"");
+        }
+        return sb.toString();
+    }
+}