diff -r 000000000000 -r 959103a6100f src/share/classes/com/sun/tools/sjavac/BuildState.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/classes/com/sun/tools/sjavac/BuildState.java	Wed Apr 27 01:34:52 2016 +0800
@@ -0,0 +1,279 @@
+/*
+ * Copyright (c) 2012, 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.  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.sun.tools.sjavac;
+
+import java.io.File;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * The build state class captures the source code and generated artifacts
+ * from a build. There are usually two build states, the previous one (prev),
+ * loaded from the javac_state file, and the current one (now).
+ *
+ * <p><b>This is NOT part of any supported API.
+ * 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></p>
+ */
+public class BuildState {
+    private Map<String,Module> modules = new HashMap<String,Module>();
+    private Map<String,Package> packages = new HashMap<String,Package>();
+    private Map<String,Source> sources = new HashMap<String,Source>();
+    private Map<String,File> artifacts = new HashMap<String,File>();
+    // Map from package to a set of packages that depend on said package.
+    private Map<String,Set<String>> dependents = new HashMap<String,Set<String>>();
+
+    public  Map<String,Module> modules() { return modules; }
+    public  Map<String,Package> packages() { return packages; }
+    public  Map<String,Source> sources() { return sources; }
+    public  Map<String,File> artifacts() { return artifacts; }
+    public  Map<String,Set<String>> dependents() { return dependents; }
+
+    /**
+     * Lookup a module from a name. Create the module if it does
+     * not exist yet.
+     */
+    public Module lookupModule(String mod) {
+        Module m = modules.get(mod);
+        if (m == null) {
+            m = new Module(mod, "???");
+            modules.put(mod, m);
+        }
+        return m;
+    }
+
+    /**
+     * Find a module from a given package name. For example:
+     * The package name "base:java.lang" will fetch the module named "base".
+     * The package name ":java.net" will fetch the default module.
+     */
+    Module findModuleFromPackageName(String pkg) {
+        int cp = pkg.indexOf(':');
+        assert(cp != -1);
+        String mod = pkg.substring(0, cp);
+        return lookupModule(mod);
+    }
+
+    /**
+     * Store references to all packages, sources and artifacts for all modules
+     * into the build state. I.e. flatten the module tree structure
+     * into global maps stored in the BuildState for easy access.
+     *
+     * @param m The set of modules.
+     */
+    public void flattenPackagesSourcesAndArtifacts(Map<String,Module> m) {
+        modules = m;
+        // Extract all the found packages.
+        for (Module i : modules.values()) {
+            for (Map.Entry<String,Package> j : i.packages().entrySet()) {
+                Package p = packages.get(j.getKey());
+                // Check that no two different packages are stored under same name.
+                assert(p == null || p == j.getValue());
+                if (p == null) {
+                    p = j.getValue();
+                    packages.put(j.getKey(),j.getValue());
+                }
+                for (Map.Entry<String,Source> k : p.sources().entrySet()) {
+                    Source s = sources.get(k.getKey());
+                    // Check that no two different sources are stored under same name.
+                    assert(s == null || s == k.getValue());
+                    if (s == null) {
+                        s = k.getValue();
+                        sources.put(k.getKey(), k.getValue());
+                    }
+                }
+                for (Map.Entry<String,File> g : p.artifacts().entrySet()) {
+                    File f = artifacts.get(g.getKey());
+                    // Check that no two artifacts are stored under the same file.
+                    assert(f == null || f == g.getValue());
+                    if (f == null) {
+                        f = g.getValue();
+                        artifacts.put(g.getKey(), g.getValue());
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * Store references to all artifacts found in the module tree into the maps
+     * stored in the build state.
+     *
+     * @param m The set of modules.
+     */
+    public void flattenArtifacts(Map<String,Module> m) {
+        modules = m;
+        // Extract all the found packages.
+        for (Module i : modules.values()) {
+            for (Map.Entry<String,Package> j : i.packages().entrySet()) {
+                Package p = packages.get(j.getKey());
+                // Check that no two different packages are stored under same name.
+                assert(p == null || p == j.getValue());
+                p = j.getValue();
+                packages.put(j.getKey(),j.getValue());
+                for (Map.Entry<String,File> g : p.artifacts().entrySet()) {
+                    File f = artifacts.get(g.getKey());
+                    // Check that no two artifacts are stored under the same file.
+                    assert(f == null || f == g.getValue());
+                    artifacts.put(g.getKey(), g.getValue());
+                }
+            }
+        }
+    }
+
+    /**
+     * Calculate the package dependents (ie the reverse of the dependencies).
+     */
+    public void calculateDependents() {
+        dependents = new HashMap<String,Set<String>>();
+        for (String s : packages.keySet()) {
+            Package p = packages.get(s);
+            for (String d : p.dependencies()) {
+                Set<String> ss = dependents.get(d);
+                if (ss == null) {
+                    ss = new HashSet<String>();
+                    dependents.put(d, ss);
+                }
+                // Add the dependent information to the global dependent map.
+                ss.add(s);
+                Package dp = packages.get(d);
+                // Also add the dependent information to the package specific map.
+                // Normally, you do not compile java.lang et al. Therefore
+                // there are several packages that p depends upon that you
+                // do not have in your state database. This is perfectly fine.
+                if (dp != null) {
+                    // But this package did exist in the state database.
+                    dp.addDependent(p.name());
+                }
+            }
+        }
+    }
+
+    /**
+     * Verify that the setModules method above did the right thing when
+     * running through the module->package->source structure.
+     */
+    public void checkInternalState(String msg, boolean linkedOnly, Map<String,Source> srcs) {
+        boolean baad = false;
+        Map<String,Source> original = new HashMap<String,Source>();
+        Map<String,Source> calculated = new HashMap<String,Source>();
+
+        for (String s : sources.keySet()) {
+            Source ss = sources.get(s);
+            if (ss.isLinkedOnly() == linkedOnly) {
+                calculated.put(s,ss);
+            }
+        }
+        for (String s : srcs.keySet()) {
+            Source ss = srcs.get(s);
+            if (ss.isLinkedOnly() == linkedOnly) {
+                original.put(s,ss);
+            }
+        }
+        if (original.size() != calculated.size()) {
+            Log.error("INTERNAL ERROR "+msg+" original and calculated are not the same size!");
+            baad = true;
+        }
+        if (!original.keySet().equals(calculated.keySet())) {
+            Log.error("INTERNAL ERROR "+msg+" original and calculated do not have the same domain!");
+            baad = true;
+        }
+        if (!baad) {
+            for (String s : original.keySet()) {
+                Source s1 = original.get(s);
+                Source s2 = calculated.get(s);
+                if (s1 == null || s2 == null || !s1.equals(s2)) {
+                    Log.error("INTERNAL ERROR "+msg+" original and calculated have differing elements for "+s);
+                }
+                baad = true;
+            }
+        }
+        if (baad) {
+            for (String s : original.keySet()) {
+                Source ss = original.get(s);
+                Source sss = calculated.get(s);
+                if (sss == null) {
+                    Log.error("The file "+s+" does not exist in calculated tree of sources.");
+                }
+            }
+            for (String s : calculated.keySet()) {
+                Source ss = calculated.get(s);
+                Source sss = original.get(s);
+                if (sss == null) {
+                    Log.error("The file "+s+" does not exist in original set of found sources.");
+                }
+            }
+        }
+    }
+
+    /**
+     * Load a module from the javac state file.
+     */
+    public Module loadModule(String l) {
+        Module m = Module.load(l);
+        modules.put(m.name(), m);
+        return m;
+    }
+
+    /**
+     * Load a package from the javac state file.
+     */
+    public Package loadPackage(Module lastModule, String l) {
+        Package p = Package.load(lastModule, l);
+        lastModule.addPackage(p);
+        packages.put(p.name(), p);
+        return p;
+    }
+
+    /**
+     * Load a source from the javac state file.
+     */
+    public Source loadSource(Package lastPackage, String l, boolean is_generated) {
+        Source s = Source.load(lastPackage, l, is_generated);
+        lastPackage.addSource(s);
+        sources.put(s.name(), s);
+        return s;
+    }
+
+    /**
+     * During an incremental compile we need to copy the old javac state
+     * information about packages that were not recompiled.
+     */
+    public void copyPackagesExcept(BuildState prev, Set<String> recompiled, Set<String> removed) {
+        for (String pkg : prev.packages().keySet()) {
+            // Do not copy recompiled or removed packages.
+            if (recompiled.contains(pkg) || removed.contains(pkg)) continue;
+            Module mnew = findModuleFromPackageName(pkg);
+            Package pprev = prev.packages().get(pkg);
+            mnew.addPackage(pprev);
+            // Do not forget to update the flattened data.
+            packages.put(pkg, pprev);
+        }
+    }
+}