--- /dev/null	2017-01-13 16:40:23.000000000 -0800
+++ new/src/java.base/share/classes/jdk/internal/module/ModuleHashesBuilder.java	2017-01-13 16:40:23.000000000 -0800
@@ -0,0 +1,312 @@
+/*
+ * Copyright (c) 2017, 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 jdk.internal.module;
+
+import java.io.PrintStream;
+import java.lang.module.Configuration;
+import java.lang.module.ResolvedModule;
+import java.net.URI;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayDeque;
+import java.util.Collections;
+import java.util.Deque;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.stream.Stream;
+import static java.util.stream.Collectors.*;
+
+/**
+ * A Builder to compute ModuleHashes from a given configuration
+ */
+public class ModuleHashesBuilder {
+    private final Configuration configuration;
+    private final Set<String> hashModuleCandidates;
+
+    /**
+     * Constructs a ModuleHashesBuilder that finds the packaged modules
+     * from the location of ModuleReference found from the given Configuration.
+     *
+     * @param config Configuration for building module hashes
+     * @param modules the candidate modules to be hashed
+     */
+    public ModuleHashesBuilder(Configuration config, Set<String> modules) {
+        this.configuration = config;
+        this.hashModuleCandidates = modules;
+    }
+
+    /**
+     * Returns a map of a module M to ModuleHashes for the modules
+     * that depend upon M directly or indirectly.
+     *
+     * The key for each entry in the returned map is a module M that has
+     * no outgoing edges to any of the candidate modules to be hashed
+     * i.e. M is a leaf node in a connected subgraph containing M and
+     * other candidate modules from the module graph filtering
+     * the outgoing edges from M to non-candidate modules.
+     */
+    public Map<String, ModuleHashes> computeHashes(Set<String> roots) {
+        // build a graph containing the the packaged modules and
+        // its transitive dependences matching --hash-modules
+        Graph.Builder<String> builder = new Graph.Builder<>();
+        Deque<ResolvedModule> deque = new ArrayDeque<>(configuration.modules());
+        Set<ResolvedModule> visited = new HashSet<>();
+        while (!deque.isEmpty()) {
+            ResolvedModule rm = deque.pop();
+            if (!visited.contains(rm)) {
+                visited.add(rm);
+                builder.addNode(rm.name());
+                for (ResolvedModule dm : rm.reads()) {
+                    if (!visited.contains(dm)) {
+                        deque.push(dm);
+                    }
+                    builder.addEdge(rm.name(), dm.name());
+                }
+            }
+        }
+
+        // each node in a transposed graph is a matching packaged module
+        // in which the hash of the modules that depend upon it is recorded
+        Graph<String> transposedGraph = builder.build().transpose();
+
+        // traverse the modules in topological order that will identify
+        // the modules to record the hashes - it is the first matching
+        // module and has not been hashed during the traversal.
+        Set<String> mods = new HashSet<>();
+        Map<String, ModuleHashes> hashes = new HashMap<>();
+        builder.build()
+               .orderedNodes()
+               .filter(mn -> roots.contains(mn) && !mods.contains(mn))
+               .forEach(mn -> {
+                   // Compute hashes of the modules that depend on mn directly and
+                   // indirectly excluding itself.
+                   Set<String> ns = transposedGraph.dfs(mn)
+                       .stream()
+                       .filter(n -> !n.equals(mn) && hashModuleCandidates.contains(n))
+                       .collect(toSet());
+                   mods.add(mn);
+                   mods.addAll(ns);
+
+                   if (!ns.isEmpty()) {
+                       Map<String, Path> moduleToPath = ns.stream()
+                           .collect(toMap(Function.identity(), this::moduleToPath));
+                       hashes.put(mn, ModuleHashes.generate(moduleToPath, "SHA-256"));
+                   }
+               });
+        return hashes;
+    }
+
+    private Path moduleToPath(String name) {
+        ResolvedModule rm = configuration.findModule(name).orElseThrow(
+            () -> new InternalError("Selected module " + name + " not on module path"));
+
+        URI uri = rm.reference().location().get();
+        Path path = Paths.get(uri);
+        String fn = path.getFileName().toString();
+        if (!fn.endsWith(".jar") && !fn.endsWith(".jmod")) {
+            throw new UnsupportedOperationException(path + " is not a modular JAR or jmod file");
+        }
+        return path;
+    }
+
+    /*
+     * Utilty class
+     */
+    static class Graph<T> {
+        private final Set<T> nodes;
+        private final Map<T, Set<T>> edges;
+
+        public Graph(Set<T> nodes, Map<T, Set<T>> edges) {
+            this.nodes = Collections.unmodifiableSet(nodes);
+            this.edges = Collections.unmodifiableMap(edges);
+        }
+
+        public Set<T> nodes() {
+            return nodes;
+        }
+
+        public Map<T, Set<T>> edges() {
+            return edges;
+        }
+
+        public Set<T> adjacentNodes(T u) {
+            return edges.get(u);
+        }
+
+        public boolean contains(T u) {
+            return nodes.contains(u);
+        }
+
+        /**
+         * Returns nodes sorted in topological order.
+         */
+        public Stream<T> orderedNodes() {
+            TopoSorter<T> sorter = new TopoSorter<>(this);
+            return sorter.result.stream();
+        }
+
+        /**
+         * Traverse this graph and performs the given action in topological order
+         */
+        public void ordered(Consumer<T> action) {
+            TopoSorter<T> sorter = new TopoSorter<>(this);
+            sorter.ordered(action);
+        }
+
+        /**
+         * Traverses this graph and performs the given action in reverse topological order
+         */
+        public void reverse(Consumer<T> action) {
+            TopoSorter<T> sorter = new TopoSorter<>(this);
+            sorter.reverse(action);
+        }
+
+        /**
+         * Returns a transposed graph from this graph
+         */
+        public Graph<T> transpose() {
+            Builder<T> builder = new Builder<>();
+            nodes.stream().forEach(builder::addNode);
+            // reverse edges
+            edges.keySet().forEach(u -> {
+                edges.get(u).stream()
+                    .forEach(v -> builder.addEdge(v, u));
+            });
+            return builder.build();
+        }
+
+        /**
+         * Returns all nodes reachable from the given root.
+         */
+        public Set<T> dfs(T root) {
+            return dfs(Set.of(root));
+        }
+
+        /**
+         * Returns all nodes reachable from the given set of roots.
+         */
+        public Set<T> dfs(Set<T> roots) {
+            Deque<T> deque = new LinkedList<>(roots);
+            Set<T> visited = new HashSet<>();
+            while (!deque.isEmpty()) {
+                T u = deque.pop();
+                if (!visited.contains(u)) {
+                    visited.add(u);
+                    if (contains(u)) {
+                        adjacentNodes(u).stream()
+                            .filter(v -> !visited.contains(v))
+                            .forEach(deque::push);
+                    }
+                }
+            }
+            return visited;
+        }
+
+        public void printGraph(PrintStream out) {
+            out.println("graph for " + nodes);
+            nodes.stream()
+                .forEach(u -> adjacentNodes(u).stream()
+                    .forEach(v -> out.format("  %s -> %s%n", u, v)));
+        }
+
+        static class Builder<T> {
+            final Set<T> nodes = new HashSet<>();
+            final Map<T, Set<T>> edges = new HashMap<>();
+
+            public void addNode(T node) {
+                if (nodes.contains(node)) {
+                    return;
+                }
+                nodes.add(node);
+                edges.computeIfAbsent(node, _e -> new HashSet<>());
+            }
+
+            public void addEdge(T u, T v) {
+                addNode(u);
+                addNode(v);
+                edges.get(u).add(v);
+            }
+
+            public Graph<T> build() {
+                return new Graph<T>(nodes, edges);
+            }
+        }
+    }
+
+    /**
+     * Topological sort
+     */
+    private static class TopoSorter<T> {
+        final Deque<T> result = new LinkedList<>();
+        final Deque<T> nodes;
+        final Graph<T> graph;
+
+        TopoSorter(Graph<T> graph) {
+            this.graph = graph;
+            this.nodes = new LinkedList<>(graph.nodes);
+            sort();
+        }
+
+        public void ordered(Consumer<T> action) {
+            result.iterator().forEachRemaining(action);
+        }
+
+        public void reverse(Consumer<T> action) {
+            result.descendingIterator().forEachRemaining(action);
+        }
+
+        private void sort() {
+            Deque<T> visited = new LinkedList<>();
+            Deque<T> done = new LinkedList<>();
+            T node;
+            while ((node = nodes.poll()) != null) {
+                if (!visited.contains(node)) {
+                    visit(node, visited, done);
+                }
+            }
+        }
+
+        private void visit(T node, Deque<T> visited, Deque<T> done) {
+            if (visited.contains(node)) {
+                if (!done.contains(node)) {
+                    throw new IllegalArgumentException("Cyclic detected: " +
+                        node + " " + graph.edges().get(node));
+                }
+                return;
+            }
+            visited.add(node);
+            graph.edges().get(node).stream()
+                .forEach(x -> visit(x, visited, done));
+            done.add(node);
+            result.addLast(node);
+        }
+    }
+}