Add preliminary support of digest in library.

- Add a MessageDigestOutputVFS, a VFS filter which add digest to a file
- Add a MessageDigestIntputVFS, a VFS filter which read digest from file
- Add a getDigest() method in InputLibrary and implementations

Change-Id: I3315011b8c1fd5d455ddb71f90c267078ed3462b

8 files changed, 417 insertions, 125 deletions

diff --git a/jack/src/com/android/jack/library/InputLibrary.java b/jack/src/com/android/jack/library/InputLibrary.java
index efd2ef62..a52a303b 100644
--- a/jack/src/com/android/jack/library/InputLibrary.java
+++ b/jack/src/com/android/jack/library/InputLibrary.java
@@ -24,6 +24,7 @@ import com.android.sched.vfs.VPath;
 import java.util.Collection;
 import java.util.Iterator;
 
+import javax.annotation.CheckForNull;
 import javax.annotation.Nonnull;
 
 /**
@@ -51,6 +52,9 @@ public interface InputLibrary extends Library {
   @Nonnull
   public InputLibraryLocation getLocation();
 
+  @CheckForNull
+  public String getDigest();
+
   @Nonnull
   public void delete(@Nonnull FileType fileType, @Nonnull VPath typePath)
       throws CannotDeleteFileException;
diff --git a/jack/src/com/android/jack/library/JackLibraryFactory.java b/jack/src/com/android/jack/library/JackLibraryFactory.java
index 824862c3..91d7befb 100644
--- a/jack/src/com/android/jack/library/JackLibraryFactory.java
+++ b/jack/src/com/android/jack/library/JackLibraryFactory.java
@@ -18,14 +18,12 @@ package com.android.jack.library;
 
 import com.android.jack.library.v0001.OutputJackLibraryImpl;
 import com.android.sched.util.config.HasKeyId;
-import com.android.sched.util.config.ThreadConfig;
 import com.android.sched.util.config.id.BooleanPropertyId;
 import com.android.sched.util.config.id.MessageDigestPropertyId;
 import com.android.sched.util.log.LoggerFactory;
 import com.android.sched.vfs.InputOutputVFS;
 import com.android.sched.vfs.InputVFS;
 import com.android.sched.vfs.InputVFile;
-import com.android.sched.vfs.MessageDigestInputOutputVFS;
 
 import java.io.IOException;
 import java.lang.reflect.Constructor;
@@ -43,11 +41,11 @@ import javax.annotation.Nonnull;
 @HasKeyId
 public abstract class JackLibraryFactory {
   @Nonnull
-  private static final BooleanPropertyId GENERATE_JACKLIB_DIGEST = BooleanPropertyId.create(
+  public static final BooleanPropertyId GENERATE_JACKLIB_DIGEST = BooleanPropertyId.create(
       "jack.library.digest", "Generate message digest in Jack library").addDefaultValue(
       Boolean.TRUE);
   @Nonnull
-  private static final MessageDigestPropertyId MESSAGE_DIGEST_ALGO = MessageDigestPropertyId
+  public static final MessageDigestPropertyId MESSAGE_DIGEST_ALGO = MessageDigestPropertyId
       .create("jack.library.digest.algo", "Message digest algorithm use in Jack library")
       .requiredIf(GENERATE_JACKLIB_DIGEST.getValue().isTrue()).addDefaultValue("SHA");
 
@@ -81,9 +79,6 @@ public abstract class JackLibraryFactory {
   @Nonnull
   public static OutputJackLibrary getOutputLibrary(@Nonnull InputOutputVFS vfs,
       @Nonnull String emitterId, @Nonnull String emitterVersion) {
-    if (ThreadConfig.get(GENERATE_JACKLIB_DIGEST).booleanValue()) {
-      vfs = new MessageDigestInputOutputVFS(vfs, ThreadConfig.get(MESSAGE_DIGEST_ALGO));
-    }
     return new OutputJackLibraryImpl(vfs, emitterId, emitterVersion);
   }
 
diff --git a/jack/src/com/android/jack/library/v0000/InputJackLibraryImpl.java b/jack/src/com/android/jack/library/v0000/InputJackLibraryImpl.java
index b8240a4c..4db3adc1 100644
--- a/jack/src/com/android/jack/library/v0000/InputJackLibraryImpl.java
+++ b/jack/src/com/android/jack/library/v0000/InputJackLibraryImpl.java
@@ -43,6 +43,7 @@ import java.util.Properties;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
+import javax.annotation.CheckForNull;
 import javax.annotation.Nonnegative;
 import javax.annotation.Nonnull;
 
@@ -193,4 +194,10 @@ public class InputJackLibraryImpl extends InputJackLibrary {
   public String getPath() {
     return vfs.getPath();
   }
+
+  @Override
+  @CheckForNull
+  public String getDigest() {
+    return null;
+  }
 }
diff --git a/jack/src/com/android/jack/library/v0001/InputJackLibraryImpl.java b/jack/src/com/android/jack/library/v0001/InputJackLibraryImpl.java
index e0402b94..d648c176 100644
--- a/jack/src/com/android/jack/library/v0001/InputJackLibraryImpl.java
+++ b/jack/src/com/android/jack/library/v0001/InputJackLibraryImpl.java
@@ -33,6 +33,7 @@ import com.android.sched.util.log.LoggerFactory;
 import com.android.sched.vfs.InputVDir;
 import com.android.sched.vfs.InputVFS;
 import com.android.sched.vfs.InputVFile;
+import com.android.sched.vfs.MessageDigestInputVFS;
 import com.android.sched.vfs.VPath;
 
 import java.io.IOException;
@@ -43,6 +44,7 @@ import java.util.Properties;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
+import javax.annotation.CheckForNull;
 import javax.annotation.Nonnegative;
 import javax.annotation.Nonnull;
 
@@ -54,7 +56,7 @@ public class InputJackLibraryImpl extends InputJackLibrary {
   private static Logger logger = LoggerFactory.getLogger();
 
   @Nonnull
-  private final InputVFS vfs;
+  private final MessageDigestInputVFS vfs;
   @Nonnegative
   private final int minorVersion;
 
@@ -84,11 +86,11 @@ public class InputJackLibraryImpl extends InputJackLibrary {
     }
   };
 
-  public InputJackLibraryImpl(@Nonnull InputVFS libraryVDir,
+  public InputJackLibraryImpl(@Nonnull InputVFS vfs,
       @Nonnull Properties libraryProperties) throws LibraryVersionException,
       LibraryFormatException {
     super(libraryProperties);
-    this.vfs = libraryVDir;
+    this.vfs = new MessageDigestInputVFS(vfs);
 
     try {
       minorVersion = Integer.parseInt(getProperty(KEY_LIB_MINOR_VERSION));
@@ -201,4 +203,10 @@ public class InputJackLibraryImpl extends InputJackLibrary {
   public String getPath() {
     return vfs.getPath();
   }
+
+  @Override
+  @CheckForNull
+  public String getDigest() {
+    return vfs.getDigest();
+  }
 }
diff --git a/jack/src/com/android/jack/library/v0001/OutputJackLibraryImpl.java b/jack/src/com/android/jack/library/v0001/OutputJackLibraryImpl.java
index e9fd999e..bf340738 100644
--- a/jack/src/com/android/jack/library/v0001/OutputJackLibraryImpl.java
+++ b/jack/src/com/android/jack/library/v0001/OutputJackLibraryImpl.java
@@ -18,16 +18,21 @@ package com.android.jack.library.v0001;
 
 import com.android.jack.library.FileType;
 import com.android.jack.library.FileTypeDoesNotExistException;
+import com.android.jack.library.JackLibraryFactory;
 import com.android.jack.library.LibraryIOException;
 import com.android.jack.library.OutputJackLibrary;
 import com.android.jack.library.OutputLibrary;
 import com.android.jack.library.OutputLibraryLocation;
+import com.android.sched.util.config.ThreadConfig;
 import com.android.sched.util.file.CannotCreateFileException;
 import com.android.sched.util.file.CannotDeleteFileException;
 import com.android.sched.util.file.NoSuchFileException;
 import com.android.sched.util.file.NotFileOrDirectoryException;
 import com.android.sched.vfs.InputOutputVFS;
+import com.android.sched.vfs.InputVFS;
 import com.android.sched.vfs.InputVFile;
+import com.android.sched.vfs.MessageDigestOutputVFS;
+import com.android.sched.vfs.OutputVFS;
 import com.android.sched.vfs.OutputVFile;
 import com.android.sched.vfs.SequentialOutputVFS;
 import com.android.sched.vfs.VPath;
@@ -49,14 +54,16 @@ public class OutputJackLibraryImpl extends OutputJackLibrary {
   private boolean closed = false;
 
   @Nonnull
-  private final InputOutputVFS vfs;
+  private final InputVFS iVfs;
+  @Nonnull
+  private final OutputVFS oVfs;
 
   @Nonnull
   private final OutputLibraryLocation location = new OutputLibraryLocation() {
     @Override
     @Nonnull
     public String getDescription() {
-      return vfs.getLocation().getDescription();
+      return oVfs.getLocation().getDescription();
     }
 
     @Override
@@ -77,10 +84,19 @@ public class OutputJackLibraryImpl extends OutputJackLibrary {
     }
   };
 
-  public OutputJackLibraryImpl(@Nonnull InputOutputVFS outputVDir, @Nonnull String emitterId,
+  public OutputJackLibraryImpl(@Nonnull InputOutputVFS vfs, @Nonnull String emitterId,
       @Nonnull String emitterVersion) {
     super(new Properties());
-    this.vfs = outputVDir;
+
+    this.iVfs = vfs;
+
+    if (ThreadConfig.get(JackLibraryFactory.GENERATE_JACKLIB_DIGEST).booleanValue()) {
+      this.oVfs =
+          new MessageDigestOutputVFS(vfs, ThreadConfig.get(JackLibraryFactory.MESSAGE_DIGEST_ALGO));
+    } else {
+      this.oVfs = vfs;
+    }
+
     putProperty(KEY_LIB_EMITTER, emitterId);
     putProperty(KEY_LIB_EMITTER_VERSION, emitterVersion);
     putProperty(KEY_LIB_MAJOR_VERSION, String.valueOf(getMajorVersion()));
@@ -94,12 +110,13 @@ public class OutputJackLibraryImpl extends OutputJackLibrary {
     assert !isClosed();
     putProperty(fileType.buildPropertyName(null /*suffix*/), String.valueOf(true));
     addFileType(fileType);
-    return vfs.getRootInputOutputVDir().createOutputVFile(fileType.buildFileVPath(typePath));
+    return oVfs.getRootOutputVDir().createOutputVFile(fileType.buildFileVPath(typePath));
   }
 
   @Override
   public boolean needsSequentialWriting() {
-    return vfs instanceof SequentialOutputVFS;
+    // XXX Rework
+    return iVfs instanceof SequentialOutputVFS;
   }
 
   @Override
@@ -114,7 +131,7 @@ public class OutputJackLibraryImpl extends OutputJackLibrary {
       OutputStream os = null;
       try {
         OutputVFile libraryPropertiesOut =
-            vfs.getRootInputOutputVDir().createOutputVFile(LIBRARY_PROPERTIES_VPATH);
+            oVfs.getRootOutputVDir().createOutputVFile(LIBRARY_PROPERTIES_VPATH);
         os = libraryPropertiesOut.openWrite();
         libraryProperties.store(os, "Library properties");
       } catch (CannotCreateFileException e) {
@@ -132,7 +149,8 @@ public class OutputJackLibraryImpl extends OutputJackLibrary {
       }
 
       try {
-        vfs.close();
+        oVfs.close();
+        iVfs.close();
       } catch (IOException e) {
         throw new LibraryIOException(getLocation(), e);
       }
@@ -154,7 +172,7 @@ public class OutputJackLibraryImpl extends OutputJackLibrary {
   @Nonnull
   public Iterator<InputVFile> iterator(@Nonnull FileType fileType) {
     List<InputVFile> inputVFiles = new ArrayList<InputVFile>();
-    fillFiles(vfs.getRootInputOutputVDir(), fileType, inputVFiles);
+    fillFiles(iVfs.getRootInputVDir(), fileType, inputVFiles);
     return inputVFiles.listIterator();
   }
 
@@ -163,7 +181,7 @@ public class OutputJackLibraryImpl extends OutputJackLibrary {
   public InputVFile getFile(@Nonnull FileType fileType, @Nonnull VPath typePath)
       throws FileTypeDoesNotExistException {
     try {
-      return vfs.getRootInputOutputVDir().getInputVFile(fileType.buildFileVPath(typePath));
+      return iVfs.getRootInputVDir().getInputVFile(fileType.buildFileVPath(typePath));
     } catch (NotFileOrDirectoryException e) {
       throw new FileTypeDoesNotExistException(getLocation(), typePath, fileType);
     } catch (NoSuchFileException e) {
@@ -176,13 +194,13 @@ public class OutputJackLibraryImpl extends OutputJackLibrary {
   public void delete(@Nonnull FileType fileType, @Nonnull VPath typePath)
       throws CannotDeleteFileException {
     assert !isClosed();
-    vfs.getRootInputOutputVDir().delete(fileType.buildFileVPath(typePath));
+    iVfs.getRootInputVDir().delete(fileType.buildFileVPath(typePath));
   }
 
   @Override
   @Nonnull
   public String getPath() {
-    return vfs.getPath();
+    return oVfs.getPath();
   }
 
   private synchronized boolean isClosed() {
diff --git a/sched/src/com/android/sched/vfs/MessageDigestInputVFS.java b/sched/src/com/android/sched/vfs/MessageDigestInputVFS.java
new file mode 100644
index 00000000..c844629b
--- /dev/null
+++ b/sched/src/com/android/sched/vfs/MessageDigestInputVFS.java
@@ -0,0 +1,250 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.sched.vfs;
+
+import com.android.sched.util.file.CannotDeleteFileException;
+import com.android.sched.util.file.NoSuchFileException;
+import com.android.sched.util.file.NotFileOrDirectoryException;
+import com.android.sched.util.location.Location;
+import com.android.sched.util.log.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
+
+/**
+ * An {@link InputVFS} which read a file with message digest of each file in the VFS.
+ */
+public class MessageDigestInputVFS extends MessageDigestVFS implements InputVFS {
+  @Nonnull
+  private static final Logger logger = LoggerFactory.getLogger();
+
+  @Nonnull
+  protected InputVFS vfs;
+  @Nonnull
+  private final MessageDigestInputVDir root;
+  @Nonnull
+  private final Map<VPath, String> digests = new HashMap<VPath, String>();
+  @CheckForNull
+  private String algorithm = null;
+  @CheckForNull
+  private String digest = null;
+
+  /**
+   * An {@link InputVFile} which have a message digest.
+   */
+  public static class MessageDigestInputVFile implements InputVFile {
+    @Nonnull
+    private final InputVFile file;
+    @CheckForNull
+    private final String digest;
+
+    public MessageDigestInputVFile(@Nonnull InputVFile file, @CheckForNull String digest) {
+      this.file = file;
+      this.digest = digest;
+    }
+
+    @Override
+    public boolean isVDir() {
+      return false;
+    }
+
+    @Override
+    @Nonnull
+    public String getName() {
+      return file.getName();
+    }
+
+    @Override
+    @Nonnull
+    public Location getLocation() {
+      return file.getLocation();
+    }
+
+    @Override
+    @Nonnull
+    public InputStream openRead() throws IOException {
+      return file.openRead();
+    }
+
+    @CheckForNull
+    public String getDigest() {
+      return digest;
+    }
+  }
+
+  /**
+   * An {@link InputVDir} which return {@link MessageDigestInputVFile}.
+   */
+  public class MessageDigestInputVDir implements InputVDir {
+    @Nonnull
+    private final InputVDir dir;
+
+    private MessageDigestInputVDir (@Nonnull InputVDir dir) {
+      this.dir = dir;
+    }
+
+    @Override
+    public boolean isVDir() {
+      return true;
+    }
+
+    @Override
+    @Nonnull
+    public String getName() {
+      return dir.getName();
+    }
+
+    @Override
+    @Nonnull
+    public Location getLocation() {
+      return dir.getLocation();
+    }
+
+    @Override
+    @Nonnull
+    public Collection<? extends InputVElement> list() {
+      return dir.list();
+    }
+
+    @Override
+    @Nonnull
+    public MessageDigestInputVDir getInputVDir(@Nonnull VPath path)
+        throws NotFileOrDirectoryException, NoSuchFileException {
+      return new MessageDigestInputVDir(dir.getInputVDir(path));
+    }
+
+    @Override
+    @Nonnull
+    public MessageDigestInputVFile getInputVFile(@Nonnull VPath path)
+        throws NotFileOrDirectoryException, NoSuchFileException {
+      // XXX Add relative VPath support
+      return new MessageDigestInputVFile(dir.getInputVFile(path), digests.get(path));
+    }
+
+    @Override
+    @Nonnull
+    public void delete(@Nonnull VPath path) throws CannotDeleteFileException {
+      dir.delete(path);
+    }
+  }
+
+  public MessageDigestInputVFS(@Nonnull InputVFS vfs) {
+    this.root = new MessageDigestInputVDir(vfs.getRootInputVDir());
+    this.vfs  = vfs;
+
+    // Reading digest directory is best effort
+    // If there is one error, let's skip that step
+    BufferedReader in = null;
+    InputVFile     file = null;
+    try {
+      try {
+        file = root.getInputVFile(new VPath(DIGEST_DIRECTORY_NAME, '/'));
+      } catch (NotFileOrDirectoryException e) {
+        logger.log(Level.WARNING, "Cannot open '" + DIGEST_DIRECTORY_NAME + "' file in {0}", vfs
+            .getLocation().getDescription());
+        logger.log(Level.WARNING, "Stacktrace", e);
+        return;
+      } catch (NoSuchFileException e) {
+        logger.log(Level.WARNING, "Cannot open '" + DIGEST_DIRECTORY_NAME + "' file in {0}", vfs
+            .getLocation().getDescription());
+        logger.log(Level.WARNING, "Stacktrace", e);
+        return;
+      }
+
+      try {
+        in = new BufferedReader(new InputStreamReader(file.openRead()));
+      } catch (IOException e) {
+        logger.log(Level.WARNING, "Cannot open {0}", file.getLocation().getDescription());
+        logger.log(Level.WARNING, "Stacktrace", e);
+        return;
+      }
+
+      try {
+        algorithm = in.readLine();
+
+        String line;
+        while ((line = in.readLine()) != null) {
+          int index = line.indexOf(':');
+          if (index < 1) {
+            logger.log(Level.WARNING, "Bad format in {0}", file.getLocation().getDescription());
+            continue;
+          }
+
+          digests.put(new VPath(line.substring(index + 1), '/'), line.substring(0, index));
+        }
+      } catch (IOException e) {
+        logger.log(Level.WARNING, "Error reading {0}", file.getLocation().getDescription());
+        return;
+      }
+
+      digest = digests.get(new VPath(MessageDigestOutputVFS.DIGEST_DIRECTORY_NAME, '/'));
+    } finally {
+      if (in != null) {
+        assert file != null;
+
+        try {
+          in.close();
+        } catch (IOException e) {
+          logger.log(Level.WARNING, "Cannot close {0}", file.getLocation().getDescription());
+        }
+      }
+    }
+  }
+
+  @Override
+  @Nonnull
+  public Location getLocation() {
+    return vfs.getLocation();
+  }
+
+  @Override
+  public synchronized void close() throws IOException {
+    vfs.close();
+  }
+
+  @Override
+  @Nonnull
+  public MessageDigestInputVDir getRootInputVDir() {
+    return root;
+  }
+
+  @Override
+  @Nonnull
+  public String getPath() {
+    return vfs.getPath();
+  }
+
+  @CheckForNull
+  public String getDigestAlgorithm() {
+    return algorithm;
+  }
+
+  @CheckForNull
+  public String getDigest() {
+    return digest;
+  }
+}
diff --git a/sched/src/com/android/sched/vfs/MessageDigestInputOutputVFS.java b/sched/src/com/android/sched/vfs/MessageDigestOutputVFS.java
index eb64b963..7d5aa3d2 100644
--- a/sched/src/com/android/sched/vfs/MessageDigestInputOutputVFS.java
+++ b/sched/src/com/android/sched/vfs/MessageDigestOutputVFS.java
@@ -16,11 +16,9 @@
 
 package com.android.sched.vfs;
 
+import com.android.sched.util.collect.Lists;
 import com.android.sched.util.config.MessageDigestFactory;
 import com.android.sched.util.file.CannotCreateFileException;
-import com.android.sched.util.file.CannotDeleteFileException;
-import com.android.sched.util.file.NoSuchFileException;
-import com.android.sched.util.file.NotFileOrDirectoryException;
 import com.android.sched.util.location.Location;
 
 import java.io.IOException;
@@ -28,31 +26,33 @@ import java.io.OutputStream;
 import java.io.PrintStream;
 import java.security.DigestOutputStream;
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.List;
 
 import javax.annotation.CheckForNull;
 import javax.annotation.Nonnull;
 
 /**
- * An {@link InputOutputVFS} which generated a file with message digest of each file in a VFS.
+ * An {@link OutputVFS} which generates a file with message digest of each file in a VFS.
  */
-public class MessageDigestInputOutputVFS implements InputOutputVFS {
+public class MessageDigestOutputVFS extends MessageDigestVFS implements OutputVFS {
   private boolean closed = false;
   @Nonnull
   protected OutputVFS vfs;
   @Nonnull
-  private final MessageDigestInputOutputVDir root;
+  private final MessageDigestOutputVDir root;
   @Nonnull
   private final MessageDigestFactory mdFactory;
+  @Nonnull
+  private final List<MessageDigestOutputVFile> files = new ArrayList<MessageDigestOutputVFile>();
 
-  private class MessageDigestOutputVFile implements OutputVFile {
+  private class MessageDigestOutputVFile implements OutputVFile,
+      Comparable<MessageDigestOutputVFile> {
     @Nonnull
     private final OutputVFile file;
     @Nonnull
     private final VPath path;
     @CheckForNull
-    private byte[] digest;
+    private String digest = null;
 
     protected MessageDigestOutputVFile(@Nonnull OutputVFile file, @Nonnull VPath path) {
       this.file = file;
@@ -82,17 +82,18 @@ public class MessageDigestInputOutputVFS implements InputOutputVFS {
       assert !isClosed();
 
       return new DigestOutputStream(file.openWrite(),
-          MessageDigestInputOutputVFS.this.mdFactory.create()) {
+          MessageDigestOutputVFS.this.mdFactory.create()) {
         @Override
         public void close() throws IOException {
           super.close();
-          MessageDigestOutputVFile.this.digest = getMessageDigest().digest();
+          MessageDigestOutputVFile.this.digest =
+              new String(encode(getMessageDigest().digest()));
         }
       };
     }
 
     @CheckForNull
-    public byte[] getDigest() {
+    public String getDigest() {
       return digest;
     }
 
@@ -100,15 +101,33 @@ public class MessageDigestInputOutputVFS implements InputOutputVFS {
     public VPath getVPath() {
       return path;
     }
+
+    @Override
+    public int compareTo(MessageDigestOutputVFile other) {
+      return path.getPathAsString('/').compareTo(other.getVPath().getPathAsString('/'));
+    }
+
+    @Override
+    public final boolean equals(Object obj) {
+      if (!(obj instanceof MessageDigestOutputVFile)) {
+        return false;
+      }
+
+      return path.getPathAsString('/').equals(
+          ((MessageDigestOutputVFile) obj).getVPath().getPathAsString('/'));
+    }
+
+    @Override
+    public final int hashCode() {
+      return path.getPathAsString('.').hashCode();
+    }
   }
 
-  private class MessageDigestInputOutputVDir implements InputOutputVDir {
-    @Nonnull
-    private final InputOutputVDir dir;
+  private class MessageDigestOutputVDir implements OutputVDir {
     @Nonnull
-    private final List<MessageDigestOutputVFile> files = new ArrayList<MessageDigestOutputVFile>();
+    private final OutputVDir dir;
 
-    protected MessageDigestInputOutputVDir (@Nonnull InputOutputVDir dir) {
+    protected MessageDigestOutputVDir (@Nonnull OutputVDir dir) {
       this.dir = dir;
     }
 
@@ -131,72 +150,21 @@ public class MessageDigestInputOutputVFS implements InputOutputVFS {
 
     @Override
     @Nonnull
-    public synchronized OutputVFile createOutputVFile(@Nonnull VPath path)
+    public synchronized MessageDigestOutputVFile createOutputVFile(@Nonnull VPath path)
         throws CannotCreateFileException {
       assert !isClosed();
 
       MessageDigestOutputVFile file =
           new MessageDigestOutputVFile(dir.createOutputVFile(path), path);
-      files.add(file);
+      addFile(file);
 
       return file;
     }
-
-    private synchronized void close() throws CannotCreateFileException, IOException {
-      OutputStream os = dir.createOutputVFile(new VPath("jack.sha1", '/')).openWrite();
-      PrintStream printer = new PrintStream(os);
-
-      for (MessageDigestOutputVFile file : files) {
-        byte[] digest = file.getDigest();
-        if (digest != null) {
-          printer.print(file.getVPath().getPathAsString('/'));
-          printer.print(':');
-          printer.print(encode(digest));
-          printer.println();
-        }
-      }
-
-      printer.close();
-    }
-
-    @Override
-    @Nonnull
-    public Collection<? extends InputVElement> list() {
-      assert !isClosed();
-
-      return dir.list();
-    }
-
-    @Override
-    @Nonnull
-    public InputVDir getInputVDir(@Nonnull VPath path) throws NotFileOrDirectoryException,
-        NoSuchFileException {
-      assert !isClosed();
-
-      return dir.getInputVDir(path);
-    }
-
-    @Override
-    @Nonnull
-    public InputVFile getInputVFile(@Nonnull VPath path) throws NotFileOrDirectoryException,
-        NoSuchFileException {
-      assert !isClosed();
-
-      return dir.getInputVFile(path);
-    }
-
-    @Override
-    @Nonnull
-    public void delete(@Nonnull VPath path) throws CannotDeleteFileException {
-      assert !isClosed();
-
-      dir.delete(path);
-    }
   }
 
-  public MessageDigestInputOutputVFS(@Nonnull InputOutputVFS vfs,
+  public MessageDigestOutputVFS(@Nonnull OutputVFS vfs,
       @Nonnull MessageDigestFactory mdFactory) {
-    this.root = new MessageDigestInputOutputVDir(vfs.getRootInputOutputVDir());
+    this.root = new MessageDigestOutputVDir(vfs.getRootOutputVDir());
     this.vfs = vfs;
     this.mdFactory = mdFactory;
   }
@@ -210,35 +178,46 @@ public class MessageDigestInputOutputVFS implements InputOutputVFS {
   @Override
   public synchronized void close() throws IOException {
     if (!closed) {
-      root.close();
+      List<MessageDigestOutputVFile> sortedFiles = Lists.<MessageDigestOutputVFile> sort(files);
+
+      DigestOutputStream os =
+          new DigestOutputStream(root.createOutputVFile(new VPath(DIGEST_DIRECTORY_NAME, '/'))
+              .openWrite(), MessageDigestOutputVFS.this.mdFactory.create());
+      PrintStream printer = new PrintStream(os);
+
+      printer.println(mdFactory.getService().getAlgorithm());
+
+      for (MessageDigestOutputVFile file : sortedFiles) {
+        String digest = file.getDigest();
+        if (digest != null) {
+          printer.print(digest);
+          printer.print(':');
+          printer.print(file.getVPath().getPathAsString('/'));
+          printer.println();
+        }
+      }
+
+      printer.flush();
+
+      String digest = new String(encode(os.getMessageDigest().digest()));
+      printer.print(digest);
+      printer.print(':' + DIGEST_DIRECTORY_NAME);
+      printer.println();
+
+      printer.close();
+
       vfs.close();
       closed = true;
     }
   }
 
-  synchronized boolean isClosed() {
+  private synchronized boolean isClosed() {
     return closed;
   }
 
   @Override
   @Nonnull
-  public OutputVDir getRootOutputVDir() {
-    assert !isClosed();
-
-    return root;
-  }
-
-  @Override
-  @Nonnull
-  public InputVDir getRootInputVDir() {
-    assert !isClosed();
-
-    return root;
-  }
-
-  @Override
-  @Nonnull
-  public InputOutputVDir getRootInputOutputVDir() {
+  public MessageDigestOutputVDir getRootOutputVDir() {
     assert !isClosed();
 
     return root;
@@ -250,17 +229,7 @@ public class MessageDigestInputOutputVFS implements InputOutputVFS {
     return vfs.getPath();
   }
 
-  @Nonnull
-  private static final byte[] code = "0123456789ABCDEF".getBytes();
-  @Nonnull
-  private static char[] encode(@Nonnull byte[] bytes) {
-    char[] array = new char[bytes.length * 2];
-
-    for (int idx = 0; idx < bytes.length; idx++) {
-      array[(idx << 1)    ] = (char) code[(bytes[idx] & 0xF0) >> 4];
-      array[(idx << 1) + 1] = (char) code[(bytes[idx] & 0x0F)     ];
-    }
-
-    return array;
+  private synchronized void addFile(@Nonnull MessageDigestOutputVFile file) {
+    files.add(file);
   }
 }
diff --git a/sched/src/com/android/sched/vfs/MessageDigestVFS.java b/sched/src/com/android/sched/vfs/MessageDigestVFS.java
new file mode 100644
index 00000000..eb8458fe
--- /dev/null
+++ b/sched/src/com/android/sched/vfs/MessageDigestVFS.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.sched.vfs;
+
+import javax.annotation.Nonnull;
+
+
+/**
+ * Abstract base class for message digest VFS.
+ */
+abstract class MessageDigestVFS {
+  static final String DIGEST_DIRECTORY_NAME = ".digest";
+
+  @Nonnull
+  private static final byte[] code = "0123456789ABCDEF".getBytes();
+  @Nonnull
+  static char[] encode(@Nonnull byte[] bytes) {
+    char[] array = new char[bytes.length * 2];
+
+    for (int idx = 0; idx < bytes.length; idx++) {
+      array[(idx << 1)    ] = (char) code[(bytes[idx] & 0xF0) >> 4];
+      array[(idx << 1) + 1] = (char) code[(bytes[idx] & 0x0F)     ];
+    }
+
+    return array;
+  }
+}