Make CachedContent store content length in ContentMetadata

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188742379

library/core/src/androidTest/java/com/google/android/exoplayer2/upstream/cache/CachedContentIndexTest.java

@@ -14,9 +14,7 @@ import java.io.IOException;
 import java.util.Collection;
 import java.util.Set;
 
-/**
+/** Tests {@link CachedContentIndex}. */
- * Tests {@link CachedContentIndex}.
- */
 public class CachedContentIndexTest extends InstrumentationTestCase {
 
   private final byte[] testIndexV1File = {
@@ -53,14 +51,14 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
     final String key3 = "key3";
 
     // Add two CachedContents with add methods
-    CachedContent cachedContent1 = new CachedContent(5, key1, 10);
+    CachedContent cachedContent1 = new CachedContent(5, key1);
     index.addNew(cachedContent1);
     CachedContent cachedContent2 = index.getOrAdd(key2);
     assertThat(cachedContent1.id != cachedContent2.id).isTrue();
 
     // add a span
-    File cacheSpanFile = SimpleCacheSpanTest
+    File cacheSpanFile =
-        .createCacheSpanFile(cacheDir, cachedContent1.id, 10, 20, 30);
+        SimpleCacheSpanTest.createCacheSpanFile(cacheDir, cachedContent1.id, 10, 20, 30);
     SimpleCacheSpan span = SimpleCacheSpan.createCacheEntry(cacheSpanFile, index);
     assertThat(span).isNotNull();
     cachedContent1.addSpan(span);
@@ -115,8 +113,12 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
   }
 
   public void testStoreV1() throws Exception {
-    index.addNew(new CachedContent(2, "KLMNO", 2560));
+    CachedContent cachedContent1 = new CachedContent(2, "KLMNO");
-    index.addNew(new CachedContent(5, "ABCDE", 10));
+    cachedContent1.setLength(2560);
+    index.addNew(cachedContent1);
+    CachedContent cachedContent2 = new CachedContent(5, "ABCDE");
+    cachedContent2.setLength(10);
+    index.addNew(cachedContent2);
 
     index.store();
 
@@ -165,8 +167,8 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
     byte[] key = "Bar12345Bar12345".getBytes(C.UTF8_NAME); // 128 bit key
     byte[] key2 = "Foo12345Foo12345".getBytes(C.UTF8_NAME); // 128 bit key
 
-    assertStoredAndLoadedEqual(new CachedContentIndex(cacheDir, key),
+    assertStoredAndLoadedEqual(
-        new CachedContentIndex(cacheDir, key));
+        new CachedContentIndex(cacheDir, key), new CachedContentIndex(cacheDir, key));
 
     // Rename the index file from the test above
     File file1 = new File(cacheDir, CachedContentIndex.FILE_NAME);
@@ -174,8 +176,8 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
     assertThat(file1.renameTo(file2)).isTrue();
 
     // Write a new index file
-    assertStoredAndLoadedEqual(new CachedContentIndex(cacheDir, key),
+    assertStoredAndLoadedEqual(
-        new CachedContentIndex(cacheDir, key));
+        new CachedContentIndex(cacheDir, key), new CachedContentIndex(cacheDir, key));
 
     assertThat(file1.length()).isEqualTo(file2.length());
     // Assert file content is different
@@ -187,8 +189,8 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
 
     boolean threw = false;
     try {
-      assertStoredAndLoadedEqual(new CachedContentIndex(cacheDir, key),
+      assertStoredAndLoadedEqual(
-          new CachedContentIndex(cacheDir, key2));
+          new CachedContentIndex(cacheDir, key), new CachedContentIndex(cacheDir, key2));
     } catch (AssertionError e) {
       threw = true;
     }
@@ -197,8 +199,8 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
         .isTrue();
 
     try {
-      assertStoredAndLoadedEqual(new CachedContentIndex(cacheDir, key),
+      assertStoredAndLoadedEqual(
-          new CachedContentIndex(cacheDir));
+          new CachedContentIndex(cacheDir, key), new CachedContentIndex(cacheDir));
     } catch (AssertionError e) {
       threw = true;
     }
@@ -207,18 +209,18 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
         .isTrue();
 
     // Non encrypted index file can be read even when encryption key provided.
-    assertStoredAndLoadedEqual(new CachedContentIndex(cacheDir),
+    assertStoredAndLoadedEqual(
-        new CachedContentIndex(cacheDir, key));
+        new CachedContentIndex(cacheDir), new CachedContentIndex(cacheDir, key));
 
     // Test multiple store() calls
     CachedContentIndex index = new CachedContentIndex(cacheDir, key);
-    index.addNew(new CachedContent(15, "key3", 110));
+    index.addNew(new CachedContent(15, "key3"));
     index.store();
     assertStoredAndLoadedEqual(index, new CachedContentIndex(cacheDir, key));
   }
 
   public void testRemoveEmptyNotLockedCachedContent() throws Exception {
-    CachedContent cachedContent = new CachedContent(5, "key1", 10);
+    CachedContent cachedContent = new CachedContent(5, "key1");
     index.addNew(cachedContent);
 
     index.maybeRemove(cachedContent.key);
@@ -227,7 +229,7 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
   }
 
   public void testCantRemoveNotEmptyCachedContent() throws Exception {
-    CachedContent cachedContent = new CachedContent(5, "key1", 10);
+    CachedContent cachedContent = new CachedContent(5, "key1");
     index.addNew(cachedContent);
     File cacheSpanFile =
         SimpleCacheSpanTest.createCacheSpanFile(cacheDir, cachedContent.id, 10, 20, 30);
@@ -240,7 +242,7 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
   }
 
   public void testCantRemoveLockedCachedContent() throws Exception {
-    CachedContent cachedContent = new CachedContent(5, "key1", 10);
+    CachedContent cachedContent = new CachedContent(5, "key1");
     cachedContent.setLocked(true);
     index.addNew(cachedContent);
 
@@ -251,7 +253,7 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
 
   private void assertStoredAndLoadedEqual(CachedContentIndex index, CachedContentIndex index2)
       throws IOException {
-    index.addNew(new CachedContent(5, "key1", 10));
+    index.addNew(new CachedContent(5, "key1"));
     index.getOrAdd("key2");
     index.store();
 
@@ -264,5 +266,4 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
       assertThat(index2.get(key).getSpans()).isEqualTo(index.get(key).getSpans());
     }
   }
-
 }

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedContent.java

@@ -28,14 +28,16 @@ import java.util.TreeSet;
  */
 /*package*/ final class CachedContent {
 
+  private static final String EXOPLAYER_METADATA_NAME_PREFIX = "exo_";
+  private static final String METADATA_NAME_LENGTH = EXOPLAYER_METADATA_NAME_PREFIX + "len";
   /** The cache file id that uniquely identifies the original stream. */
   public final int id;
   /** The cache key that uniquely identifies the original stream. */
   public final String key;
   /** The cached spans of this content. */
   private final TreeSet<SimpleCacheSpan> cachedSpans;
-  /** The length of the original stream, or {@link C#LENGTH_UNSET} if the length is unknown. */
+  /** Metadata values. */
-  private long length;
+  private DefaultContentMetadata metadata;
   /** Whether the content is locked. */
   private boolean locked;
 
@@ -45,8 +47,13 @@ import java.util.TreeSet;
    * @param input Input stream containing values needed to initialize CachedContent instance.
    * @throws IOException If an error occurs during reading values.
    */
-  public CachedContent(DataInputStream input) throws IOException {
+  public static CachedContent readFromStream(DataInputStream input) throws IOException {
-    this(input.readInt(), input.readUTF(), input.readLong());
+    int id = input.readInt();
+    String key = input.readUTF();
+    long length = input.readLong();
+    CachedContent cachedContent = new CachedContent(id, key);
+    cachedContent.setLength(length);
+    return cachedContent;
   }
 
   /**
@@ -54,12 +61,11 @@ import java.util.TreeSet;
    *
    * @param id The cache file id.
    * @param key The cache stream key.
-   * @param length The length of the original stream.
    */
-  public CachedContent(int id, String key, long length) {
+  public CachedContent(int id, String key) {
     this.id = id;
     this.key = key;
-    this.length = length;
+    this.metadata = new DefaultContentMetadata();
     this.cachedSpans = new TreeSet<>();
   }
 
@@ -72,17 +78,21 @@ import java.util.TreeSet;
   public void writeToStream(DataOutputStream output) throws IOException {
     output.writeInt(id);
     output.writeUTF(key);
-    output.writeLong(length);
+    output.writeLong(getLength());
   }
 
-  /** Returns the length of the content. */
+  /**
+   * Returns the length of the original stream, or {@link C#LENGTH_UNSET} if the length is unknown.
+   */
   public long getLength() {
-    return length;
+    return metadata.get(METADATA_NAME_LENGTH, C.LENGTH_UNSET);
   }
 
   /** Sets the length of the content. */
   public void setLength(long length) {
-    this.length = length;
+    ContentMetadataMutations mutations =
+        new ContentMetadataMutations().set(METADATA_NAME_LENGTH, length);
+    metadata = new DefaultContentMetadata(metadata, mutations);
   }
 
   /** Returns whether the content is locked. */
@@ -194,6 +204,7 @@ import java.util.TreeSet;
 
   /** Calculates a hash code for the header of this {@code CachedContent}. */
   public int headerHashCode() {
+    long length = getLength();
     int result = id;
     result = 31 * result + key.hashCode();
     result = 31 * result + (int) (length ^ (length >>> 32));

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CachedContentIndex.java

@@ -45,9 +45,7 @@ import javax.crypto.NoSuchPaddingException;
 import javax.crypto.spec.IvParameterSpec;
 import javax.crypto.spec.SecretKeySpec;
 
-/**
+/** Maintains the index of cached content. */
- * This class maintains the index of cached content.
- */
 /*package*/ class CachedContentIndex {
 
   public static final String FILE_NAME = "cached_content_index.exi";
@@ -259,7 +257,7 @@ import javax.crypto.spec.SecretKeySpec;
       int count = input.readInt();
       int hashCode = 0;
       for (int i = 0; i < count; i++) {
-        CachedContent cachedContent = new CachedContent(input);
+        CachedContent cachedContent = CachedContent.readFromStream(input);
         add(cachedContent);
         hashCode += cachedContent.headerHashCode();
       }
@@ -339,7 +337,8 @@ import javax.crypto.spec.SecretKeySpec;
 
   private CachedContent addNew(String key, long length) {
     int id = getNewId(idToKey);
-    CachedContent cachedContent = new CachedContent(id, key, length);
+    CachedContent cachedContent = new CachedContent(id, key);
+    cachedContent.setLength(length);
     addNew(cachedContent);
     return cachedContent;
   }

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadata.java

@@ -15,63 +15,9 @@
  */
 package com.google.android.exoplayer2.upstream.cache;
 
-import com.google.android.exoplayer2.upstream.cache.Cache.CacheException;
-
 /** Interface for accessing cached content metadata which is stored as name, value pairs. */
 public interface ContentMetadata {
 
-  /**
-   * Interface for modifying values in a {@link ContentMetadata} object. The changes you make in an
-   * editor are not copied back to the original {@link ContentMetadata} until you call {@link
-   * #commit()}.
-   */
-  interface Editor {
-    /**
-     * Sets a metadata value, to be committed once {@link #commit()} is called. Passing {@code null}
-     * as {@code value} isn't allowed. {@code value} byte array shouldn't be modified after passed
-     * to this method.
-     *
-     * @param name The name of the metadata value.
-     * @param value The value to be set.
-     * @return This Editor instance, for convenience.
-     */
-    Editor set(String name, byte[] value);
-    /**
-     * Sets a metadata value, to be committed once {@link #commit()} is called. Passing {@code null}
-     * as value isn't allowed.
-     *
-     * @param name The name of the metadata value.
-     * @param value The value to be set.
-     * @return This Editor instance, for convenience.
-     */
-    Editor set(String name, String value);
-    /**
-     * Sets a metadata value, to be committed once {@link #commit()} is called.
-     *
-     * @param name The name of the metadata value.
-     * @param value The value to be set.
-     * @return This Editor instance, for convenience.
-     */
-    Editor set(String name, long value);
-    /**
-     * Sets a metadata value, to be committed once {@link #commit()} is called. Passing {@code null}
-     * as value isn't allowed.
-     *
-     * @param name The name of the metadata value.
-     * @return This Editor instance, for convenience.
-     */
-    Editor remove(String name);
-    /**
-     * Commits changes. It can be called only once.
-     *
-     * @throws CacheException If the commit fails.
-     */
-    void commit() throws CacheException;
-  }
-
-  /** Returns an editor to change metadata values. */
-  Editor edit();
-
   /**
    * Returns a metadata value.
    *

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/ContentMetadataMutations.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2018 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.google.android.exoplayer2.upstream.cache;
+
+import com.google.android.exoplayer2.util.Assertions;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/** Defines multiple mutations on metadata value which are applied atomically. */
+public class ContentMetadataMutations {
+
+  private final Map<String, Object> editedValues;
+  private final List<String> removedValues;
+
+  /** Constructs a DefaultMetadataMutations. */
+  public ContentMetadataMutations() {
+    editedValues = new HashMap<>();
+    removedValues = new ArrayList<>();
+  }
+
+  /**
+   * Adds a mutation to set a metadata value. Passing {@code null} as {@code value} isn't allowed.
+   *
+   * @param name The name of the metadata value.
+   * @param value The value to be set.
+   * @return This Editor instance, for convenience.
+   */
+  public ContentMetadataMutations set(String name, String value) {
+    return checkAndSet(name, value);
+  }
+
+  /**
+   * Adds a mutation to set a metadata value.
+   *
+   * @param name The name of the metadata value.
+   * @param value The value to be set.
+   * @return This Editor instance, for convenience.
+   */
+  public ContentMetadataMutations set(String name, long value) {
+    return checkAndSet(name, value);
+  }
+
+  /**
+   * Adds a mutation to set a metadata value. Passing {@code null} as {@code value} isn't allowed.
+   * {@code value} byte array shouldn't be modified after passed to this method.
+   *
+   * @param name The name of the metadata value.
+   * @param value The value to be set.
+   * @return This Editor instance, for convenience.
+   */
+  public ContentMetadataMutations set(String name, byte[] value) {
+    return checkAndSet(name, value);
+  }
+
+  /**
+   * Adds a mutation to remove a metadata value.
+   *
+   * @param name The name of the metadata value.
+   * @return This Editor instance, for convenience.
+   */
+  public ContentMetadataMutations remove(String name) {
+    removedValues.add(name);
+    editedValues.remove(name);
+    return this;
+  }
+
+  /**
+   * Returns a list of names of metadata values to be removed. The returned array shouldn't be
+   * modified.
+   */
+  public List<String> getRemovedValues() {
+    return removedValues;
+  }
+
+  /**
+   * Returns a map of metadata name, value pairs to be set. The returned map and the values in it
+   * shouldn't be modified.
+   */
+  public Map<String, Object> getEditedValues() {
+    return editedValues;
+  }
+
+  private ContentMetadataMutations checkAndSet(String name, Object value) {
+    editedValues.put(name, Assertions.checkNotNull(value));
+    removedValues.remove(name);
+    return this;
+  }
+}

library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/DefaultContentMetadata.java

@@ -15,59 +15,30 @@
  */
 package com.google.android.exoplayer2.upstream.cache;
 
-import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
-import com.google.android.exoplayer2.upstream.cache.Cache.CacheException;
-import com.google.android.exoplayer2.util.Assertions;
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
-import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 /** Default implementation of {@link ContentMetadata}. Values are stored as byte arrays. */
 public final class DefaultContentMetadata implements ContentMetadata {
 
-  /** Listener for metadata change event. */
-  public interface ChangeListener {
-    /**
-     * Called when any metadata value is changed or removed.
-     *
-     * @param contentMetadata The reporting instance.
-     * @param metadataValues All metadata name, value pairs. It shouldn't be accessed out of this
-     *     method.
-     */
-    void onChange(DefaultContentMetadata contentMetadata, Map<String, byte[]> metadataValues)
-        throws CacheException;
-  }
-
   private final Map<String, byte[]> metadata;
-  @Nullable private ChangeListener changeListener;
 
+  /** Constructs an empty {@link DefaultContentMetadata}. */
   public DefaultContentMetadata() {
     this.metadata = new HashMap<>();
   }
 
   /**
-   * Constructs a {@link DefaultContentMetadata} using name, value pairs data which was passed to
+   * Constructs a {@link DefaultContentMetadata} by copying metadata values from {@code other} and
-   * {@link ChangeListener#onChange(DefaultContentMetadata, Map)}.
+   * applying {@code mutations}.
-   *
-   * @param metadata Initial name, value pairs.
    */
-  public DefaultContentMetadata(Map<String, byte[]> metadata) {
+  public DefaultContentMetadata(DefaultContentMetadata other, ContentMetadataMutations mutations) {
-    this.metadata = new HashMap<>(metadata);
+    this.metadata = new HashMap<>(other.metadata);
-  }
+    applyMutations(mutations);
-
-  /** Sets a {@link ChangeListener}. This method can be called once. */
-  public void setChangeListener(ChangeListener changeListener) {
-    Assertions.checkState(this.changeListener == null);
-    this.changeListener = Assertions.checkNotNull(changeListener);
-  }
-
-  @Override
-  public final Editor edit() {
-    return new EditorImpl();
   }
 
   @Override
@@ -112,60 +83,28 @@ public final class DefaultContentMetadata implements ContentMetadata {
     }
   }
 
-  private void apply(ArrayList<String> removedValues, Map<String, byte[]> editedValues)
+  private void applyMutations(ContentMetadataMutations mutations) {
-      throws CacheException {
+    List<String> removedValues = mutations.getRemovedValues();
-    synchronized (metadata) {
+    for (int i = 0; i < removedValues.size(); i++) {
-      for (int i = 0; i < removedValues.size(); i++) {
+      metadata.remove(removedValues.get(i));
-        metadata.remove(removedValues.get(i));
+    }
-      }
+    Map<String, Object> editedValues = mutations.getEditedValues();
-      metadata.putAll(editedValues);
+    for (String name : editedValues.keySet()) {
-      if (changeListener != null) {
+      Object value = editedValues.get(name);
-        changeListener.onChange(this, Collections.unmodifiableMap(metadata));
+      metadata.put(name, getBytes(value));
-      }
     }
   }
 
-  private class EditorImpl implements Editor {
+  private static byte[] getBytes(Object value) {
-
+    if (value instanceof Long) {
-    private final Map<String, byte[]> editedValues;
+      return ByteBuffer.allocate(8).putLong((Long) value).array();
-    private final ArrayList<String> removedValues;
+    } else if (value instanceof String) {
-
+      return ((String) value).getBytes(Charset.forName(C.UTF8_NAME));
-    private EditorImpl() {
+    } else if (value instanceof byte[]) {
-      editedValues = new HashMap<>();
+      return (byte[]) value;
-      removedValues = new ArrayList<>();
+    } else {
-    }
+      throw new IllegalStateException();
-
-    @Override
-    public Editor set(String name, String value) {
-      set(name, value.getBytes());
-      return this;
-    }
-
-    @Override
-    public Editor set(String name, long value) {
-      set(name, ByteBuffer.allocate(8).putLong(value).array());
-      return this;
-    }
-
-    @Override
-    public Editor set(String name, byte[] value) {
-      editedValues.put(name, Assertions.checkNotNull(value));
-      removedValues.remove(name);
-      return this;
-    }
-
-    @Override
-    public Editor remove(String name) {
-      removedValues.add(name);
-      editedValues.remove(name);
-      return this;
-    }
-
-    @Override
-    public void commit() throws CacheException {
-      apply(removedValues, editedValues);
-      removedValues.clear();
-      editedValues.clear();
     }
   }
+
 }

library/core/src/test/java/com/google/android/exoplayer2/upstream/cache/DefaultContentMetadataTest.java

@@ -17,15 +17,6 @@ package com.google.android.exoplayer2.upstream.cache;
 
 import static com.google.common.truth.Truth.assertThat;
 
-import com.google.android.exoplayer2.C;
-import com.google.android.exoplayer2.upstream.cache.Cache.CacheException;
-import com.google.android.exoplayer2.upstream.cache.ContentMetadata.Editor;
-import com.google.android.exoplayer2.upstream.cache.DefaultContentMetadata.ChangeListener;
-import java.nio.charset.Charset;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Map;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -36,11 +27,9 @@ import org.robolectric.RobolectricTestRunner;
 public class DefaultContentMetadataTest {
 
   private DefaultContentMetadata contentMetadata;
-  private FakeChangeListener changeListener;
 
   @Before
   public void setUp() throws Exception {
-    changeListener = new FakeChangeListener();
     contentMetadata = createAbstractContentMetadata();
   }
 
@@ -67,124 +56,85 @@ public class DefaultContentMetadataTest {
   }
 
   @Test
-  public void testEditReturnsAnEditor() throws Exception {
+  public void testEmptyMutationDoesNotFail() throws Exception {
-    assertThat(contentMetadata.edit()).isNotNull();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
-  }
+    new DefaultContentMetadata(new DefaultContentMetadata(), mutations);
-
-  @Test
-  public void testEditReturnsAnotherEditorEveryTime() throws Exception {
-    assertThat(contentMetadata.edit()).isNotEqualTo(contentMetadata.edit());
-  }
-
-  @Test
-  public void testCommitWithoutEditDoesNotFail() throws Exception {
-    Editor editor = contentMetadata.edit();
-    editor.commit();
   }
 
   @Test
   public void testAddNewMetadata() throws Exception {
-    Editor editor = contentMetadata.edit();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
-    editor.set("metadata name", "value");
+    mutations.set("metadata name", "value");
-    editor.commit();
+    contentMetadata = new DefaultContentMetadata(contentMetadata, mutations);
     assertThat(contentMetadata.get("metadata name", "default value")).isEqualTo("value");
   }
 
   @Test
   public void testAddNewIntMetadata() throws Exception {
-    Editor editor = contentMetadata.edit();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
-    editor.set("metadata name", 5);
+    mutations.set("metadata name", 5);
-    editor.commit();
+    contentMetadata = new DefaultContentMetadata(contentMetadata, mutations);
     assertThat(contentMetadata.get("metadata name", 0)).isEqualTo(5);
   }
 
   @Test
   public void testAddNewByteArrayMetadata() throws Exception {
-    Editor editor = contentMetadata.edit();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
     byte[] value = {1, 2, 3};
-    editor.set("metadata name", value);
+    mutations.set("metadata name", value);
-    editor.commit();
+    contentMetadata = new DefaultContentMetadata(contentMetadata, mutations);
     assertThat(contentMetadata.get("metadata name", new byte[] {})).isEqualTo(value);
   }
 
   @Test
   public void testNewMetadataNotWrittenBeforeCommitted() throws Exception {
-    Editor editor = contentMetadata.edit();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
-    editor.set("metadata name", "value");
+    mutations.set("metadata name", "value");
     assertThat(contentMetadata.get("metadata name", "default value")).isEqualTo("default value");
   }
 
   @Test
   public void testEditMetadata() throws Exception {
     contentMetadata = createAbstractContentMetadata("metadata name", "value");
-    Editor editor = contentMetadata.edit();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
-    editor.set("metadata name", "edited value");
+    mutations.set("metadata name", "edited value");
-    editor.commit();
+    contentMetadata = new DefaultContentMetadata(contentMetadata, mutations);
     assertThat(contentMetadata.get("metadata name", "default value")).isEqualTo("edited value");
   }
 
   @Test
   public void testRemoveMetadata() throws Exception {
     contentMetadata = createAbstractContentMetadata("metadata name", "value");
-    Editor editor = contentMetadata.edit();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
-    editor.remove("metadata name");
+    mutations.remove("metadata name");
-    editor.commit();
+    contentMetadata = new DefaultContentMetadata(contentMetadata, mutations);
     assertThat(contentMetadata.get("metadata name", "default value")).isEqualTo("default value");
   }
 
   @Test
   public void testAddAndRemoveMetadata() throws Exception {
-    Editor editor = contentMetadata.edit();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
-    editor.set("metadata name", "value");
+    mutations.set("metadata name", "value");
-    editor.remove("metadata name");
+    mutations.remove("metadata name");
-    editor.commit();
+    contentMetadata = new DefaultContentMetadata(contentMetadata, mutations);
     assertThat(contentMetadata.get("metadata name", "default value")).isEqualTo("default value");
   }
 
   @Test
   public void testRemoveAndAddMetadata() throws Exception {
-    Editor editor = contentMetadata.edit();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
-    editor.remove("metadata name");
+    mutations.remove("metadata name");
-    editor.set("metadata name", "value");
+    mutations.set("metadata name", "value");
-    editor.commit();
+    contentMetadata = new DefaultContentMetadata(contentMetadata, mutations);
     assertThat(contentMetadata.get("metadata name", "default value")).isEqualTo("value");
   }
 
-  @Test
-  public void testOnChangeIsCalledWhenMetadataEdited() throws Exception {
-    contentMetadata =
-        createAbstractContentMetadata(
-            "metadata name", "value", "metadata name2", "value2", "metadata name3", "value3");
-    Editor editor = contentMetadata.edit();
-    editor.set("metadata name", "edited value");
-    editor.remove("metadata name2");
-    editor.commit();
-    assertThat(changeListener.remainingValues).containsExactly("metadata name", "metadata name3");
-  }
-
   private DefaultContentMetadata createAbstractContentMetadata(String... pairs) {
     assertThat(pairs.length % 2).isEqualTo(0);
-    HashMap<String, byte[]> map = new HashMap<>();
+    ContentMetadataMutations mutations = new ContentMetadataMutations();
     for (int i = 0; i < pairs.length; i += 2) {
-      map.put(pairs[i], getBytes(pairs[i + 1]));
+      mutations.set(pairs[i], pairs[i + 1]);
-    }
-    DefaultContentMetadata metadata = new DefaultContentMetadata(Collections.unmodifiableMap(map));
-    metadata.setChangeListener(changeListener);
-    return metadata;
-  }
-
-  private static byte[] getBytes(String value) {
-    return value.getBytes(Charset.forName(C.UTF8_NAME));
-  }
-
-  private static class FakeChangeListener implements ChangeListener {
-
-    private ArrayList<String> remainingValues;
-
-    @Override
-    public void onChange(DefaultContentMetadata contentMetadata, Map<String, byte[]> metadataValues)
-        throws CacheException {
-      remainingValues = new ArrayList<>(metadataValues.keySet());
     }
+    return new DefaultContentMetadata(new DefaultContentMetadata(), mutations);
   }
 }