Add getContentMetadata and applyContentMetadataMutations to SimpleCache

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=189169899

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

@@ -144,10 +144,10 @@ public class CachedContentIndexTest extends InstrumentationTestCase {
   }
 
   public void testStore() throws Exception {
-    CachedContent cachedContent1 = index.getOrAdd("KLMNO");
+    index.getOrAdd("KLMNO");
-    cachedContent1.setLength(2560);
+    index.setContentLength("KLMNO", 2560);
-    CachedContent cachedContent2 = index.getOrAdd("ABCDE");
+    index.getOrAdd("ABCDE");
-    cachedContent2.setLength(10);
+    index.setContentLength("ABCDE", 10);
 
     index.store();
 

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

@@ -54,13 +54,12 @@ import java.util.TreeSet;
       throws IOException {
     int id = input.readInt();
     String key = input.readUTF();
-    CachedContent cachedContent;
+    CachedContent cachedContent = new CachedContent(id, key);
     if (version < VERSION_METADATA_INTRODUCED) {
-      cachedContent = new CachedContent(id, key);
       long length = input.readLong();
       cachedContent.setLength(length);
     } else {
-      cachedContent = new CachedContent(id, key, DefaultContentMetadata.readFromStream(input));
+      cachedContent.metadata = DefaultContentMetadata.readFromStream(input);
     }
     return cachedContent;
   }
@@ -72,13 +71,9 @@ import java.util.TreeSet;
    * @param key The cache stream key.
    */
   public CachedContent(int id, String key) {
-    this(id, key, new DefaultContentMetadata());
-  }
-
-  private CachedContent(int id, String key, DefaultContentMetadata metadata) {
     this.id = id;
     this.key = key;
-    this.metadata = metadata;
+    this.metadata = DefaultContentMetadata.EMPTY;
     this.cachedSpans = new TreeSet<>();
   }
 
@@ -94,6 +89,16 @@ import java.util.TreeSet;
     metadata.writeToStream(output);
   }
 
+  /** Returns the metadata. */
+  public ContentMetadata getMetadata() {
+    return metadata;
+  }
+
+  /** Applies {@code mutations} to the metadata. */
+  public void applyMetadataMutations(ContentMetadataMutations mutations) {
+    this.metadata = new DefaultContentMetadata(metadata, mutations);
+  }
+
   /**
    * Returns the length of the original stream, or {@link C#LENGTH_UNSET} if the length is unknown.
    */
@@ -103,9 +108,7 @@ import java.util.TreeSet;
 
   /** Sets the length of the content. */
   public void setLength(long length) {
-    ContentMetadataMutations mutations =
+    applyMetadataMutations(new ContentMetadataMutations().set(METADATA_NAME_LENGTH, length));
-        new ContentMetadataMutations().set(METADATA_NAME_LENGTH, length);
-    metadata = new DefaultContentMetadata(metadata, mutations);
   }
 
   /** Returns whether the content is locked. */

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

@@ -218,6 +218,21 @@ import javax.crypto.spec.SecretKeySpec;
     return cachedContent == null ? C.LENGTH_UNSET : cachedContent.getLength();
   }
 
+  /**
+   * Applies {@code mutations} to the {@link ContentMetadata} for the given key. A new {@link
+   * CachedContent} is added if there isn't one already with the given key.
+   */
+  public void applyContentMetadataMutations(String key, ContentMetadataMutations mutations) {
+    CachedContent cachedContent = getOrAdd(key);
+    cachedContent.applyMetadataMutations(mutations);
+  }
+
+  /** Returns a snapshot of the {@link ContentMetadata} for the given key. */
+  public ContentMetadata getContentMetadataSnapshot(String key) {
+    CachedContent cachedContent = get(key);
+    return cachedContent != null ? cachedContent.getMetadata() : DefaultContentMetadata.EMPTY;
+  }
+
   private boolean readFile() {
     DataInputStream input = null;
     try {

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

@@ -31,6 +31,10 @@ import java.util.Map.Entry;
 /** Default implementation of {@link ContentMetadata}. Values are stored as byte arrays. */
 public final class DefaultContentMetadata implements ContentMetadata {
 
+  /** An empty DefaultContentMetadata. */
+  public static final DefaultContentMetadata EMPTY =
+      new DefaultContentMetadata(Collections.<String, byte[]>emptyMap());
+
   private static final int MAX_VALUE_LENGTH = 10 * 1024 * 1024;
   private int hashCode;
 
@@ -59,11 +63,6 @@ public final class DefaultContentMetadata implements ContentMetadata {
 
   private final Map<String, byte[]> metadata;
 
-  /** Constructs an empty {@link DefaultContentMetadata}. */
-  public DefaultContentMetadata() {
-    this(Collections.<String, byte[]>emptyMap());
-  }
-
   /**
    * Constructs a {@link DefaultContentMetadata} by copying metadata values from {@code other} and
    * applying {@code mutations}.
@@ -165,13 +164,20 @@ public final class DefaultContentMetadata implements ContentMetadata {
   private static Map<String, byte[]> applyMutations(
       Map<String, byte[]> otherMetadata, ContentMetadataMutations mutations) {
     HashMap<String, byte[]> metadata = new HashMap<>(otherMetadata);
-    List<String> removedValues = mutations.getRemovedValues();
+    removeValues(metadata, mutations.getRemovedValues());
-    for (int i = 0; i < removedValues.size(); i++) {
+    addValues(metadata, mutations.getEditedValues());
-      metadata.remove(removedValues.get(i));
+    return metadata;
+  }
+
+  private static void removeValues(HashMap<String, byte[]> metadata, List<String> names) {
+    for (int i = 0; i < names.size(); i++) {
+      metadata.remove(names.get(i));
     }
-    Map<String, Object> editedValues = mutations.getEditedValues();
+  }
-    for (String name : editedValues.keySet()) {
+
-      Object value = editedValues.get(name);
+  private static void addValues(HashMap<String, byte[]> metadata, Map<String, Object> values) {
+    for (String name : values.keySet()) {
+      Object value = values.get(name);
       byte[] bytes = getBytes(value);
       if (bytes.length > MAX_VALUE_LENGTH) {
         throw new IllegalArgumentException(
@@ -181,7 +187,6 @@ public final class DefaultContentMetadata implements ContentMetadata {
       }
       metadata.put(name, bytes);
     }
-    return metadata;
   }
 
   private static byte[] getBytes(Object value) {

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

@@ -412,4 +412,27 @@ public final class SimpleCache implements Cache {
     return index.getContentLength(key);
   }
 
+  /**
+   * Applies {@code mutations} to the {@link ContentMetadata} for the given key. A new {@link
+   * CachedContent} is added if there isn't one already with the given key.
+   *
+   * @param key The cache key for the data.
+   * @param mutations Contains mutations to be applied to the metadata.
+   * @throws CacheException If an error is encountered.
+   */
+  public void applyContentMetadataMutations(String key, ContentMetadataMutations mutations)
+      throws CacheException {
+    index.applyContentMetadataMutations(key, mutations);
+    index.store();
+  }
+
+  /**
+   * Returns a snapshot of the {@link ContentMetadata} for the given key.
+   *
+   * @param key The cache key for the data.
+   * @return A snapshot of the {@link ContentMetadata} for the given key.
+   */
+  public ContentMetadata getContentMetadataSnapshot(String key) {
+    return index.getContentMetadataSnapshot(key);
+  }
 }

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

@@ -62,7 +62,7 @@ public class DefaultContentMetadataTest {
   @Test
   public void testEmptyMutationDoesNotFail() throws Exception {
     ContentMetadataMutations mutations = new ContentMetadataMutations();
-    new DefaultContentMetadata(new DefaultContentMetadata(), mutations);
+    new DefaultContentMetadata(DefaultContentMetadata.EMPTY, mutations);
   }
 
   @Test
@@ -194,6 +194,6 @@ public class DefaultContentMetadataTest {
         throw new IllegalArgumentException();
       }
     }
-    return new DefaultContentMetadata(new DefaultContentMetadata(), mutations);
+    return new DefaultContentMetadata(DefaultContentMetadata.EMPTY, mutations);
   }
 }