Backport B+ tree implementation from Dart to Java.

editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/PageManager.java

Index: editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/PageManager.java
diff --git a/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/PageManager.java b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/PageManager.java
new file mode 100644
index 0000000000000000000000000000000000000000..8505f085140b3aa94ad42b4762ba39827c416d13
--- /dev/null
+++ b/editor/tools/plugins/com.google.dart.engine/src/com/google/dart/engine/internal/index/structure/btree/PageManager.java
@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2014, the Dart project authors.
+ * 
+ * Licensed under the Eclipse Public License v1.0 (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.eclipse.org/legal/epl-v10.html
+ * 
+ * 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.dart.engine.internal.index.structure.btree;
+
+import java.nio.ByteBuffer;
+
+/**
+ * [PageManager] allows to allocate, read, write and free [Uint8List] pages.
+ * 
+ * @coverage dart.engine.index.structure
+ */
+public interface PageManager {
+  /**
+   * Allocates a new page and returns its identifier.
+   */
+  int alloc();
+
+  /**
+   * Frees the page with the given identifier.
+   */
+  void free(int id);
+
+  /**
+   * The size of pages provided by this [PageManager].
+   */
+  int getPageSizeInBytes();
+
+  /**
+   * Reads the page with the given identifier and returns its content. An internal representation of
+   * the page is returned, any changes made to it may be accessible to other clients reading the
+   * same page.
+   */
+  ByteBuffer read(int id);
+
+  /**
+   * Writes the given page.
+   */
+  void write(int id, ByteBuffer page);
+}