Pull cacheinvalidations code directory into chromium repo.

third_party/cacheinvalidation/src/java/com/google/ipc/invalidation/common/DigestFunction.java

+/*
+ * Copyright 2011 Google Inc.
+ *
+ * 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.ipc.invalidation.common;
+
+/**
+ * Interface specifying a function to compute digests.
+ *
+ */
+public interface DigestFunction {
+  /** Clears the digest state. */
+  void reset();
+
+  /** Adds {@code data} to the digest being computed. */
+  void update(byte[] data);
+
+  /**
+   * Returns the digest of the data added by {@link #update}. After this call has been made,
+   * reset must be called before {@link #update} and {@link #getDigest} can be called.
+   */
+  byte[] getDigest();
+}