Pull cacheinvalidations code directory into chromium repo.

third_party/cacheinvalidation/src/java/com/google/ipc/invalidation/common/ObjectIdDigestUtils.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;
+
+import com.google.ipc.invalidation.util.Bytes;
+import com.google.ipc.invalidation.util.Preconditions;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+/**
+ * Digest-related utilities for object ids.
+ *
+ */
+public class ObjectIdDigestUtils {
+  /**
+   * Implementation of {@link DigestFunction} using SHA-1.
+   */
+  public static class Sha1DigestFunction
+      implements DigestFunction {
+    /** Digest implementation. */
+    private MessageDigest sha1;
+
+    /**
+     * Whether the {@link #reset()} method needs to be called. This is set to true
+     * when {@link #getDigest()} is called and aims to prevent subtle bugs caused by
+     * failing to reset the object before computing a new digest.
+     */
+    private boolean resetNeeded = false;
+
+    public Sha1DigestFunction() {
+      try {
+      this.sha1 = MessageDigest.getInstance("SHA-1");
+      } catch (NoSuchAlgorithmException exception) {
+        throw new RuntimeException(exception);
+      }
+    }
+
+    @Override
+    public void reset() {
+      resetNeeded = false;
+      sha1.reset();
+    }
+
+    @Override
+    public void update(byte[] data) {
+      Preconditions.checkState(!resetNeeded);
+      sha1.update(data);
+    }
+
+    @Override
+    public byte[] getDigest() {
+      Preconditions.checkState(!resetNeeded);
+      resetNeeded = true;
+      return sha1.digest();
+    }
+  }
+
+  /**
+   * Returns the digest of {@code objectIdDigests} using {@code digestFn}.
+   * <p>
+   * REQUIRES: {@code objectIdDigests} iterate in sorted order.
+   */
+  public static Bytes getDigest(Iterable<Bytes> objectIdDigests, DigestFunction digestFn) {
+    digestFn.reset();
+    for (Bytes objectIdDigest : objectIdDigests) {
+      digestFn.update(objectIdDigest.getByteArray());
+    }
+    return new Bytes(digestFn.getDigest());
+  }
+
+  /**
+   * Returns the digest for the object id with source {@code objectSource} and name
+   * {@code objectName} using {@code digestFn}.
+   */
+  public static Bytes getDigest(int objectSource, byte[] objectName, DigestFunction digestFn) {
+    digestFn.reset();
+    ByteBuffer buffer = ByteBuffer.allocate(Integer.SIZE / 8).order(ByteOrder.LITTLE_ENDIAN);
+    buffer.putInt(objectSource);
+
+    // Little endian number for type followed by bytes.
+    digestFn.update(buffer.array());
+    digestFn.update(objectName);
+    return new Bytes(digestFn.getDigest());
+  }
+}