Adding utility functions to compute ContentDigests for various types; in

particular, ActionKeys, which are a type of ContentDigest.

The digests are a SHA1 of the contents. For proto messages, for now we compute
the digest using the serialized form of the message, which is something we will
probably want to rethink in the future.

--
MOS_MIGRATED_REVID=132690105

1 files changed, 85 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/remote/ContentDigests.java b/src/main/java/com/google/devtools/build/lib/remote/ContentDigests.java
new file mode 100644
index 0000000000..b9a653a125
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/remote/ContentDigests.java
@@ -0,0 +1,85 @@
+// Copyright 2016 The Bazel Authors. All rights reserved.
+//
+// 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.devtools.build.lib.remote;
+
+import com.google.common.hash.HashCode;
+import com.google.common.hash.Hashing;
+import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
+import com.google.devtools.build.lib.remote.RemoteProtocol.Action;
+import com.google.devtools.build.lib.remote.RemoteProtocol.ContentDigest;
+import com.google.devtools.build.lib.vfs.Path;
+import com.google.protobuf.ByteString;
+import com.google.protobuf.Message;
+import java.io.IOException;
+
+/** Helper methods relating to computing ContentDigest messages for remote execution. */
+@ThreadSafe
+public final class ContentDigests {
+  private ContentDigests() {}
+
+  public static ContentDigest computeDigest(byte[] blob) {
+    return buildDigest(Hashing.sha1().hashBytes(blob).asBytes(), blob.length);
+  }
+
+  // TODO(olaola): cache these in ActionInputFileCache!
+  public static ContentDigest computeDigest(Path file) throws IOException {
+    return buildDigest(file.getSHA1Digest(), file.getFileSize());
+  }
+
+  /**
+   * Computes a digest of the given proto message. Currently, we simply rely on message output as
+   * bytes, but this implementation relies on the stability of the proto encoding, in particular
+   * between different platforms and languages.
+   * TODO(olaola): upgrade to a better implementation!
+   */
+  public static ContentDigest computeDigest(Message message) {
+    return computeDigest(message.toByteArray());
+  }
+
+  /**
+   * A special type of ContentDigest that is used only as a remote action cache key.
+   * This is a separate type in order to prevent accidentally using other ContentDigests
+   * as action keys.
+   */
+  public static final class ActionKey {
+    private final ContentDigest digest;
+
+    public ContentDigest getDigest() {
+      return digest;
+    }
+
+    private ActionKey(ContentDigest digest) {
+      this.digest = digest;
+    }
+  }
+
+  public static ActionKey computeActionKey(Action action) {
+    return new ActionKey(computeDigest(action));
+  }
+  
+  public static ContentDigest buildDigest(byte[] digest, long size) {
+    ContentDigest.Builder b = ContentDigest.newBuilder();
+    b.setDigest(ByteString.copyFrom(digest)).setSizeBytes(size);
+    return b.build();
+  }
+
+  public static String toHexString(ContentDigest digest) {
+    return HashCode.fromBytes(digest.getDigest().toByteArray()).toString();
+  }
+
+  public static String toString(ContentDigest digest) {
+    return "<digest: " + toHexString(digest) + ", size: " + digest.getSizeBytes() + " bytes>";
+  }
+}