Split FileAndMetadataCache into two classes, since most of the shared functionality is gone.

--
MOS_MIGRATED_REVID=90289916
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/PerActionFileCache.java b/src/main/java/com/google/devtools/build/lib/skyframe/PerActionFileCache.java
new file mode 100644
index 0000000..5dde5a5
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/PerActionFileCache.java
@@ -0,0 +1,107 @@
+// Copyright 2014 Google Inc. 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.skyframe;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Interner;
+import com.google.common.collect.Interners;
+import com.google.common.io.BaseEncoding;
+import com.google.devtools.build.lib.actions.ActionInput;
+import com.google.devtools.build.lib.actions.ActionInputFileCache;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.protobuf.ByteString;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import javax.annotation.Nullable;
+
+/**
+ * Cache provided by an {@link ActionExecutionFunction}, allowing Blaze to obtain artifact metadata
+ * from the graph.
+ *
+ * <p>Data for the action's inputs is injected into this cache on construction, using the graph as
+ * the source of truth.
+ */
+class PerActionFileCache implements ActionInputFileCache {
+  private final Map<Artifact, FileArtifactValue> inputArtifactData;
+  private final File execRoot;
+  // Populated lazily, on calls to #getDigest.
+  private final Map<ByteString, Artifact> reverseMap = new ConcurrentHashMap<>();
+
+  private static final Interner<ByteString> BYTE_INTERNER = Interners.newWeakInterner();
+
+  /**
+   * @param inputArtifactData Map from artifact to metadata, used to return metadata upon request.
+   * @param execRoot Path to the execution root, used to convert Artifacts' relative paths into
+   * absolute ones in the execution root.
+   */
+  PerActionFileCache(Map<Artifact, FileArtifactValue> inputArtifactData,
+      File execRoot) {
+    this.inputArtifactData = Preconditions.checkNotNull(inputArtifactData);
+    this.execRoot = Preconditions.checkNotNull(execRoot);
+  }
+
+  @Nullable
+  private FileArtifactValue getInputFileArtifactValue(ActionInput input) {
+    if (!(input instanceof Artifact)) {
+      return null;
+    }
+    return Preconditions.checkNotNull(inputArtifactData.get(input), input);
+  }
+
+  @Override
+  public long getSizeInBytes(ActionInput input) throws IOException {
+    FileArtifactValue metadata = getInputFileArtifactValue(input);
+    if (metadata != null) {
+      return metadata.getSize();
+    }
+    return -1;
+  }
+
+  @Nullable
+  @Override
+  public File getFileFromDigest(ByteString digest) throws IOException {
+    Artifact artifact = reverseMap.get(digest);
+    if (artifact != null) {
+      String relPath = artifact.getExecPathString();
+      return new File(execRoot, relPath);
+    }
+    return null;
+  }
+
+  @Nullable
+  @Override
+  public ByteString getDigest(ActionInput input) throws IOException {
+    FileArtifactValue value = getInputFileArtifactValue(input);
+    if (value != null) {
+      byte[] bytes = value.getDigest();
+      if (bytes != null) {
+        ByteString digest = ByteString.copyFrom(BaseEncoding.base16().lowerCase().encode(bytes)
+            .getBytes(StandardCharsets.US_ASCII));
+        reverseMap.put(BYTE_INTERNER.intern(digest), (Artifact) input);
+        return digest;
+      }
+    }
+    return null;
+  }
+
+  @Override
+  public boolean contentsAvailableLocally(ByteString digest) {
+    return reverseMap.containsKey(digest);
+  }
+}