Introduce Root class.

This class represents a root (such as a package path or an output root) used for file lookups and artifacts. It is meant to be as opaque as possible in order to hide the user's environment from sky keys and sky functions.

Roots are used by RootedPaths and ArtifactRoots.

This CL attempts to make the minimum number of modifications necessary to change RootedPath and ArtifactRoot to use these fields. Deprecated methods and invasive accessors are permitted to minimise the risk of any observable changes.

RELNOTES: None
PiperOrigin-RevId: 182271759

1 files changed, 179 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/vfs/Root.java b/src/main/java/com/google/devtools/build/lib/vfs/Root.java
new file mode 100644
index 0000000000..41f65de8c9
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/vfs/Root.java
@@ -0,0 +1,179 @@
+// Copyright 2018 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.vfs;
+
+import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.skyframe.serialization.ObjectCodec;
+import com.google.devtools.build.lib.skyframe.serialization.SerializationException;
+import com.google.protobuf.CodedInputStream;
+import com.google.protobuf.CodedOutputStream;
+import java.io.IOException;
+import java.io.Serializable;
+
+/**
+ * A root path used in {@link RootedPath} and in artifact roots.
+ *
+ * <p>A typical root could be the exec path, a package root, or an output root specific to some
+ * configuration.
+ */
+public interface Root extends Comparable<Root>, Serializable {
+
+  static ObjectCodec<Root> getCodec(PathCodec pathCodec) {
+    return new RootCodec(pathCodec);
+  }
+
+  /** Constructs a root from a path. */
+  static Root fromPath(Path path) {
+    return new PathRoot(path);
+  }
+
+  /** Returns a root from the file system's root directory. */
+  static Root fromFileSystemRoot(FileSystem fileSystem) {
+    return fileSystem.getRoot();
+  }
+
+  /** Returns a path by concatenating the root and the root-relative path. */
+  Path getRelative(PathFragment relativePath);
+
+  /** Returns a path by concatenating the root and the root-relative path. */
+  Path getRelative(String relativePath);
+
+  /** Returns the relative path between the root and the given path. */
+  PathFragment relativize(Path path);
+
+  @Deprecated
+  PathFragment relativize(PathFragment relativePath);
+
+  /** Returns whether the given path is under this root. */
+  boolean contains(Path path);
+
+  @Deprecated
+  boolean contains(PathFragment relativePath);
+
+  /**
+   * Returns the underlying path. Please avoid using this method. Roots may eventually not be
+   * directly backed by paths.
+   */
+  Path asPath();
+
+  @Deprecated
+  boolean isRootDirectory();
+
+  /** Implementation of Root that is backed by a {@link Path}. */
+  final class PathRoot implements Root {
+    private final Path path;
+
+    PathRoot(Path path) {
+      this.path = path;
+    }
+
+    @Override
+    public Path getRelative(PathFragment relativePath) {
+      return path.getRelative(relativePath);
+    }
+
+    @Override
+    public Path getRelative(String relativePath) {
+      return path.getRelative(relativePath);
+    }
+
+    @Override
+    public PathFragment relativize(Path path) {
+      return path.relativeTo(this.path);
+    }
+
+    @Override
+    public PathFragment relativize(PathFragment relativePath) {
+      Preconditions.checkArgument(relativePath.isAbsolute());
+      return relativePath.relativeTo(path.asFragment());
+    }
+
+    @Override
+    public boolean contains(Path path) {
+      return path.startsWith(this.path);
+    }
+
+    @Override
+    public boolean contains(PathFragment relativePath) {
+      return relativePath.isAbsolute() && relativePath.startsWith(path.asFragment());
+    }
+
+    @Override
+    public Path asPath() {
+      return path;
+    }
+
+    @Override
+    public boolean isRootDirectory() {
+      return path.isRootDirectory();
+    }
+
+    @Override
+    public String toString() {
+      return path.toString();
+    }
+
+    @Override
+    public int compareTo(Root o) {
+      return path.compareTo(((PathRoot) o).path);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+      if (this == o) {
+        return true;
+      }
+      if (o == null || getClass() != o.getClass()) {
+        return false;
+      }
+      PathRoot pathRoot = (PathRoot) o;
+      return path.equals(pathRoot.path);
+    }
+
+    @Override
+    public int hashCode() {
+      return path.hashCode();
+    }
+  }
+
+  /** Codec to serialize {@link Root}s. */
+  class RootCodec implements ObjectCodec<Root> {
+    private final PathCodec pathCodec;
+
+    private RootCodec(PathCodec pathCodec) {
+      this.pathCodec = pathCodec;
+    }
+
+    @Override
+    public Class<Root> getEncodedClass() {
+      return Root.class;
+    }
+
+    @Override
+    public void serialize(Root obj, CodedOutputStream codedOut)
+        throws SerializationException, IOException {
+      if (obj instanceof PathRoot) {
+        pathCodec.serialize(((PathRoot) obj).path, codedOut);
+      } else {
+        throw new AssertionError("Unknown Root subclass: " + obj.getClass().getName());
+      }
+    }
+
+    @Override
+    public Root deserialize(CodedInputStream codedIn) throws SerializationException, IOException {
+      Path path = pathCodec.deserialize(codedIn);
+      return new PathRoot(path);
+    }
+  }
+}