src/main/java/com/google/devtools/build/lib/syntax/ParserInputSource.java

// Copyright 2014 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.syntax;

import com.google.common.base.Joiner;
import com.google.devtools.build.lib.vfs.PathFragment;
import java.io.IOException;
import javax.annotation.Nullable;

/** An abstraction for reading input from a file or taking it as a pre-cooked char[] or String. */
// TODO(adonovan): make this final and concrete;
// create returns the only implementation that matters.
// TODO(adonovan): rename to "ParserInput".
public abstract class ParserInputSource {

  protected ParserInputSource() {}

  /** Returns the content of the input source. */
  public abstract char[] getContent();

  /**
   * Returns the (non-null) path of the input source. Note: Once constructed, this object will never
   * re-read the content from path.
   */
  // TODO(adonovan): use Strings, to avoid dependency on vfs; but first we need to avoid depending
  // on events.Location.
  public abstract PathFragment getPath();

  /** Returns an unnamed input source that reads from a list of strings, joined by newlines. */
  public static ParserInputSource fromLines(String... lines) {
    return create(Joiner.on("\n").join(lines), null);
  }

  /**
   * Returns an import source that reads from a Latin-1 encoded byte array. The path specifies the
   * name of the file, for use in source locations and error messages; a null path implies the empty
   * string.
   */
  public static ParserInputSource create(byte[] bytes, @Nullable PathFragment path)
      throws IOException {
    char[] content = convertFromLatin1(bytes);
    return create(content, path);
  }

  /**
   * Create an input source from the given content, and associate path with this source. Path will
   * be used in error messages etc. but we will *never* attempt to read the content from path. A
   * null path implies the empty string.
   */
  public static ParserInputSource create(String content, @Nullable PathFragment path) {
    return create(content.toCharArray(), path);
  }

  /**
   * Create an input source from the given content, and associate path with
   * this source.  Path will be used in error messages etc. but we will *never*
   * attempt to read the content from path.
   */
  public static ParserInputSource create(final char[] content, final PathFragment path) {
    return new ParserInputSource() {
      @Override
      public char[] getContent() {
        return content;
      }

      @Override
      public PathFragment getPath() {
        return path == null ? PathFragment.EMPTY_FRAGMENT : path;
      }
    };
  }

  private static char[] convertFromLatin1(byte[] content) {
    char[] latin1 = new char[content.length];
    for (int i = 0; i < latin1.length; i++) { // yeah, latin1 is this easy! :-)
      latin1[i] = (char) (0xff & content[i]);
    }
    return latin1;
  }
}