src/main/java/com/google/devtools/build/lib/actions/ParameterFile.java

// 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.actions;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.devtools.build.lib.util.FileType;
import com.google.devtools.build.lib.util.ShellEscaper;
import com.google.devtools.build.lib.vfs.FileSystemUtils;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;

import java.io.IOException;
import java.nio.charset.Charset;
import java.util.List;

/**
 * Support for parameter file generation (as used by gcc and other tools, e.g.
 * {@code gcc @param_file}. Note that the parameter file needs to be explicitly
 * deleted after use. Different tools require different parameter file formats,
 * which can be selected via the {@link ParameterFileType} enum.
 *
 * <p>The default charset is ISO-8859-1 (latin1). This also has to match the
 * expectation of the tool.
 *
 * <p>Don't use this class for new code. Use the ParameterFileWriteAction
 * instead!
 */
public class ParameterFile {

  /**
   * Different styles of parameter files.
   */
  public static enum ParameterFileType {
    /**
     * A parameter file with every parameter on a separate line. This format
     * cannot handle newlines in parameters. It is currently used for most
     * tools, but may not be interpreted correctly if parameters contain
     * white space or other special characters. It should be avoided for new
     * development.
     */
    UNQUOTED,

    /**
     * A parameter file where each parameter is correctly quoted for shell
     * use, and separated by white space (space, tab, newline). This format is
     * safe for all characters, but must be specially supported by the tool. In
     * particular, it must not be used with gcc and related tools, which do not
     * support this format as it is.
     */
    SHELL_QUOTED;
  }

  // Parameter file location.
  private final Path execRoot;
  private final PathFragment execPath;
  private final Charset charset;
  private final ParameterFileType type;

  @VisibleForTesting
  public static final FileType PARAMETER_FILE = FileType.of(".params");

  /**
   * Creates a parameter file with the given parameters.
   */
  public ParameterFile(Path execRoot, PathFragment execPath, Charset charset,
      ParameterFileType type) {
    Preconditions.checkNotNull(type);
    this.execRoot = execRoot;
    this.execPath = execPath;
    this.charset = Preconditions.checkNotNull(charset);
    this.type = Preconditions.checkNotNull(type);
  }

  /**
   * Derives an exec path from a given exec path by appending <code>".params"</code>.
   */
  public static PathFragment derivePath(PathFragment original) {
    return original.replaceName(original.getBaseName() + "-2.params");
  }

  /**
   * Returns the path for the parameter file.
   */
  public Path getPath() {
    return execRoot.getRelative(execPath);
  }

  /**
   * Writes the arguments from the list into the parameter file according to
   * the style selected in the constructor.
   */
  public void writeContent(List<String> arguments) throws ExecException {
    Iterable<String> actualArgs = (type == ParameterFileType.SHELL_QUOTED) ?
        ShellEscaper.escapeAll(arguments) : arguments;
    Path file = getPath();
    try {
      FileSystemUtils.writeLinesAs(file, charset, actualArgs);
    } catch (IOException e) {
      throw new EnvironmentalExecException("could not write param file '" + file + "'", e);
    }
  }
}