src/main/java/com/google/devtools/common/options/LegacyParamsFilePreProcessor.java

// Copyright 2017 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.common.options;

import java.io.IOException;
import java.io.Reader;
import java.nio.charset.StandardCharsets;
import java.nio.file.FileSystem;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * A {@link ParamsFilePreProcessor} that processes a parameter file using a custom format. This
 * format assumes each parameter is separated by whitespace and allows arguments to use single and
 * double quotes and quote and whitespace escaping.
 */
public class LegacyParamsFilePreProcessor extends ParamsFilePreProcessor {

  public LegacyParamsFilePreProcessor(FileSystem fs) {
    super(fs);
  }

  @Override
  protected List<String> parse(Path paramsFile) throws IOException, OptionsParsingException {
    try (Reader params = Files.newBufferedReader(paramsFile, StandardCharsets.UTF_8)) {
      List<String> newArgs = new ArrayList<>();
      StringBuilder arg = new StringBuilder();
      CharIterator iterator = CharIterator.wrap(params);
      while (iterator.hasNext()) {
        char next = iterator.next();
        if (Character.isWhitespace(next) && !iterator.isInQuote() && !iterator.isEscaped()) {
          newArgs.add(unescape(arg.toString()));
          arg = new StringBuilder();
        } else {
          arg.append(next);
        }
      }
      // If there is an arg in the buffer, add it.
      if (arg.length() > 0) {
        newArgs.add(arg.toString());
      }
      // If we're still in a quote by the end of the file, throw an error.
      if (iterator.isInQuote()) {
        throw new OptionsParsingException(
            String.format(ERROR_MESSAGE_FORMAT, paramsFile, iterator.getUnmatchedQuoteMessage()));
      }
      return newArgs;
    }
  }

  private String unescape(String arg) {
    if (arg.startsWith("'") && arg.endsWith("'")) {
      String unescaped = arg.replace("'\\''", "'");
      return unescaped.substring(1, unescaped.length() - 1);
    }
    return arg;
  }

  // Doesn't implement iterator to avoid autoboxing and to throw exceptions.
  private static class CharIterator {

    private final Reader reader;
    private int readerPosition = 0;
    private int singleQuoteStart = -1;
    private int doubleQuoteStart = -1;
    private boolean escaped = false;
    private char lastChar = (char) -1;

    public static CharIterator wrap(Reader reader) {
      return new CharIterator(reader);
    }

    public CharIterator(Reader reader) {
      this.reader = reader;
    }

    public boolean hasNext() throws IOException {
      return peek() != -1;
    }

    private int peek() throws IOException {
      reader.mark(1);
      int next = reader.read();
      reader.reset();
      return next;
    }

    public boolean isInQuote() {
      return singleQuoteStart != -1 || doubleQuoteStart != -1;
    }

    public boolean isEscaped() {
      return escaped;
    }

    public String getUnmatchedQuoteMessage() {
      StringBuilder message = new StringBuilder();
      if (singleQuoteStart != -1) {
        message.append(String.format(UNFINISHED_QUOTE_MESSAGE_FORMAT, "'", singleQuoteStart));
      }
      if (doubleQuoteStart != -1) {
        message.append(String.format(UNFINISHED_QUOTE_MESSAGE_FORMAT, "\"", doubleQuoteStart));
      }
      return message.toString();
    }

    public char next() throws IOException {
      if (!hasNext()) {
        throw new NoSuchElementException();
      }
      char current = (char) reader.read();

      // check for \r\n line endings. If found, drop the \r for normalized parsing.
      if (current == '\r' && peek() == '\n') {
        current = (char) reader.read();
      }

      // check to see if the current position is escaped
      escaped = (lastChar == '\\');

      if (!escaped && current == '\'') {
        singleQuoteStart = singleQuoteStart == -1 ? readerPosition : -1;
      }
      if (!escaped && current == '"') {
        doubleQuoteStart = doubleQuoteStart == -1 ? readerPosition : -1;
      }

      readerPosition++;
      lastChar = current;
      return current;
    }
  }
}