code: /*
   * Copyright (c) 2020, The Regents of the University of California
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   * 1. Redistributions of source code must retain the above copyright
   * notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   * notice, this list of conditions and the following disclaimer in the
   * documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  package edu.berkeley.cs.jqf.fuzz.util;
  
  import java.io.File;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.util.Arrays;
  import java.util.Comparator;
  
  /**
   * Utility class containing static methods for common I/O operations
   *
   * @author Rohan Padhye
   */
  public class IOUtils {
  
      /**
       * Resolves an input file or a directory of files.
       *
       * This is useful for operations like providing seed inputs to a
       * fuzzing engine or repro'ing a corpus of test inputs.
       *
       * @param file a file or directory
       * @return a listing of files, if `file` is a directory;
       *         a list containing only `file`, if it is a regular file;
       *         `null` if `file` is also `null`
       * @throws FileNotFoundException if {@code file} does not exist
       */
      public static File[] resolveInputFileOrDirectory(File file) throws FileNotFoundException {
          if (file == null) {
              return null;
          } else if (file.isDirectory()) {
              File[] files = file.listFiles();
              Arrays.sort(files, Comparator.comparing(File::getName));
              return files;
          } else if (file.isFile()) {
              return new File[]{file};
          } else {
              throw new FileNotFoundException("Could not find file: " + file);
          }
      }
  
      /**
       * Creates a new writable directory in a given parent directory.
       *
       * @param parent the parent directory
       * @param name   the name of the new directory to create
       * @return the newly created directory
       * @throws IOException if a writable directory was not created
       */
      public static File createDirectory(File parent, String name) throws IOException {
          File newDir = new File(parent, name);
          return createDirectory(newDir);
      }
  
      /**
       * Creates a new writable directory.
       *
       * @param newDir the new directory to create
       * @return the newly created directory (same as `newDir`)
       * @throws IOException if a writable directory was not created
       */
      public static File createDirectory(File newDir) throws IOException {
          newDir.mkdirs();
  
          if (!newDir.isDirectory() || !newDir.canWrite()) {
              throw new IOException("Could not create directory: " + newDir.getAbsolutePath());
          } else {
              return newDir;
          }
      }
  
  }
  