/*
 * Copyright 2015 Google Inc.
 *
 * 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 java.io;

import static com.google.gwt.core.shared.impl.InternalPreconditions.checkNotNull;

/**
 * Provides a series of utilities to be reused between IO classes.
 *
 * TODO(chehayeb): move these checks to InternalPreconditions.
 */
final class IOUtils {

  /**
   * Validates the offset and the byte count for the given array of bytes.
   *
   * @param buffer Array of bytes to be checked.
   * @param byteOffset Starting offset in the array.
   * @param byteCount Total number of bytes to be accessed.
   * @throws NullPointerException if the given reference to the buffer is null.
   * @throws IndexOutOfBoundsException if {@code byteOffset} is negative, {@code byteCount} is
   *     negative or their sum exceeds the buffer length.
   */
  public static void checkOffsetAndCount(byte[] buffer, int byteOffset, int byteCount) {
    // Ensure we throw a NullPointerException instead of a JavascriptException in case the
    // given buffer is null.
    checkNotNull(buffer);
    checkOffsetAndCount(buffer.length, byteOffset, byteCount);
  }

  /**
   * Validates the offset and the byte count for the given array of characters.
   *
   * @param buffer Array of characters to be checked.
   * @param charOffset Starting offset in the array.
   * @param charCount Total number of characters to be accessed.
   * @throws NullPointerException if the given reference to the buffer is null.
   * @throws IndexOutOfBoundsException if {@code charOffset} is negative, {@code charCount} is
   *     negative or their sum exceeds the buffer length.
   */
  public static void checkOffsetAndCount(char[] buffer, int charOffset, int charCount) {
    // Ensure we throw a NullPointerException instead of a JavascriptException in case the
    // given buffer is null.
    checkNotNull(buffer);
    checkOffsetAndCount(buffer.length, charOffset, charCount);
  }

  /**
   * Validates the offset and the byte count for the given array length.
   *
   * @param length Length of the array to be checked.
   * @param offset Starting offset in the array.
   * @param count Total number of elements to be accessed.
   * @throws IndexOutOfBoundsException if {@code offset} is negative, {@code count} is negative or
   *     their sum exceeds the given {@code length}.
   */
  private static void checkOffsetAndCount(int length, int offset, int count) {
    if ((offset < 0) || (count < 0) || ((offset + count) > length)) {
      throw new IndexOutOfBoundsException();
    }
  }

  private IOUtils() {
  }
}