ImageFormatCheckerUtils.java

/*
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.imageformat;

import java.io.UnsupportedEncodingException;

import com.facebook.common.internal.Preconditions;

/**
 * {@link ImageFormatChecker} utility methods
 */
public class ImageFormatCheckerUtils {

  /**
   * Helper method that transforms provided string into it's byte representation
   * using ASCII encoding.
   * @param value the string to use
   * @return byte array representing ascii encoded value
   */
  public static byte[] asciiBytes(String value) {
    Preconditions.checkNotNull(value);
    try {
      return value.getBytes("ASCII");
    } catch (UnsupportedEncodingException uee) {
      // won't happen
      throw new RuntimeException("ASCII not found!", uee);
    }
  }

  /**
   * Checks if byteArray interpreted as sequence of bytes starts with pattern
   * starting at position equal to offset.
   * @param byteArray the byte array to be checked
   * @param pattern the pattern to check
   * @return true if byteArray starts with pattern
   */
  public static boolean startsWithPattern(
      final byte[] byteArray,
      final byte[] pattern) {
    Preconditions.checkNotNull(byteArray);
    Preconditions.checkNotNull(pattern);
    if (pattern.length > byteArray.length) {
      return false;
    }

    for (int i = 0; i < pattern.length; ++i) {
      if (byteArray[i] != pattern[i]) {
        return false;
      }
    }

    return true;
  }

  private ImageFormatCheckerUtils() {}
}