content: /*
   * plist - An open source library to parse and generate property lists
   * Copyright (C) 2022 Daniel Dreibrodt
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   */
  
  package com.dd.plist;
  
  /**
   * Reads Byte Order Marks for various Unicode encodings.
   * @author Daniel Dreibrodt
   */
  class ByteOrderMarkReader {
      private static final int[][] BOMs = {
          { 0xEF, 0xBB, 0xBF },
          { 0xFE, 0xFF },
          { 0xFF, 0xFE},
          { 0x00, 0x00, 0xFE, 0xFF },
          { 0xFF, 0xFE, 0x00, 0x00 },
      };
  
      private static final String[] Charsets = {
          "UTF-8",
          "UTF-16BE",
          "UTF-16LE",
          "UTF-32BE",
          "UTF-32LE"
      };
  
      private final boolean[] charsetPossible = { true, true, true, true, true};
      private int offset;
      private String charset;
  
      /**
       * Gets the charset that was detected.
       * @return The name of the detected charset, or <c>null</c> if no charset was detected.
       */
      public String getDetectedCharset() {
          return this.charset;
      }
  
      /**
       * Processes a byte that was read from the input.
       * @param b The byte to process.
       * @return <c>true</c> if the input so far could potentially be a BOM; otherwise, <c>false</c>.
       */
      public boolean readByte(int b) {
          boolean matchingCharset = false;
          for (int c = 0; c < Charsets.length; c++) {
              if (this.charsetPossible[c]) {
                  int[] bom = BOMs[c];
                  boolean match = this.offset < bom.length && bom[this.offset] == b;
                  if (match) {
                      matchingCharset = true;
                      if (this.offset + 1 == bom.length) {
                          this.charset = Charsets[c];
                      }
                  }
                  else {
                      this.charsetPossible[c] = false;
                  }
              }
          }
  
          this.offset++;
          return matchingCharset;
      }
  
      /**
       * Detects the encoding of input data that is available as a complete byte array.
       * @param bytes The input data.
       * @return The name of the detected charset, or <c>null</c> if no BOM was detected.
       */
      public static String detect(byte[] bytes) {
          // Check for byte order marks
          if (bytes.length > 2) {
              if (bytes[0] == (byte)0xFE && bytes[1] == (byte)0xFF) {
                  return "UTF-16";
              }
              else if (bytes[0] == (byte)0xFF && bytes[1] == (byte)0xFE) {
                  if (bytes.length > 4 && bytes[2] == (byte)0x00 && bytes[3] == (byte)0x00) {
                      return "UTF-32";
                  }
                  return "UTF-16";
              }
              else if (bytes.length > 3) {
                  if (bytes[0] == (byte)0xEF && bytes[1] == (byte)0xBB && bytes[2] == (byte)0xBF) {
                      return "UTF-8";
                  }
                  else if (bytes.length > 4 && bytes[0] == (byte)0x00 && bytes[1] == (byte)0x00 && bytes[2] == (byte)0xFE && bytes[3] == (byte)0xFF) {
                      return "UTF-32";
                  }
              }
          }
  
          return null;
      }
  }
  