content: /**
   * This file was modified by Amazon:
   * Copyright 2015-2016 Amazon.com, Inc. or its affiliates. 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.
   * A copy of the License is located at
   *
   *     http://aws.amazon.com/apache2.0/
   *
   * or in the "license" file accompanying this file. This file 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.
   */
  /*
   * Copyright (C) 2011 George Yunaev @ Ulduzsoft
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   */
  package com.amazon.android.contentbrowser.helper;
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.RandomAccessFile;
  
  /**
   * The class which loads the TTF file, parses it and returns the TTF font name.
   *
   * Url: http://www.ulduzsoft.com/2012/01/enumerating-the-fonts-on-android-platform/
   */
  class TTFAnalyzer {
  
      /**
       * This function parses the TTF file and returns the font name specified in the file.
       *
       * @param fontFilename File absolute name.
       * @return Font name embedded in the file.
       */
      public String getTtfFontName(String fontFilename) {
  
          try {
              // Parses the TTF file format.
              // See http://developer.apple.com/fonts/ttrefman/rm06/Chap6.html
              m_file = new RandomAccessFile(fontFilename, "r");
  
              // Read the version first
              int version = readDword();
  
              // The version must be either 'true' (0x74727565) or 0x00010000
              if (version != 0x74727565 && version != 0x00010000)
                  return null;
  
              // The TTF file consist of several sections called "tables", and we need to know how
              // many of them are there.
              int numTables = readWord();
  
              // Skip the rest in the header
              readWord(); // skip searchRange
              readWord(); // skip entrySelector
              readWord(); // skip rangeShift
  
              // Now we can read the tables
              for (int i = 0; i < numTables; i++) {
                  // Read the table entry
                  int tag = readDword();
                  readDword(); // skip checksum
                  int offset = readDword();
                  int length = readDword();
  
                  // Now here' the trick. 'name' field actually contains the textual string name.
                  // So the 'name' string in characters equals to 0x6E616D65
                  if (tag == 0x6E616D65) {
                      // Here's the name section. Read it completely into the allocated buffer
                      byte[] table = new byte[length];
  
                      m_file.seek(offset);
                      read(table);
  
                      // This is also a table. See http://developer.apple
                      // .com/fonts/ttrefman/rm06/Chap6name.html
                      // According to Table 36, the total number of table records is stored in the
                      // second word, at the offset 2.
                      // Getting the count and string offset - remembering it's big endian.
                      int count = getWord(table, 2);
                      int string_offset = getWord(table, 4);
  
                      // Record starts from offset 6
                      for (int record = 0; record < count; record++) {
                          // Table 37 tells us that each record is 6 words -> 12 bytes, and that
                          // the nameID is 4th word so its offset is 6.
                          // We also need to account for the first 6 bytes of the header above
                          // (Table 36), so...
                          int nameid_offset = record * 12 + 6;
                          int platformID = getWord(table, nameid_offset);
                          int nameid_value = getWord(table, nameid_offset + 6);
  
                          // Table 42 lists the valid name Identifiers. We're interested in 4 but
                          // not in Unicode encoding (for simplicity).
                          // The encoding is stored as PlatformID and we're interested in Mac encoding
                          if (nameid_value == 4 && platformID == 1) {
                              // We need the string offset and length, which are the word 6 and 5
                              // respectively
                              int name_length = getWord(table, nameid_offset + 8);
                              int name_offset = getWord(table, nameid_offset + 10);
  
                              // The real name string offset is calculated by adding the string_offset
                              name_offset = name_offset + string_offset;
  
                              // Make sure it is inside the array
                              if (name_offset >= 0 && name_offset + name_length < table.length)
                                  return new String(table, name_offset, name_length);
                          }
                      }
                  }
              }
  
              return null;
          }
          catch (FileNotFoundException e) {
              // Permissions?
              return null;
          }
          catch (IOException e) {
              // Most likely a corrupted font file
              return null;
          }
      }
  
      /**
       * Font file must be seekable.
       */
      private RandomAccessFile m_file = null;
  
      /**
       * Helper I/O functions
       */
      private int readByte() throws IOException {
  
          return m_file.read() & 0xFF;
      }
  
      private int readWord() throws IOException {
  
          int b1 = readByte();
          int b2 = readByte();
  
          return b1 << 8 | b2;
      }
  
      private int readDword() throws IOException {
  
          int b1 = readByte();
          int b2 = readByte();
          int b3 = readByte();
          int b4 = readByte();
  
          return b1 << 24 | b2 << 16 | b3 << 8 | b4;
      }
  
      private void read(byte[] array) throws IOException {
  
          if (m_file.read(array) != array.length)
              throw new IOException();
      }
  
      /**
       * Helper.
       */
      private int getWord(byte[] array, int offset) {
  
          int b1 = array[offset] & 0xFF;
          int b2 = array[offset + 1] & 0xFF;
  
          return b1 << 8 | b2;
      }
  }
  