package org.jaudiotagger.audio.mp3;

 import org.jaudiotagger.audio.exceptions.InvalidAudioFrameException;

 import java.nio.ByteBuffer;

 public class ByteArrayMP3AudioHeader extends MP3AudioHeader

 {

     public ByteArrayMP3AudioHeader(byte[] fileBytes)

     {

         // This is substantially faster than updating the filechannels position

         long filePointerCount = 0;

         // Read into Byte Buffer in Chunks

         ByteBuffer bb = ByteBuffer.wrap(fileBytes);

         boolean syncFound = false;

         do

         {

             if (MPEGFrameHeader.isMPEGFrame(bb))

             {

                 try

                 {

                     mp3FrameHeader = MPEGFrameHeader.parseMPEGHeader(bb);

                     syncFound = true;

                     if (XingFrame.isXingFrame(bb, mp3FrameHeader))

                     {

                         try

                         {

                             // Parses Xing frame without modifying position of main buffer

                             mp3XingFrame = XingFrame.parseXingFrame();

                         }

                         catch (InvalidAudioFrameException ex)

                         {

                             // We Ignore because even if Xing Header is corrupted

                             // doesn't mean file is corrupted

                         }

                         break;

                     }

                     // There is a small but real chance that an unsynchronised ID3 Frame could fool the MPEG

                     // Parser into thinking it was an MPEG Header. If this happens the chances of the next bytes

                     // forming a Xing frame header are very remote. On the basis that most files these days have

                     // Xing headers we do an additional check for when an apparent frame header has been found

                     // but is not followed by a Xing Header:We check the next header this wont impose a large

                     // overhead because wont apply to most Mpegs anyway ( Most likely to occur if audio

                     // has an APIC frame which should have been unsynchronised but has not been) , or if the frame

                     // has been encoded with as Unicode LE because these have a BOM of 0xFF 0xFE

                     else

                     {

                         syncFound = isNextFrameValid(bb);

                         if (syncFound)

                         {

                             break;

                         }

                     }

                 }

                 catch (InvalidAudioFrameException ex)

                 {

                     // We Ignore because likely to be incorrect sync bits ,

                     // will just continue in loop

                 }

             }

             bb.position(bb.position() + 1);

             filePointerCount++;

         }

         while (!syncFound);

         setFileSize(fileBytes.length);

         setMp3StartByte(filePointerCount);

         setTimePerFrame();

         setNumberOfFrames();

         setTrackLength();

         setBitRate();

         setEncoder();

     }

     private boolean isNextFrameValid(ByteBuffer bb)

     {

         boolean result = false;

         int currentPosition = bb.position();

         bb.position(bb.position() + mp3FrameHeader.getFrameLength());

         if (MPEGFrameHeader.isMPEGFrame(bb))

         {

             try

             {

                 MPEGFrameHeader.parseMPEGHeader(bb);

                 MP3AudioHeader.logger.finer("Check next frame confirms is an audio header ");

                 result = true;

             }

             catch (InvalidAudioFrameException ex)

             {

                 MP3AudioHeader.logger.finer("Check next frame has identified this is not an audio header");

                 result = false;

             }

         }

         // Set back to the start of the previous frame

         bb.position(currentPosition);

         return result;

     }

 }