Buffering using Array and reading parts of it.

Well, let's say that the parts are 64000bytes (array with size 64000), and you have 50 parts, then the for-loop which should read the array 50 times * 64000bytes - it takes around 5minutes for 2MB file. The size of files is every time different - once will be 2, once will be 7MB or even 30MB. The files are stored in 64KB-parts in the filesystem and I am using bufferedinputstream which reads data to a byte[] with size 64000, and then add the contents of this byte[] to a bigger array.

mihailmileva at 2007-7-14 18:35:45 >

This is an application for a smartphone device, but the problem is in the basics.

Status.show("Starting playback...", 300);

String sSongName = (String)lfldc.get(lfld, lfld.getSelectedIndex());

currPlaying = sSongName;

RecordStore rs = null;

byte[] data = new byte[0]; //main which will store all data

byte[] temp = new byte[0]; //temporary one for data

byte[] buffer = new byte[64000]; // we will read from the filesystem here

int y = 0;

rs = RecordStore.openRecordStore("Mp3Player:" + sSongName, false); //open file

data = rs.getRecord(1);

rs.closeRecordStore();

int iFileParts = Integer.parseInt(new String(data), 10);

/******* HERE IS THE PROBLEMATIC FOR-LOOP ********/

for(int i = 1; i <= iFileParts; i++) {

Status.show("Buffering! Please wait ..." + i + "/" + iFileParts, 500);

rs = RecordStore.openRecordStore("Mp3Player:" + sSongName + ":" + i, false); //open file

buffer = rs.getRecord(1); //get file data

rs.closeRecordStore();

temp = data; //save old data

data = new byte[temp.length + 64000]; //add 64000bytes to length

for(int z = 0; z < temp.length; z++)

data[z] = temp[z]; //return back old data

for(int z = temp.length; z < data.length; z++) {

if(y < buffer.length) {

data[z] = buffer[y]; //add new data

y++;

}

else break;

}

y = 0;

}

/*********END OF THE LOOP ***********/

p = javax.microedition.media.Manager.createPlayer(new ByteArrayInputStream(data), "audio/mpeg"); //create player

p.realize();

p.prefetch();

vc = (VolumeControl)p.getControl("VolumeControl");

p.addPlayerListener(new MusicListener());

vc.setLevel(preferredVolume);

p.start(); //play

mihailmileva at 2007-7-14 18:35:45 >

So it is not actually a File but a databse record! I do just this to store large documents in a database. My extraction code is

public void extract(int fileID, OutputStream os) throws SQLException, IOException

{

String extractFileSQL = "SELECT file_content FROM FILE_CONTENT where file_id = ? ORDER BY ID";

PreparedStatement stmnt = connection_.prepareStatement(extractFileSQL);

stmnt.setInt(1, fileID);

ResultSet rs = stmnt.executeQuery();

int len = 0;

int index = 0;

while (rs.next())

{

index++;

InputStream is = rs.getBinaryStream(1);

IOCopy.copyInputStreamToOutputStream(is, os);

is.close();

}

rs.close();

}

This load 64MByte from a MySQL database and writes it to a file in about a second.

The IOCopy.copyInputStreamToOutputStream() method is

static public OutputStream copyInputStreamToOutputStream(InputStream istrm, OutputStream ostrm, int bufferLength) throws IOException

{

if (bufferLength < 128)

bufferLength = 128;

else if (bufferLength > 65536)

bufferLength = 65536;

byte[] buffer = new byte[bufferLength];

for (int bytesRead = 0; (bytesRead = istrm.read(buffer)) >= 0;)

{

ostrm.write(buffer, 0, bytesRead);

}

ostrm.flush();

return ostrm;

}

but I wrote this some time age before NIO so it could be made faster.

You can write the output into a ByteArrayOutputSteam and get the bytes from it. This will save a load of copying.

I also use this to to write database content to my home grown MP3 and OGG player and I don't even have to buffer it. I just write the byte straight to the the MP3/OGG bit streams.

sabre150a at 2007-7-14 18:35:45 >