Solved

Reading incorrect values?

Posted on 2013-05-28
5
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Last Modified: 2013-05-28
I have the follow class, extending Thread. The idea is to extract the date inside the thread, and everything goes well, until the sometime when the received data is larger than a few kilobytes, and then i am starting to reading complete incorrect data. The first few hundreds of readings for lat and lng is correct, but next ones is completely incorrect.
public class ThreadBooksPositions extends Thread
{

    public ThreadBooksPositions()
    {
    }
    ..
    // default constructors

public byte[] inputStreamToByteArray( InputStream iS )
{
    ByteArrayOutputStream out = new ByteArrayOutputStream();

    byte[] bf;
    try
    {
        bf = new byte[ iS.available() ];

        while ( iS.read( bf ) != -1) 
            out.write( bf ); //copy streams

        out.flush();
    }
    catch ( IOException e )
    {
        e.printStackTrace();
    }

    byte[] bO = out.toByteArray();

    if( out != null )
    {
        try
        {
            out.close();
        }
        catch ( IOException e )
        {
            e.printStackTrace();
        }
    }

    return bO; 
}

public ByteBuffer inputStreamToByteBuffer( InputStream iS )
{
    return ByteBuffer.wrap( inputStreamToByteArray( iS ) );
}

    public void run()
    {
        InputStream       iSS           = null;
        HttpURLConnection connection    = null;
        Integer sectionsDescriptorSize1 = 0;
        Integer sectionsDescriptorSize2 = 0;

        try
        {

            URL url = new URL( "192.168.1.4/bookstore.asp?getbooks" );
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod( "GET" );
            connection.connect();

            iSS = connection.getInputStream();

            BufferedInputStream bIS = new BufferedInputStream( iSS );

            if( bIS.available() > 4 )
            {
                Float   lat           = 0F;
                Float   lng           = 0F;

                ByteArrayOutputStream out = new ByteArrayOutputStream();

                ByteBuffer data = inputStreamToByteBuffer( bIS );

                sectionsDescriptorSize1 = data.getInt();
                sectionsDescriptorSize2 = data.getInt();

                ByteBuffer sectionData;

                try
                {
                    if( sectionsDescriptorSize1 > 0 )
                    {
                        byte[] bAS0 = new byte[ sectionsDescriptorSize1 ];
                        data.get( bAS0 );
                    }

                    if( sectionsDescriptorSize2 > 1 )
                    {
                        // trajectory
                        byte[] bAS1 = new byte[ sectionsDescriptorSize2 ];
                        data.get( bAS1, 0, sectionsDescriptorSize2 );

                        sectionData = ByteBuffer.wrap( bAS1 );

                        Boolean readingFailed = true;

                        if( sectionData != null )
                        {
                            while( sectionData.available() > 1 )
                            {
                                try
                                {
                                    readingFailed = false;
                                    lat           = sectionData.getFloat();      // 4
                                    lng           = sectionData.getFloat();      // 4

                                }
                                catch( Exception e )
                                {
                                    readingFailed = true;
                                }

                                try
                                {
                                    if( readingFailed == false )
                                    {
                                        addBookStorePosition( lat, lng );
                                    }
                                }
                                catch (Exception e) 
                                {
                                }
                            }
                        }

                }
                catch( Error e )
                {
                }
            }
        }
        catch( IOException e )
        {

        }
        finally
        {
            if( iSS != null )
            {
                try
                {
                    iSS.close();
                }
                catch( IOException e )
                {

                }           
            }

            if( connection != null )
            {
                connection.disconnect();
            }
        }
    }

}

Open in new window


- What cause reading of incorrect data, and how to fix it ?
0
Comment
Question by:YordanYanakiev
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5 Comments
 
LVL 86

Assisted Solution

by:CEHJ
CEHJ earned 500 total points
ID: 39200931
You can't use available like that. Read the api docs carefully and you'll see (and hopefully remember) why. See http://technojeeves.com/joomla/index.php/free/51-copying-streams
0
 
LVL 1

Author Comment

by:YordanYanakiev
ID: 39200938
Is this the issue ?
What can I do to make it right ?
0
 
LVL 86

Accepted Solution

by:
CEHJ earned 500 total points
ID: 39200949
Use the code at the link i gave you? (It contains a method called ... inputStreamToByteArray)
URL url = new URL( "192.168.1.4/bookstore.asp?getbooks" );

Open in new window

If that ASP script sets the Content-Length header, you can use that to size the byte array. Otherwise, you have no other accurate way of knowing the size.
0
 
LVL 1

Author Closing Comment

by:YordanYanakiev
ID: 39200983
Thank You! This finally worked :)
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 39201012
:)
0

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