DataCommon.java

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package edu.rice.cs.hpc.data.db;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

/***************************************************
 * 
 * Class to read and store common header of a database
 * This class only works with hpcprof format version 3.0 
 *
 ***************************************************/
abstract public class DataCommon 
{
    private final static int HEADER_COMMON_SIZE = 256;
    private final static int MESSAGE_SIZE       = 32;
    private final static int MAGIC              = 0x06870630;
    
    protected long format;
    protected long num_threads;
    protected long num_cctid;
    protected long num_metric;
    
    protected String filename;
    
    /*******
     * Open a file and read the first HEADER_COMMON_SIZE bytes
     * 
     * @param file : a string of the filename
     * @throws IOException
     */
    public void open(final String file) 
            throws IOException
    {
        filename = file;
        
        final FileInputStream fis = new FileInputStream(filename);
        final FileChannel channel  = fis.getChannel();
        
        ByteBuffer buffer = ByteBuffer.allocate(HEADER_COMMON_SIZE);
        int numBytes      = channel.read(buffer);
        if (numBytes > 0) 
        {
            // read the common header
            readHeader(file, fis, buffer);
            
            // -------------------------------------------------------------
            // Read the next header (implemented by derived class)
            // -------------------------------------------------------------
            if ( readNext(channel) ) 
            {
                // the implementer can perform other operations
            }
        }

        channel.close();
        fis.close();
    }
    
    /******
     * print out the information of the content of the file
     * @param out : the output stream (can be the standard output)
     */
    public void printInfo( PrintStream out)
    {
        out.println("Format: "      + format);
        out.println("Num threads: " + num_threads);
        out.println("Num cctid: "   + num_cctid);
        out.println("Num metric: "  + num_metric);
    }
    
    /***
     * Free the allocated resources. To be called by the caller at the end.
     * @throws IOException 
     */
    public void dispose() throws IOException
    {
        // to be implemented
    }
    
    /******
     * Default implementation to read the first HEADER_COMMON_SIZE bytes
     * 
     * @param file  : filename
     * @param fis   : input file stread (to be closed in case of exception) 
     * @param buffer : the current buffer containing the first 256 bytes
     * 
     * @throws IOException
     */
    protected void readHeader(String file, FileInputStream fis, ByteBuffer buffer) 
            throws IOException
    {
        // -------------------------------------------------------------
        // get the message header file
        // -------------------------------------------------------------
        final byte []bytes = new byte[MESSAGE_SIZE]; 
        buffer.flip();
        buffer.get(bytes, 0, MESSAGE_SIZE);

        // -------------------------------------------------------------
        // get the magic number
        // -------------------------------------------------------------
        long magic_number = buffer.getLong();
        if (magic_number != MAGIC)
        {
            throw_exception(fis, "Magic number is incorrect: " + magic_number);
        }
        
        // -------------------------------------------------------------
        // check the version
        // -------------------------------------------------------------
        final long version = buffer.getLong();
        if (version < 3)
        {
            throw_exception(fis, "Incorrect file version: " + version);
        }

        // -------------------------------------------------------------
        // check the type
        // -------------------------------------------------------------
        final long type = buffer.getLong();         
        if (!isTypeFormatCorrect(type))
        {
            throw_exception(fis, file + " has inconsistent type " + type);
        }
        
        // -------------------------------------------------------------
        // check the format
        // -------------------------------------------------------------
        // to be ignored at the moment
        format = buffer.getLong();
        
        // -------------------------------------------------------------
        // read number of cct
        // -------------------------------------------------------------
        num_cctid = buffer.getLong();
        
        // -------------------------------------------------------------
        // read number of metrics
        // -------------------------------------------------------------
        num_metric = buffer.getLong();
        
        // -------------------------------------------------------------
        // read number of threads
        // -------------------------------------------------------------
        num_threads = buffer.getLong();
        
        if (num_threads <= 0 || num_cctid <= 0 || num_metric <=0) 
        {
            // warning: empty database.
            // this doesn't mean the file is invalid, but just anomaly
        }
    }
    
    /*******
     * function to close the input stream and thrown an  IO exception
     * 
     * @param input : the io to be closed
     * @param message : message to be thrown
     * 
     * @throws IOException
     */
    private void throw_exception(FileInputStream input, String message)
            throws IOException
    {
        input.close();
        throw new IOException(message);
    }
    
    protected abstract boolean isTypeFormatCorrect(long type);
    protected abstract boolean isFileHeaderCorrect(String header);
    protected abstract boolean readNext(FileChannel input) throws IOException;
}