package elte.java2_utikalauz5.io;

import java.io.*;
import java.nio.*;
import java.nio.channels.*;

/**
Bufferkezelés.

@link.forrásfájl {@docRoot}/../data/io/src SumBuffer2.java
@link.letöltés {@docRoot}/../data/io SumBuffer2.jar
@since Java 2 Útikalauz programozóknak 5.0
*/
public class SumBuffer2 {
    static double osszeg( ReadableByteChannel in ) throws IOException {
       double osszeg = 0.0;
       ByteBuffer buffer = ByteBuffer.allocate(1024);
       FloatBuffer adatok = buffer.asFloatBuffer();
       while ( in.read((ByteBuffer)buffer.clear()) != -1 ) {
          adatok.position(0).limit(buffer.remaining()/4);
          while ( adatok.hasRemaining() ) osszeg += adatok.get();
       }
       return osszeg;
    }

  public static void main( String[] args ) throws IOException {
      ByteBuffer buffer = ByteBuffer.allocate(1024);
      for ( byte b=0; b<10; ++b ) buffer.put( b );
      buffer.position(3).limit(7);
      ByteBuffer szelet = buffer.slice();
      for ( int i=0; i<szelet.capacity(); ++i ) {
         byte b = szelet.get(i);
         b *= 11;
         szelet.put( i, b );
      }
      buffer.position(0).limit(10);
      System.out.print("Szelet: ");
      while( buffer.remaining() > 0 )System.out.print( buffer.get() + " " );
      System.out.println();

    String fájl = "sum.dat";
    { // kiírás
      FileOutputStream     fout = new FileOutputStream(fájl);
      BufferedOutputStream bout = new BufferedOutputStream(fout);
      DataOutputStream     dout = new DataOutputStream(bout);
      for( int i=0; i<10; i++ ){ dout.writeFloat((float)i); }
      dout.close();
    }
    FileInputStream fin = new FileInputStream(fájl);
    try {
       FileChannel in = fin.getChannel();
       System.out.println("Összeg: "+osszeg(in));
    } finally { fin.close(); }
  }
}