import java.nio.file.*;
import java.nio.channels.ReadableByteChannel;
import java.io.IOException;
import java.nio.ByteBuffer;

public class ReadPrimesMixedData2 {

  public static void main(String[] args) {
    Path file = Paths.get(System.getProperty("user.home")).resolve("Beginning Java Stuff").resolve("primes.txt");
    if(!Files.exists(file)) {
      System.out.println(file + " does not exist. Terminating program.");
      System.exit(1);
    }

    try(ReadableByteChannel inCh = Files.newByteChannel(file)) {
      ByteBuffer buf = ByteBuffer.allocateDirect(256);
      buf.position(buf.limit());                                       // Set the position for the loop operation
      int strLength = 0;                                               // Stores the string length
      byte[] strChars = null;                                          // Array to hold the bytes for the string

      while(true) {
        if(buf.remaining() < 8) {                                      // Verify enough bytes for string length
          if(inCh.read(buf.compact()) == -1)
            break;                                                     // EOF reached
          buf.flip();
         }
         strLength = (int)buf.getDouble();                             // Get the string length

         // Verify enough bytes for complete string
         if(buf.remaining() < 2*strLength) {
           if(inCh.read(buf.compact()) == -1) {
            System.err.println("EOF found reading the prime string.");
            break;                                                     // EOF reached
           }
           buf.flip();
        }
        strChars = new byte[2*strLength];                              // Array for string bytes
        buf.get(strChars);                                             // Get the bytes

        if(buf.remaining() < 8) {                                      // Verify enough bytes for prime value
          if(inCh.read(buf.compact()) == -1) {
            System.err.println("EOF found reading the binary prime value.");
            break;                          // EOF reached
          }
          buf.flip();
        }

        System.out.printf("String length: %3s  String: %-12s  Binary Value: %3d%n",
                strLength, ByteBuffer.wrap(strChars).asCharBuffer(),buf.getLong());
      }

      System.out.println("\nEOF reached.");

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