/** 
  * Creates a text file of keywords
  * @author Robert J Morton
  * @version 17 July 2009
*/

// Also relative filespecs for visual checking of the index integrity.

import java.io.*;

class list_index {
  static Writer kwf;
  static String KW = "";
  static int N, a, b, c, d, e, f, L;
  static byte INDEX[];




  /* CONVERT A 4-BYTE TRAIN TO AN INTEGER. Called from 2 places in
  getKeyword(), getFS(), kwlist() and 5 places in main(). */

  private static int getInt(int i) {
    int x0 = INDEX[i];
    x0 &= 0xff;
    x0 <<= 24;

    int
      x1 = INDEX[i + 1];  // 1. Promote each byte to an int
    x1 &= 0xff;           // 2. Chop off propagated 1s in case high bit set
    x1 <<= 16;            // 3. Shift it into its correct position in the int

    int
      x2 = INDEX[i + 2];
    x2 &= 0xff;
    x2 <<= 8;

    int
      x3 = INDEX[i + 3];
    x3 &= 0xff;
    return x0 | x1 | x2 | x3;  // 'or' them all together
  }                            // to form the complete integer




  /* GET THE Nth KEYWORD IN THE KEYWORD INDEX.
  Called from only one place in kwlist(). */

  private static String getKeyword(int n) {
    int
      p = getInt(20 + (  n << 2)),  // start pointer of this keyword's text
      q = getInt(20 + (++n << 2));  // start pointer of next keyword's text
    String s = "";
    while(p < q)
      s += (char)INDEX[a + p++];
    return s;  // return the keyword as a string
  }




  /* RETRIEVE THE HTML FILE'S FILESPEC FROM THE INDEX
  Called from  only one place in kwlist(). */

  private static String getFS(int fsp, int fsi) {
    int
      p = fsp + (fsi << 1),  // form byte reference of required filespec
      x2 = INDEX[p++];
    x2 &= 0xff;
    x2 <<= 8;                // make the two adjacent bytes form
    int                      // a 16-bit integer (short)rn
      x3 = INDEX[p];
    x3 &= 0xff;
    int
      rn = x2 | x3,

      // form the start pointer of the filespec text
      P = e + getInt(d + (  rn << 2)),

      // form the 'end' pointer of the filespec text
      Q = e + getInt(d + (++rn << 2));

    String s = "";
    while(P < Q)
      s += (char)INDEX[P++];
    return s;
  }




  // LIST THE KEYWORDS. Called from only one place in main().

  private static void kwlist() throws IOException {
    kwf = new FileWriter("index.txt");
    for(int i = 0; i < N; i++) {  // for each keyword in the index
      KW = getKeyword(i); 
      kwf.write(KW + '\n');  // write the keyword to the index text file
      int
        fsp = c + getInt(b + (i << 2)),
        fse = (c + getInt(b + ((i + 1) << 2)) - fsp) >> 1;
      for(int j = 0; j < fse; j++) 
        kwf.write('\t' + getFS(fsp, j) + '\n');
    }
    kwf.close();
  }




  public static void main(String args[]) throws IOException {
    File
      f = new File("index.dat");  // create a new file object for index.dat
    InputStream
      I = new FileInputStream(f); // input file stream for index.dat
    L = (int)f.length();
    INDEX = new byte[L];  // big byte array to hold the whole index
    int x, i = 0;

    // while we have not yet reached the end of the file
    while((x = I.read()) != -1)
      INDEX[i++] = (byte)x;  // copy next byte from file to byte array
    a = getInt(0);           // start pointer of keywords text section
    N = (a >> 2) - 1;        // total number of keywords
    a += 20;
    b = getInt( 4) + 20;  // start byte of filespec reference pointers
    c = getInt( 8) + 20;  // start byte of filespec reference numbers
    d = getInt(12) + 20;  // start byte of filespec text pointers
    e = getInt(16) + 20;  // start byte of filespec text stream
    I.close();            // close the URL Connection's input stream

    System.out.println("Total number of keywords in index........ " + N);
    System.out.println("Start byte of keywords text section...... " + a);
    System.out.println("Start byte of filespec reference pointers " + b);
    System.out.println("Start byte of filespec reference numbers  " + c);
    System.out.println("Start byte of filespec text pointers..... " + d);
    System.out.println("Start byte of filespec text section...... " + e);
    System.out.println("End byte of filespec text section........ " + (L - 1));
    kwlist();
  }
}