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The core random number generators

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package prng.utility;

/**
 * Utility functions for printing out binary data in a nice format.
 *
 * @author Simon Greatrix
 */
public class BLOBPrint {

  /** Hexadecimal digits */
  private static final char[] HEX = new char[]{'0', '1', '2', '3', '4', '5',
      '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};


  /**
   * Dump a binary buffer to a nice text format.
   *
   * @param buf the buffer
   *
   * @return nicely formatted text
   */
  public static String toString(byte[] buf) {
    if (buf == null) {
      return "null";
    }
    return toString(buf, 0, buf.length);
  }


  /**
   * Dump a binary buffer to a nice text format.
   *
   * @param buf the buffer
   * @param off where to start printing. If out of range, starts at beginning of array.
   * @param len number of bytes to print. If negative or too large, runs to end of array.
   *
   * @return nicely formatted text
   */
  public static String toString(byte[] buf, int off, int len) {
    if (buf == null) {
      return "null";
    }
    if (off < 0) {
      off = 0;
    }
    if ((len < 0) || (off + len > buf.length)) {
      len = buf.length - off;
    }

    StringBuilder buffer = new StringBuilder();
    buffer.append('\n');
    StringBuilder bufBytes = new StringBuilder();
    StringBuilder bufChars = new StringBuilder();
    for (int i = 0; i < len; i++) {
      int v = 0xff & buf[i + off];
      bufBytes.append(HEX[v >> 4]).append(HEX[v & 0xf]).append(' ');
      bufChars.append(((32 <= v) && (v <= 126)) ? ((char) v) : '.');
      if ((i % 16) == 7) {
        // half way break
        bufBytes.append("  ");
        bufChars.append(" ");
      } else if ((i % 16) == 15) {
        // end of line
        buffer.append(String.format("%06x  %-50s  %-17s\n",
            Integer.valueOf(i - 15), bufBytes.toString(),
            bufChars.toString()));
        bufBytes.setLength(0);
        bufChars.setLength(0);
      }
    }

    // add last line
    if (len % 16 != 0) {
      buffer.append(String.format("%06x  %-50s  %-17s\n",
          Integer.valueOf(16 * (len / 16)), bufBytes.toString(),
          bufChars.toString()));
    }

    return buffer.toString();
  }
}