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There is a newer version: 3.8.2.9
package water.fvec;

import water.*;
import water.util.UnsafeUtils;

/**
 * The scale/bias function, where data is in SIGNED bytes before scaling.
 */
public class C2SChunk extends Chunk {
  static protected final int _OFF=8+8;
  private transient double _scale;
  public double scale() { return _scale; }
  private transient long _bias;
  public boolean hasFloat(){ return _scale != (long)_scale; }
  C2SChunk( byte[] bs, long bias, double scale ) { _mem=bs; _start = -1; set_len((_mem.length-_OFF)>>1);
    _bias = bias; _scale = scale;
    UnsafeUtils.set8d(_mem, 0, scale);
    UnsafeUtils.set8 (_mem,8,bias );
  }
  @Override protected final long at8_impl( int i ) {
    long res = UnsafeUtils.get2(_mem,(i<<1)+_OFF);
    if( res == C2Chunk._NA ) throw new IllegalArgumentException("at8_abs but value is missing");
    return (long)((res + _bias)*_scale);
  }
  @Override protected final double atd_impl( int i ) {
    long res = UnsafeUtils.get2(_mem,(i<<1)+_OFF);
    return (res == C2Chunk._NA)?Double.NaN:(res + _bias)*_scale;
  }
  @Override protected final boolean isNA_impl( int i ) { return UnsafeUtils.get2(_mem,(i<<1)+_OFF) == C2Chunk._NA; }
  @Override boolean set_impl(int idx, long l) {
    long res = (long)(l/_scale)-_bias; // Compressed value
    double d = (res+_bias)*_scale;     // Reverse it
    if( (long)d != l ) return false;   // Does not reverse cleanly?
    if( !(Short.MIN_VALUE < res && res <= Short.MAX_VALUE) ) return false; // Out-o-range for a short array
    UnsafeUtils.set2(_mem,(idx<<1)+_OFF,(short)res);
    return true;
  }
  @Override boolean set_impl(int i, double d) {
    short s = (short)((d/_scale)-_bias);
    if( s == C2Chunk._NA ) return false;
    double d2 = (s+_bias)*_scale;
    if( d!=d2 ) return false;
    UnsafeUtils.set2(_mem,(i<<1)+_OFF,s);
    return true;
  }
  @Override boolean set_impl(int i, float f ) { return false; }
  @Override boolean setNA_impl(int idx) { UnsafeUtils.set2(_mem,(idx<<1)+_OFF,(short)C2Chunk._NA); return true; }
  @Override public NewChunk inflate_impl(NewChunk nc) {
    double dx = Math.log10(_scale);
    assert water.util.PrettyPrint.fitsIntoInt(dx);
    nc.set_sparseLen(0);
    nc.set_len(0);
    final int len = _len;
    for( int i=0; i>1);
    _scale= UnsafeUtils.get8d(_mem,0);
    _bias = UnsafeUtils.get8 (_mem,8);
  }

  /**
   * Dense bulk interface, fetch values from the given range
   * @param vals
   * @param from
   * @param to
   */
  @Override
  public double [] getDoubles(double [] vals, int from, int to, double NA){
    for(int i = from; i < to; ++i) {
      long res = UnsafeUtils.get2(_mem,(i<<1)+_OFF);
      vals[i-from] = res != C2Chunk._NA?(res + _bias)*_scale:NA;
    }
    return vals;
  }
  /**
   * Dense bulk interface, fetch values from the given ids
   * @param vals
   * @param ids
   */
  @Override
  public double [] getDoubles(double [] vals, int [] ids){
    int j = 0;
    for(int i:ids) {
      long res = UnsafeUtils.get2(_mem,(i<<1)+_OFF);
      vals[j++] = res != C2Chunk._NA?(res + _bias)*_scale:Double.NaN;
    }
    return vals;
  }

}