content: /* ***** BEGIN LICENSE BLOCK *****
   * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   *
   * The contents of this file are subject to the Mozilla Public License Version
   * 1.1 (the "License"); you may not use this file except in compliance with
   * the License. You may obtain a copy of the License at
   * http://www.mozilla.org/MPL/
   *
   * Software distributed under the License is distributed on an "AS IS" basis,
   * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
   * for the specific language governing rights and limitations under the
   * License.
   *
   * The Original Code is Mozilla Universal charset detector code.
   *
   * The Initial Developer of the Original Code is
   * Netscape Communications Corporation.
   * Portions created by the Initial Developer are Copyright (C) 2001
   * the Initial Developer. All Rights Reserved.
   *
   * Contributor(s):
   *          Shy Shalom <shooshX@gmail.com>
   *          Kohei TAKETA <k-tak@void.in> (Java port)
   *
   * Alternatively, the contents of this file may be used under the terms of
   * either the GNU General Public License Version 2 or later (the "GPL"), or
   * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
   * in which case the provisions of the GPL or the LGPL are applicable instead
   * of those above. If you wish to allow use of your version of this file only
   * under the terms of either the GPL or the LGPL, and not to allow others to
   * use your version of this file under the terms of the MPL, indicate your
   * decision by deleting the provisions above and replace them with the notice
   * and other provisions required by the GPL or the LGPL. If you do not delete
   * the provisions above, a recipient may use your version of this file under
   * the terms of any one of the MPL, the GPL or the LGPL.
   *
   * ***** END LICENSE BLOCK ***** */
  
  package org.mozilla.universalchardet.prober;
  
  import org.mozilla.universalchardet.prober.sequence.SequenceModel;
  
  public class SingleByteCharsetProber extends CharsetProber {
      ////////////////////////////////////////////////////////////////
      // constants
      ////////////////////////////////////////////////////////////////
      public static final int     SAMPLE_SIZE = 64;
      public static final int     SB_ENOUGH_REL_THRESHOLD = 1024;
      public static final float   POSITIVE_SHORTCUT_THRESHOLD = 0.95f;
      public static final float   NEGATIVE_SHORTCUT_THRESHOLD = 0.05f;
      public static final int     SYMBOL_CAT_ORDER = 250;
      public static final int     NUMBER_OF_SEQ_CAT = 4;
      public static final int     POSITIVE_CAT = NUMBER_OF_SEQ_CAT-1;
      public static final int     NEGATIVE_CAT = 0;
      
  
      ////////////////////////////////////////////////////////////////
      // fields
      ////////////////////////////////////////////////////////////////
      private ProbingState    state;
      private SequenceModel   model;
      private boolean         reversed;
      
      private short           lastOrder;
  
      private int             totalSeqs;
      private int[]           seqCounters;
      
      private int             totalChar;
      private int             freqChar;
      
      private CharsetProber   nameProber;
      
      
      ////////////////////////////////////////////////////////////////
      // methods
      ////////////////////////////////////////////////////////////////
  	public SingleByteCharsetProber(SequenceModel model) {
          super();
          this.model = model;
          this.reversed = false;
          this.nameProber = null;
          this.seqCounters = new int[NUMBER_OF_SEQ_CAT];
          reset();
      }
      
      public SingleByteCharsetProber(
              SequenceModel model,
              boolean reversed,
              CharsetProber nameProber)
      {
          super();
          this.model = model;
          this.reversed = reversed;
          this.nameProber = nameProber;
          this.seqCounters = new int[NUMBER_OF_SEQ_CAT];
          reset();
      }
      
  	boolean keepEnglishLetters() {
          return this.model.getKeepEnglishLetter();
      }
  
      @Override
  	public String getCharSetName() {
          if (this.nameProber == null) {
              return this.model.getCharsetName();
          } else {
              return this.nameProber.getCharSetName();
          }
      }
  
      @Override
  	public float getConfidence() {
          if (this.totalSeqs > 0) {
              float r = 1.0f * this.seqCounters[POSITIVE_CAT] / this.totalSeqs / this.model.getTypicalPositiveRatio();
              r = r * this.freqChar / this.totalChar;
              if (r >= 1.0f) {
                  r = 0.99f;
              }
              return r;
          }
  
          return 0.01f;
      }
  
      @Override
  	public ProbingState getState() {
          return this.state;
      }
  
      @Override
  	public ProbingState handleData(byte[] buf, int offset, int length) {
          short order;
          
          int maxPos = offset + length;
          for (int i=offset; i<maxPos; ++i) {
              order = this.model.getOrder(buf[i]);
              
              if (order < SYMBOL_CAT_ORDER) {
                  ++this.totalChar;
              }
              if (order < SAMPLE_SIZE) {
                  ++this.freqChar;
                  if (this.lastOrder < SAMPLE_SIZE) {
                      ++this.totalSeqs;
                      if (!this.reversed) {
                          ++(this.seqCounters[this.model.getPrecedence(this.lastOrder*SAMPLE_SIZE+order)]);
                      } else {
                          ++(this.seqCounters[this.model.getPrecedence(order*SAMPLE_SIZE+this.lastOrder)]);
                      }
                  }
              }
              this.lastOrder = order;
          }
          
          if (this.state == ProbingState.DETECTING) {
              if (this.totalSeqs > SB_ENOUGH_REL_THRESHOLD) {
                  float cf = getConfidence();
                  if (cf > POSITIVE_SHORTCUT_THRESHOLD) {
                      this.state = ProbingState.FOUND_IT;
                  } else if (cf < NEGATIVE_SHORTCUT_THRESHOLD){
                      this.state = ProbingState.NOT_ME;
                  }
              }
          }
          
          return this.state;
      }
  
      @Override
  	public final void reset() {
          this.state = ProbingState.DETECTING;
          this.lastOrder = 255;
          for (int i=0; i<NUMBER_OF_SEQ_CAT; ++i) {
              this.seqCounters[i] = 0;
          }
          this.totalSeqs = 0;
          this.totalChar = 0;
          this.freqChar = 0;
      }
  
      @Override
      public void setOption()
      {}
  }
  