remove shannon entropy as something computed

[wikiq] / disorder.c

diff --git a/disorder.c b/disorder.c
deleted file mode 100644 (file)
index a5f7c35..0000000
--- a/disorder.c
+++ /dev/null
@@ -1,192 +0,0 @@
-/***************************************************************************
- *  libdisorder: A Library for Measuring Byte Stream Entropy
- *  Copyright (C) 2010 Michael E. Locasto
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful, but
- *  WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- *  General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License
- *  along with this program; if not, write to the:
- *       Free Software Foundation, Inc.
- *       59 Temple Place, Suite 330
- *       Boston, MA  02111-1307  USA
- *
- * $Id$
- **************************************************************************/
-
-#include <math.h> //for log2()
-#include <stdio.h> //for NULL
-#include "disorder.h"
-
-#if defined(__FreeBSD__)
-#define        log2(x) (log((x)) * (1./M_LN2))
-#endif
-
-/** Frequecies for each byte */
-static int m_token_freqs[LIBDO_MAX_BYTES]; //frequency of each token in sample
-static float m_token_probs[LIBDO_MAX_BYTES]; //P(each token appearing)
-static int m_num_tokens = 0; //actual number of `seen' tokens, max 256 
-static float m_maxent = 0.0;
-static float m_ratio = 0.0;
-static int LIBDISORDER_INITIALIZED = 0;
-
-static void
-initialize_lib()
-{
-  int i = 0;
-  if(1==LIBDISORDER_INITIALIZED)
-    return;
-
-  m_num_tokens = 0;
-
-  for(i=0;i<LIBDO_MAX_BYTES;i++)
-  {
-    m_token_freqs[i]=0;
-    m_token_probs[i]=0.0;
-  }
-
-  LIBDISORDER_INITIALIZED = 1;
-}
-
-/**
- * Set m_num_tokens by iterating over m_token_freq[] and maintaining
- * a counter of each position that does not hold the value of zero.
- */
-static void
-count_num_tokens()
-{
-  int i = 0;
-  int counter = 0;
-  for(i=0;i<LIBDO_MAX_BYTES;i++)
-  {
-    if(0!=m_token_freqs[i])
-    {
-      counter++;
-    }
-  }
-  m_num_tokens = counter;
-  return;
-}
-
-/**
- * Sum frequencies for each token (i.e., byte values 0 through 255)
- * We assume the `length' parameter is correct.
- *
- * This function is available only to functions in this file.
- */
-static void
-get_token_frequencies(char* buf, 
-                     long long length)
-{
-  int i=0;
-  char* itr=NULL;
-  unsigned char c=0;
-
-  itr = buf;
-
-  //reset number of tokens
-  m_num_tokens = 0;
-
-  //make sure freqency and probability arrays are cleared
-  for(i=0;i<LIBDO_MAX_BYTES;i++)
-  {
-    m_token_freqs[i] = 0;
-    m_token_probs[i] = 0.0;
-  }
-
-  for(i=0;i<length;i++)
-  {
-    c = (unsigned char)*itr;
-    //assert(0<=c<LIBDO_MAX_BYTES);
-    m_token_freqs[c]++;
-    itr++;
-  }
-}
-
-/**
- * Return entropy (in bits) of this buffer of bytes. We assume that the
- * `length' parameter is correct. This implementation is a translation
- * of the PHP code found here:
- *
- *    http://onlamp.com/pub/a/php/2005/01/06/entropy.html
- *
- * with a helpful hint on the `foreach' statement from here:
- *
- *    http://php.net/manual/en/control-structures.foreach.php
- */
-float
-shannon_H(char* buf, 
-         long long length)
-{
-  int i = 0;
-  float bits = 0.0;
-  char* itr=NULL; //values of itr should be zero to 255
-  unsigned char token;
-  int num_events = 0; //`length' parameter
-  float freq = 0.0; //loop variable for holding freq from m_token_freq[]
-  float entropy = 0.0; //running entropy sum
-
-  if(NULL==buf || 0==length)
-    return 0.0;
-
-  if(0==LIBDISORDER_INITIALIZED)
-    initialize_lib();
-
-  itr = buf;
-  m_maxent = 0.0;
-  m_ratio = 0.0;
-  num_events = length;
-  get_token_frequencies(itr, num_events); //modifies m_token_freqs[]
-  //set m_num_tokens by counting unique m_token_freqs entries
-  count_num_tokens(); 
-
-  if(m_num_tokens>LIBDO_MAX_BYTES)
-  {
-    //report error somehow?
-    return 0.0;
-  }
-
-  //iterate through whole m_token_freq array, but only count
-  //spots that have a registered token (i.e., freq>0)
-  for(i=0;i<LIBDO_MAX_BYTES;i++)
-  {
-    if(0!=m_token_freqs[i])
-    {
-      token = i;
-      freq = ((float)m_token_freqs[token]); 
-      m_token_probs[token] = (freq / ((float)num_events));
-      entropy += m_token_probs[token] * log2(m_token_probs[token]);
-    }
-  }
-
-  bits = -1.0 * entropy;
-  m_maxent = log2(m_num_tokens);
-  m_ratio = bits / m_maxent;
-
-  return bits;
-}
-
-int 
-get_num_tokens()
-{
-  return m_num_tokens;
-}
-
-float 
-get_max_entropy()
-{
-  return m_maxent;
-}
-
-float 
-get_entropy_ratio()
-{
-  return m_ratio;
-}