From fd20cb1bc83a8062f951fc43ef7dd16d4da1ab04 Mon Sep 17 00:00:00 2001
From: Benjamin Mako Hill <mako@atdot.cc>
Date: Fri, 11 Apr 2014 19:56:45 -0700
Subject: [PATCH] remove shannon entropy as something computed

It's really just nothing something most people will use it and it's
somewhat expensive to compute.
---
 Makefile   |   3 +-
 disorder.c | 192 -----------------------------------------------------
 disorder.h |  70 -------------------
 wikiq.cpp  |   5 +-
 4 files changed, 2 insertions(+), 268 deletions(-)
 delete mode 100644 disorder.c
 delete mode 100644 disorder.h

diff --git a/Makefile b/Makefile
index cc0e56f..b7df471 100644
--- a/Makefile
+++ b/Makefile
@@ -1,13 +1,12 @@
 CXXFLAGS = -O3 
 CFLAGS = $(CXXFLAGS)
-OBJECTS = wikiq.o md5.o disorder.o 
+OBJECTS = wikiq.o md5.o 
 
 all: wikiq
 
 wikiq: $(OBJECTS)
 	$(CXX) $(CXXFLAGS) $(OBJECTS) -lpcrecpp -lpcre -lexpat -o wikiq
 
-disorder.o: disorder.h
 md5.o: md5.h
 
 clean:
diff --git a/disorder.c b/disorder.c
deleted file mode 100644
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;
-}
diff --git a/disorder.h b/disorder.h
deleted file mode 100644
index 91ec47d..0000000
--- a/disorder.h
+++ /dev/null
@@ -1,70 +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
- *
- * $Id$
- **************************************************************************/
-
-#ifndef __DISORDER_H_
-#define __DISORDER_H_
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/** Max number of bytes (i.e., tokens) */
-#define LIBDO_MAX_BYTES      256
-
-/** A convienance value for clients of this library. Feel free to change
- * if you plan to use a larger buffer. You can also safely ignore it, as
- * libdisorder does not use this value internally; it relies on the
- * client-supplied `length' parameter.
- *
- * NB: Might become deprecated because it is potentially misleading and
- * has zero relationship to any library internal state.
- */
-#define LIBDO_BUFFER_LEN   16384
-
-/** 
- * Given a pointer to an array of bytes, return a float indicating the
- * level of entropy in bits (a number between zero and eight),
- * assuming a space of 256 possible byte values. The second argument
- * indicates the number of bytes in the sequence. If this sequence
- * runs into unallocated memory, this function should fail with a
- * SIGSEGV.
- */
-float    shannon_H(char*, long long);
-
-/** Report the number of (unique) tokens seen. This is _not_ the
-    number of individual events seen. For example, if the library sees
-    the string `aaab', the number of events is 4 and the number of
-    tokens is 2. */
-int      get_num_tokens(void);
-
-/** Returns maximum entropy for byte distributions log2(256)=8 bits*/
-float    get_max_entropy(void);
-
-/** Returns the ratio of entropy to maxentropy */
-float    get_entropy_ratio(void);
-
-#ifdef __cplusplus
-};
-#endif
-
-#endif
diff --git a/wikiq.cpp b/wikiq.cpp
index ea82f3a..6a20481 100644
--- a/wikiq.cpp
+++ b/wikiq.cpp
@@ -11,7 +11,6 @@
 #include <stdlib.h>
 #include "expat.h"
 #include <getopt.h>
-#include "disorder.h"
 #include "md5.h"
 #include "dtl/dtl.hpp"
 #include <vector>
@@ -345,7 +344,6 @@ write_row(revisionData *data)
         << data->editorid << "\t"
         << ((data->minor) ? "TRUE" : "FALSE") << "\t"
         << (unsigned int) data->text_size << "\t"
-        << shannon_H(data->text, data->text_size) << "\t"
         << md5_hex_output << "\t"
         << reverted_to << "\t"
         << (int) additions.size() << "\t"
@@ -540,7 +538,7 @@ void print_usage(char* argv[]) {
          << "a tab-separated stream of revisions on standard out:" << endl
          << endl
          << "title, articleid, revid, timestamp, anon, editor, editorid, minor," << endl
-         << "text_length, text_entropy, text_md5, reversion, additions_size, deletions_size" << endl
+         << "text_length, text_md5, reversion, additions_size, deletions_size" << endl
          << ".... and additional fields for each regex executed against add/delete diffs" << endl
          << endl
          << "Boolean fields are TRUE/FALSE except in the case of reversion, which is blank" << endl
@@ -642,7 +640,6 @@ main(int argc, char *argv[])
         << "editor_id" << "\t"
         << "minor" << "\t"
         << "text_size" << "\t"
-        << "text_entropy" << "\t"
         << "text_md5" << "\t"
         << "reversion" << "\t"
         << "additions_size" << "\t"
-- 
2.39.5