CXX = g++
CFLAGS = -O3
+OBJECTS = disorder.o
all: wikiq
-wikiq: wikiq.c
- $(CXX) $(CFLAGS) wikiq.c -o wikiq -lexpat
+wikiq: wikiq.c $(OBJECTS)
+ $(CXX) $(CFLAGS) wikiq.c $(OBJECTS) -o wikiq -lexpat
+
+disorder.o: disorder.c
+ $(CXX) $(CFLAGS) -c disorder.c
clean:
- rm -f wikiq
+ rm -f wikiq $(OBJECTS)
gprof:
$(MAKE) CFLAGS=-pg wikiq
--- /dev/null
+/***************************************************************************
+ * 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;
+}
--- /dev/null
+/***************************************************************************
+ * 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_
+
+/** 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);
+
+#endif
#include <stdlib.h>
#include "expat.h"
#include <getopt.h>
+#include "disorder.h"
// timestamp of the form 2003-11-07T00:43:23Z
#define DATE_LENGTH 10
switch (data->output_type)
{
case SIMPLE:
- printf("\t%i\n", (unsigned int) strlen(data->text));
+ printf("\t%i\t%f\n", (unsigned int) strlen(data->text), shannon_H(data->text, data->text_size));
//printf("\n");
break;
case FULL:
}
-char
-*append(char *entry, char *newstr)
-{
- char *newbuff;
- int len;
- len = (strlen(entry)+strlen(newstr))*sizeof(char) + 1;
- newbuff = (char*) realloc(entry, len);
- strcat(newbuff, newstr);
- return newbuff;
-}
-
-char
-*cache(char *entry, char *newstr)
-{
- char *newbuff;
- int len;
- len = strlen(newstr)*sizeof(char) + 1; // include space for the '\0' !
- newbuff = (char*) malloc(len);
- strcpy(newbuff,newstr);
- return newbuff;
-
-}
-
-char
-*store(char *entry, char *newstr)
-{
- char *newbuff;
- if (entry == NULL)
- newbuff = cache(entry, newstr);
- else
- newbuff = append(entry, newstr);
- return newbuff;
-}
-
void
split_timestamp(revisionData *data)
{
strncpy(data->time, timeinstamp, TIME_LENGTH);
}
-/* currently unused */
-static int
-is_whitespace(char *string) {
- int len = strlen(string);
- while (isspace(string[0]) && strlen(string) > 0) {
- string++;
- }
- if (strcmp(string, "") == 0)
- return 1;
- else
- return 0;
-}
-
// like strncat but with previously known length
char*
strlcatn(char *dest, const char *src, size_t dest_len, size_t n)
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