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Justine Tunney
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267
tool/decode/ent.c
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267
tool/decode/ent.c
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/* PUBLIC DOMAIN */
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/* clang-format off */
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/*
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ENT -- Entropy calculation and analysis of putative
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random sequences.
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Designed and implemented by John "Random" Walker in May 1985.
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Multiple analyses of random sequences added in December 1985.
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Bit stream analysis added in September 1997.
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Terse mode output, getopt() command line processing,
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optional stdin input, and HTML documentation added in
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October 1998.
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Documentation for the -t (terse output) option added
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in July 2006.
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Replaced table look-up for chi square to probability
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conversion with algorithmic computation in January 2008.
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For additional information and the latest version,
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see http://www.fourmilab.ch/random/
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*/
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#include "libc/calls/calls.h"
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#include "libc/math.h"
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#include "libc/rand/rand.h"
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#include "libc/stdio/stdio.h"
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#include "libc/str/str.h"
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#include "third_party/getopt/getopt.h"
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#define UPDATE "January 28th, 2008"
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#define FALSE 0
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#define TRUE 1
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#ifdef M_PI
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#define PI M_PI
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#else
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#define PI 3.14159265358979323846
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#endif
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/* ISO 8859/1 Latin-1 alphabetic and upper and lower case bit vector tables. */
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#define isISOspace(x) \
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((isascii(((unsigned char)(x))) && isspace(((unsigned char)(x)))) || \
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((x) == 0xA0))
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#define isISOalpha(x) \
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((isoalpha[(((unsigned char)(x))) / 8] & \
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(0x80 >> ((((unsigned char)(x))) % 8))) != 0)
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#define isISOupper(x) \
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((isoupper[(((unsigned char)(x))) / 8] & \
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(0x80 >> ((((unsigned char)(x))) % 8))) != 0)
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#define isISOlower(x) \
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((isolower[(((unsigned char)(x))) / 8] & \
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(0x80 >> ((((unsigned char)(x))) % 8))) != 0)
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#define isISOprint(x) ((((x) >= ' ') && ((x) <= '~')) || ((x) >= 0xA0))
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#define toISOupper(x) \
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(isISOlower(x) \
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? (isascii(((unsigned char)(x))) ? toupper(x) \
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: (((((unsigned char)(x)) != 0xDF) && \
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(((unsigned char)(x)) != 0xFF)) \
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? (((unsigned char)(x)) - 0x20) \
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: (x))) \
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: (x))
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#define toISOlower(x) \
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(isISOupper(x) \
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? (isascii(((unsigned char)(x))) ? tolower(x) \
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: (((unsigned char)(x)) + 0x20)) \
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: (x))
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unsigned char isoalpha[32] = {
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0, 0, 0, 0, 0, 0, 0, 0, 127, 255, 255, 224, 127, 255, 255, 224,
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0, 0, 0, 0, 0, 0, 0, 0, 255, 255, 254, 255, 255, 255, 254, 255};
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unsigned char isoupper[32] = {0, 0, 0, 0, 0, 0, 0, 0, 127, 255, 255,
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224, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 255, 255, 254, 254, 0, 0, 0, 0};
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unsigned char isolower[32] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 127, 255, 255, 224, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 1, 255, 255, 254, 255};
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/* HELP -- Print information on how to call */
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static void help(void)
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{
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printf("ent -- Calculate entropy of file. Call");
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printf("\n with ent [options] [input-file]");
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printf("\n");
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printf("\n Options: -b Treat input as a stream of bits");
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printf("\n -c Print occurrence counts");
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printf("\n -f Fold upper to lower case letters");
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printf("\n -t Terse output in CSV format");
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printf("\n -u Print this message\n");
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printf("\nBy John Walker");
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printf("\n http://www.fourmilab.ch/");
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printf("\n %s\n", UPDATE);
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}
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/* Main program */
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int main(int argc, char *argv[])
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{
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int i, oc, opt;
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long ccount[256]; /* Bins to count occurrences of values */
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long totalc = 0; /* Total character count */
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char *samp;
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double montepi, chip,
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scc, ent, mean, chisq;
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FILE *fp = stdin;
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int counts = FALSE, /* Print character counts */
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fold = FALSE, /* Fold upper to lower */
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binary = FALSE, /* Treat input as a bitstream */
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terse = FALSE; /* Terse (CSV format) output */
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while ((opt = getopt(argc, argv, "bcftu?BCFTU")) != -1) {
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switch (toISOlower(opt)) {
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case 'b':
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binary = TRUE;
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break;
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case 'c':
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counts = TRUE;
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break;
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case 'f':
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fold = TRUE;
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break;
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case 't':
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terse = TRUE;
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break;
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case '?':
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case 'u':
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help();
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return 0;
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}
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}
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if (optind < argc) {
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if (optind != (argc - 1)) {
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printf("Duplicate file name.\n");
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help();
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return 2;
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}
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if ((fp = fopen(argv[optind], "rb")) == NULL) {
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printf("Cannot open file %s\n", argv[optind]);
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return 2;
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}
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}
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samp = binary ? "bit" : "byte";
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memset(ccount, 0, sizeof ccount);
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/* Initialise for calculations */
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rt_init(binary);
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/* Scan input file and count character occurrences */
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while ((oc = fgetc(fp)) != EOF) {
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unsigned char ocb;
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if (fold && isISOalpha(oc) && isISOupper(oc)) {
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oc = toISOlower(oc);
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}
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ocb = (unsigned char) oc;
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totalc += binary ? 8 : 1;
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if (binary) {
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int b;
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unsigned char ob = ocb;
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for (b = 0; b < 8; b++) {
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ccount[ob & 1]++;
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ob >>= 1;
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}
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} else {
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ccount[ocb]++; /* Update counter for this bin */
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}
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rt_add(&ocb, 1);
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}
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fclose(fp);
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/* Complete calculation and return sequence metrics */
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rt_end(&ent, &chisq, &mean, &montepi, &scc);
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if (terse) {
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printf("0,File-%ss,Entropy,Chi-square,Mean,Monte-Carlo-Pi,Serial-Correlation\n",
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binary ? "bit" : "byte");
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printf("1,%ld,%f,%f,%f,%f,%f\n",
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totalc, ent, chisq, mean, montepi, scc);
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}
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/* Calculate probability of observed distribution occurring from
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the results of the Chi-Square test */
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chip = pochisq(chisq, (binary ? 1 : 255));
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/* Print bin counts if requested */
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if (counts) {
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if (terse) {
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printf("2,Value,Occurrences,Fraction\n");
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} else {
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printf("Value Char Occurrences Fraction\n");
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}
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for (i = 0; i < (binary ? 2 : 256); i++) {
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if (terse) {
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printf("3,%d,%ld,%f\n", i,
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ccount[i], ((double) ccount[i] / totalc));
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} else {
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if (ccount[i] > 0) {
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printf("%3d %c %10ld %f\n", i,
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/* The following expression shows ISO 8859-1
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Latin1 characters and blanks out other codes.
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The test for ISO space replaces the ISO
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non-blanking space (0xA0) with a regular
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ASCII space, guaranteeing it's rendered
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properly even when the font doesn't contain
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that character, which is the case with many
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X fonts. */
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(!isISOprint(i) || isISOspace(i)) ? ' ' : i,
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ccount[i], ((double) ccount[i] / totalc));
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}
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}
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}
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if (!terse) {
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printf("\nTotal: %10ld %f\n\n", totalc, 1.0);
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}
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}
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/* Print calculated results */
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if (!terse) {
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printf("Entropy = %f bits per %s.\n", ent, samp);
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printf("\nOptimum compression would reduce the size\n");
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printf("of this %ld %s file by %d percent.\n\n", totalc, samp,
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(short) ((100 * ((binary ? 1 : 8) - ent) /
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(binary ? 1.0 : 8.0))));
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printf(
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"Chi square distribution for %ld samples is %1.2f, and randomly\n",
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totalc, chisq);
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if (chip < 0.0001) {
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printf("would exceed this value less than 0.01 percent of the times.\n\n");
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} else if (chip > 0.9999) {
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printf("would exceed this value more than than 99.99 percent of the times.\n\n");
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} else {
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printf("would exceed this value %1.2f percent of the times.\n\n",
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chip * 100);
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}
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printf(
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"Arithmetic mean value of data %ss is %1.4f (%.1f = random).\n",
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samp, mean, binary ? 0.5 : 127.5);
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printf("Monte Carlo value for Pi is %1.9f (error %1.2f percent).\n",
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montepi, 100.0 * (fabs(PI - montepi) / PI));
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printf("Serial correlation coefficient is ");
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if (scc >= -99999) {
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printf("%1.6f (totally uncorrelated = 0.0).\n", scc);
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} else {
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printf("undefined (all values equal!).\n");
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}
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}
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return 0;
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}
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