Histogram Generator

/*
 * Compute a histogram of the input file. 
 *
 * Author: Tom Bennet
 */

#include <iostream>
#include <iomanip>
#include <string>
#include <string.h>
#include <cctype>
#include <math.h>
#include <stdlib.h>

using namespace std;

/* 
 * Print one line of the histogram.  It receives the character to print,
 * the number of times it apeared, the maximum count, and the number of
 * digits to display in the character count values. 
 */
void prhistline(int chcode, int count, int maxct, int cntdigits)
{
        // Names for the low-valued control characters of the ASCII set.
        string ascnames[] = {
                "nul", "soh", "stx", "etx", "eot",
                "enq", "ack", "bel", "bs ", "ht ",
                "lf ", "vt ", "ff ", "cr ", "so ",
                "si ", "dle", "dc1", "dc2", "dc3",
                "dc4", "nak", "syn", "etb", "can",
                "em ", "sub", "esc", "fs ", "gs ", 
                "rs " };

        // If the count is zero, omit the line.
        if(count == 0) return;

        // Print the character code, base 16 filled with zeros to width 2.
        cout << "x" << setw(2) << setfill('0') << hex << chcode << " "
             << setfill(' ') << dec;

        /* Print the character. */

        // See if it is one of the ASCII control codes.
        if(chcode < sizeof ascnames / sizeof ascnames[0])
                // Low ASCII control codes.
                cout << ascnames[chcode];
        else if(chcode == 127)
                // The only high ASCII control code.
                cout << "del";
        else if(chcode > 127)
                // Byte above the ASCII set.  Input must be a binary file.
                // Just put spaces here.
                cout << "   ";
        else 
                // An actual character.
                cout << (char)chcode << "  ";

        // Print the count.
        cout << " " << setw(cntdigits) << count << " ";

        // Print the bar.  This takes the ratio of the actual count to the
        // maximum count, then computes that portion of the available space
        // as the bar length. */
        int barsize = (79 - 9 - cntdigits) * 
                ((double)count / (double)maxct) + 0.5;
        while(barsize--) cout << "#";
        cout << endl;
}

/*
 * Read the file and print the histogram.
 */

const int HISSIZE = 256;
int main() 
{
        int hist[HISSIZE];              /* Count of bytes. */
        int maxct = 0;                  /* Maximum of any count. */
        int cntdigits;                  /* Num digits for printing count. */

        // Zero out all the counts. */
        memset(hist, 0, sizeof hist);

        /* Read the input file and count each character. */
        char inch;
        while(cin.get(inch)) {
                /* Update the count, and the maximum. */
                if(++hist[inch] > maxct)
                        maxct = hist[inch];
        }

        /* Compute the number of spaces needed for printing the counts */
        cntdigits = log10((float)maxct) + 1.00001;

        /* Print the histogram. */
        for(int m = 0; m < HISSIZE; ++m)
                prhistline(m, hist[m], maxct, cntdigits);
}