Chapter 5 - Pointers and Arrays 12

Extend entab and detab to accept the shorthand entab -m +n to mean tab stops every n columns, starting at column m. Choose convenient (for the user) default behavior.

Solution by Franz Fritsche

/*
 * entab.c (Exercise 5-12)
 * Author   :   Franz Fritsche
 * About    :   Replaces strings of blanks with the minimum number
 *              of tabs and blanks to achieve the same spacing.
 * Usage    :   entab -m +n
 *              (tab stops every n columns, starting at column m)
 * Date     :   March 23, 2007
 */

#include <stdio.h>
#include <stdlib.h>

#define TABSIZE 4    /* default tab size */

int main(int argc, char *argv[])
{
    int c, pos, spaces, i;
    int tabsize[2] = {TABSIZE, TABSIZE};

    while (--argc > 0 && (**++argv == '-' || **argv == '+'))
        switch (**argv)
        {
            case '-':
                if ((pos = atoi(*argv + 1)) > 0)
                    tabsize[0] = pos;
                break;
            case '+':
                if ((pos = atoi(*argv + 1)) > 0)
                    tabsize[1] = pos;
                break;
        }
   
    pos = 0;
    spaces = 0;
    i = 0;
    while ((c = getchar()) != EOF)
    {
        if (c == ' ')
        {
            if (pos < tabsize[i]-1)
            {
                ++pos;
                ++spaces;
            }
            else
            {
                putchar('\t');
                pos = 0;
                spaces = 0;
                if (i < 1)
                    i++;
            }
        }
        else
        {
            if (c != '\t')
                while (spaces)
                {
                    putchar(' ');
                    --spaces;
                }
               
            putchar(c);
           
            if (c == '\n')
            {
                pos = 0;
                spaces = 0;
                i = 0;
            }
            else if  (c == '\t')
            {
                pos = 0;
                spaces = 0;
                if (i < 1)
                    i++;
            }               
            else /* normal character */
            {
                ++pos;
           
                if (pos == tabsize[i])
                {
                    pos = 0;
                    if (i < 1)
                        i++;
                }
            }
        }
    }
   
    while (spaces) /* may be left to do */
    {
        putchar(' ');
        --spaces;
    }

    return 0;
}

/*
 * detab.c (Exercise 5-12)
 * Author   :   Franz Fritsche
 * About    :   Replaces tabs in the input with the proper number
 *              of blanks to space to the next tab stop.
 * Usage    :   detab -m +n
 *              (tab stops every n columns, starting at column m)
 * Date     :   March 23, 2007
 */

#include <stdio.h>
#include <stdlib.h>

#define TABSIZE 4    /* default tab size */

int main(int argc, char *argv[])
{
    int c, pos, i;
    int tabsize[2] = {TABSIZE, TABSIZE};

    while (--argc > 0 && (**++argv == '-' || **argv == '+'))
        switch (**argv)
        {
            case '-':
                if ((pos = atoi(*argv + 1)) > 0)
                    tabsize[0] = pos;
                break;
            case '+':
                if ((pos = atoi(*argv + 1)) > 0)
                    tabsize[1] = pos;
                break;
        }
   
    pos = 0;
    i = 0;
    while ((c = getchar()) != EOF)
    {
        if (c == '\t')
        {
            while (pos < tabsize[i])
            {
                putchar(' ');
                ++pos;
            }
            pos = 0;
            if (i < 1)
                i++;
        }
        else 
        {
            putchar(c);
           
            if (c == '\n')
            {
                pos = 0;
                i = 0;
            }
            else /* normal character */
            {
                ++pos;
           
                if (pos == tabsize[i])
                {
                    pos = 0;
                    if (i < 1)
                        i++;
                }
            }
        }
    }

    return 0;
}