K & R : Exercise 1.22 - Fold long lines

Problem

Write a program to fold long input lines into two or more shorter lines after last non blank character that occurs before the nth column of input. Make sure your program does something intelligent with very long lines. If there are no blanks or tabs before the specified column.

Solution

Lets assume the nth column to be 80 characters. Hence we need to buffer those 80 characters before any decision is taken. For any inputs which has more 80 characters of spaces lets just insert one more blank line. Putting all the ideas we get the following code

#include <stdio.h>
#define COLUMN_LEN_MAX 80
int main()
{
  char buf[COLUMN_LEN_MAX] = {'\0', };
  int ch, count = 0, tcount = 0, i, j;
  char temp[COLUMN_LEN_MAX] = {'\0', };

  while((ch = getchar()) != EOF){
    buf[count] = ch;
    count++;
    if((ch == '\n') && (count < COLUMN_LEN_MAX - 1)) {
      /* Given line is small and just dump 
         it no folding required */
      for(i = 0; i < count; i++) {
        putchar(buf[i]);
      }
      count = 0;
    }else if(count >= COLUMN_LEN_MAX - 1) {
      /* Now the given line is 80 characters */
      for(i = 0; i < count; i++) {
        /* store all the space till we hit non white characters */
        if(buf[i] == ' ' || buf[i] == '\t') {
          temp[tcount] = buf[i];
          tcount++;
        }else {
          /* Putchar all white space before putchar non-white space */
          if(tcount > 1) {
            for(j = 0; j < tcount; j++) {
              putchar(temp[j]);
            }
            putchar(buf[i]);
            tcount = 0;
          }else {
            putchar(buf[i]);
          }
        }
      }
      putchar('\n');
      count = 0;
    }
  }
  return 0;
}

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