Exercise 1-23 (continued)

Exercise 1-23  Write a program to remove all comments from a C program.  Don't forget to handle quoted strings and character constants properly.  C comments do not nest.

#include <stdio.h>

static int buffer_slash = 0;

void remove_comments(char current, char last)

{

  static int comment = 0;

  static int skip = 0;

  if (skip)

    skip = 0;    /* Avoid what happens when you have / * / in sequence */

  else if (comment == 0)

  {

    if (current == '/')

      buffer_slash = 1;

    else if (last == '/' && current == '*')

    {

      buffer_slash = 0;

      comment = 1;

      skip = 1;

    }

    else

    {

      if (buffer_slash)

      {

        buffer_slash = 0;

        putchar('/');

      }

      putchar(current);

    }

  }

  else  /* comment == 1 */

  {

    if (last == '*' && current == '/')

      comment = 0;

  }

}

void remove_double_quotes(char current, char last)

{

  static int quotes_open = 0;

  if (quotes_open)

    putchar(current);

  else

    remove_comments(current, last);

  if (current=='\"')

    quotes_open = !quotes_open;

}

void parse_single_quotes(char current, char last)

{

  static int single_quote_open = 0;

  /* If we're in single quotes, then " does not open a string literal. */

  if (single_quote_open)

    remove_comments(current, last);

  else

    remove_double_quotes(current, last);

  if ((last!='\\') && (current=='\''))

      single_quote_open = !single_quote_open;

}

int main(void)

{

  int last = 0;

  int current;

  while (current = getchar(), current!=EOF)

  {

    parse_single_quotes(current, last);

    last = current;

  }

  if (buffer_slash)

    putchar('/');

  return 0;

}