ansi_c_pg34_ch01_ex23.c

/*
 * 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 don't nest.
 */

#include <stdio.h>

#define	ST_PRC_NOR_COD 1			/* processing C code */
#define	ST_ABT_ENT_CMT 2			/* about to enter a comment block */
#define ST_INS_NOR_CMT 3			/* inside a C comment block */
#define ST_ABT_EXT_CMT 4			/* about to exit C comment block */
#define ST_INS_QUT_STR 5			/* inside a quoted string */
#define	ST_INS_QUT_ESC 6			/*
									 * inside a quoted string, and secaping
									 * the next character
									 */
#define	ST_INS_SQT_STR 7			/* inside single quoted string */
#define ST_INS_SQT_ESC 8			/*
									 * inside a quoted string, and escaping
									 * the next character
									 */

int
main() {

	int state = ST_PRC_NOR_COD;
	int c;


	while ((c = getchar()) !=EOF) {
		switch (state) {
			case ST_PRC_NOR_COD:
				switch (c) {
					case '/':
						state = ST_ABT_ENT_CMT;
					break;
					case '"':
						state = ST_INS_QUT_STR;
						putchar(c);
					break;
					case '\'':
						state = ST_INS_SQT_STR;
						putchar(c);
					break;
					default:
						putchar(c);
					break;
				}
			break;

			case ST_ABT_ENT_CMT:
				switch (c) {
					case '/':
						state = ST_ABT_ENT_CMT;
						putchar(c);
					break;
					case '*':
						state = ST_INS_NOR_CMT;
					break;
					default:
						state = ST_PRC_NOR_COD;
						putchar('/');
						putchar(c);
					break;
				}
			break;

			case ST_INS_NOR_CMT:
				switch (c) {
					case '*':
						state = ST_ABT_EXT_CMT;
					break;
				}
			break;
			case ST_ABT_EXT_CMT:
				switch (c) {
					case '/':
						state = ST_PRC_NOR_COD;
					break;
					case '*':
						state = ST_ABT_EXT_CMT;
					break;
					default:
						state = ST_INS_NOR_CMT;
					break;
				}
			break;
			case ST_INS_QUT_STR:
				switch (c) {
					case '\\':
						state = ST_INS_QUT_ESC;
						putchar(c);
					break;
					case '"':
						state = ST_PRC_NOR_COD;
						putchar(c);
					break;
					default:
						putchar(c);
					break;
				}
			break;


			case ST_INS_QUT_ESC:
				switch (c) {
					case '\\':
						putchar (c);
					break;
					default:
						state = ST_INS_QUT_STR;
						putchar (c);
					break;
				}
			break;

			case ST_INS_SQT_STR:
				switch(c) {
					case '\\':
						state = ST_INS_SQT_ESC;
						putchar(c);
					break;
					case '\'':
						state = ST_PRC_NOR_COD;
						putchar(c);
					break;
					default:
						state = ST_INS_SQT_STR;
						putchar(c);
					break;
				}
			break;

			case ST_INS_SQT_ESC:
				switch (c) {
					case '\\':
						putchar(c);
					break;
					default:
						state = ST_INS_SQT_STR;
						putchar(c);
					break;
				}
			break;
		}
	}

	return (0);
}