ansi_c_pg058_ch03_ex03.c

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


#define ST_EXP	0
#define ST_BEG	1
#define ST_HYP	2
#define ST_RDY	3
#define ST_ESC	4

#define XP_INV	0
#define XP_SML	1
#define XP_CAP	2
#define XP_NUM	3

int
is_valid_to_expand(char beg, char end) {
	if (beg >= 'a' && beg <= 'z' && end >= 'a' && end <= 'z')
		return XP_SML;
	else if (beg >= 'A' && beg <= 'Z' && end >= 'A' && end <= 'Z')
		return XP_CAP;
	else if (beg >= '0' && beg <= '9' && end >= '0' && end <= '9')
		return XP_NUM;
	else
		return XP_INV;
}


char* escape(char* s1, char* s2) {
	char beg, end;
	char c;
	int i, j, st, inc;

	i = j = 0;
	st = ST_EXP;

	while(c = s1[i++]) {
		switch(st) {
			case ST_EXP:
				if (c == '-') { /* we should escape the next expansion */
					st = ST_ESC;
					s2[j++] = c;
				} else {
					beg = c;
					st = ST_BEG;
				}
			break;
			case ST_BEG:
				if (c == '-') {
					st = ST_HYP;
				} else {
					s2[j++] = beg;
					beg = c;
				}
			break;
			case ST_HYP:
				end = c;
				st = ST_RDY;
			break;
			case ST_RDY:
				if (c == '-' || !is_valid_to_expand(beg, end)) {
					/* this expansion was escaped  or invalid to expand */
					s2[j++] = beg;
					s2[j++] = '-';
					s2[j++] = end;
					s2[j++] = c;
				} else {
					inc = (beg < end)?1:((beg == end)?0:-1);
					s2[j++] = beg;
					do {
						beg += inc;
						s2[j++] = beg;
					} while (beg != end);

				}
				st = ST_EXP;
			break;
			case ST_ESC:
				if (c == '-') {
					s2[j++] = c;
				} else {
					s2[j++] = c;
					st = ST_EXP;
				}
			break;
		}
	}


	if(st == ST_HYP) {
		s2[j++] = beg;
		s2[j++] = '-';
	} else if (st == ST_BEG) {
		s2[j++] = beg;
	} else if (st == ST_RDY) {
		if (is_valid_to_expand(beg, end)) {

			inc = (beg < end)?1:((beg == end)?0:-1);
			s2[j++] = beg;

			do {
				beg += inc;
				s2[j++] = beg;
			} while (beg != end);

		} else {
			s2[j++] = beg;
			s2[j++] = '-';
			s2[j++] = end;
		}

	} else if (st == ST_ESC) {
		s2[j++] = '-';
	}

	s2[j++] = '\0';
}

int
main (int argc, char** argv) {

	char *s2;
	s2 = malloc(sizeof(char) * 1000);
	escape(argv[1], s2);
	printf("%s\n", s2);

	return (0);

}