ex-3-2.c

/*
 * Exercise 3-2. Write a function  escape(s,t) that converts characters like 
 * newline and tab into visible escape sequences like \n and \t as it copies 
 * the string t to s. Use a switch. Write a function for the other direction 
 * as well, converting escape sequences into the real characters.  
 */

#include <stdio.h>
#define MAXLEN 1000
int escape(char s[], const char t[]);
int unescape(char s[], const char t[]);

int escape(char s[], const char t[]) {
	int i = 0, j = 0, count = 0;
	while (t[i] != '\0') {
		switch (t[i]) {
			case '\n':
				s[j++] = '\\';
				s[j++] = 'n';
				count++;
				break;
			case '\t':
				s[j++] = '\\';
				s[j++] = 't';
				count++;
				break;
			default:
				s[j++] = t[i];
				break;
		}
		i++;
	}
	s[j] = '\0';
	return count;
}

int unescape(char s[], const char t[]) {
	int i = 0, j = 0, count = 0;
	while (t[i] != '\0') {
		if (t[i] == '\\') {
				switch (t[++i]) {
					case 't':
						s[j++] = '\t';
						count++;
						break;
					case 'n':
						s[j++] = '\n';
						count++;
						break;
					case '\0':
						s[j++] = '\\';
						s[j] = '\0';
						return count;
					default:
						s[j++] = '\\';
						s[j++] = t[i];
						break;
				}
		} else {
			s[j++] = t[i];
		}
		i++;
	}
	s[j] = '\0';
	return count;
}


int main(void) {
	char t[] = "fjdla	jdja		fldjsl	fdlsaj\n";
	char s[MAXLEN];
	char u[MAXLEN];
	escape(s, t);
	unescape(u, s);
	printf("t -> %s\n", t);
	printf("s -> %s\n", s);
	printf("u -> %s\n", u);
	return 0;
}