/* copies input to output, replacing each tab, backspace, and
 * backslash with their escaped equivalents.
 */

#include <stdio.h>

void escape(char s[], char t[]) {
     int i, j;

     for (i = j = 0; t[i] != '\0'; i++) {
	  switch (t[i]) {
	  case '\n':
	       s[j++] = '\\';
	       s[j++] = 'n';
	       break;
	  case '\t':
	       s[j++] = '\\';
	       s[j++] = 't';
	       break;
	  case '\b':
	       s[j++] = '\\';
	       s[j++] = 'b';
	       break;
	  case '\\':
	       s[j++] = '\\';
	       s[j++] = '\\';
	       break;
	  default:
	       s[j++] = s[i];
	       break;
	  }
     }
     
     s[j] = '\0';
}

/* converts escape sequences into real characters */
void unescape(char s[], char t[]) {
     int i, j;

     for (i = j = 0; t[i] != '\0'; i++) {
	  if (t[i] == '\\')
	       switch (t[++i]) {
	       case 't':
		    s[j++] = '\t';
		    break;
	       case 'n':
		    s[j++] = '\n';
		    break;
	       case 'b':
		    s[j++] = '\b';
		    break;
	       case 'a':
		    s[j++] = '\a';
		    break;
	       default:
		    s[j++] = t[i];
		    break;
	       }
	  else
	       s[j++] = t[i];
     }
}