K&R C Bible Exercise 3-2

/***************************************************/*Answer to Exercise 3-2, page 60 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>void escape(char * s, char * t);void unescape(char * s, char * t);int main(void) {char text1[50] = "/aHello,/n/tWorld! Mistakee/b was /"Extra 'e'/"!/n";char text2[51];printf("Original string:/n%s/n", text1);escape(text2, text1);printf("Escaped string:/n%s/n", text2);unescape(text1, text2);printf("Unescaped string:/n%s/n", text1);return 0;}/* Copies string t to string s, converting specialcharacters into their appropriate escape sequences.The "complete set of escape sequences" found inK&R Chapter 2 is used, with the exception of:/? /' /ooo /xhhas these can be typed directly into the source code,(i.e. without using the escape sequences themselves)and translating them is therefore ambiguous. */void escape(char * s, char * t) {int i, j;i = j = 0;while ( t[i] ) {/* Translate the special character, if we have one */switch( t[i] ) {case '/n':s[j++] = '//';s[j] = 'n';break;case '/t':s[j++] = '//';s[j] = 't';break;case '/a':s[j++] = '//';s[j] = 'a';break;case '/b':s[j++] = '//';s[j] = 'b';break;case '/f':s[j++] = '//';s[j] = 'f';break;case '/r':s[j++] = '//';s[j] = 'r';break;case '/v':s[j++] = '//';s[j] = 'v';break;case '//':s[j++] = '//';s[j] = '//';break;case '/"': s[j++]= '//';s[j] = '/"';break;default:/* This is not a special character, so just copy it */s[j] = t[i];break;}++i;++j;}s[j] = t[i]; /* Don't forget the null character */}/* Copies string t to string s, converting escape sequencesinto their appropriate special characters. See the commentfor escape() for remarks regarding which escape sequencesare translated. */void unescape(char * s, char * t) {int i, j;i = j = 0;while ( t[i] ) {switch ( t[i] ) {case '//':/* We've found an escape sequence, so translate it */switch( t[++i] ) {case 'n':s[j] = '/n';break;case 't':s[j] = '/t';break;case 'a':s[j] = '/a';break;case 'b':s[j] = '/b';break;case 'f':s[j] = '/f';break;case 'r':s[j] = '/r';break;case 'v':s[j] = '/v';break;case '//':s[j] = '//';break;case '/"':s[j] = '/"';break;default:/* We don't translate this escapesequence, so just copy it verbatim */s[j++] = '//';s[j] = t[i];}break;default:/* Not an escape sequence, so just copy the character */s[j] = t[i];}++i;++j;}s[j] = t[i]; /* Don't forget the null character */}