Solve Exercise 3-2: escape/unescape

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diff --git a/ch3/3-02_escape.c b/ch3/3-02_escape.c
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+#include <stdio.h>
+
+/* The C Programming Language: 2nd Edition
+ *
+ * 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.
+ *
+ * Answer: Fun! Switches can be used as shorthand if-else chains.
+ */
+
+#define STRMAX 80
+
+void escape(char s[], char t[]) {
+	// i for t, j for s
+	int i, j;
+	j = 0;
+	for (i = 0; t[i] != '\0'; i++) {
+		switch(t[i]) {
+			case '\n':
+				s[j++] = '\\';
+				s[j++] = 'n';
+				break;
+			case '\t':
+				s[j++] = '\\';
+				s[j++] = 't';
+				break;
+			default:
+				s[j++] = t[i];
+				break;
+		}
+	}
+	s[j] = '\0';
+}
+
+void unescape(char s[], char t[]) {
+	// i for t, j for s
+	int i, j;
+	j = 0;
+	for (i = 0; t[i] != '\0'; i++) {
+		if (t[i] == '\\') {
+			switch (t[i + 1]) {
+				case 'n':
+					s[j++] = '\n';
+					break;
+				case 't':
+					s[j++] = '\t';
+					break;
+			}
+		} else {
+			s[j++] = t[i];
+		}
+	}
+	s[j] = '\0';
+}
+
+int main() {
+	char src[STRMAX] = "foo\nbar\t\tbaz\nnozzle";
+	char dest[STRMAX] = "";
+	/* Let's escape it... */
+	escape(dest, src);
+	printf("%s\n", dest);
+	/* ...and unescape it! */
+	unescape(dest, src);
+	printf("%s\n", dest);
+	return 0;
+}