Fixed rot-13 for non-ASCII

rot-13.c

@@ -11,25 +11,26 @@
 
 /*************************** HEADER FILES ***************************/
 #include <string.h>
+#include <ctype.h>
 #include "rot-13.h"
 
 /*********************** FUNCTION DEFINITIONS ***********************/
-void rot13(char str[])
+void rot13(BYTE *buf, size_t len)
 {
-   int case_type, idx, len;
+    int idx;
 
-   for (idx = 0, len = strlen(str); idx < len; idx++) {
-      // Only process alphabetic characters.
-      if (str[idx] < 'A' || (str[idx] > 'Z' && str[idx] < 'a') || str[idx] > 'z')
-         continue;
-      // Determine if the char is upper or lower case.
-      if (str[idx] >= 'a')
-         case_type = 'a';
-      else
-         case_type = 'A';
-      // Rotate the char's value, ensuring it doesn't accidentally "fall off" the end.
-      str[idx] = (str[idx] + 13) % (case_type + 26);
-      if (str[idx] < 26)
-         str[idx] += case_type;
-   }
+    for (idx = 0; idx < len; idx++) {
+
+	// Only process alphabetic characters
+	if (isalpha(buf[idx])) {
+
+	    // lower case rotation
+	    if (islower(buf[idx])) {
+		buf[idx] = (((buf[idx] - 'a') + 13) % 26) + 'a';
+	    // UPPER case rotation
+	    } else {
+		buf[idx] = (((buf[idx] - 'A') + 13) % 26) + 'A';
+	    }
+	}
+    }
 }

rot-13.h

@@ -11,10 +11,17 @@
 
 /*************************** HEADER FILES ***************************/
 #include <stddef.h>
+#include <stdint.h>
+
+/**************************** DATA TYPES ****************************/
+#if !defined(CRYPTO_TYPES)
+typedef uint8_t BYTE;            // 8-bit byte
+#define CRYPTO_TYPES
+#endif
 
 /*********************** FUNCTION DECLARATIONS **********************/
 // Performs IN PLACE rotation of the input. Assumes input is NULL terminated.
 // Preserves each charcter's case. Ignores non alphabetic characters.
-void rot13(char str[]);
+void rot13(BYTE *buf, size_t len);
 
 #endif   // ROT13_H

rot-13_test.c

@@ -24,15 +24,18 @@ int rot13_test()
 	char code[] = {"NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm"};
 	char buf[1024];
 	int pass = 1;
+	size_t len;
 
 	// To encode, just apply ROT-13.
-	strcpy(buf, text);
-	rot13(buf);
-	pass = pass && !strcmp(code, buf);
+	memset(buf, 0, sizeof(buf));
+	len = sizeof(text);
+	memcpy(buf, text, len);
+	rot13((BYTE *)buf, len);
+	pass = pass && (memcmp(code, buf, len) == 0);
 
 	// To decode, just re-apply ROT-13.
-	rot13(buf);
-	pass = pass && !strcmp(text, buf);
+	rot13((BYTE *)buf, len);
+	pass = pass && (memcmp(text, buf, len) == 0);
 
 	return(pass);
 }