RolandWH/caesarcrypt
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support lower case with new modulo

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Roland W-H 2022-11-05 10:36:25 +00:00
parent 2f58a337f1
commit c6b5f1bad7
1 changed files with 15 additions and 5 deletions
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20
src/crypt.c
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@ -9,6 +9,8 @@
*/ */
#include "crypt.h" #include "crypt.h"
#include <stdbool.h>
// Which of the two below functions is faster (find out!) // Which of the two below functions is faster (find out!)
inline int mod(int a, int b) inline int mod(int a, int b)
@ -23,15 +25,22 @@ inline int fast_mod(int a, int b)
return result >= 0 ? result : result + b; return result >= 0 ? result : result + b;
} }
// Below two functions do NOT work for lower case letters (fix this!)
inline bool isupper(char c)
{
return c >= 'A' && c <= 'Z';
}
void caesar_encrypt(char* str, int size, int key) void caesar_encrypt(char* str, int size, int key)
{ {
for (int i = 0; i < size && str[i] != '\n'; i++) for (int i = 0; i < size && str[i] != '\n'; i++)
if (str[i] != ' ') if (str[i] != ' ')
{ {
str[i] += key - 65; bool upper = isupper(str[i]);
str[i] += key - (upper ? 65 : 97);
str[i] %= 26; str[i] %= 26;
str[i] += 65; str[i] += (upper ? 65 : 97);
} }
} }
@ -41,8 +50,9 @@ void caesar_decrypt(char* str, int size, int key)
for (int i = 0; i < size && str[i] != '\n'; i++) for (int i = 0; i < size && str[i] != '\n'; i++)
if (str[i] != ' ') if (str[i] != ' ')
{ {
str[i] = str[i] - key - 65; bool upper = isupper(str[i]);
str[i] = str[i] - key - (upper ? 65 : 97);
str[i] = mod(str[i], 26); str[i] = mod(str[i], 26);
str[i] += 65; str[i] += (upper ? 65 : 97);
} }
} }