RolandWH/caesarcrypt
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fix modulo when key is below 26

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Roland W-H 2022-11-04 11:12:30 +00:00
parent 79dd09da1a
commit 2f58a337f1
1 changed files with 25 additions and 2 deletions
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27
src/crypt.c
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@ -10,16 +10,39 @@
#include "crypt.h" #include "crypt.h"
// Which of the two below functions is faster (find out!)
inline int mod(int a, int b)
{
return (a % b + b) % b;
}
inline int fast_mod(int a, int b)
{
const int result = a % b;
return result >= 0 ? result : result + b;
}
// Below two functions do NOT work for lower case letters (fix this!)
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] != ' ') str[i] += key % 26; if (str[i] != ' ')
{
str[i] += key - 65;
str[i] %= 26;
str[i] += 65;
}
} }
void caesar_decrypt(char* str, int size, int key) 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] != ' ') str[i] -= key % 26; if (str[i] != ' ')
{
str[i] = str[i] - key - 65;
str[i] = mod(str[i], 26);
str[i] += 65;
}
} }