ROT13 Function in C

rot13.c

#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/*
ROT13 is a simple letter substitution cipher that replaces a letter with the letter 13 letters after it in the alphabet.
ROT13 is an example of the Caesar cipher.

This function takes a string and returns the string ciphered with Rot13. 
If there are numbers or special characters included in the string, they are returned as they are. 
Only letters from the latin/english alphabet are shifted, like in the original Rot13 "implementation".
*/

char *rot13(const char *src)
{
    if(src == NULL){
      return NULL;
    }
  
    char* result = malloc(strlen(src)+1);
    
    if(result != NULL){
      strcpy(result, src);
      char* current_char = result;
      
      while(*current_char != '\0'){
        //Only increment alphabet characters
        if((*current_char >= 97 && *current_char <= 122) || (*current_char >= 65 && *current_char <= 90)){
          if(*current_char > 109 || (*current_char > 77 && *current_char < 91)){
            //Characters that wrap around to the start of the alphabet
            *current_char -= 13;
          }else{
            //Characters that can be safely incremented
            *current_char += 13;
          }
        }
        current_char++;
      }
    }
    return result;
}

thanks.

you need fix it. (strlen() + plus null terminator)

21 char* result = malloc(strlen(src))+1;
26 result[strlen(src)] = 0x0;

thanks.

you need fix it. (strlen() + plus null terminator)

21 char* result = malloc(strlen(src))+1; 26 result[strlen(src)] = 0x0;

Thanks for your input! I have updated the gist to now allocate 1 extra byte for the null character as strlen does not include this. However specifying the final character as the null character is not necessary as strcpy will include this when copying the original string. Thanks again 😀