get_last_ex - get_last but throws excpetions

get_last_ex.c

// returns position of the last byte in an array or string whose length is known.
size_t get_last_byte_ex(const char* const bytes, const char byte,size_t len, _Bool* const exists){
    while(bytes[len]!=byte){
        if(!len){
            *exists=0;
            return 0;
        }
        len--;
    }
    
    *exists=1;
    return len;
}

// returns position of the last character of a string whose length is not known. 
size_t get_last_char_ex(const char* const str, const char byte, _Bool* const exists){
    size_t pos=0;
    for(size_t i=0;str[i];i++)
        if(str[i]==byte) pos=i;

    if(!pos) *exists=0;
    else*exists=1;
    
    return pos;
}