my.h

#ifndef LIB_MY_H
    #define LIB_MY_H

    #include <stdarg.h>
    #include <stddef.h>
    #include <stdint.h>

    #define ABS(x) (((x) > 0) ? (x) : (-x))
    #define MIN(x, y) ((x > y) ? (y) : (x))

    #define C_UP(c) ((c) | ' ')
    #define BOUNDS(c, lo, hi) (((c) >= (lo)) && ((c) <= (hi)))

    #define IS_LOWER(c) (BOUNDS(c, 'a', 'z'))
    #define IS_UPPER(c) (BOUNDS(c, 'A', 'Z'))
    #define IS_DIGIT(c) (BOUNDS(c, '0', '9'))
    #define IS_PRINT(c) (BOUNDS(c, ' ', '~'))

    #define IS_ALPHA(c) (IS_LOWER(C_UP(c)))
    #define IS_ALNUM(c) (IS_ALPHA(c) || IS_DIGIT(c))

    #define TO_DIGIT(c) ((int)(c) & 0xf)

    #define ATTR(key) __attribute__((key))
    #define UNUSED ATTR(unused)

    #define LENGTH_OF(arr) (sizeof (arr) / sizeof(arr[0]))

    /* String litterals have their length known at compile-time
     * as they are treated like (char []). Note that a extra byte is taken
     * by the null-terminator.
     **/
    #define SSTR_LEN(s) (LENGTH_OF(s) - 1)

int my_base_len(int base, size_t n);
int my_intlen(intmax_t i);
int my_pow(int nb, int p);
int my_putnbr(char *s, intmax_t nb);
int my_putnbr_base(char *s, size_t base, size_t n);
int my_stridx(const char *str, char c);
int my_strncmp(char const *s1, char const *s2, int n);
int my_strnlen(char const *str, int n);

// Delivery
int my_printf(const char *format, ...)
__attribute__((format(printf, 1, 2)));

int my_vdprintf(int fd, const char *fmt, va_list ap);
void my_int_to_hex(char *buff, int input);

#endif