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

int strcmp(const char *a, const char *b)
{
  while (*a != '\0' && *b != '\0') {
    if (*a != *b)
      return (*a > *b) - (*a < *b);
    a++, b++;
  }
  if (*a == '\0' && *b == '\0')
    return 0;

  if (*a == '\0')
    return -1;
  return 1;
}

char *strcpy(char *destination, const char *source)
{
  char *ret = destination;
  while (*source != '\0')
    *destination++ = *source++;
  *destination = '\0';
  
  return ret;
}

size_t strlen(const char *str)
{
  size_t ret = 0;
  while (*str != '\0')
    ++ret, ++str;

  return ret;
}

char *strtok_r(char *restrict str, const char *restrict delimiters,
               char **restrict saveptr)
{
  if (str)
    *saveptr = str;
  for (char *ret = *saveptr; **saveptr != '\0'; ++(*saveptr)) {
    for (int i = 0; delimiters[i] != '\0'; i++)
      if (**saveptr == delimiters[i]) {
        *(*saveptr)++ = '\0';
        return ret;
      }
  }
  return 0x0;
}

void *memcpy(void *dest, const void *src, size_t count)
{
  void *ret = dest;
  for (const uint8_t *p = src; count > 0; --count, ++p, ++dest)
    *(uint8_t *)dest = *p;

  return ret;
}

void *memzero(void *start, void *end)
{
  void *ret = start;
  for (uint8_t *p = start; p < (uint8_t *)end; ++p)
    *p = 0;
  
  return ret;
}