string.c

#include "string.h"

int k_strcmp(const char *s1, const char *s2) {
  while (*s1 && (*s1 == *s2)) {
    s1++;
    s2++;
  }
  return *(unsigned char *)s1 - *(unsigned char *)s2;
}

size_t k_strlen(const char *str) {
  size_t len = 0;
  while (str[len])
    len++;
  return len;
}

char *k_strcpy(char *dest, const char *src) {
  char *ret = dest;
  while ((*dest++ = *src++))
    ;
  return ret;
}

void *k_memset(void *s, int c, size_t n) {
  unsigned char *p = s;
  while (n--)
    *p++ = (unsigned char)c;
  return s;
}

void *k_memcpy(void *dest, const void *src, size_t n) {
  char *d = dest;
  const char *s = src;
  while (n--)
    *d++ = *s++;
  return dest;
}

 
void *k_memmove(void *dest, const void *src, size_t n) {
  unsigned char *d = dest;
  const unsigned char *s = src;
  if (d < s) {
    while (n--)
      *d++ = *s++;
  } else {
    d += n;
    s += n;
    while (n--)
      *--d = *--s;
  }
  return dest;
}

int k_strncmp(const char *s1, const char *s2, size_t n) {
  while (n && *s1 && (*s1 == *s2)) {
    s1++;
    s2++;
    n--;
  }
  if (n == 0)
    return 0;
  return *(unsigned char *)s1 - *(unsigned char *)s2;
}

static void reverse(char s[]) {
  int i, j;
  char c;

  for (i = 0, j = k_strlen(s) - 1; i < j; i++, j--) {
    c = s[i];
    s[i] = s[j];
    s[j] = c;
  }
}

void itoa(int n, char s[], int base) {
  int i, sign;

  if ((sign = n) < 0)
    n = -n;
  i = 0;
  do {
    s[i++] = n % base + '0';
  } while ((n /= base) > 0);
  if (sign < 0)
    s[i++] = '-';
  s[i] = '\0';
  reverse(s);
}