字符串其他操作

char *
simple_memcpy (char *dst, const char *src, size_t n)
{
  char *ret = dst;
  while (n--)
    *dst++ = *src++;
  return ret;
}

char *
simple_memchr (const char *s, int c, size_t n)
{
  while (n--)
    if (*s++ == (char) c)
      return (char *) s - 1;
  return NULL;
}

int
simple_memcmp (const char *s1, const char *s2, size_t n)
{
  int ret = 0;

  while (n--
         && (ret = *(unsigned char *) s1++ - *(unsigned char *) s2++) == 0);
  return ret;
}

void *
simple_memmem (const void *haystack, size_t haystack_len, const void *needle,
               size_t needle_len)
{
  const char *begin;
  const char *const last_possible
    = (const char *) haystack + haystack_len - needle_len;

  if (needle_len == 0)
    return (void *) haystack;

  if (haystack_len < needle_len)
    return NULL;

  for (begin = (const char *) haystack; begin <= last_possible; ++begin)
    if (begin[0] == ((const char *) needle)[0] &&
        !memcmp ((const void *) &begin[1],
                 (const void *) ((const char *) needle + 1),
                 needle_len - 1))
      return (void *) begin;

  return NULL;
}

char *
simple_memmove (char *dst, const char *src, size_t n)
{
  char *ret = dst;
  if (src < dst)
    {
      dst += n;
      src += n;
      while (n--)
        *--dst = *--src;
    }
  else
    while (n--)
      *dst++ = *src++;
  return ret;
}


char *
simple_memset (char *s, int c, size_t n)
{
  char *r = s, *end = s + n;
  while (r < end)
    *r++ = c;
  return s;
}

char *
simple_stpcpy (char *dst, const char *src)
{
  while ((*dst++ = *src++) != '\0');
  return dst - 1;
}

char *
simple_stpncpy (char *dst, const char *src, size_t n)
{
  while (n--)
    if ((*dst++ = *src++) == '\0')
      {
        size_t i;

        for (i = 0; i < n; ++i)
          dst[i] = '\0';
        return dst - 1;
      }
  return dst;
}

char *
simple_strcat (char *dst, const char *src)
{
  char *ret = dst;
  while (*dst++ != '\0');
  --dst;
  while ((*dst++ = *src++) != '\0');
  return ret;
}

char *
simple_strchr (const char *s, int c)
{
  for (; *s != (char) c; ++s)
    if (*s == '\0')
      return NULL;
  return (char *) s;
}

int
simple_strcmp (const char *s1, const char *s2)
{
  int ret;

  while ((ret = *(unsigned char *) s1 - *(unsigned char *) s2++) == 0
         && *s1++);
  return ret;
}

char *
simple_strcpy (char *dst, const char *src)
{
  char *ret = dst;
  while ((*dst++ = *src++) != '\0');
  return ret;
}

size_t
simple_strspn (const char *s, const char *acc)
{
  const char *r, *str = s;
  char c;

  while ((c = *s++) != '\0')
    {
      for (r = acc; *r != '\0'; ++r)
        if (*r == c)
          break;
      if (*r == '\0')
        return s - str - 1;
    }
  return s - str - 1;
}

size_t
simple_strcspn (const char *s, const char *rej)
{
  const char *r, *str = s;
  char c;

  while ((c = *s++) != '\0')
    for (r = rej; *r != '\0'; ++r)
      if (*r == c)
        return s - str - 1;
  return s - str - 1;
}

size_t
simple_strlen (const char *s)
{
  const char *p;

  for (p = s; *p; ++p);
  return p - s;
}

int
simple_strncmp (const char *s1, const char *s2, size_t n)
{
  int ret = 0;

  while (n-- && (ret = *(unsigned char *) s1 - * (unsigned char *) s2++) == 0
         && *s1++);
  return ret;
}

char *
simple_strncpy (char *dst, const char *src, size_t n)
{
  char *ret = dst;
  while (n--)
    if ((*dst++ = *src++) == '\0')
      {
        while (n--)
          *dst++ = '\0';
        return ret;
      }
  return ret;
}

char *
simple_strpbrk (const char *s, const char *rej)
{
  const char *r;
  char c;

  while ((c = *s++) != '\0')
    for (r = rej; *r != '\0'; ++r)
      if (*r == c)
        return (char *) s - 1;
  return NULL;
}

char *
simple_strrchr (const char *s, int c)
{
  const char *ret = NULL;

  for (; *s != '\0'; ++s)
    if (*s == (char) c)
      ret = s;

  return (char *) (c == '\0' ? s : ret);
}