#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <string.h>

/*
 * Copy n bytes from src to dst. The regions may overlap, so the copy
 * direction is chosen by the relative positions: forward when dst starts
 * at or before src, or at or after the end of src; backward when dst
 * starts inside src. Word-at-a-time in both directions, with byte heads
 * and tails; word loads and stores go through __builtin_memcpy.
 */
void *
memmove(void *dst, const void *src, size_t n) // NOLINT(bugprone-easily-swappable-parameters)
{
    const unsigned long word = sizeof(unsigned long);
    unsigned char *d = dst;
    const unsigned char *s = src;

    if (d <= s || d >= s + n)
    {
        /* Forward copy. */
        for (; (unsigned long)d % word != 0 && n != 0; n--)
        {
            *d++ = *s++;
        }
        while (n >= word)
        {
            unsigned long w;

            __builtin_memcpy(&w, s, sizeof w); // NOLINT(clang-analyzer-security.insecureAPI.*)
            __builtin_memcpy(d, &w, sizeof w); // NOLINT(clang-analyzer-security.insecureAPI.*)
            d += word;
            s += word;
            n -= word;
        }
        while (n != 0)
        {
            *d++ = *s++;
            n--;
        }
    }
    else
    {
        /* Backward copy, starting from the last byte. */
        d += n;
        s += n;
        for (; (unsigned long)d % word != 0 && n != 0; n--)
        {
            *--d = *--s;
        }
        while (n >= word)
        {
            unsigned long w;

            d -= word;
            s -= word;
            __builtin_memcpy(&w, s, sizeof w); // NOLINT(clang-analyzer-security.insecureAPI.*)
            __builtin_memcpy(d, &w, sizeof w); // NOLINT(clang-analyzer-security.insecureAPI.*)
            n -= word;
        }
        while (n != 0)
        {
            *--d = *--s;
            n--;
        }
    }

    return dst;
}