memset

static inline void *memsetq(void *ptr, ullong uval, size_t qwords)
{
    size_t n;
    ullong *uptr = (ullong *)ptr;

    for (n = 0; n < qwords; n++) {
        *(uptr + n) = uval;
    }

    return ptr;
}

void *memset(void *ptr, int val, size_t bytes)
{
    uchar *uptr = (uchar *)ptr;
    const size_t qwords = bytes/QWORD_SIZE;

    // get rid of everything after the first byte
    val = val & 0xFF;

    // deal with bytes before start of the first qword
    while (((ullong)uptr % QWORD_ALIGN) > 0 && bytes--) {
        *uptr++ = (uchar)val;
    }

    // move qword by qword
    if (qwords) {
        const ullong uval = ((ullong)val << 56) | ((ullong)val << 48)
                          | ((ullong)val << 40) | ((ullong)val << 32)
                          | ((ullong)val << 24) | ((ullong)val << 16)
                          | ((ullong)val <<  8) | ((ullong)val);

        memsetq(uptr, uval, qwords);

        uptr += qwords * QWORD_SIZE;
        bytes %= QWORD_SIZE;
    }

    // deal with what's left
    while (bytes--) {
        *uptr++ = (uchar)val;
    }

    return ptr;
}

//
//  Set "bytes"-many bytes starting from ptr to 0
//
void *memzero(void *ptr, size_t bytes)
{
    return memset(ptr, 0, bytes);
}