gistfile1.c

st_hash(const void *ptr, size_t len, st_index_t h)
{
    const char *data = ptr;
    st_index_t t = 0;

    h += 0xdeadbeef;

#define data_at(n) (st_index_t)((unsigned char)data[(n)])
#define UNALIGNED_ADD_4 UNALIGNED_ADD(2); UNALIGNED_ADD(1); UNALIGNED_ADD(0)
#if SIZEOF_ST_INDEX_T > 4
#define UNALIGNED_ADD_8 UNALIGNED_ADD(6); UNALIGNED_ADD(5); UNALIGNED_ADD(4); UNALIGNED_ADD(3); UNALIGNED_ADD_4
#if SIZEOF_ST_INDEX_T > 8
#define UNALIGNED_ADD_16 UNALIGNED_ADD(14); UNALIGNED_ADD(13); UNALIGNED_ADD(12); UNALIGNED_ADD(11); \
    UNALIGNED_ADD(10); UNALIGNED_ADD(9); UNALIGNED_ADD(8); UNALIGNED_ADD(7); UNALIGNED_ADD_8
#define UNALIGNED_ADD_ALL UNALIGNED_ADD_16
#endif
#define UNALIGNED_ADD_ALL UNALIGNED_ADD_8
#else
#define UNALIGNED_ADD_ALL UNALIGNED_ADD_4
#endif
    if (len >= sizeof(st_index_t)) {
#if !UNALIGNED_WORD_ACCESS
	int align = (int)((st_data_t)data % sizeof(st_index_t));
	if (align) {
	    st_index_t d = 0;
	    int sl, sr, pack;

	    switch (align) {
#ifdef WORDS_BIGENDIAN
# define UNALIGNED_ADD(n) case SIZEOF_ST_INDEX_T - (n) - 1: \
		t |= data_at(n) << CHAR_BIT*(SIZEOF_ST_INDEX_T - (n) - 2)
#else
# define UNALIGNED_ADD(n) case SIZEOF_ST_INDEX_T - (n) - 1:	\
		t |= data_at(n) << CHAR_BIT*(n)
#endif
		UNALIGNED_ADD_ALL;
#undef UNALIGNED_ADD
	    }

#ifdef WORDS_BIGENDIAN
	    t >>= (CHAR_BIT * align) - CHAR_BIT;
#else
	    t <<= (CHAR_BIT * align);
#endif

	    data += sizeof(st_index_t)-align;
	    len -= sizeof(st_index_t)-align;

	    sl = CHAR_BIT * (SIZEOF_ST_INDEX_T-align);
	    sr = CHAR_BIT * align;

	    while (len >= sizeof(st_index_t)) {
		d = *(st_index_t *)data;
#ifdef WORDS_BIGENDIAN
		t = (t << sr) | (d >> sl);
#else
		t = (t >> sr) | (d << sl);
#endif
		h = murmur_step(h, t);
		t = d;
		data += sizeof(st_index_t);
		len -= sizeof(st_index_t);
	    }

	    pack = len < (size_t)align ? (int)len : align;
	    d = 0;
	    switch (pack) {
#ifdef WORDS_BIGENDIAN
# define UNALIGNED_ADD(n) case (n) + 1: \
		d |= data_at(n) << CHAR_BIT*(SIZEOF_ST_INDEX_T - (n) - 1)
#else
# define UNALIGNED_ADD(n) case (n) + 1: \
		d |= data_at(n) << CHAR_BIT*(n)
#endif
		UNALIGNED_ADD_ALL;
#undef UNALIGNED_ADD
	    }
#ifdef WORDS_BIGENDIAN
	    t = (t << sr) | (d >> sl);
#else
	    t = (t >> sr) | (d << sl);
#endif

#if MURMUR == 2
	    if (len < (size_t)align) goto skip_tail;
#endif
	    h = murmur_step(h, t);
	    data += pack;
	    len -= pack;
	}
	else
#endif
	{
	    do {
		h = murmur_step(h, *(st_index_t *)data);
		data += sizeof(st_index_t);
		len -= sizeof(st_index_t);
	    } while (len >= sizeof(st_index_t));
	}
    }

    t = 0;
    switch (len) {
#ifdef WORDS_BIGENDIAN
# define UNALIGNED_ADD(n) case (n) + 1: \
	t |= data_at(n) << CHAR_BIT*(SIZEOF_ST_INDEX_T - (n) - 1)
#else
# define UNALIGNED_ADD(n) case (n) + 1: \
	t |= data_at(n) << CHAR_BIT*(n)
#endif
	UNALIGNED_ADD_ALL;
#undef UNALIGNED_ADD
#if MURMUR == 1
	h = murmur_step(h, t);
#elif MURMUR == 2
# if !UNALIGNED_WORD_ACCESS
      skip_tail:
# endif
	h ^= t;
	h *= MurmurMagic;
#endif
    }

    return murmur_finish(h);
}