ecl/src/c/newhash.h

/* -*- mode: c; c-basic-offset: 8 -*- */
/********************
 * HASHING ROUTINES *
 ********************/

/*
 * SBCL's newest algorithm. Leads to few collisions, and it is faster.
 */

#if FIXNUM_BITS > 32
/*
 * 64 bit version
 */
#define GOLDEN_RATIO 0x9e3779b97f4a7c13L
#define mix(a,b,c)				\
	{					\
		a=a-b;  a=a-c;  a=a^(c>>43);	\
		b=b-c;  b=b-a;  b=b^(a<<9);	\
		c=c-a;  c=c-b;  c=c^(b>>8);	\
		a=a-b;  a=a-c;  a=a^(c>>38);	\
		b=b-c;  b=b-a;  b=b^(a<<23);	\
		c=c-a;  c=c-b;  c=c^(b>>5);	\
		a=a-b;  a=a-c;  a=a^(c>>35);	\
		b=b-c;  b=b-a;  b=b^(a<<49);	\
		c=c-a;  c=c-b;  c=c^(b>>11);	\
		a=a-b;  a=a-c;  a=a^(c>>12);	\
		b=b-c;  b=b-a;  b=b^(a<<18);	\
		c=c-a;  c=c-b;  c=c^(b>>22);	\
	}

#define extract_word(k)							\
	(k[0]+((cl_index)k[1]<<8)+((cl_index)k[2]<<16)+((cl_index)k[3]<<24)+ \
	 ((cl_index)k[4]<<32)+((cl_index)k[5]<<40)+((cl_index)k[6]<<48)+ \
	 ((cl_index)k[7]<<52))

static cl_index
hash_string(cl_index initval, const unsigned char *k, cl_index length)
{
	register cl_index a = GOLDEN_RATIO, b = GOLDEN_RATIO, c = initval;
	register cl_index len;
	for (len = length; len >= 24; len -= 24) {
		a += extract_word(k); k+=8;
		b += extract_word(k); k+=8;
		c += extract_word(k); k+=8;
		mix(a,b,c);
	}

	/*------------------------------------- handle the last 11 bytes */
	c += length;
	switch(len) {
		/* all the case statements fall through */
	case 23: c+=((cl_index)k[22]<<52);
	case 22: c+=((cl_index)k[21]<<48);
	case 21: c+=((cl_index)k[20]<<40);
	case 20: c+=((cl_index)k[19]<<32);
	case 19: c+=((cl_index)k[18]<<24);
	case 18: c+=((cl_index)k[17]<<16);
	case 17: c+=((cl_index)k[16]<<8);
		/* the first byte of c is reserved for the length */
	case 16: b+=((cl_index)k[15]<<52);
	case 15: b+=((cl_index)k[14]<<48);
	case 14: b+=((cl_index)k[13]<<40);
	case 13: b+=((cl_index)k[12]<<32);
	case 12: b+=((cl_index)k[11]<<24);
	case 11: b+=((cl_index)k[10]<<16);
	case 10: b+=((cl_index)k[9]<<8);
	case 9 : b+=k[8];
	case 8 : a+=((cl_index)k[7]<<52);
	case 7 : a+=((cl_index)k[6]<<48);
	case 6 : a+=((cl_index)k[5]<<40);
	case 5 : a+=((cl_index)k[4]<<32);
	case 4 : a+=((cl_index)k[3]<<24);
	case 3 : a+=((cl_index)k[2]<<16);
	case 2 : a+=((cl_index)k[1]<<8);
	case 1 : a+=k[0];
		/* case 0: nothing left to add */
	}
	mix(a,b,c);
	/*-------------------------------------------- report the result */
	return c;
}

#else
/*
 * 32 bit version
 */

#define GOLDEN_RATIO 0x9e3779b9L
#define mix(a,b,c)				\
	{					\
		a -= b; a -= c; a ^= (c>>13);	\
		b -= c; b -= a; b ^= (a<<8);	\
		c -= a; c -= b; c ^= (b>>13);	\
		a -= b; a -= c; a ^= (c>>12);	\
		b -= c; b -= a; b ^= (a<<16);	\
		c -= a; c -= b; c ^= (b>>5);	\
		a -= b; a -= c; a ^= (c>>3);	\
		b -= c; b -= a; b ^= (a<<10);	\
		c -= a; c -= b; c ^= (b>>15);	\
	}
#define extract_word(k)							\
	(k[0]+((cl_index)k[1]<<8)+((cl_index)k[2]<<16)+((cl_index)k[3]<<24))

static cl_index
hash_string(cl_index initval, const unsigned char *k, cl_index length)
{
	register cl_index a = GOLDEN_RATIO, b = GOLDEN_RATIO, c = initval;
	register cl_index len;
	for (len = length; len >= 12; len -= 12) {
		a += extract_word(k); k += 4;
		b += extract_word(k); k += 4;
		c += extract_word(k); k += 4;
		mix(a,b,c);
	}

	/*------------------------------------- handle the last 11 bytes */
	c += length;
	switch(len) {
		/* all the case statements fall through */
	case 11: c+=((cl_index)k[10]<<24);
	case 10: c+=((cl_index)k[9]<<16);
	case 9 : c+=((cl_index)k[8]<<8);
		/* the first byte of c is reserved for the length */
	case 8 : b+=((cl_index)k[7]<<24);
	case 7 : b+=((cl_index)k[6]<<16);
	case 6 : b+=((cl_index)k[5]<<8);
	case 5 : b+=k[4];
	case 4 : a+=((cl_index)k[3]<<24);
	case 3 : a+=((cl_index)k[2]<<16);
	case 2 : a+=((cl_index)k[1]<<8);
	case 1 : a+=k[0];
		/* case 0: nothing left to add */
	}
	mix(a,b,c);
	/*-------------------------------------------- report the result */
	return c;
}
#endif

static cl_index hash_word(cl_index c, cl_index w)
{
	cl_index a = w + GOLDEN_RATIO, b = GOLDEN_RATIO;
	mix(a, b, c);
	return c;
}

static cl_index hash_base_string(const ecl_base_char *s, cl_index len, cl_index h)
{
	cl_index a = GOLDEN_RATIO, b = GOLDEN_RATIO, i;
	for (i = len; i >= 3; i -= 3) {
		a += *s; s++;
		b += *s; s++;
		h += *s; s++;
		mix(a, b, h);
	}
	switch (i) {
	case 2: a += *s; s++;
	case 1: b += *s;
	default: h += len;
	}
	mix(a, b, h);
	return h;
}

#ifdef ECL_UNICODE
static cl_index hash_full_string(const ecl_character *s, cl_index len, cl_index h)
{
	cl_index a = GOLDEN_RATIO, b = GOLDEN_RATIO, i;
	for (i = len; i >= 3; i -= 3) {
		a += (*s); s++;
		b += (*s); s++;
		h += (*s); s++;
		mix(a, b, h);
	}
	switch (i) {
	case 2: a += (*s); s++;
	case 1: b += (*s);
	default: h += len;
	}
	mix(a, b, h);
	return h;
}
#endif