/*-
 * Copyright 2000 Hans Reiser
 * See README for licensing and copyright details
 * 
 * Ported to FreeBSD by Jean-Sébastien Pédron <jspedron@club-internet.fr>
 * 
 * $FreeBSD: src/sys/gnu/fs/reiserfs/reiserfs_hashes.c,v 1.1 2005/06/18 17:06:09 dumbbell Exp $
 */

#include <gnu/fs/reiserfs/reiserfs_fs.h>

/*
 * Keyed 32-bit hash function using TEA in a Davis-Meyer function
 *   H0 = Key
 *   Hi = E Mi(Hi-1) + Hi-1
 *
 * (see Applied Cryptography, 2nd edition, p448).
 *
 * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998
 *
 * Jeremy has agreed to the contents of README. -Hans
 * Yura's function is added (04/07/2000)
 */

/*
 * keyed_hash
 * yura_hash
 * r5_hash
 */

#define	DELTA		0x9E3779B9
#define	FULLROUNDS	10  /* 32 is overkill, 16 is strong crypto */
#define	PARTROUNDS	6   /* 6 gets complete mixing */

/* a, b, c, d - data; h0, h1 - accumulated hash */
#define TEACORE(rounds)							\
    do {								\
	    int n;							\
	    uint32_t b0, b1;						\
	    uint32_t sum;						\
									\
	    n = rounds;							\
	    sum = 0;							\
	    b0 = h0;							\
	    b1 = h1;							\
									\
	    do {							\
		    sum += DELTA;					\
		    b0 += ((b1 << 4) + a) ^ (b1+sum) ^ ((b1 >> 5) + b);	\
		    b1 += ((b0 << 4) + c) ^ (b0+sum) ^ ((b0 >> 5) + d);	\
	    } while (--n);						\
									\
	    h0 += b0;							\
	    h1 += b1;							\
    } while (0)

uint32_t
keyed_hash(const signed char *msg, int len)
{
	uint32_t k[] = { 0x9464a485, 0x542e1a94, 0x3e846bff, 0xb75bcfc3 };

	uint32_t h0, h1;
	uint32_t a, b, c, d;
	uint32_t pad;
	int i;

	h0 = k[0];
	h1 = k[1];

	pad = (uint32_t)len | ((uint32_t)len << 8);
	pad |= pad << 16;

	while(len >= 16) {
		a = (uint32_t)msg[ 0]       |
		    (uint32_t)msg[ 1] <<  8 |
		    (uint32_t)msg[ 2] << 16 |
		    (uint32_t)msg[ 3] << 24;
		b = (uint32_t)msg[ 4]       |
		    (uint32_t)msg[ 5] <<  8 |
		    (uint32_t)msg[ 6] << 16 |
		    (uint32_t)msg[ 7] << 24;
		c = (uint32_t)msg[ 8]       |
		    (uint32_t)msg[ 9] <<  8 |
		    (uint32_t)msg[10] << 16 |
		    (uint32_t)msg[11] << 24;
		d = (uint32_t)msg[12]       |
		    (uint32_t)msg[13] <<  8 |
		    (uint32_t)msg[14] << 16 |
		    (uint32_t)msg[15] << 24;

		TEACORE(PARTROUNDS);

		len -= 16;
		msg += 16;
	}

	if (len >= 12) {
		a = (uint32_t)msg[ 0]       |
		    (uint32_t)msg[ 1] <<  8 |
		    (uint32_t)msg[ 2] << 16 |
		    (uint32_t)msg[ 3] << 24;
		b = (uint32_t)msg[ 4]       |
		    (uint32_t)msg[ 5] <<  8 |
		    (uint32_t)msg[ 6] << 16 |
		    (uint32_t)msg[ 7] << 24;
		c = (uint32_t)msg[ 8]       |
		    (uint32_t)msg[ 9] <<  8 |
		    (uint32_t)msg[10] << 16 |
		    (uint32_t)msg[11] << 24;

		d = pad;
		for(i = 12; i < len; i++) {
			d <<= 8;
			d |= msg[i];
		}
	} else if (len >= 8) {
		a = (uint32_t)msg[ 0]     |
		    (uint32_t)msg[ 1] <<  8 |
		    (uint32_t)msg[ 2] << 16 |
		    (uint32_t)msg[ 3] << 24;
		b = (uint32_t)msg[ 4]     |
		    (uint32_t)msg[ 5] <<  8 |
		    (uint32_t)msg[ 6] << 16 |
		    (uint32_t)msg[ 7] << 24;

		c = d = pad;
		for(i = 8; i < len; i++) {
			c <<= 8;
			c |= msg[i];
		}
	} else if (len >= 4) {
		a = (uint32_t)msg[ 0]     |
		    (uint32_t)msg[ 1] <<  8 |
		    (uint32_t)msg[ 2] << 16 |
		    (uint32_t)msg[ 3] << 24;

		b = c = d = pad;
		for(i = 4; i < len; i++) {
			b <<= 8;
			b |= msg[i];
		}
	} else {
		a = b = c = d = pad;
		for(i = 0; i < len; i++) {
			a <<= 8;
			a |= msg[i];
		}
	}

	TEACORE(FULLROUNDS);

	/* return 0; */
	return (h0 ^ h1);
}

/*
 * What follows in this file is copyright 2000 by Hans Reiser, and the
 * licensing of what follows is governed by README
 * */
uint32_t
yura_hash(const signed char *msg, int len)
{
	int i;
	int j, pow;
	uint32_t a, c;

	for (pow = 1, i = 1; i < len; i++)
		pow = pow * 10;

	if (len == 1)
		a = msg[0] - 48;
	else
		a = (msg[0] - 48) * pow;

	for (i = 1; i < len; i++) {
		c = msg[i] - 48;
		for (pow = 1, j = i; j < len - 1; j++)
			pow = pow * 10;
		a = a + c * pow;
	}

	for (; i < 40; i++) {
		c = '0' - 48;
		for (pow = 1, j = i; j < len - 1; j++)
			pow = pow * 10;
		a = a + c * pow;
	}

	for (; i < 256; i++) {
		c = i;
		for (pow = 1, j = i; j < len - 1; j++)
			pow = pow * 10;
		a = a + c * pow;
	}

	a = a << 7;
	return (a);
}

uint32_t
r5_hash(const signed char *msg, int len)
{
	uint32_t a;
	const signed char *start;

	a = 0;
	start = msg;

	while (*msg && msg < start + len) {
		a += *msg << 4;
		a += *msg >> 4;
		a *= 11;
		msg++;
	}

	return (a);
}
