1/*
  2 * fs/f2fs/hash.c
  3 *
  4 * Copyright (c) 2012 Samsung Electronics Co., Ltd.
  5 *             http://www.samsung.com/
  6 *
  7 * Portions of this code from linux/fs/ext3/hash.c
  8 *
  9 * Copyright (C) 2002 by Theodore Ts'o
 10 *
 11 * This program is free software; you can redistribute it and/or modify
 12 * it under the terms of the GNU General Public License version 2 as
 13 * published by the Free Software Foundation.
 14 */
 15#include <linux/types.h>
 16#include <linux/fs.h>
 17#include <linux/f2fs_fs.h>
 18#include <linux/cryptohash.h>
 19#include <linux/pagemap.h>
 20
 21#include "f2fs.h"
 22
 23/*
 24 * Hashing code copied from ext3
 25 */
 26#define DELTA 0x9E3779B9
 27
 28static void TEA_transform(unsigned int buf[4], unsigned int const in[])
 29{
 30	__u32 sum = 0;
 31	__u32 b0 = buf[0], b1 = buf[1];
 32	__u32 a = in[0], b = in[1], c = in[2], d = in[3];
 33	int n = 16;
 34
 35	do {
 36		sum += DELTA;
 37		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
 38		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
 39	} while (--n);
 40
 41	buf[0] += b0;
 42	buf[1] += b1;
 43}
 44
 45static void str2hashbuf(const char *msg, size_t len, unsigned int *buf, int num)
 46{
 47	unsigned pad, val;
 48	int i;
 49
 50	pad = (__u32)len | ((__u32)len << 8);
 51	pad |= pad << 16;
 52
 53	val = pad;
 54	if (len > num * 4)
 55		len = num * 4;
 56	for (i = 0; i < len; i++) {
 57		if ((i % 4) == 0)
 58			val = pad;
 59		val = msg[i] + (val << 8);
 60		if ((i % 4) == 3) {
 61			*buf++ = val;
 62			val = pad;
 63			num--;
 64		}
 65	}
 66	if (--num >= 0)
 67		*buf++ = val;
 68	while (--num >= 0)
 69		*buf++ = pad;
 70}
 71
 72f2fs_hash_t f2fs_dentry_hash(const char *name, size_t len)
 73{
 74	__u32 hash;
 75	f2fs_hash_t f2fs_hash;
 76	const char *p;
 77	__u32 in[8], buf[4];
 78
 79	if ((len <= 2) && (name[0] == '.') &&
 80		(name[1] == '.' || name[1] == '\0'))
 81		return 0;
 82
 83	/* Initialize the default seed for the hash checksum functions */
 84	buf[0] = 0x67452301;
 85	buf[1] = 0xefcdab89;
 86	buf[2] = 0x98badcfe;
 87	buf[3] = 0x10325476;
 88
 89	p = name;
 90	while (1) {
 91		str2hashbuf(p, len, in, 4);
 92		TEA_transform(buf, in);
 93		p += 16;
 94		if (len <= 16)
 95			break;
 96		len -= 16;
 97	}
 98	hash = buf[0];
 99	f2fs_hash = cpu_to_le32(hash & ~F2FS_HASH_COL_BIT);
100	return f2fs_hash;
101}