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diff --git a/src/ext4_hash.c b/src/ext4_hash.c
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+/*
+ * Copyright (c) 2013 Grzegorz Kostka (kostka.grzegorz@gmail.com)
+ *
+ * FreeBSD:
+ * Copyright (c) 2010, 2013 Zheng Liu <lz@freebsd.org>
+ * Copyright (c) 2012, Vyacheslav Matyushin
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+/*
+ * The following notice applies to the code in ext2_half_md4():
+ *
+ * Copyright (C) 1990-2, RSA Data Security, Inc. All rights reserved.
+ *
+ * License to copy and use this software is granted provided that it
+ * is identified as the "RSA Data Security, Inc. MD4 Message-Digest
+ * Algorithm" in all material mentioning or referencing this software
+ * or this function.
+ *
+ * License is also granted to make and use derivative works provided
+ * that such works are identified as "derived from the RSA Data
+ * Security, Inc. MD4 Message-Digest Algorithm" in all material
+ * mentioning or referencing the derived work.
+ *
+ * RSA Data Security, Inc. makes no representations concerning either
+ * the merchantability of this software or the suitability of this
+ * software for any particular purpose. It is provided "as is"
+ * without express or implied warranty of any kind.
+ *
+ * These notices must be retained in any copies of any part of this
+ * documentation and/or software.
+ */
+
+/** @addtogroup lwext4
+ * @{
+ */
+/**
+ * @file  ext4_hash.c
+ * @brief Directory indexing hash functions.
+ */
+
+#include "ext4_config.h"
+#include "ext4_types.h"
+#include "ext4_errno.h"
+
+#include <string.h>
+
+/* F, G, and H are MD4 functions */
+#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
+#define G(x, y, z) (((x) & (y)) | ((x) & (z)) | ((y) & (z)))
+#define H(x, y, z) ((x) ^ (y) ^ (z))
+
+/* ROTATE_LEFT rotates x left n bits */
+#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32 - (n))))
+
+/*
+ * FF, GG, and HH are transformations for rounds 1, 2, and 3.
+ * Rotation is separated from addition to prevent recomputation.
+ */
+#define FF(a, b, c, d, x, s)                                                   \
+	{                                                                      \
+		(a) += F((b), (c), (d)) + (x);                                 \
+		(a) = ROTATE_LEFT((a), (s));                                   \
+	\
+}
+
+#define GG(a, b, c, d, x, s)                                                   \
+	{                                                                      \
+		(a) += G((b), (c), (d)) + (x) + (uint32_t)0x5A827999;          \
+		(a) = ROTATE_LEFT((a), (s));                                   \
+	\
+}
+
+#define HH(a, b, c, d, x, s)                                                   \
+	{                                                                      \
+		(a) += H((b), (c), (d)) + (x) + (uint32_t)0x6ED9EBA1;          \
+		(a) = ROTATE_LEFT((a), (s));                                   \
+	\
+}
+
+/*
+ * MD4 basic transformation.  It transforms state based on block.
+ *
+ * This is a half md4 algorithm since Linux uses this algorithm for dir
+ * index.  This function is derived from the RSA Data Security, Inc. MD4
+ * Message-Digest Algorithm and was modified as necessary.
+ *
+ * The return value of this function is uint32_t in Linux, but actually we don't
+ * need to check this value, so in our version this function doesn't return any
+ * value.
+ */
+static void ext2_half_md4(uint32_t hash[4], uint32_t data[8])
+{
+	uint32_t a = hash[0], b = hash[1], c = hash[2], d = hash[3];
+
+	/* Round 1 */
+	FF(a, b, c, d, data[0], 3);
+	FF(d, a, b, c, data[1], 7);
+	FF(c, d, a, b, data[2], 11);
+	FF(b, c, d, a, data[3], 19);
+	FF(a, b, c, d, data[4], 3);
+	FF(d, a, b, c, data[5], 7);
+	FF(c, d, a, b, data[6], 11);
+	FF(b, c, d, a, data[7], 19);
+
+	/* Round 2 */
+	GG(a, b, c, d, data[1], 3);
+	GG(d, a, b, c, data[3], 5);
+	GG(c, d, a, b, data[5], 9);
+	GG(b, c, d, a, data[7], 13);
+	GG(a, b, c, d, data[0], 3);
+	GG(d, a, b, c, data[2], 5);
+	GG(c, d, a, b, data[4], 9);
+	GG(b, c, d, a, data[6], 13);
+
+	/* Round 3 */
+	HH(a, b, c, d, data[3], 3);
+	HH(d, a, b, c, data[7], 9);
+	HH(c, d, a, b, data[2], 11);
+	HH(b, c, d, a, data[6], 15);
+	HH(a, b, c, d, data[1], 3);
+	HH(d, a, b, c, data[5], 9);
+	HH(c, d, a, b, data[0], 11);
+	HH(b, c, d, a, data[4], 15);
+
+	hash[0] += a;
+	hash[1] += b;
+	hash[2] += c;
+	hash[3] += d;
+}
+
+/*
+ * Tiny Encryption Algorithm.
+ */
+static void ext2_tea(uint32_t hash[4], uint32_t data[8])
+{
+	uint32_t tea_delta = 0x9E3779B9;
+	uint32_t sum;
+	uint32_t x = hash[0], y = hash[1];
+	int n = 16;
+	int i = 1;
+
+	while (n-- > 0) {
+		sum = i * tea_delta;
+		x += ((y << 4) + data[0]) ^ (y + sum) ^ ((y >> 5) + data[1]);
+		y += ((x << 4) + data[2]) ^ (x + sum) ^ ((x >> 5) + data[3]);
+		i++;
+	}
+
+	hash[0] += x;
+	hash[1] += y;
+}
+
+static uint32_t ext2_legacy_hash(const char *name, int len, int unsigned_char)
+{
+	uint32_t h0, h1 = 0x12A3FE2D, h2 = 0x37ABE8F9;
+	uint32_t multi = 0x6D22F5;
+	const unsigned char *uname = (const unsigned char *)name;
+	const signed char *sname = (const signed char *)name;
+	int val, i;
+
+	for (i = 0; i < len; i++) {
+		if (unsigned_char)
+			val = (unsigned int)*uname++;
+		else
+			val = (int)*sname++;
+
+		h0 = h2 + (h1 ^ (val * multi));
+		if (h0 & 0x80000000)
+			h0 -= 0x7FFFFFFF;
+		h2 = h1;
+		h1 = h0;
+	}
+
+	return (h1 << 1);
+}
+
+static void ext2_prep_hashbuf(const char *src, uint32_t slen, uint32_t *dst,
+			      int dlen, int unsigned_char)
+{
+	uint32_t padding = slen | (slen << 8) | (slen << 16) | (slen << 24);
+	uint32_t buf_val;
+	int len, i;
+	int buf_byte;
+	const unsigned char *ubuf = (const unsigned char *)src;
+	const signed char *sbuf = (const signed char *)src;
+
+	if (slen > (uint32_t)dlen)
+		len = dlen;
+	else
+		len = slen;
+
+	buf_val = padding;
+
+	for (i = 0; i < len; i++) {
+		if (unsigned_char)
+			buf_byte = (unsigned int)ubuf[i];
+		else
+			buf_byte = (int)sbuf[i];
+
+		if ((i % 4) == 0)
+			buf_val = padding;
+
+		buf_val <<= 8;
+		buf_val += buf_byte;
+
+		if ((i % 4) == 3) {
+			*dst++ = buf_val;
+			dlen -= sizeof(uint32_t);
+			buf_val = padding;
+		}
+	}
+
+	dlen -= sizeof(uint32_t);
+	if (dlen >= 0)
+		*dst++ = buf_val;
+
+	dlen -= sizeof(uint32_t);
+	while (dlen >= 0) {
+		*dst++ = padding;
+		dlen -= sizeof(uint32_t);
+	}
+}
+
+int ext2_htree_hash(const char *name, int len, const uint32_t *hash_seed,
+		    int hash_version, uint32_t *hash_major,
+		    uint32_t *hash_minor)
+{
+	uint32_t hash[4];
+	uint32_t data[8];
+	uint32_t major = 0, minor = 0;
+	int unsigned_char = 0;
+
+	if (!name || !hash_major)
+		return (-1);
+
+	if (len < 1 || len > 255)
+		goto error;
+
+	hash[0] = 0x67452301;
+	hash[1] = 0xEFCDAB89;
+	hash[2] = 0x98BADCFE;
+	hash[3] = 0x10325476;
+
+	if (hash_seed)
+		memcpy(hash, hash_seed, sizeof(hash));
+
+	switch (hash_version) {
+	case EXT2_HTREE_TEA_UNSIGNED:
+		unsigned_char = 1;
+	case EXT2_HTREE_TEA:
+		while (len > 0) {
+			ext2_prep_hashbuf(name, len, data, 16, unsigned_char);
+			ext2_tea(hash, data);
+			len -= 16;
+			name += 16;
+		}
+		major = hash[0];
+		minor = hash[1];
+		break;
+	case EXT2_HTREE_LEGACY_UNSIGNED:
+		unsigned_char = 1;
+	case EXT2_HTREE_LEGACY:
+		major = ext2_legacy_hash(name, len, unsigned_char);
+		break;
+	case EXT2_HTREE_HALF_MD4_UNSIGNED:
+		unsigned_char = 1;
+	case EXT2_HTREE_HALF_MD4:
+		while (len > 0) {
+			ext2_prep_hashbuf(name, len, data, 32, unsigned_char);
+			ext2_half_md4(hash, data);
+			len -= 32;
+			name += 32;
+		}
+		major = hash[1];
+		minor = hash[2];
+		break;
+	default:
+		goto error;
+	}
+
+	major &= ~1;
+	if (major == (EXT2_HTREE_EOF << 1))
+		major = (EXT2_HTREE_EOF - 1) << 1;
+	*hash_major = major;
+	if (hash_minor)
+		*hash_minor = minor;
+
+	return EOK;
+
+error:
+	*hash_major = 0;
+	if (hash_minor)
+		*hash_minor = 0;
+	return ENOTSUP;
+}
+
+/**
+ * @}
+ */