/*
 *  linux/fs/ext4/hash.c
 *
 * Copyright (C) 2002 by Theodore Ts'o
 *
 * This file is released under the GPL v2.
 *
 * This file may be redistributed under the terms of the GNU Public
 * License.
 */

#include <linux/fs.h>
#include <linux/cryptohash.h>
#include "ext4.h"

#define DELTA 0x9E3779B9

static void TEA_transform(__u32 buf[4], __u32 const in[])
{
        __u32   sum = 0;
        __u32   b0 = buf[0], b1 = buf[1];
        __u32   a = in[0], b = in[1], c = in[2], d = in[3];
        int     n = 16;

        do {
                sum += DELTA;
                b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
                b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
        } while (--n);

        buf[0] += b0;
        buf[1] += b1;
}


/* The old legacy hash */
static __u32 dx_hack_hash_unsigned(const char *name, int len)
{
        __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
        const unsigned char *ucp = (const unsigned char *) name;

        while (len--) {
                hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));

                if (hash & 0x80000000)
                        hash -= 0x7fffffff;
                hash1 = hash0;
                hash0 = hash;
        }
        return hash0 << 1;
}

static __u32 dx_hack_hash_signed(const char *name, int len)
{
        __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
        const signed char *scp = (const signed char *) name;

        while (len--) {
                hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));

                if (hash & 0x80000000)
                        hash -= 0x7fffffff;
                hash1 = hash0;
                hash0 = hash;
        }
        return hash0 << 1;
}

static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
{
        __u32   pad, val;
        int     i;
        const signed char *scp = (const signed char *) msg;

        pad = (__u32)len | ((__u32)len << 8);
        pad |= pad << 16;

        val = pad;
        if (len > num*4)
                len = num * 4;
        for (i = 0; i < len; i++) {
                if ((i % 4) == 0)
                        val = pad;
                val = ((int) scp[i]) + (val << 8);
                if ((i % 4) == 3) {
                        *buf++ = val;
                        val = pad;
                        num--;
                }
        }
        if (--num >= 0)
                *buf++ = val;
        while (--num >= 0)
                *buf++ = pad;
}

static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
{
        __u32   pad, val;
        int     i;
        const unsigned char *ucp = (const unsigned char *) msg;

        pad = (__u32)len | ((__u32)len << 8);
        pad |= pad << 16;

        val = pad;
        if (len > num*4)
                len = num * 4;
        for (i = 0; i < len; i++) {
                if ((i % 4) == 0)
                        val = pad;
                val = ((int) ucp[i]) + (val << 8);
                if ((i % 4) == 3) {
                        *buf++ = val;
                        val = pad;
                        num--;
                }
        }
        if (--num >= 0)
                *buf++ = val;
        while (--num >= 0)
                *buf++ = pad;
}

/*
 * Returns the hash of a filename.  If len is 0 and name is NULL, then
 * this function can be used to test whether or not a hash version is
 * supported.
 *
 * The seed is an 4 longword (32 bits) "secret" which can be used to
 * uniquify a hash.  If the seed is all zero's, then some default seed
 * may be used.
 *
 * A particular hash version specifies whether or not the seed is
 * represented, and whether or not the returned hash is 32 bits or 64
 * bits.  32 bit hashes will return 0 for the minor hash.
 */
int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
{
        __u32   hash;
        __u32   minor_hash = 0;
        const char      *p;
        int             i;
        __u32           in[8], buf[4];
        void            (*str2hashbuf)(const char *, int, __u32 *, int) =
                                str2hashbuf_signed;

        /* Initialize the default seed for the hash checksum functions */
        buf[0] = 0x67452301;
        buf[1] = 0xefcdab89;
        buf[2] = 0x98badcfe;
        buf[3] = 0x10325476;

        /* Check to see if the seed is all zero's */
        if (hinfo->seed) {
                for (i = 0; i < 4; i++) {
                        if (hinfo->seed[i]) {
                                memcpy(buf, hinfo->seed, sizeof(buf));
                                break;
                        }
                }
        }

        switch (hinfo->hash_version) {
        case DX_HASH_LEGACY_UNSIGNED:
                hash = dx_hack_hash_unsigned(name, len);
                break;
        case DX_HASH_LEGACY:
                hash = dx_hack_hash_signed(name, len);
                break;
        case DX_HASH_HALF_MD4_UNSIGNED:
                str2hashbuf = str2hashbuf_unsigned;
        case DX_HASH_HALF_MD4:
                p = name;
                while (len > 0) {
                        (*str2hashbuf)(p, len, in, 8);
                        half_md4_transform(buf, in);
                        len -= 32;
                        p += 32;
                }
                minor_hash = buf[2];
                hash = buf[1];
                break;
        case DX_HASH_TEA_UNSIGNED:
                str2hashbuf = str2hashbuf_unsigned;
        case DX_HASH_TEA:
                p = name;
                while (len > 0) {
                        (*str2hashbuf)(p, len, in, 4);
                        TEA_transform(buf, in);
                        len -= 16;
                        p += 16;
                }
                hash = buf[0];
                minor_hash = buf[1];
                break;
        default:
                hinfo->hash = 0;
                return -1;
        }
        hash = hash & ~1;
        if (hash == (EXT4_HTREE_EOF_32BIT << 1))
                hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
        hinfo->hash = hash;
        hinfo->minor_hash = minor_hash;
        return 0;
}