273 lines
6.2 KiB
C
273 lines
6.2 KiB
C
/*
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* linux/fs/ext4/hash.c
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*
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* Copyright (C) 2002 by Theodore Ts'o
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*
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* This file is released under the GPL v2.
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*
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* This file may be redistributed under the terms of the GNU Public
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* License.
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*/
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#include <linux/fs.h>
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#include <linux/compiler.h>
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#include <linux/bitops.h>
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#include "ext4.h"
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#define DELTA 0x9E3779B9
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static void TEA_transform(__u32 buf[4], __u32 const in[])
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{
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__u32 sum = 0;
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__u32 b0 = buf[0], b1 = buf[1];
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__u32 a = in[0], b = in[1], c = in[2], d = in[3];
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int n = 16;
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do {
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sum += DELTA;
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b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
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b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
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} while (--n);
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buf[0] += b0;
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buf[1] += b1;
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}
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/* F, G and H are basic MD4 functions: selection, majority, parity */
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#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
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#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
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#define H(x, y, z) ((x) ^ (y) ^ (z))
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/*
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* The generic round function. The application is so specific that
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* we don't bother protecting all the arguments with parens, as is generally
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* good macro practice, in favor of extra legibility.
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* Rotation is separate from addition to prevent recomputation
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*/
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#define ROUND(f, a, b, c, d, x, s) \
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(a += f(b, c, d) + x, a = rol32(a, s))
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#define K1 0
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#define K2 013240474631UL
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#define K3 015666365641UL
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/*
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* Basic cut-down MD4 transform. Returns only 32 bits of result.
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*/
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static __u32 half_md4_transform(__u32 buf[4], __u32 const in[8])
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{
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__u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];
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/* Round 1 */
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ROUND(F, a, b, c, d, in[0] + K1, 3);
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ROUND(F, d, a, b, c, in[1] + K1, 7);
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ROUND(F, c, d, a, b, in[2] + K1, 11);
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ROUND(F, b, c, d, a, in[3] + K1, 19);
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ROUND(F, a, b, c, d, in[4] + K1, 3);
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ROUND(F, d, a, b, c, in[5] + K1, 7);
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ROUND(F, c, d, a, b, in[6] + K1, 11);
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ROUND(F, b, c, d, a, in[7] + K1, 19);
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/* Round 2 */
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ROUND(G, a, b, c, d, in[1] + K2, 3);
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ROUND(G, d, a, b, c, in[3] + K2, 5);
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ROUND(G, c, d, a, b, in[5] + K2, 9);
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ROUND(G, b, c, d, a, in[7] + K2, 13);
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ROUND(G, a, b, c, d, in[0] + K2, 3);
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ROUND(G, d, a, b, c, in[2] + K2, 5);
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ROUND(G, c, d, a, b, in[4] + K2, 9);
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ROUND(G, b, c, d, a, in[6] + K2, 13);
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/* Round 3 */
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ROUND(H, a, b, c, d, in[3] + K3, 3);
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ROUND(H, d, a, b, c, in[7] + K3, 9);
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ROUND(H, c, d, a, b, in[2] + K3, 11);
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ROUND(H, b, c, d, a, in[6] + K3, 15);
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ROUND(H, a, b, c, d, in[1] + K3, 3);
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ROUND(H, d, a, b, c, in[5] + K3, 9);
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ROUND(H, c, d, a, b, in[0] + K3, 11);
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ROUND(H, b, c, d, a, in[4] + K3, 15);
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buf[0] += a;
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buf[1] += b;
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buf[2] += c;
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buf[3] += d;
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return buf[1]; /* "most hashed" word */
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}
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#undef ROUND
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#undef K1
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#undef K2
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#undef K3
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#undef F
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#undef G
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#undef H
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/* The old legacy hash */
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static __u32 dx_hack_hash_unsigned(const char *name, int len)
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{
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__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
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const unsigned char *ucp = (const unsigned char *) name;
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while (len--) {
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hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
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if (hash & 0x80000000)
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hash -= 0x7fffffff;
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hash1 = hash0;
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hash0 = hash;
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}
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return hash0 << 1;
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}
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static __u32 dx_hack_hash_signed(const char *name, int len)
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{
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__u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
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const signed char *scp = (const signed char *) name;
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while (len--) {
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hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));
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if (hash & 0x80000000)
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hash -= 0x7fffffff;
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hash1 = hash0;
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hash0 = hash;
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}
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return hash0 << 1;
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}
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static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
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{
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__u32 pad, val;
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int i;
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const signed char *scp = (const signed char *) msg;
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pad = (__u32)len | ((__u32)len << 8);
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pad |= pad << 16;
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val = pad;
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if (len > num*4)
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len = num * 4;
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for (i = 0; i < len; i++) {
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val = ((int) scp[i]) + (val << 8);
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if ((i % 4) == 3) {
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*buf++ = val;
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val = pad;
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num--;
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}
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}
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if (--num >= 0)
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*buf++ = val;
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while (--num >= 0)
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*buf++ = pad;
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}
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static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
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{
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__u32 pad, val;
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int i;
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const unsigned char *ucp = (const unsigned char *) msg;
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pad = (__u32)len | ((__u32)len << 8);
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pad |= pad << 16;
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val = pad;
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if (len > num*4)
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len = num * 4;
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for (i = 0; i < len; i++) {
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val = ((int) ucp[i]) + (val << 8);
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if ((i % 4) == 3) {
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*buf++ = val;
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val = pad;
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num--;
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}
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}
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if (--num >= 0)
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*buf++ = val;
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while (--num >= 0)
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*buf++ = pad;
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}
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/*
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* Returns the hash of a filename. If len is 0 and name is NULL, then
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* this function can be used to test whether or not a hash version is
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* supported.
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*
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* The seed is an 4 longword (32 bits) "secret" which can be used to
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* uniquify a hash. If the seed is all zero's, then some default seed
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* may be used.
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*
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* A particular hash version specifies whether or not the seed is
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* represented, and whether or not the returned hash is 32 bits or 64
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* bits. 32 bit hashes will return 0 for the minor hash.
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*/
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int ext4fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
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{
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__u32 hash;
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__u32 minor_hash = 0;
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const char *p;
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int i;
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__u32 in[8], buf[4];
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void (*str2hashbuf)(const char *, int, __u32 *, int) =
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str2hashbuf_signed;
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/* Initialize the default seed for the hash checksum functions */
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buf[0] = 0x67452301;
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buf[1] = 0xefcdab89;
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buf[2] = 0x98badcfe;
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buf[3] = 0x10325476;
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/* Check to see if the seed is all zero's */
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if (hinfo->seed) {
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for (i = 0; i < 4; i++) {
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if (hinfo->seed[i]) {
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memcpy(buf, hinfo->seed, sizeof(buf));
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break;
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}
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}
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}
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switch (hinfo->hash_version) {
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case DX_HASH_LEGACY_UNSIGNED:
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hash = dx_hack_hash_unsigned(name, len);
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break;
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case DX_HASH_LEGACY:
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hash = dx_hack_hash_signed(name, len);
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break;
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case DX_HASH_HALF_MD4_UNSIGNED:
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str2hashbuf = str2hashbuf_unsigned;
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case DX_HASH_HALF_MD4:
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p = name;
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while (len > 0) {
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(*str2hashbuf)(p, len, in, 8);
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half_md4_transform(buf, in);
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len -= 32;
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p += 32;
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}
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minor_hash = buf[2];
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hash = buf[1];
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break;
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case DX_HASH_TEA_UNSIGNED:
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str2hashbuf = str2hashbuf_unsigned;
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case DX_HASH_TEA:
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p = name;
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while (len > 0) {
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(*str2hashbuf)(p, len, in, 4);
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TEA_transform(buf, in);
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len -= 16;
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p += 16;
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}
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hash = buf[0];
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minor_hash = buf[1];
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break;
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default:
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hinfo->hash = 0;
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return -1;
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}
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hash = hash & ~1;
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if (hash == (EXT4_HTREE_EOF_32BIT << 1))
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hash = (EXT4_HTREE_EOF_32BIT - 1) << 1;
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hinfo->hash = hash;
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hinfo->minor_hash = minor_hash;
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return 0;
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}
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