918dc9d0ab
On transformation of str to hash, computed value is initialised before first byte modulo 4. But it is already initialised before entering loop and after processing last byte modulo 4. So the corresponding test and initialisation could be removed. Signed-off-by: Damien Guibouret <damien.guibouret@partition-saving.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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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