152 lines
3.1 KiB
C
152 lines
3.1 KiB
C
/*
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* linux/fs/ext3/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/jbd.h>
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#include <linux/ext3_fs.h>
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#include <linux/cryptohash.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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/* The old legacy hash */
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static __u32 dx_hack_hash (const char *name, int len)
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{
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__u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
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while (len--) {
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__u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
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if (hash & 0x80000000) 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(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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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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if ((i % 4) == 0)
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val = pad;
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val = msg[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 ext3fs_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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/* 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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break;
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}
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if (i < 4)
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memcpy(buf, hinfo->seed, sizeof(buf));
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}
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switch (hinfo->hash_version) {
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case DX_HASH_LEGACY:
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hash = dx_hack_hash(name, len);
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break;
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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:
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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 == (EXT3_HTREE_EOF << 1))
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hash = (EXT3_HTREE_EOF-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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