/* * 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/jbd2.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(const char *name, int len) { __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9; while (len--) { __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373)); if (hash & 0x80000000) hash -= 0x7fffffff; hash1 = hash0; hash0 = hash; } return (hash0 << 1); } static void str2hashbuf(const char *msg, int len, __u32 *buf, int num) { __u32 pad, val; int i; 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 = msg[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]; /* 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]) break; } if (i < 4) memcpy(buf, hinfo->seed, sizeof(buf)); } switch (hinfo->hash_version) { case DX_HASH_LEGACY: hash = dx_hack_hash(name, len); break; 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: 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 << 1)) hash = (EXT4_HTREE_EOF-1) << 1; hinfo->hash = hash; hinfo->minor_hash = minor_hash; return 0; }