190 lines
5.0 KiB
C
190 lines
5.0 KiB
C
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/*
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* This file is part of UBIFS.
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*
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* Copyright (C) 2006-2008 Nokia Corporation.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* Authors: Artem Bityutskiy (Битюцкий Артём)
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* Adrian Hunter
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*/
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/*
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* This header contains various key-related definitions and helper function.
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* UBIFS allows several key schemes, so we access key fields only via these
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* helpers. At the moment only one key scheme is supported.
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*
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* Simple key scheme
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* ~~~~~~~~~~~~~~~~~
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*
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* Keys are 64-bits long. First 32-bits are inode number (parent inode number
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* in case of direntry key). Next 3 bits are node type. The last 29 bits are
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* 4KiB offset in case of inode node, and direntry hash in case of a direntry
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* node. We use "r5" hash borrowed from reiserfs.
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*/
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#ifndef __UBIFS_KEY_H__
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#define __UBIFS_KEY_H__
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/**
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* key_mask_hash - mask a valid hash value.
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* @val: value to be masked
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*
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* We use hash values as offset in directories, so values %0 and %1 are
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* reserved for "." and "..". %2 is reserved for "end of readdir" marker. This
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* function makes sure the reserved values are not used.
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*/
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static inline uint32_t key_mask_hash(uint32_t hash)
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{
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hash &= UBIFS_S_KEY_HASH_MASK;
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if (unlikely(hash <= 2))
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hash += 3;
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return hash;
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}
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/**
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* key_r5_hash - R5 hash function (borrowed from reiserfs).
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* @s: direntry name
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* @len: name length
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*/
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static inline uint32_t key_r5_hash(const char *s, int len)
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{
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uint32_t a = 0;
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const signed char *str = (const signed char *)s;
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len = len;
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while (*str) {
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a += *str << 4;
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a += *str >> 4;
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a *= 11;
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str++;
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}
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return key_mask_hash(a);
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}
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/**
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* key_test_hash - testing hash function.
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* @str: direntry name
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* @len: name length
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*/
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static inline uint32_t key_test_hash(const char *str, int len)
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{
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uint32_t a = 0;
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len = min_t(uint32_t, len, 4);
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memcpy(&a, str, len);
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return key_mask_hash(a);
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}
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/**
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* ino_key_init - initialize inode key.
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* @c: UBIFS file-system description object
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* @key: key to initialize
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* @inum: inode number
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*/
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static inline void ino_key_init(union ubifs_key *key, ino_t inum)
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{
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key->u32[0] = inum;
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key->u32[1] = UBIFS_INO_KEY << UBIFS_S_KEY_BLOCK_BITS;
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}
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/**
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* dent_key_init - initialize directory entry key.
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* @c: UBIFS file-system description object
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* @key: key to initialize
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* @inum: parent inode number
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* @nm: direntry name and length
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*/
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static inline void dent_key_init(const struct ubifs_info *c,
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union ubifs_key *key, ino_t inum,
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const struct qstr *nm)
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{
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uint32_t hash = c->key_hash(nm->name, nm->len);
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ubifs_assert(!(hash & ~UBIFS_S_KEY_HASH_MASK));
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key->u32[0] = inum;
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key->u32[1] = hash | (UBIFS_DENT_KEY << UBIFS_S_KEY_HASH_BITS);
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}
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/**
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* data_key_init - initialize data key.
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* @c: UBIFS file-system description object
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* @key: key to initialize
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* @inum: inode number
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* @block: block number
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*/
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static inline void data_key_init(union ubifs_key *key, ino_t inum,
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unsigned int block)
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{
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ubifs_assert(!(block & ~UBIFS_S_KEY_BLOCK_MASK));
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key->u32[0] = inum;
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key->u32[1] = block | (UBIFS_DATA_KEY << UBIFS_S_KEY_BLOCK_BITS);
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}
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/**
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* key_write - transform a key from in-memory format.
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* @c: UBIFS file-system description object
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* @from: the key to transform
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* @to: the key to store the result
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*/
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static inline void key_write(const union ubifs_key *from, void *to)
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{
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union ubifs_key *t = to;
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t->j32[0] = cpu_to_le32(from->u32[0]);
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t->j32[1] = cpu_to_le32(from->u32[1]);
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memset(to + 8, 0, UBIFS_MAX_KEY_LEN - 8);
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}
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/**
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* key_write_idx - transform a key from in-memory format for the index.
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* @c: UBIFS file-system description object
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* @from: the key to transform
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* @to: the key to store the result
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*/
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static inline void key_write_idx(const union ubifs_key *from, void *to)
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{
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union ubifs_key *t = to;
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t->j32[0] = cpu_to_le32(from->u32[0]);
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t->j32[1] = cpu_to_le32(from->u32[1]);
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}
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/**
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* keys_cmp - compare keys.
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* @c: UBIFS file-system description object
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* @key1: the first key to compare
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* @key2: the second key to compare
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*
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* This function compares 2 keys and returns %-1 if @key1 is less than
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* @key2, 0 if the keys are equivalent and %1 if @key1 is greater than @key2.
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*/
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static inline int keys_cmp(const union ubifs_key *key1,
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const union ubifs_key *key2)
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{
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if (key1->u32[0] < key2->u32[0])
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return -1;
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if (key1->u32[0] > key2->u32[0])
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return 1;
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if (key1->u32[1] < key2->u32[1])
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return -1;
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if (key1->u32[1] > key2->u32[1])
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return 1;
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return 0;
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}
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#endif /* !__UBIFS_KEY_H__ */
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