ext_attr.c revision b91f14b870d5b4a4d71b62d81b078f2eb40878ae 
1/*
2 * ext_attr.c --- extended attribute blocks
3 *
4 * Copyright (C) 2001 Andreas Gruenbacher, <a.gruenbacher@computer.org>
5 *
6 * Copyright (C) 2002 Theodore Ts'o.
7 *
8 * %Begin-Header%
9 * This file may be redistributed under the terms of the GNU Public
10 * License.
11 * %End-Header%
12 */
13
14#include <stdio.h>
15#if HAVE_UNISTD_H
16#include <unistd.h>
17#endif
18#include <string.h>
19#include <time.h>
20
21#include "ext2_fs.h"
22#include "ext2_ext_attr.h"
23
24#include "ext2fs.h"
25
26#define NAME_HASH_SHIFT 5
27#define VALUE_HASH_SHIFT 16
28
29/*
30 * ext2_xattr_hash_entry()
31 *
32 * Compute the hash of an extended attribute.
33 */
34__u32 ext2fs_ext_attr_hash_entry(struct ext2_ext_attr_entry *entry, void *data)
35{
36	__u32 hash = 0;
37	char *name = ((char *) entry) + sizeof(struct ext2_ext_attr_entry);
38	int n;
39
40	for (n = 0; n < entry->e_name_len; n++) {
41		hash = (hash << NAME_HASH_SHIFT) ^
42		       (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
43		       *name++;
44	}
45
46	/* The hash needs to be calculated on the data in little-endian. */
47	if (entry->e_value_block == 0 && entry->e_value_size != 0) {
48		__u32 *value = (__u32 *)data;
49		for (n = (entry->e_value_size + EXT2_EXT_ATTR_ROUND) >>
50			 EXT2_EXT_ATTR_PAD_BITS; n; n--) {
51			hash = (hash << VALUE_HASH_SHIFT) ^
52			       (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
53			       ext2fs_le32_to_cpu(*value++);
54		}
55	}
56
57	return hash;
58}
59
60#undef NAME_HASH_SHIFT
61#undef VALUE_HASH_SHIFT
62
63errcode_t ext2fs_read_ext_attr2(ext2_filsys fs, blk64_t block, void *buf)
64{
65	errcode_t	retval;
66
67	retval = io_channel_read_blk64(fs->io, block, 1, buf);
68	if (retval)
69		return retval;
70#ifdef WORDS_BIGENDIAN
71	ext2fs_swap_ext_attr(buf, buf, fs->blocksize, 1);
72#endif
73	return 0;
74}
75
76errcode_t ext2fs_read_ext_attr(ext2_filsys fs, blk_t block, void *buf)
77{
78	return ext2fs_read_ext_attr2(fs, block, buf);
79}
80
81errcode_t ext2fs_write_ext_attr2(ext2_filsys fs, blk64_t block, void *inbuf)
82{
83	errcode_t	retval;
84	char		*write_buf;
85	char		*buf = NULL;
86
87#ifdef WORDS_BIGENDIAN
88	retval = ext2fs_get_mem(fs->blocksize, &buf);
89	if (retval)
90		return retval;
91	write_buf = buf;
92	ext2fs_swap_ext_attr(buf, inbuf, fs->blocksize, 1);
93#else
94	write_buf = (char *) inbuf;
95#endif
96	retval = io_channel_write_blk64(fs->io, block, 1, write_buf);
97	if (buf)
98		ext2fs_free_mem(&buf);
99	if (!retval)
100		ext2fs_mark_changed(fs);
101	return retval;
102}
103
104errcode_t ext2fs_write_ext_attr(ext2_filsys fs, blk_t block, void *inbuf)
105{
106	return ext2fs_write_ext_attr2(fs, block, inbuf);
107}
108
109/*
110 * This function adjusts the reference count of the EA block.
111 */
112errcode_t ext2fs_adjust_ea_refcount2(ext2_filsys fs, blk64_t blk,
113				    char *block_buf, int adjust,
114				    __u32 *newcount)
115{
116	errcode_t	retval;
117	struct ext2_ext_attr_header *header;
118	char	*buf = 0;
119
120	if ((blk >= fs->super->s_blocks_count) ||
121	    (blk < fs->super->s_first_data_block))
122		return EXT2_ET_BAD_EA_BLOCK_NUM;
123
124	if (!block_buf) {
125		retval = ext2fs_get_mem(fs->blocksize, &buf);
126		if (retval)
127			return retval;
128		block_buf = buf;
129	}
130
131	retval = ext2fs_read_ext_attr2(fs, blk, block_buf);
132	if (retval)
133		goto errout;
134
135	header = (struct ext2_ext_attr_header *) block_buf;
136	header->h_refcount += adjust;
137	if (newcount)
138		*newcount = header->h_refcount;
139
140	retval = ext2fs_write_ext_attr2(fs, blk, block_buf);
141	if (retval)
142		goto errout;
143
144errout:
145	if (buf)
146		ext2fs_free_mem(&buf);
147	return retval;
148}
149
150errcode_t ext2fs_adjust_ea_refcount(ext2_filsys fs, blk_t blk,
151					char *block_buf, int adjust,
152					__u32 *newcount)
153{
154	return ext2fs_adjust_ea_refcount(fs, blk, block_buf, adjust, newcount);
155}
156