ext_attr.c revision 543547a52a20cb7e69d74921b2f691078fd55d83 
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 Library
10 * General Public License, version 2.
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_attr(ext2_filsys fs, blk_t block, void *buf)
64{
65	errcode_t	retval;
66
67 	retval = io_channel_read_blk(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_write_ext_attr(ext2_filsys fs, blk_t block, void *inbuf)
77{
78	errcode_t	retval;
79	char		*write_buf;
80	char		*buf = NULL;
81
82#ifdef WORDS_BIGENDIAN
83	retval = ext2fs_get_mem(fs->blocksize, &buf);
84	if (retval)
85		return retval;
86	write_buf = buf;
87	ext2fs_swap_ext_attr(buf, inbuf, fs->blocksize, 1);
88#else
89	write_buf = (char *) inbuf;
90#endif
91 	retval = io_channel_write_blk(fs->io, block, 1, write_buf);
92	if (buf)
93		ext2fs_free_mem(&buf);
94	if (!retval)
95		ext2fs_mark_changed(fs);
96	return retval;
97}
98
99/*
100 * This function adjusts the reference count of the EA block.
101 */
102errcode_t ext2fs_adjust_ea_refcount(ext2_filsys fs, blk_t blk,
103				    char *block_buf, int adjust,
104				    __u32 *newcount)
105{
106	errcode_t	retval;
107	struct ext2_ext_attr_header *header;
108	char	*buf = 0;
109
110	if ((blk >= fs->super->s_blocks_count) ||
111	    (blk < fs->super->s_first_data_block))
112		return EXT2_ET_BAD_EA_BLOCK_NUM;
113
114	if (!block_buf) {
115		retval = ext2fs_get_mem(fs->blocksize, &buf);
116		if (retval)
117			return retval;
118		block_buf = buf;
119	}
120
121	retval = ext2fs_read_ext_attr(fs, blk, block_buf);
122	if (retval)
123		goto errout;
124
125	header = (struct ext2_ext_attr_header *) block_buf;
126	header->h_refcount += adjust;
127	if (newcount)
128		*newcount = header->h_refcount;
129
130	retval = ext2fs_write_ext_attr(fs, blk, block_buf);
131	if (retval)
132		goto errout;
133
134errout:
135	if (buf)
136		ext2fs_free_mem(&buf);
137	return retval;
138}
139