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/*
* ext_attr.c --- extended attribute blocks
*
* Copyright (C) 2001 Andreas Gruenbacher, <a.gruenbacher@computer.org>
*
* Copyright (C) 2002 Theodore Ts'o.
*
* %Begin-Header%
* This file may be redistributed under the terms of the GNU Public
* License.
* %End-Header%
*/
#include <stdio.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <string.h>
#include <time.h>
#include "ext2_fs.h"
#include "ext2_ext_attr.h"
#include "ext2fs.h"
#define NAME_HASH_SHIFT 5
#define VALUE_HASH_SHIFT 16
/*
* ext2_xattr_hash_entry()
*
* Compute the hash of an extended attribute.
*/
__u32 ext2fs_ext_attr_hash_entry(struct ext2_ext_attr_entry *entry, void *data)
{
__u32 hash = 0;
char *name = ((char *) entry) + sizeof(struct ext2_ext_attr_entry);
int n;
for (n = 0; n < entry->e_name_len; n++) {
hash = (hash << NAME_HASH_SHIFT) ^
(hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
*name++;
}
/* The hash needs to be calculated on the data in little-endian. */
if (entry->e_value_block == 0 && entry->e_value_size != 0) {
__u32 *value = (__u32 *)data;
for (n = (entry->e_value_size + EXT2_EXT_ATTR_ROUND) >>
EXT2_EXT_ATTR_PAD_BITS; n; n--) {
hash = (hash << VALUE_HASH_SHIFT) ^
(hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
ext2fs_le32_to_cpu(*value++);
}
}
return hash;
}
#undef NAME_HASH_SHIFT
#undef VALUE_HASH_SHIFT
errcode_t ext2fs_read_ext_attr(ext2_filsys fs, blk_t block, void *buf)
{
errcode_t retval;
retval = io_channel_read_blk(fs->io, block, 1, buf);
if (retval)
return retval;
#ifdef WORDS_BIGENDIAN
ext2fs_swap_ext_attr(buf, buf, fs->blocksize, 1);
#endif
return 0;
}
errcode_t ext2fs_write_ext_attr(ext2_filsys fs, blk_t block, void *inbuf)
{
errcode_t retval;
char *write_buf;
char *buf = NULL;
#ifdef WORDS_BIGENDIAN
retval = ext2fs_get_mem(fs->blocksize, &buf);
if (retval)
return retval;
write_buf = buf;
ext2fs_swap_ext_attr(buf, inbuf, fs->blocksize, 1);
#else
write_buf = (char *) inbuf;
#endif
retval = io_channel_write_blk(fs->io, block, 1, write_buf);
if (buf)
ext2fs_free_mem(&buf);
if (!retval)
ext2fs_mark_changed(fs);
return retval;
}
/*
* This function adjusts the reference count of the EA block.
*/
errcode_t ext2fs_adjust_ea_refcount(ext2_filsys fs, blk_t blk,
char *block_buf, int adjust,
__u32 *newcount)
{
errcode_t retval;
struct ext2_ext_attr_header *header;
char *buf = 0;
if ((blk >= fs->super->s_blocks_count) ||
(blk < fs->super->s_first_data_block))
return EXT2_ET_BAD_EA_BLOCK_NUM;
if (!block_buf) {
retval = ext2fs_get_mem(fs->blocksize, &buf);
if (retval)
return retval;
block_buf = buf;
}
retval = ext2fs_read_ext_attr(fs, blk, block_buf);
if (retval)
goto errout;
header = (struct ext2_ext_attr_header *) block_buf;
header->h_refcount += adjust;
if (newcount)
*newcount = header->h_refcount;
retval = ext2fs_write_ext_attr(fs, blk, block_buf);
if (retval)
goto errout;
errout:
if (buf)
ext2fs_free_mem(&buf);
return retval;
}
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