lib/ext2fs/ext_attr.c

   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 "config.h"
  15 #include <stdio.h>
  16 #if HAVE_UNISTD_H
  17 #include <unistd.h>
  18 #endif
  19 #include <string.h>
  20 #include <time.h>
  21
  22 #include "ext2_fs.h"
  23 #include "ext2_ext_attr.h"
  24
  25 #include "ext2fs.h"
  26
  27 #define NAME_HASH_SHIFT 5
  28 #define VALUE_HASH_SHIFT 16
  29
  30 /*
  31  * ext2_xattr_hash_entry()
  32  *
  33  * Compute the hash of an extended attribute.
  34  */
  35 __u32 ext2fs_ext_attr_hash_entry(struct ext2_ext_attr_entry *entry, void *data)
  36 {
  37         __u32 hash = 0;
  38         char *name = ((char *) entry) + sizeof(struct ext2_ext_attr_entry);
  39         int n;
  40
  41         for (n = 0; n < entry->e_name_len; n++) {
  42                 hash = (hash << NAME_HASH_SHIFT) ^
  43                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
  44                        *name++;
  45         }
  46
  47         /* The hash needs to be calculated on the data in little-endian. */
  48         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
  49                 __u32 *value = (__u32 *)data;
  50                 for (n = (entry->e_value_size + EXT2_EXT_ATTR_ROUND) >>
  51                          EXT2_EXT_ATTR_PAD_BITS; n; n--) {
  52                         hash = (hash << VALUE_HASH_SHIFT) ^
  53                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
  54                                ext2fs_le32_to_cpu(*value++);
  55                 }
  56         }
  57
  58         return hash;
  59 }
  60
  61 #undef NAME_HASH_SHIFT
  62 #undef VALUE_HASH_SHIFT
  63
  64 errcode_t ext2fs_read_ext_attr2(ext2_filsys fs, blk64_t block, void *buf)
  65 {
  66         errcode_t       retval;
  67
  68         retval = io_channel_read_blk64(fs->io, block, 1, buf);
  69         if (retval)
  70                 return retval;
  71 #ifdef WORDS_BIGENDIAN
  72         ext2fs_swap_ext_attr(buf, buf, fs->blocksize, 1);
  73 #endif
  74         return 0;
  75 }
  76
  77 errcode_t ext2fs_read_ext_attr(ext2_filsys fs, blk_t block, void *buf)
  78 {
  79         return ext2fs_read_ext_attr2(fs, block, buf);
  80 }
  81
  82 errcode_t ext2fs_write_ext_attr2(ext2_filsys fs, blk64_t block, void *inbuf)
  83 {
  84         errcode_t       retval;
  85         char            *write_buf;
  86 #ifdef WORDS_BIGENDIAN
  87         char            *buf = NULL;
  88
  89         retval = ext2fs_get_mem(fs->blocksize, &buf);
  90         if (retval)
  91                 return retval;
  92         write_buf = buf;
  93         ext2fs_swap_ext_attr(buf, inbuf, fs->blocksize, 1);
  94 #else
  95         write_buf = (char *) inbuf;
  96 #endif
  97         retval = io_channel_write_blk64(fs->io, block, 1, write_buf);
  98 #ifdef WORDS_BIGENDIAN
  99         ext2fs_free_mem(&buf);
 100 #endif
 101         if (!retval)
 102                 ext2fs_mark_changed(fs);
 103         return retval;
 104 }
 105
 106 errcode_t ext2fs_write_ext_attr(ext2_filsys fs, blk_t block, void *inbuf)
 107 {
 108         return ext2fs_write_ext_attr2(fs, block, inbuf);
 109 }
 110
 111 /*
 112  * This function adjusts the reference count of the EA block.
 113  */
 114 errcode_t ext2fs_adjust_ea_refcount2(ext2_filsys fs, blk64_t blk,
 115                                     char *block_buf, int adjust,
 116                                     __u32 *newcount)
 117 {
 118         errcode_t       retval;
 119         struct ext2_ext_attr_header *header;
 120         char    *buf = 0;
 121
 122         if ((blk >= ext2fs_blocks_count(fs->super)) ||
 123             (blk < fs->super->s_first_data_block))
 124                 return EXT2_ET_BAD_EA_BLOCK_NUM;
 125
 126         if (!block_buf) {
 127                 retval = ext2fs_get_mem(fs->blocksize, &buf);
 128                 if (retval)
 129                         return retval;
 130                 block_buf = buf;
 131         }
 132
 133         retval = ext2fs_read_ext_attr2(fs, blk, block_buf);
 134         if (retval)
 135                 goto errout;
 136
 137         header = (struct ext2_ext_attr_header *) block_buf;
 138         header->h_refcount += adjust;
 139         if (newcount)
 140                 *newcount = header->h_refcount;
 141
 142         retval = ext2fs_write_ext_attr2(fs, blk, block_buf);
 143         if (retval)
 144                 goto errout;
 145
 146 errout:
 147         if (buf)
 148                 ext2fs_free_mem(&buf);
 149         return retval;
 150 }
 151
 152 errcode_t ext2fs_adjust_ea_refcount(ext2_filsys fs, blk_t blk,
 153                                         char *block_buf, int adjust,
 154                                         __u32 *newcount)
 155 {
 156         return ext2fs_adjust_ea_refcount(fs, blk, block_buf, adjust, newcount);
 157 }