STATIC __u16 ext2fs_group_desc_csum(ext2_filsys fs, dgrp_t group)
{
__u16 crc = 0;
struct ext2_group_desc *desc;
desc = &fs->group_desc[group];
if (fs->super->s_feature_ro_compat & EXT4_FEATURE_RO_COMPAT_GDT_CSUM) {
int offset = offsetof(struct ext2_group_desc, bg_checksum);
#ifdef WORDS_BIGENDIAN
struct ext2_group_desc swabdesc = *desc;
ext2fs_swap_group_desc(&swabdesc);
desc = &swabdesc;
group = ext2fs_swab32(group);
#endif
crc = ext2fs_crc16(~0, fs->super->s_uuid,
sizeof(fs->super->s_uuid));
crc = ext2fs_crc16(crc, &group, sizeof(group));
crc = ext2fs_crc16(crc, desc, offset);
offset += sizeof(desc->bg_checksum);
assert(offset == sizeof(*desc));
if (offset < fs->super->s_desc_size) {
crc = ext2fs_crc16(crc, (char *)desc + offset,
fs->super->s_desc_size - offset);
}
}
__u16 ext2fs_group_desc_csum(ext2_filsys fs, dgrp_t group)
{
__u16 crc = 0;
struct ext2_group_desc *desc;
size_t size;
size = fs->super->s_desc_size;
if (size < EXT2_MIN_DESC_SIZE)
size = EXT2_MIN_DESC_SIZE;
if (size > sizeof(struct ext4_group_desc)) {
printf("%s: illegal s_desc_size(%zd)\n", __func__, size);
size = sizeof(struct ext4_group_desc);
}
desc = ext2fs_group_desc(fs, fs->group_desc, group);
if (fs->super->s_feature_ro_compat & EXT4_FEATURE_RO_COMPAT_GDT_CSUM) {
size_t offset = offsetof(struct ext2_group_desc, bg_checksum);
#ifdef WORDS_BIGENDIAN
struct ext4_group_desc swabdesc;
/* Have to swab back to little-endian to do the checksum */
memcpy(&swabdesc, desc, size);
ext2fs_swap_group_desc2(fs,
(struct ext2_group_desc *) &swabdesc);
desc = (struct ext2_group_desc *) &swabdesc;
group = ext2fs_swab32(group);
#endif
crc = ext2fs_crc16(~0, fs->super->s_uuid,
sizeof(fs->super->s_uuid));
crc = ext2fs_crc16(crc, &group, sizeof(group));
crc = ext2fs_crc16(crc, desc, offset);
offset += sizeof(desc->bg_checksum); /* skip checksum */
/* for checksum of struct ext4_group_desc do the rest...*/
if (offset < size) {
crc = ext2fs_crc16(crc, (char *)desc + offset,
size - offset);
}
}
