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Diffstat (limited to 'fs/squashfs/fragment.c')
| -rw-r--r-- | fs/squashfs/fragment.c | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/fs/squashfs/fragment.c b/fs/squashfs/fragment.c new file mode 100644 index 00000000000..b5a2c15bbbc --- /dev/null +++ b/fs/squashfs/fragment.c @@ -0,0 +1,98 @@ +/* + * Squashfs - a compressed read only filesystem for Linux + * + * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008 + * Phillip Lougher <phillip@lougher.demon.co.uk> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2, + * or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * + * fragment.c + */ + +/* + * This file implements code to handle compressed fragments (tail-end packed + * datablocks). + * + * Regular files contain a fragment index which is mapped to a fragment + * location on disk and compressed size using a fragment lookup table. + * Like everything in Squashfs this fragment lookup table is itself stored + * compressed into metadata blocks. A second index table is used to locate + * these. This second index table for speed of access (and because it + * is small) is read at mount time and cached in memory. + */ + +#include <linux/fs.h> +#include <linux/vfs.h> +#include <linux/slab.h> +#include <linux/zlib.h> + +#include "squashfs_fs.h" +#include "squashfs_fs_sb.h" +#include "squashfs_fs_i.h" +#include "squashfs.h" + +/* + * Look-up fragment using the fragment index table. Return the on disk + * location of the fragment and its compressed size + */ +int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment, + u64 *fragment_block) +{ + struct squashfs_sb_info *msblk = sb->s_fs_info; + int block = SQUASHFS_FRAGMENT_INDEX(fragment); + int offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment); + u64 start_block = le64_to_cpu(msblk->fragment_index[block]); + struct squashfs_fragment_entry fragment_entry; + int size; + + size = squashfs_read_metadata(sb, &fragment_entry, &start_block, + &offset, sizeof(fragment_entry)); + if (size < 0) + return size; + + *fragment_block = le64_to_cpu(fragment_entry.start_block); + size = le32_to_cpu(fragment_entry.size); + + return size; +} + + +/* + * Read the uncompressed fragment lookup table indexes off disk into memory + */ +__le64 *squashfs_read_fragment_index_table(struct super_block *sb, + u64 fragment_table_start, unsigned int fragments) +{ + unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments); + __le64 *fragment_index; + int err; + + /* Allocate fragment lookup table indexes */ + fragment_index = kmalloc(length, GFP_KERNEL); + if (fragment_index == NULL) { + ERROR("Failed to allocate fragment index table\n"); + return ERR_PTR(-ENOMEM); + } + + err = squashfs_read_table(sb, fragment_index, fragment_table_start, + length); + if (err < 0) { + ERROR("unable to read fragment index table\n"); + kfree(fragment_index); + return ERR_PTR(err); + } + + return fragment_index; +} |