/*
   * Squashfs - a compressed read only filesystem for Linux
   *
   * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
   * Phillip Lougher <phillip@squashfs.org.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 "squashfs_fs.h"
  #include "squashfs_fs_sb.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, u64 next_table, unsigned int fragments)
  {
  	unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
  	__le64 *table;
  
  	/*
  	 * Sanity check, length bytes should not extend into the next table -
  	 * this check also traps instances where fragment_table_start is
  	 * incorrectly larger than the next table start
  	 */
  	if (fragment_table_start + length > next_table)
  		return ERR_PTR(-EINVAL);
  
  	table = squashfs_read_table(sb, fragment_table_start, length);
  
  	/*
  	 * table[0] points to the first fragment table metadata block, this
  	 * should be less than fragment_table_start
  	 */
  	if (!IS_ERR(table) && le64_to_cpu(table[0]) >= fragment_table_start) {
  		kfree(table);
  		return ERR_PTR(-EINVAL);
  	}
  
  	return table;
  }