fs/cromfs/cromfs.h

/****************************************************************************
 * fs/cromfs/cromfs.h
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

#ifndef __FS_CROMFS_CROMFS_H
#define __FS_CROMFS_CROMFS_H

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <sys/types.h>
#include <stdint.h>

/****************************************************************************
 * Public Types
 ****************************************************************************/

/* Maximum size of an offset.  This should normally be size_t since this is
 * an in-memory file system.  However, uint32_t is 32-bits on most 32-bit
 * target machines but 64-bits on 64-host machines.  We restrict offsets to
 * 32-bits for commonality (limiting the size of the CROMFS image to 4Gb).
 *
 * REVISIT: What about small memory systems where the size_t is only 16-bits?
 *
 * Similarly, the NuttX mode_t is only 16-bits so uint16_t is explicitly used
 * for NuttX file modes.
 */

/* This structure describes the CROMFS volume.  It provides most of the
 * information needed for statfs() including:
 *
 *   f_type     - Type of filesystem
 *                Return cv_magic (CROMFS_MAGIC)
 *   f_namelen  - Maximum length of filenames
 *                Return NAME_MAX
 *   f_bsize    - Optimal block size for transfers
 *                Return cv_bsize, the block size used when file system was
 *                compressed
 *   f_blocks   - Total data blocks in the file system
 *              - Return cv_nblocks
 *   f_bfree    - Free blocks in the file system
 *                Return 0
 *   f_bavail   - Free blocks avail to non-superuser
 *                Return 0
 *   f_files    - Total file nodes in the file system
 *              - Return cv_nnodes
 *   f_ffree    - Free file nodes in the file system
 *                Return 0
 *
 * The volume header is followed immediately by the root directory node.  An
 * offset to that node is used to permit future variable length data (such as
 * a volume name) which may intervene.
 */

struct cromfs_volume_s
{
  uint32_t cv_magic;   /* Must be first.  Must be CROMFS_MAGIC */
  uint16_t cv_nnodes;  /* Total number of nodes in-use */
  uint16_t cv_nblocks; /* Total number of data blocks in-use */
  uint32_t cv_root;    /* Offset to the first node in the root file system */
  uint32_t cv_fsize;   /* Size of the compressed file system image */
  uint32_t cv_bsize;   /* Optimal block size for transfers */
};

/* This describes one node in the CROMFS file system. It holds node meta data
 * that provides the information that will be return by stat() or fstat()
 * and also provides the information needed by the CROMFS file system to
 * access the node data.
 *
 * Relationship to struct stat:
 *
 *   st_mode    - File type, attributes, and access mode bits
 *                Return cn_mode from the node structure
 *   st_size    - Size of file/directory, in bytes
 *                Return cn_size from the node structure
 *   st_blksize - Block size used for filesystem I/O
 *                Return cv_bsize from the volume header.
 *   st_blocks  - Number of blocks allocated
 *                Return (cn_size + (cv_bsize - 1)) / cv_bsize
 *   st_atime   - Time of last access
 *                Return 0
 *   st_mtime   - Time of last modification
 *                Return 0
 *   st_ctime   - Time of last status change
 *                Return 0
 */

begin_packed_struct struct cromfs_node_s
{
  uint16_t cn_mode; /* File type, attributes, and access mode bits */
  uint16_t cn_pad;  /* Not used */
  uint32_t cn_name; /* Offset from the beginning of the volume header to the
                     * node name string.  NUL-terminated. */
  uint32_t cn_size; /* Size of the uncompressed data (in bytes) */
  uint32_t cn_peer; /* Offset to next node in this directory (for readdir()) */
  union
  {
    uint32_t cn_child;  /* Offset to first node in sub-directory (directories only) */
    uint32_t cn_link;   /* Offset to an arbitrary node (for hard link) */
    uint32_t cn_blocks; /* Offset to first block of compressed data (for read) */
  } u;
} end_packed_struct;    /* Use packed access since cromfs nodes may be unaligned */

#endif /* __FS_CROMFS_CROMFS_H */