nxffs.h

/****************************************************************************
 * fs/nxffs/nxffs.h
 *
 *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
 *
 * References: Linux/Documentation/filesystems/romfs.txt
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

#ifndef __FS_NXFFS_NXFFS_H
#define __FS_NXFFS_NXFFS_H

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

#include <nuttx/config.h>

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

#include <nuttx/mtd.h>
#include <nuttx/nxffs.h>

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/
/* NXFFS Definitions ********************************************************/
/* General NXFFS organization.  The following example assumes 4 logical
 * blocks per FLASH erase block.  The actual relationship is determined by
 * the FLASH geometry reported by the MTD driver.
 *
 * ERASE LOGICAL                   Inodes begin with a inode header.  inode may
 * BLOCK BLOCK       CONTENTS      be marked as "deleted," pending re-packing.
 *   n   4*n     --+--------------+
 *                 |BBBBBBBBBBBBBB| Logic block header
 *                 |IIIIIIIIIIIIII| Inodes begin with a inode header
 *                 |DDDDDDDDDDDDDD| Data block containing inode data block
 *                 | (Inode Data) |
 *       4*n+1   --+--------------+
 *                 |BBBBBBBBBBBBBB| Logic block header
 *                 |DDDDDDDDDDDDDD| Inodes may consist of multiple data blocks
 *                 | (Inode Data) |
 *                 |IIIIIIIIIIIIII| Next inode header
 *                 |              | Possibly a few unused bytes at the end of a block
 *       4*n+2   --+--------------+
 *                 |BBBBBBBBBBBBBB| Logic block header
 *                 |DDDDDDDDDDDDDD|
 *                 | (Inode Data) |
 *       4*n+3   --+--------------+
 *                 |BBBBBBBBBBBBBB| Logic block header
 *                 |IIIIIIIIIIIIII| Next inode header
 *                 |DDDDDDDDDDDDDD|
 *                 | (Inode Data) |
 *  n+1  4*(n+1) --+--------------+
 *                 |BBBBBBBBBBBBBB| Logic block header
 *                 |              | All FLASH is unused after the end of the final
 *                 |              | inode.
 *               --+--------------+
 *
 * General operation:
 *   Inodes are written starting at the beginning of FLASH.  As inodes are
 *   deleted, they are marked as deleted but not removed.  As new inodes are
 *   written, allocations  proceed to toward the end of the FLASH -- thus,
 *   supporting wear leveling by using all FLASH blocks equally.
 *
 *   When the FLASH becomes full (no more space at the end of the FLASH), a
 *   re-packing operation must be performed:  All inodes marked deleted are
 *   finally removed and the remaining inodes are packed at the beginning of
 *   the FLASH.  Allocations then continue at the freed FLASH memory at the
 *   end of the FLASH.
 *
 * BLOCK HEADER:
 *   The block header is used to determine if the block has every been
 *   formatted and also indicates bad blocks which should never be used.
 *
 * INODE HEADER:
 *   Each inode begins with an inode header that contains, among other things,
 *   the name of the inode, the offset to the first data block, and the
 *   length of the inode data.
 *
 *   At present, the only kind of inode support is a file.  So for now, the
 *   term file and inode are interchangeable.
 *
 * INODE DATA HEADER:
 *   Inode data is enclosed in a data header.  For a given inode, there
 *   is at most one inode data block per logical block.  If the inode data
 *   spans more than one logical block, then the inode data may be enclosed
 *   in multiple data blocks, one per logical block.
 *
 * NXFFS Limitations:
 * 1. Since the files are contiguous in FLASH and since allocations always
 *    proceed toward the end of the FLASH, there can only be one file opened
 *    for writing at a time.  Multiple files may be opened for reading.
 * 2. Files may not be increased in size after they have been closed.  The
 *    O_APPEND open flag is not supported.
 * 3. Files are always written sequential.  Seeking within a file opened for
 *    writing will not work.
 * 4. There are no directories, however, '/' may be used within a file name
 *    string providing some illusion of directories.
 * 5. Files may be opened for reading or for writing, but not both: The O_RDWR
 *    open flag is not supported.
 * 6. The re-packing process occurs only during a write when the free FLASH
 *    memory at the end of the FLASH is exhausted.  Thus, occasionally, file
 *    writing may take a long time.
 * 7. Another limitation is that there can be only a single NXFFS volume
 *    mounted at any time.  This has to do with the fact that we bind to
 *    an MTD driver (instead of a block driver) and bypass all of the normal
 *    mount operations.
 */

/* Values for logical block state.  Basically, there are only two, perhaps
 * three, states:
 *
 * BLOCK_STATE_GOOD - The block is not known to be bad.
 * BLOCK_STATE_BAD  - An error was found on the block and it is marked bad.
 * Other values     - The block is bad and has an invalid state.
 *
 * Care is taken so that the GOOD to BAD transition only involves burning
 * bits from the erased to non-erased state.
 */

#define BLOCK_STATE_GOOD          (CONFIG_NXFFS_ERASEDSTATE ^ 0x44)
#define BLOCK_STATE_BAD           (CONFIG_NXFFS_ERASEDSTATE ^ 0x55)

/* Values for NXFFS inode state.  Similar there are 2 (maybe 3) inode states:
 *
 * INODE_STATE_FILE    - The inode is a valid usuable, file
 * INODE_STATE_DELETED - The inode has been deleted.
 * Other values        - The inode is bad and has an invalid state.
 *
 * Care is taken so that the VALID to DELETED transition only involves burning
 * bits from the erased to non-erased state.
 */

#define INODE_STATE_FILE          (CONFIG_NXFFS_ERASEDSTATE ^ 0x22)
#define INODE_STATE_DELETED       (CONFIG_NXFFS_ERASEDSTATE ^ 0xaa)

/* Number of bytes in an the NXFFS magic sequences */

#define NXFFS_MAGICSIZE	          4

/* When we allocate FLASH for a new inode data block, we will require that
 * space is available to hold this minimum number of data bytes in addition
 * to the size of the data block headeer.
 */

#define NXFFS_MINDATA             16

/* Internal definitions *****************************************************/
/* If we encounter this number of erased bytes, we assume that all of the
 * flash beyond this point is erased.
 */

#define NXFFS_NERASED             128

/* Quasi-standard definitions */

#ifndef MIN
#  define MIN(a,b)                (a < b ? a : b)
#endif

#ifndef MAX
#  define MAX(a,b)                (a > b ? a : b)
#endif

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

/* This structure defines each packed block on the FLASH media */

struct nxffs_block_s
{
  uint8_t                   magic[4];  /* 0-3: Magic number for valid block */
  uint8_t                   state;     /* 4: Block state: See BLOCK_STATE_* */
};
#define SIZEOF_NXFFS_BLOCK_HDR 5

/* This structure defines each packed NXFFS inode header on the FLASH media */

struct nxffs_inode_s
{
  uint8_t                   magic[4];  /* 0-3: Magic number for valid inode */
  uint8_t                   state;     /* 4: Inode state: See INODE_STATE_* */
  uint8_t                   namlen;    /* 5: Length of the inode name */
  uint8_t                   noffs[4];  /* 6-9: FLASH offset to the file name */
  uint8_t                   doffs[4];  /* 10-13: FLASH offset to the first data block */
  uint8_t                   utc[4];    /* 14-17: Creation time */
  uint8_t                   crc[4];    /* 18-21: CRC32 */
  uint8_t                   datlen[4]; /* 22-25: Length of data in bytes */
};
#define SIZEOF_NXFFS_INODE_HDR 26

/* This structure defines each packed NXFFS data header on the FLASH media */

struct nxffs_data_s
{
  uint8_t                   magic[4];  /* 0-3: Magic number for valid data */
  uint8_t                   crc[4];    /* 4-7: CRC32 */
  uint8_t                   datlen[2]; /* 8-9: Length of data in bytes */
};
#define SIZEOF_NXFFS_DATA_HDR 10

/* This is an in-memory representation of the NXFFS inode as extracted from
 * FLASH and with additional state information.
 */

struct nxffs_entry_s
{
  off_t                     hoffset;   /* FLASH offset to the inode header */
  off_t                     noffset;   /* FLASH offset to the inode name */
  off_t                     doffset;   /* FLASH offset to the first data header */
  FAR char                 *name;      /* inode name */
  uint32_t                  utc;       /* Time stamp */
  uint32_t                  datlen;    /* Length of inode data */
};

/* This structure describes int in-memory representation of the data block */

struct nxffs_blkentry_s
{
  off_t                     hoffset;  /* Offset to the block data header */
  uint16_t                  datlen;   /* Length of data following the header */
  uint16_t                  foffset;  /* Offset to start of data */
};

/* This structure describes the state of one open file.  This structure
 * is protected by the volume semaphore.
 */

struct nxffs_ofile_s
{
  struct nxffs_ofile_s     *flink;     /* Supports a singly linked list */
  int16_t                   crefs;     /* Reference count */
  mode_t                    oflags;    /* Open mode */
  struct nxffs_entry_s      entry;     /* Describes the NXFFS inode entry */
};

/* A file opened for writing require some additional information */

struct nxffs_wrfile_s
{
  /* The following fields provide the common open file information. */

  struct nxffs_ofile_s      ofile;

  /* The following fields are required to support the write operation */

  bool                      truncate;   /* Delete a file of the same name */
  uint16_t                  datlen;     /* Number of bytes written in data block */
  off_t                     doffset;    /* FLASH offset to the current data header */
  uint32_t                  crc;        /* Accumulated data block CRC */
};

/* This structure represents the overall state of on NXFFS instance. */

struct nxffs_volume_s
{
  FAR struct mtd_dev_s     *mtd;       /* Supports FLASH access */
  sem_t                     exclsem;   /* Used to assure thread-safe access */
  sem_t                     wrsem;     /* Enforces single writer restriction */
  struct mtd_geometry_s     geo;       /* Device geometry */
  uint8_t                   blkper;    /* R/W blocks per erase block */
  uint16_t                  iooffset;  /* Next offset in read/write access (in ioblock) */
  off_t                     inoffset;  /* Offset to the first valid inode header */
  off_t                     froffset;  /* Offset to the first free byte */
  off_t                     nblocks;   /* Number of R/W blocks on volume */
  off_t                     ioblock;   /* Current block number being accessed */
  off_t                     cblock;    /* Starting block number in cache */
  FAR struct nxffs_ofile_s *ofiles;    /* A singly-linked list of open files */
  FAR uint8_t              *cache;     /* On cached erase block for general I/O */
  FAR uint8_t              *pack;      /* A full erase block to support packing */
};

/* This structure describes the state of the blocks on the NXFFS volume */

struct nxffs_blkstats_s
{
  off_t                     nblocks;    /* Total number of FLASH blocks */
  off_t                     ngood;      /* Number of good FLASH blocks found */
  off_t                     nbad;       /* Number of well-formatted FLASH blocks marked as bad */
  off_t                     nunformat;  /* Number of unformatted FLASH blocks */
  off_t                     ncorrupt;   /* Number of blocks with correupted format info */
};

/****************************************************************************
 * Public Variables
 ****************************************************************************/

/* The magic number that appears that the beginning of each NXFFS (logical)
 * block
 */

extern const uint8_t g_blockmagic[NXFFS_MAGICSIZE];

/* The magic number that appears that the beginning of each NXFFS inode */

extern const uint8_t g_inodemagic[NXFFS_MAGICSIZE];

/* The magic number that appears that the beginning of each NXFFS inode
 * data block.
 */

extern const uint8_t g_datamagic[NXFFS_MAGICSIZE];

/* If CONFIG_NXFSS_PREALLOCATED is defined, then this is the single, pre-
 * allocated NXFFS volume instance.
 */

#ifdef CONFIG_NXFSS_PREALLOCATED
extern struct nxffs_volume_s g_volume;
#endif

/****************************************************************************
 * Public Function Prototypes
 ****************************************************************************/

/****************************************************************************
 * Name: nxffs_limits
 *
 * Description:
 *   Recalculate file system limits:  (1) the FLASH offset to the first,
 *   valid inode, and (2) the FLASH offset to the first, unused byte after
 *   the last inode (invalid or not).
 *
 *   The first, lower limit must be recalculated: (1) initially, (2)
 *   whenever the first inode is deleted, or (3) whenever inode is moved
 *   as part of the file system packing operation.
 *
 *   The second, upper limit must be (1) incremented whenever new file
 *   data is written, or (2) recalculated as part of the file system packing
 *   operation.
 *
 * Input Parameters:
 *   volume - Identifies the NXFFS volume
 *
 * Returned Value:
 *   Zero on success. Otherwise, a negated error is returned indicating the
 *   nature of the failure.
 *
 * Defined in nxffs_initialize.c
 *
 ****************************************************************************/

extern int nxffs_limits(FAR struct nxffs_volume_s *volume);

/****************************************************************************
 * Name: nxffs_rdle16
 *
 * Description:
 *   Get a (possibly unaligned) 16-bit little endian value.
 *
 * Input Parameters:
 *   val - A pointer to the first byte of the little endian value.
 *
 * Returned Values:
 *   A uint16_t representing the whole 16-bit integer value
 *
 * Defined in nxffs_util.c
 *
 ****************************************************************************/

extern uint16_t nxffs_rdle16(FAR const uint8_t *val);

/****************************************************************************
 * Name: nxffs_wrle16
 *
 * Description:
 *   Put a (possibly unaligned) 16-bit little endian value.
 *
 * Input Parameters:
 *   dest - A pointer to the first byte to save the little endian value.
 *   val - The 16-bit value to be saved.
 *
 * Returned Values:
 *   None
 *
 * Defined in nxffs_util.c
 *
 ****************************************************************************/

extern void nxffs_wrle16(uint8_t *dest, uint16_t val);

/****************************************************************************
 * Name: nxffs_rdle32
 *
 * Description:
 *   Get a (possibly unaligned) 32-bit little endian value.
 *
 * Input Parameters:
 *   val - A pointer to the first byte of the little endian value.
 *
 * Returned Values:
 *   A uint32_t representing the whole 32-bit integer value
 *
 * Defined in nxffs_util.c
 *
 ****************************************************************************/

extern uint32_t nxffs_rdle32(FAR const uint8_t *val);

/****************************************************************************
 * Name: nxffs_wrle32
 *
 * Description:
 *   Put a (possibly unaligned) 32-bit little endian value.
 *
 * Input Parameters:
 *   dest - A pointer to the first byte to save the little endian value.
 *   val - The 32-bit value to be saved.
 *
 * Returned Value:
 *   None
 *
 * Defined in nxffs_util.c
 *
 ****************************************************************************/

extern void nxffs_wrle32(uint8_t *dest, uint32_t val);

/****************************************************************************
 * Name: nxffs_erased
 *
 * Description:
 *   Check if a block of memory is in the erased state.
 *
 * Input Parameters:
 *   buffer - Address of the start of the memory to check.
 *   buflen - The number of bytes to check.
 *
 * Returned Values:
 *   The number of erased bytes found at the beginning of the memory region.
 *
 * Defined in nxffs_util.c
 *
 ****************************************************************************/

extern size_t nxffs_erased(FAR const uint8_t *buffer, size_t buflen);

/****************************************************************************
 * Name: nxffs_rdcache
 *
 * Description:
 *   Read one I/O block into the volume cache memory.
 *
 * Input Parameters:
 *   volume - Describes the current volume
 *   block  - The first logical block to read
 *
 * Returned Value:
 *   Negated errnos are returned only in the case of MTD reported failures.
 *   Nothing in the volume data itself will generate errors.
 *
 * Defined in nxffs_cache.c
 *
 ****************************************************************************/

extern int nxffs_rdcache(FAR struct nxffs_volume_s *volume, off_t block);

/****************************************************************************
 * Name: nxffs_wrcache
 *
 * Description:
 *   Write one or more logical blocks from the volume cache memory.
 *
 * Input Parameters:
 *   volume - Describes the current volume
 *
 * Returned Value:
 *   Negated errnos are returned only in the case of MTD reported failures.
 *
 * Defined in nxffs_cache.c
 *
 ****************************************************************************/

extern int nxffs_wrcache(FAR struct nxffs_volume_s *volume);

/****************************************************************************
 * Name: nxffs_ioseek
 *
 * Description:
 *   Seek to a position in FLASH memory.  This simply sets up the offsets
 *   and pointer values.  This is a necessary step prior to using
 *   nxffs_getc().
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume
 *   offset - The physical offset in bytes from the beginning of the FLASH
 *     in bytes.
 *
 * Defined in nxffs_cache.c
 *
 ****************************************************************************/

extern void nxffs_ioseek(FAR struct nxffs_volume_s *volume, off_t offset);

/****************************************************************************
 * Name: nxffs_iotell
 *
 * Description:
 *   Report the current position.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume
 *
 * Returned Value:
 *   The offset from the beginning of FLASH to the current seek position.
 *
 * Defined in nxffs_cache.c
 *
 ****************************************************************************/

extern off_t nxffs_iotell(FAR struct nxffs_volume_s *volume);

/****************************************************************************
 * Name: nxffs_getc
 *
 * Description:
 *   Get the next byte from FLASH.  This function allows the data in the
 *   formatted FLASH blocks to be read as a continuous byte stream, skipping
 *   over bad blocks and block headers as necessary.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume.  The paramters ioblock and iooffset
 *     in the volume structure determine the behavior of nxffs_getc().
 *   reserve - If less than this much space is available at the end of the
 *     block, then skip to the next block.
 *
 * Returned Value:
 *   Zero is returned on success.  Otherwise, a negated errno indicating the
 *   nature of the failure.
 *   
 * Defined in nxffs_cache.c
 *
 ****************************************************************************/

extern int nxffs_getc(FAR struct nxffs_volume_s *volume, uint16_t reserve);

/****************************************************************************
 * Name: nxffs_freeentry
 *
 * Description:
 *   The inode values returned by nxffs_nextentry() include allocated memory
 *   (specifically, the file name string).  This function should be called
 *   to dispose of that memory when the inode entry is no longer needed.
 *
 *   Note that the nxffs_entry_s containing structure is not freed.  The
 *   caller may call kfree upon return of this function if necessary to
 *   free the entry container.
 *
 * Input parameters:
 *   entry  - The entry to be freed.
 *
 * Returned Value:
 *   None
 *
 * Defined in nxffs_inode.c
 *
 ****************************************************************************/

extern void nxffs_freeentry(FAR struct nxffs_entry_s *entry);

/****************************************************************************
 * Name: nxffs_nextentry
 *
 * Description:
 *   Search for the next valid inode starting at the provided FLASH offset.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume.
 *   offset - The FLASH memory offset to begin searching.
 *   entry  - A pointer to memory provided by the caller in which to return
 *     the inode description.
 *  
 * Returned Value:
 *   Zero is returned on success. Otherwise, a negated errno is returned
 *   that indicates the nature of the failure.
 *
 * Defined in nxffs_inode.c
 *
 ****************************************************************************/

extern int nxffs_nextentry(FAR struct nxffs_volume_s *volume, off_t offset,
                           FAR struct nxffs_entry_s *entry);

/****************************************************************************
 * Name: nxffs_findinode
 *
 * Description:
 *   Search for an inode with the provided name starting with the first
 *   valid inode and proceeding to the end FLASH or until the matching
 *   inode is found.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume
 *   name   - The name of the inode to find
 *   entry  - The location to return information about the inode.
 *
 * Returned Value:
 *   Zero is returned on success. Otherwise, a negated errno is returned
 *   that indicates the nature of the failure.
 *
 * Defined in nxffs_inode.c
 *
 ****************************************************************************/

extern int nxffs_findinode(FAR struct nxffs_volume_s *volume,
                           FAR const char *name,
                           FAR struct nxffs_entry_s *entry);

/****************************************************************************
 * Name: nxffs_inodeend
 *
 * Description:
 *   Return an *approximiate* FLASH offset to end of the inode data.  The
 *   returned value is guaranteed to be be less then or equal to the offset
 *   of the thing-of-interest in FLASH.  Parsing for interesting things
 *   can begin at that point.
 *
 *   Assumption:  The inode header has been verified by the caller and is
 *   known to contain valid data.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume
 *   entry  - Describes the inode.
 *
 * Returned Value:
 *   A FLASH offset to the (approximate) end of the inode data.  No errors
 *   are detected.
 *
 * Defined in nxffs_inode.c
 *
 ****************************************************************************/

extern off_t nxffs_inodeend(FAR struct nxffs_volume_s *volume,
                            FAR struct nxffs_entry_s *entry);

/****************************************************************************
 * Name: nxffs_verifyblock
 *
 * Description:
 *   Assure the the provided (logical) block number is in the block cache
 *   and that it has a valid block header (i.e., proper magic and
 *   marked good)
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume
 *   block - The (logical) block number to load and verify.
 *
 * Returned Values:
 *   Zero is returned on success.  Otherwise, a negated errno value is
 *   returned indicating the nature of the failure.
 *
 * Defined in nxffs_block.c
 *
 ****************************************************************************/

extern int nxffs_verifyblock(FAR struct nxffs_volume_s *volume, off_t block);

/****************************************************************************
 * Name: nxffs_validblock
 *
 * Description:
 *   Find the next valid (logical) block in the volume.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume
 *   block  - On entry, this provides the starting block number.  If the
 *     function is succesfful, then this memory location will hold the
 *     block number of the next valid block on return.
 *
 *  Returned Value:
 *    Zero on success otherwise a negated errno value indicating the nature
 *    of the failure.
 *
 * Defined in nxffs_block.c
 *
 ****************************************************************************/

extern int nxffs_validblock(struct nxffs_volume_s *volume, off_t *block);

/****************************************************************************
 * Name: nxffs_blockstats
 *
 * Description:
 *   Analyze the NXFFS volume.  This operation must be performed when the
 *   volume is first mounted in order to detect if the volume has been
 *   formatted and contains a usable NXFFS file system.
 *
 * Input Parameters:
 *   volume - Describes the current NXFFS volume.
 *   stats  - On return, will hold nformation describing the state of the
 *     volume.
 *
 * Returned Value:
 *   Negated errnos are returned only in the case of MTD reported failures.
 *   Nothing in the volume data itself will generate errors.
 *
 * Defined in nxffs_blockstats.c
 *
 ****************************************************************************/

extern int nxffs_blockstats(FAR struct nxffs_volume_s *volume,
                            FAR struct nxffs_blkstats_s *stats);

/****************************************************************************
 * Name: nxffs_reformat
 *
 * Description:
 *   Erase and reformat the entire volume.  Verify each block and mark
 *   improperly erased blocks as bad.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume to be reformatted.
 *
 * Returned Value:
 *   Zero on success or a negated errno on a failure.  Failures will be
 *   returned n the case of MTD reported failures o.
 *   Nothing in the volume data itself will generate errors.
 *
 * Defined in nxffs_reformat.c
 *
 ****************************************************************************/

extern int nxffs_reformat(FAR struct nxffs_volume_s *volume);

/****************************************************************************
 * Name: nxffs_findofile
 *
 * Description:
 *   Search the list of already opened files to see if the inode of this
 *   name is one of the opened files.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume.
 *   name - The name of the inode to check.
 *
 * Returned Value:
 *   If an inode of this name is found in the list of opened inodes, then
 *   a reference to the open file structure is returned.  NULL is returned
 *   otherwise.
 *
 * Defined in nxffs_open.c
 *
 ****************************************************************************/

extern FAR struct nxffs_ofile_s *nxffs_findofile(FAR struct nxffs_volume_s *volume,
                                                 FAR const char *name);

/****************************************************************************
 * Name: nxffs_findwriter
 *
 * Description:
 *   Search the list of already opened files and return the open file
 *   instance for the write.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume.
 *
 * Returned Value:
 *   If there is an active writer of the volume, its open file instance is
 *   returned.  NULL is returned otherwise.
 *
 * Defined in nxffs_open.c
 *
 ****************************************************************************/

extern FAR struct nxffs_wrfile_s *nxffs_findwriter(FAR struct nxffs_volume_s *volume);

/****************************************************************************
 * Name: nxffs_wrinode
 *
 * Description:
 *   Write the inode header (only to FLASH.  This is done in two contexts:
 *
 *   1. When an inode is closed, or
 *   2. As part of the file system packing logic when an inode is moved.
 *
 * Note that in either case, the inode name has already been written to
 * FLASH.
 *
 * Input parameters
 *   volume - Describes the NXFFS volume
 *   entry  - Describes the inode header to write
 *
 * Returned Value:
 *   Zero is returned on success; Otherwise, a negated errno value is returned
 *   indicating the nature of the failure.
 *
 * Defined in nxffs_open.c
 *
 ****************************************************************************/

extern int nxffs_wrinode(FAR struct nxffs_volume_s *volume,
                         FAR struct nxffs_entry_s *entry);

/****************************************************************************
 * Name: nxffs_updateinode
 *
 * Description:
 *   The packing logic has moved an inode.  Check if any open files are using
 *   this inode and, if so, move the data in the open file structure as well.
 *
 * Input parameters
 *   volume - Describes the NXFFS volume
 *   entry  - Describes the new inode entry
 *
 * Returned Value:
 *   Zero is returned on success; Otherwise, a negated errno value is returned
 *   indicating the nature of the failure.
 *
 ****************************************************************************/

extern int nxffs_updateinode(FAR struct nxffs_volume_s *volume,
                           FAR struct nxffs_entry_s *entry);

/****************************************************************************
 * Name: nxffs_wrreserve
 *
 * Description:
 *   Find a valid location for a file system object of 'size'.  A valid
 *   location will have these properties:
 *
 *   1. It will lie in the free flash region.
 *   2. It will have enough contiguous memory to hold the entire object
 *   3. The memory at this location will be fully erased.
 *
 *   This function will only perform the checks of 1) and 2).  The
 *   end-of-filesystem offset, froffset, is update past this memory which,
 *   in effect, reserves the memory.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume
 *   size - The size of the object to be reserved.
 *
 * Returned Value:
 *   Zero is returned on success.  Otherwise, a negated errno value is
 *   returned indicating the nature of the failure.  Of special interest
 *   the return error of -ENOSPC which means that the FLASH volume is
 *   full and should be repacked.
 *
 *   On successful return the following are also valid:
 *
 *   volume->ioblock - Read/write block number of the block containing the
 *     candidate oject position
 *   volume->iooffset - The offset in the block to the candidate object
 *     position.
 *   volume->froffset - Updated offset to the first free FLASH block after
 *     the reserved memory.
 *
 * Defined in nxffs_write.c
 *
 ****************************************************************************/

extern int nxffs_wrreserve(FAR struct nxffs_volume_s *volume, size_t size);

/****************************************************************************
 * Name: nxffs_wrverify
 *
 * Description:
 *   Find a valid location for the object.  A valid location will have
 *   these properties:
 *
 *   1. It will lie in the free flash region.
 *   2. It will have enough contiguous memory to hold the entire header
 *      (excluding the file name which may lie in the next block).
 *   3. The memory at this location will be fully erased.
 *
 *   This function will only perform the check 3). On entry it assumes the
 *   following settings (left by nxffs_wrreserve()):
 *
 *   volume->ioblock - Read/write block number of the block containing the
 *     candidate oject position
 *   volume->iooffset - The offset in the block to the candidate object
 *     position.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume
 *   size - The size of the object to be verifed.
 *
 * Returned Value:
 *   Zero is returned on success.  Otherwise, a negated errno value is
 *   returned indicating the nature of the failure.  Of special interest
 *   the return error of -ENOSPC which means that the FLASH volume is
 *   full and should be repacked.
 *
 *   On successful return the following are also valid:
 *
 *   volume->ioblock - Read/write block number of the block containing the
 *     verified object position
 *   volume->iooffset - The offset in the block to the verified object
 *     position.
 *   volume->froffset - Updated offset to the first free FLASH block.
 *
 * Defined in nxffs_write.c
 *
 ****************************************************************************/

extern int nxffs_wrverify(FAR struct nxffs_volume_s *volume, size_t size);

/****************************************************************************
 * Name: nxffs_wrblkhdr
 *
 * Description:
 *   Write the block header information.  This is done (1) whenever the end-
 *   block is encountered and (2) also when the file is closed in order to
 *   flush the final block of data to FLASH.
 *
 * Input Parameters:
 *   volume - Describes the state of the NXFFS volume
 *   wrfile - Describes the state of the open file
 *
 * Returned Value:
 *   Zero is returned on success; Otherwise, a negated errno value is
 *   returned to indicate the nature of the failure.
 *
 * Defined in nxffs_write.c
 *
 ****************************************************************************/

extern int nxffs_wrblkhdr(FAR struct nxffs_volume_s *volume,
                          FAR struct nxffs_wrfile_s *wrfile);

/****************************************************************************
 * Name: nxffs_nextblock
 *
 * Description:
 *   Search for the next valid data block starting at the provided
 *   FLASH offset.
 *
 * Input Parameters:
 *   volume - Describes the NXFFS volume.
 *   datlen  - A memory location to return the data block length.
 *  
 * Returned Value:
 *   Zero is returned on success. Otherwise, a negated errno is returned
 *   that indicates the nature of the failure.
 *
 * Defined in nxffs_read.c
 *
 ****************************************************************************/

extern int nxffs_nextblock(FAR struct nxffs_volume_s *volume, off_t offset,
                           FAR struct nxffs_blkentry_s *blkentry);

/****************************************************************************
 * Name: nxffs_rdblkhdr
 *
 * Description:
 *   Read and verify the data block header at the specified offset.
 *
 * Input Parameters:
 *   volume - Describes the current volume.
 *   offset - The byte offset from the beginning of FLASH where the data block
 *     header is expected.
 *   datlen  - A memory location to return the data block length.
 *
 * Returned Value:
 *   Zero on success.  Otherwise, a negated errno value is returned
 *   indicating the nature of the failure.
 *
 * Defined in nxffs_read.c
 *
 ****************************************************************************/

extern int nxffs_rdblkhdr(FAR struct nxffs_volume_s *volume, off_t offset,
                          FAR uint16_t *datlen);

/****************************************************************************