int nxffs_limits(FAR struct nxffs_volume_s *volume)
{
FAR struct nxffs_entry_s entry;
off_t block;
off_t offset;
bool noinodes = false;
int nerased;
int ret;
/* Get the offset to the first valid block on the FLASH */
block = 0;
ret = nxffs_validblock(volume, &block);
if (ret < 0)
{
fdbg("Failed to find a valid block: %d\n", -ret);
return ret;
}
/* Then find the first valid inode in or beyond the first valid block */
offset = block * volume->geo.blocksize;
ret = nxffs_nextentry(volume, offset, &entry);
if (ret < 0)
{
/* The value -ENOENT is special. This simply means that the FLASH
* was searched to the end and no valid inode was found... the file
* system is empty (or, in more perverse cases, all inodes are
* deleted or corrupted).
*/
if (ret != -ENOENT)
{
fdbg("nxffs_nextentry failed: %d\n", -ret);
return ret;
}
/* Set a flag the just indicates that no inodes were found. Later,
* we will set the location of the first inode to be the same as
* the location of the free FLASH region.
*/
fvdbg("No inodes found\n");
noinodes = true;
}
else
{
/* Save the offset to the first inode */
volume->inoffset = entry.hoffset;
fvdbg("First inode at offset %d\n", volume->inoffset);
/* Discard this entry and set the next offset. */
offset = nxffs_inodeend(volume, &entry);
nxffs_freeentry(&entry);
}
/* Now, search for the last valid entry */
if (!noinodes)
{
while ((ret = nxffs_nextentry(volume, offset, &entry)) == OK)
{
/* Discard the entry and guess the next offset. */
offset = nxffs_inodeend(volume, &entry);
nxffs_freeentry(&entry);
}
fvdbg("Last inode before offset %d\n", offset);
}
/* No inodes were found after this offset. Now search for a block of
* erased flash.
*/
nxffs_ioseek(volume, offset);
nerased = 0;
for (;;)
{
int ch = nxffs_getc(volume, 1);
if (ch < 0)
{
/* Failed to read the next byte... this could mean that the FLASH
* is full?
*/
if (volume->ioblock + 1 >= volume->nblocks &&
volume->iooffset + 1 >= volume->geo.blocksize)
{
/* Yes.. the FLASH is full. Force the offsets to the end of FLASH */
volume->froffset = volume->nblocks * volume->geo.blocksize;
fvdbg("Assume no free FLASH, froffset: %d\n", volume->froffset);
if (noinodes)
{
volume->inoffset = volume->froffset;
fvdbg("No inodes, inoffset: %d\n", volume->inoffset);
}
return OK;
}
// No? Then it is some other failure that we do not know how to handle
fdbg("nxffs_getc failed: %d\n", -ch);
return ch;
}
/* Check for another erased byte */
else if (ch == CONFIG_NXFFS_ERASEDSTATE)
{
/* If we have encountered NXFFS_NERASED number of consecutive
* erased bytes, then presume we have reached the end of valid
* data.
*/
if (++nerased >= NXFFS_NERASED)
{
/* Okay.. we have a long stretch of erased FLASH in a valid
* FLASH block. Let's say that this is the beginning of
* the free FLASH region.
*/
volume->froffset = offset;
fvdbg("Free FLASH region begins at offset: %d\n", volume->froffset);
if (noinodes)
{
volume->inoffset = offset;
fvdbg("First inode at offset %d\n", volume->inoffset);
}
return OK;
}
}
else
{
offset += nerased + 1;
nerased = 0;
}
}
/* Won't get here */
return OK;
}
int nxffs_nextblock(FAR struct nxffs_volume_s *volume, off_t offset,
FAR struct nxffs_blkentry_s *blkentry)
{
int nmagic;
int ch;
int nerased;
int ret;
/* Seek to the first FLASH offset provided by the caller. */
nxffs_ioseek(volume, offset);
/* Skip the block header */
if (volume->iooffset < SIZEOF_NXFFS_BLOCK_HDR)
{
volume->iooffset = SIZEOF_NXFFS_BLOCK_HDR;
}
/* Then begin searching */
nerased = 0;
nmagic = 0;
for (;;)
{
/* Read the next character */
ch = nxffs_getc(volume, SIZEOF_NXFFS_DATA_HDR - nmagic);
if (ch < 0)
{
fdbg("ERROR: nxffs_getc failed: %d\n", -ch);
return ch;
}
/* Check for another erased byte */
else if (ch == CONFIG_NXFFS_ERASEDSTATE)
{
/* If we have encountered NXFFS_NERASED number of consecutive
* erased bytes, then presume we have reached the end of valid
* data.
*/
if (++nerased >= NXFFS_NERASED)
{
fvdbg("No entry found\n");
return -ENOENT;
}
}
else
{
nerased = 0;
/* Check for the magic sequence indicating the start of an NXFFS
* data block or start of the next inode. There is the possibility
* of this magic sequnce occurring in FLASH data. However, the
* data block CRC should distinguish between real NXFFS data blocks
* headers and such false alarms.
*/
if (ch != g_datamagic[nmagic])
{
/* Ooops... this is the not the right character for the magic
* Sequence. Check if we need to restart or to cancel the sequence:
*/
if (ch == g_datamagic[0])
{
nmagic = 1;
}
else
{
nmagic = 0;
}
}
else if (nmagic < NXFFS_MAGICSIZE - 1)
{
/* We have one more character in the magic sequence */
nmagic++;
}
/* We have found the magic sequence in the FLASH data that may
* indicate the beginning of an NXFFS data block.
*/
else
{
/* The offset to the header must be 4 bytes before the current
* FLASH seek location.
*/
blkentry->hoffset = nxffs_iotell(volume) - NXFFS_MAGICSIZE;
/* Read the block header and verify the block at that address */
ret = nxffs_rdblkhdr(volume, blkentry->hoffset, &blkentry->datlen);
if (ret == OK)
{
fvdbg("Found a valid data block, offset: %d datlen: %d\n",
blkentry->hoffset, blkentry->datlen);
return OK;
}
/* False alarm.. Restore the volume cache position (that was
* destroyed by nxfs_rdblkhdr()) and keep looking.
*/
nxffs_ioseek(volume, blkentry->hoffset + NXFFS_MAGICSIZE);
nmagic = 0;
}
}
}
/* We won't get here, but to keep some compilers happy: */
return -ENOENT;
}
int nxffs_nextentry(FAR struct nxffs_volume_s *volume, off_t offset,
FAR struct nxffs_entry_s *entry)
{
int nmagic;
int ch;
int nerased;
int ret;
/* Seek to the first FLASH offset provided by the caller. */
nxffs_ioseek(volume, offset);
/* Then begin searching */
nerased = 0;
nmagic = 0;
for (;;)
{
/* Read the next character */
ch = nxffs_getc(volume, SIZEOF_NXFFS_INODE_HDR - nmagic);
if (ch < 0)
{
fdbg("ERROR: nxffs_getc failed: %d\n", -ch);
return ch;
}
/* Check for another erased byte */
else if (ch == CONFIG_NXFFS_ERASEDSTATE)
{
/* If we have encountered NXFFS_NERASED number of consecutive
* erased bytes, then presume we have reached the end of valid
* data.
*/
if (++nerased >= NXFFS_NERASED)
{
fvdbg("No entry found\n");
return -ENOENT;
}
}
else
{
nerased = 0;
/* Check for the magic sequence indicating the start of an NXFFS
* inode. There is the possibility of this magic sequnce occurring
* in FLASH data. However, the header CRC should distinguish
* between real NXFFS inode headers and such false alarms.
*/
if (ch != g_inodemagic[nmagic])
{
/* Ooops... this is the not the right character for the magic
* Sequence. Check if we need to restart or to cancel the sequence:
*/
if (ch == g_inodemagic[0])
{
nmagic = 1;
}
else
{
nmagic = 0;
}
}
else if (nmagic < NXFFS_MAGICSIZE - 1)
{
/* We have one more character in the magic sequence */
nmagic++;
}
/* We have found the magic sequence in the FLASH data that may
* indicate the beginning of an NXFFS inode.
*/
else
{
/* The the FLASH offset where we found the matching magic number */
offset = nxffs_iotell(volume) - NXFFS_MAGICSIZE;
/* Try to extract the inode header from that position */
ret = nxffs_rdentry(volume, offset, entry);
if (ret == OK)
{
fvdbg("Found a valid fileheader, offset: %d\n", offset);
return OK;
}
/* False alarm.. keep looking */
nmagic = 0;
}
}
}
/* We won't get here, but to keep some compilers happy: */
return -ENOENT;
}