int nxffs_rdblkhdr(FAR struct nxffs_volume_s *volume, off_t offset,
FAR uint16_t *datlen)
{
struct nxffs_data_s blkhdr;
uint32_t ecrc;
uint32_t crc;
uint16_t doffset;
uint16_t dlen;
int ret;
/* Make sure that the block containing the data block header is in the cache */
nxffs_ioseek(volume, offset);
ret = nxffs_rdcache(volume, volume->ioblock);
if (ret < 0)
{
fdbg("ERROR: Failed to read data into cache: %d\n", ret);
return ret;
}
/* Read the header at the FLASH offset */
doffset = volume->iooffset;
memcpy(&blkhdr, &volume->cache[doffset], SIZEOF_NXFFS_DATA_HDR);
/* Extract the data length */
dlen = nxffs_rdle16(blkhdr.datlen);
/* Get the offset to the beginning of the data */
doffset += SIZEOF_NXFFS_DATA_HDR;
/* Make sure that all of the data fits within the block */
if ((uint32_t)doffset + (uint32_t)dlen > (uint32_t)volume->geo.blocksize)
{
fdbg("ERROR: Data length=%d is unreasonable at offset=%d\n", dlen, doffset);
return -EIO;
}
/* Extract the expected CRC and calculate the CRC of the data block */
ecrc = nxffs_rdle32(blkhdr.crc);
nxffs_wrle32(blkhdr.crc, 0);
crc = crc32((FAR const uint8_t *)&blkhdr, SIZEOF_NXFFS_DATA_HDR);
crc = crc32part(&volume->cache[doffset], dlen, crc);
if (crc != ecrc)
{
fdbg("ERROR: CRC failure\n");
return -EIO;
}
/* Looks good! Return the data length and success */
*datlen = dlen;
return OK;
}
static inline int nxffs_wrname(FAR struct nxffs_volume_s *volume,
FAR struct nxffs_entry_s *entry,
int namlen)
{
int ret;
/* Seek to the inode name position and assure that it is in the volume
* cache.
*/
nxffs_ioseek(volume, entry->noffset);
ret = nxffs_rdcache(volume, volume->ioblock);
if (ret < 0)
{
fdbg("ERROR: Failed to read inode name block %d: %d\n",
volume->ioblock, -ret);
return ret;
}
/* Copy the inode name to the volume cache and write the inode name block */
memcpy(&volume->cache[volume->iooffset], entry->name, namlen);
ret = nxffs_wrcache(volume);
if (ret < 0)
{
fdbg("ERROR: Failed to write inode header block %d: %d\n",
volume->ioblock, -ret);
}
return ret;
}
static ssize_t nxffs_rdseek(FAR struct nxffs_volume_s *volume,
FAR struct nxffs_entry_s *entry,
off_t fpos,
FAR struct nxffs_blkentry_s *blkentry)
{
size_t datstart;
size_t datend;
off_t offset;
int ret;
/* The initial FLASH offset will be the offset to first data block of
* the inode
*/
offset = entry->doffset;
if (offset == 0)
{
/* Zero length files will have no data blocks */
return -ENOSPC;
}
/* Loop until we read the data block containing the desired position */
datend = 0;
do
{
/* Check if the next data block contains the sought after file position */
ret = nxffs_nextblock(volume, offset, blkentry);
if (ret < 0)
{
fdbg("ERROR: nxffs_nextblock failed: %d\n", -ret);
return ret;
}
/* Get the range of data offsets for this data block */
datstart = datend;
datend += blkentry->datlen;
/* Offset to search for the next data block */
offset = blkentry->hoffset + SIZEOF_NXFFS_DATA_HDR + blkentry->datlen;
}
while (datend <= fpos);
/* Return the offset to the data within the current data block */
blkentry->foffset = fpos - datstart;
nxffs_ioseek(volume, blkentry->hoffset + SIZEOF_NXFFS_DATA_HDR + blkentry->foffset);
return OK;
}
int nxffs_wrinode(FAR struct nxffs_volume_s *volume,
FAR struct nxffs_entry_s *entry)
{
FAR struct nxffs_inode_s *inode;
uint32_t crc;
int namlen;
int ret;
/* Seek to the inode header position and assure that it is in the volume
* cache.
*/
nxffs_ioseek(volume, entry->hoffset);
ret = nxffs_rdcache(volume, volume->ioblock);
if (ret < 0)
{
fdbg("ERROR: Failed to read inode header block %d: %d\n",
volume->ioblock, -ret);
goto errout;
}
/* Get the length of the inode name */
namlen = strlen(entry->name);
DEBUGASSERT(namlen < CONFIG_NXFFS_MAXNAMLEN); /* This was verified earlier */
/* Initialize the inode header */
inode = (FAR struct nxffs_inode_s *)&volume->cache[volume->iooffset];
memcpy(inode->magic, g_inodemagic, NXFFS_MAGICSIZE);
inode->state = CONFIG_NXFFS_ERASEDSTATE;
inode->namlen = namlen;
nxffs_wrle32(inode->noffs, entry->noffset);
nxffs_wrle32(inode->doffs, entry->doffset);
nxffs_wrle32(inode->utc, entry->utc);
nxffs_wrle32(inode->crc, 0);
nxffs_wrle32(inode->datlen, entry->datlen);
/* Calculate the CRC */
crc = crc32((FAR const uint8_t *)inode, SIZEOF_NXFFS_INODE_HDR);
crc = crc32part((FAR const uint8_t *)entry->name, namlen, crc);
/* Finish the inode header */
inode->state = INODE_STATE_FILE;
nxffs_wrle32(inode->crc, crc);
/* Write the block with the inode header */
ret = nxffs_wrcache(volume);
if (ret < 0)
{
fdbg("ERROR: Failed to write inode header block %d: %d\n",
volume->ioblock, -ret);
}
/* The volume is now available for other writers */
errout:
sem_post(&volume->wrsem);
return ret;
}
int nxffs_rminode(FAR struct nxffs_volume_s *volume, FAR const char *name)
{
FAR struct nxffs_ofile_s *ofile;
FAR struct nxffs_inode_s *inode;
struct nxffs_entry_s entry;
int ret;
/* Check if the file is open */
ofile = nxffs_findofile(volume, name);
if (ofile)
{
/* We can't remove the inode if it is open */
fdbg("Inode '%s' is open\n", name);
ret = -EBUSY;
goto errout;
}
/* Find the NXFFS inode */
ret = nxffs_findinode(volume, name, &entry);
if (ret < 0)
{
fdbg("Inode '%s' not found\n", name);
goto errout;
}
/* Set the position to the FLASH offset of the file header (nxffs_findinode
* should have left the block in the cache).
*/
nxffs_ioseek(volume, entry.hoffset);
/* Make sure that the block is in the cache */
ret = nxffs_rdcache(volume, volume->ioblock);
if (ret < 0)
{
fdbg("Failed to read data into cache: %d\n", ret);
goto errout_with_entry;
}
/* Change the file status... it is no longer valid */
inode = (FAR struct nxffs_inode_s *)&volume->cache[volume->iooffset];
inode->state = INODE_STATE_DELETED;
/* Then write the cached block back to FLASH */
ret = nxffs_wrcache(volume);
if (ret < 0)
{
fdbg("Failed to read data into cache: %d\n", ret);
}
errout_with_entry:
nxffs_freeentry(&entry);
errout:
return ret;
}
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_wrblkhdr(FAR struct nxffs_volume_s *volume,
FAR struct nxffs_wrfile_s *wrfile)
{
FAR struct nxffs_data_s *dathdr;
int ret;
/* Write the data block header to memory */
nxffs_ioseek(volume, wrfile->doffset);
dathdr = (FAR struct nxffs_data_s *)&volume->cache[volume->iooffset];
memcpy(dathdr->magic, g_datamagic, NXFFS_MAGICSIZE);
nxffs_wrle32(dathdr->crc, 0);
nxffs_wrle16(dathdr->datlen, wrfile->datlen);
/* Update the entire data block CRC (including the header) */
wrfile->crc = crc32(&volume->cache[volume->iooffset], wrfile->datlen + SIZEOF_NXFFS_DATA_HDR);
nxffs_wrle32(dathdr->crc, wrfile->crc);
/* And write the data block to FLASH */
ret = nxffs_wrcache(volume);
if (ret < 0)
{
fdbg("ERROR: nxffs_wrcache failed: %d\n", -ret);
goto errout;
}
/* After the block has been successfully written to flash, update the inode
* statistics and reset the write state.
*
* volume:
* froffset - The offset the next free FLASH region. Set to just after
* the inode data block that we just wrote. This is where we will
* begin the search for the next inode header or data block.
*/
volume->froffset = (wrfile->doffset + wrfile->datlen + SIZEOF_NXFFS_DATA_HDR);
/* wrfile->file.entry:
* datlen: Total file length accumulated so far. When the file is
* closed, this will hold the file length.
* doffset: Offset to the first data block. Only the offset to the
* first data block is saved.
*/
wrfile->ofile.entry.datlen += wrfile->datlen;
if (wrfile->ofile.entry.doffset == 0)
{
wrfile->ofile.entry.doffset = wrfile->doffset;
}
/* Return success */
ret = OK;
errout:
wrfile->crc = 0;
wrfile->doffset = 0;
wrfile->datlen = 0;
return ret;
}
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_wrreserve(FAR struct nxffs_volume_s *volume, size_t size)
{
int ret;
/* Seek to the beginning of the free FLASH region */
nxffs_ioseek(volume, volume->froffset);
/* Check for a seek past the end of the volume */
if (volume->ioblock >= volume->nblocks)
{
/* Return -ENOSPC to indicate that the volume is full */
return -ENOSPC;
}
/* Skip over block headers */
if (volume->iooffset < SIZEOF_NXFFS_BLOCK_HDR)
{
volume->iooffset = SIZEOF_NXFFS_BLOCK_HDR;
}
/* Make sure that there is space there to hold the entire object */
if (volume->iooffset + size > volume->geo.blocksize)
{
/* We will need to skip to the next block. But first, check if we are
* already at the final block.
*/
if (volume->ioblock + 1 >= volume->nblocks)
{
/* Return -ENOSPC to indicate that the volume is full */
fdbg("ERROR: No space in last block\n");
return -ENOSPC;
}
/* This is not the last block in the volume, so just seek to the
* beginning of the next, valid block.
*/
volume->ioblock++;
ret = nxffs_validblock(volume, &volume->ioblock);
if (ret < 0)
{
fdbg("ERROR: No more valid blocks\n");
return ret;
}
volume->iooffset = SIZEOF_NXFFS_BLOCK_HDR;
}
/* Update the pointer to the first next free FLASH memory -- reserving this
* block of memory.
*/
volume->froffset = nxffs_iotell(volume) + size;
return OK;
}
ssize_t nxffs_write(FAR struct file *filep, FAR const char *buffer, size_t buflen)
{
FAR struct nxffs_volume_s *volume;
FAR struct nxffs_wrfile_s *wrfile;
ssize_t remaining;
ssize_t nwritten;
ssize_t total;
int ret;
fvdbg("Write %d bytes to offset %d\n", buflen, filep->f_pos);
/* Sanity checks */
DEBUGASSERT(filep->f_priv != NULL && filep->f_inode != NULL);
/* Recover the open file state from the struct file instance */
wrfile = (FAR struct nxffs_wrfile_s *)filep->f_priv;
/* Recover the volume state from the open file */
volume = (FAR struct nxffs_volume_s *)filep->f_inode->i_private;
DEBUGASSERT(volume != NULL);
/* Get exclusive access to the volume. Note that the volume exclsem
* protects the open file list.
*/
ret = sem_wait(&volume->exclsem);
if (ret != OK)
{
ret = -errno;
fdbg("ERROR: sem_wait failed: %d\n", ret);
goto errout;
}
/* Check if the file was opened with write access */
if ((wrfile->ofile.oflags & O_WROK) == 0)
{
fdbg("ERROR: File not open for write access\n");
ret = -EACCES;
goto errout_with_semaphore;
}
/* Loop until we successfully appended all of the data to the file (or an
* error occurs)
*/
for (total = 0; total < buflen; )
{
remaining = buflen - total;
/* Have we already allocated the data block? */
if (wrfile->doffset == 0)
{
/* No, allocate the data block now, re-packing if necessary. */
wrfile->datlen = 0;
ret = nxffs_wralloc(volume, wrfile, remaining);
if (ret < 0)
{
fdbg("ERROR: Failed to allocate a data block: %d\n", -ret);
goto errout_with_semaphore;
}
}
/* Seek to the FLASH block containing the data block */
nxffs_ioseek(volume, wrfile->doffset);
/* Verify that the FLASH data that was previously written is still intact */
ret = nxffs_reverify(volume, wrfile);
if (ret < 0)
{
fdbg("ERROR: Failed to verify FLASH data block: %d\n", -ret);
goto errout_with_semaphore;
}
/* Append the data to the end of the data block and write the updated
* block to flash.
*/
nwritten = nxffs_wrappend(volume, wrfile, &buffer[total], remaining);
if (nwritten < 0)
{
fdbg("ERROR: Failed to append to FLASH to a data block: %d\n", -ret);
goto errout_with_semaphore;
}
/* Decrement the number of bytes remaining to be written */
total += nwritten;
}
/* Success.. return the number of bytes written */
ret = total;
filep->f_pos = wrfile->datlen;
errout_with_semaphore:
sem_post(&volume->exclsem);
errout:
return ret;
}
static inline int nxffs_wralloc(FAR struct nxffs_volume_s *volume,
FAR struct nxffs_wrfile_s *wrfile,
size_t size)
{
bool packed;
int ret;
/* Allocate FLASH memory for the data block.
*
* Loop until the data block header is configured or until a failure
* occurs. Note that nothing is written to FLASH. The data block header
* is not written until either (1) the file is closed, or (2) the data
* region is fully populated.
*/
packed = false;
for (;;)
{
size_t mindata = MIN(NXFFS_MINDATA, size);
/* File a valid location to position the data block. Start with
* the first byte in the free FLASH region.
*/
ret = nxffs_hdrpos(volume, wrfile, mindata);
if (ret == OK)
{
/* Find a region of memory in the block that is fully erased */
ret = nxffs_hdrerased(volume, wrfile, mindata);
if (ret == OK)
{
/* Valid memory for the data block was found. Return success. */
return OK;
}
}
/* If no valid memory is found searching to the end of the volume,
* then -ENOSPC will be returned. Other errors are not handled.
*/
if (ret != -ENOSPC || packed)
{
fdbg("ERROR: Failed to find inode header memory: %d\n", -ret);
return -ENOSPC;
}
/* -ENOSPC is a special case.. It means that the volume is full.
* Try to pack the volume in order to free up some space.
*/
ret = nxffs_pack(volume);
if (ret < 0)
{
fdbg("ERROR: Failed to pack the volume: %d\n", -ret);
return ret;
}
/* After packing the volume, froffset will be updated to point to the
* new free flash region. Try again.
*/
nxffs_ioseek(volume, volume->froffset);
packed = true;
}
/* Can't get here */
return OK;
}
static int nxffs_rdentry(FAR struct nxffs_volume_s *volume, off_t offset,
FAR struct nxffs_entry_s *entry)
{
struct nxffs_inode_s inode;
uint32_t ecrc;
uint32_t crc;
uint8_t state;
int namlen;
int ret;
DEBUGASSERT(volume && entry);
memset(entry, 0, sizeof(struct nxffs_entry_s));
/* Read the header at the FLASH offset */
nxffs_ioseek(volume, offset);
memcpy(&inode, &volume->cache[volume->iooffset], SIZEOF_NXFFS_INODE_HDR);
/* Check if the file state is recognized. */
state = inode.state;
if (state != INODE_STATE_FILE && state != INODE_STATE_DELETED)
{
/* This can't be a valid inode.. don't bother with the rest */
ret = -ENOENT;
goto errout_no_offset;
}
/* Copy the packed header into the user-friendly buffer */
entry->hoffset = offset;
entry->noffset = nxffs_rdle32(inode.noffs);
entry->doffset = nxffs_rdle32(inode.doffs);
entry->utc = nxffs_rdle32(inode.utc);
entry->datlen = nxffs_rdle32(inode.datlen);
/* Modify the packed header and perform the (partial) CRC calculation */
ecrc = nxffs_rdle32(inode.crc);
inode.state = CONFIG_NXFFS_ERASEDSTATE;
memset(inode.crc, 0, 4);
crc = crc32((FAR const uint8_t *)&inode, SIZEOF_NXFFS_INODE_HDR);
/* Allocate memory to hold the variable-length file name */
namlen = inode.namlen;
entry->name = (FAR char *)kmalloc(namlen + 1);
if (!entry->name)
{
fdbg("ERROR: Failed to allocate name, namlen: %d\n", namlen);
ret = -ENOMEM;
goto errout_no_offset;
}
/* Seek to the expected location of the name in FLASH */
nxffs_ioseek(volume, entry->noffset);
/* Make sure that the block is in memory (the name may not be in the
* same block as the inode header.
*/
ret = nxffs_rdcache(volume, volume->ioblock);
if (ret < 0)
{
fdbg("ERROR: nxffsx_rdcache failed: %d\n", -ret);
goto errout_with_name;
}
/* Read the file name from the expected offset in FLASH */
memcpy(entry->name, &volume->cache[volume->iooffset], namlen);
entry->name[namlen] = '\0';
/* Finish the CRC calculation and verify the entry */
crc = crc32part((FAR const uint8_t *)entry->name, namlen, crc);
if (crc != ecrc)
{
fdbg("ERROR: CRC entry: %08x CRC calculated: %08x\n", ecrc, crc);
ret = -EIO;
goto errout_with_name;
}
/* We have a good inode header.. but it still could a deleted file.
* Check the file state.
*/
if (state != INODE_STATE_FILE)
{
/* It is a deleted file. But still, the data offset and the
* start size are good so we can use this information to advance
* further in FLASH memory and reduce the search time.
*/
offset = nxffs_inodeend(volume, entry);
nxffs_freeentry(entry);
ret = -ENOENT;
goto errout;
}
/* Everything is good.. leave the offset pointing to the valid inode
* header.
*/
return OK;
/* On errors where we are suspicious of the validity of the inode header,
* we need to increment the file position to just after the "good" magic
* word.
*/
errout_with_name:
nxffs_freeentry(entry);
errout_no_offset:
offset += NXFFS_MAGICSIZE;
errout:
nxffs_ioseek(volume, offset);
return ret;
}
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;
}