diff options
Diffstat (limited to 'nuttx/fs/nxffs/nxffs_read.c')
-rw-r--r-- | nuttx/fs/nxffs/nxffs_read.c | 473 |
1 files changed, 473 insertions, 0 deletions
diff --git a/nuttx/fs/nxffs/nxffs_read.c b/nuttx/fs/nxffs/nxffs_read.c new file mode 100644 index 000000000..6ba49ca72 --- /dev/null +++ b/nuttx/fs/nxffs/nxffs_read.c @@ -0,0 +1,473 @@ +/**************************************************************************** + * fs/nxffs/nxffs_read.c + * + * 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. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +#include <string.h> +#include <fcntl.h> +#include <crc32.h> +#include <assert.h> +#include <errno.h> +#include <debug.h> + +#include <nuttx/fs/fs.h> +#include <nuttx/mtd.h> + +#include "nxffs.h" + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +/**************************************************************************** + * Public Types + ****************************************************************************/ + +/**************************************************************************** + * Public Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: nxffs_rdseek + * + * Description: + * Seek to the file position before read or write access. Note that the + * simplier nxffs_ioseek() cannot be used for this purpose. File offsets + * are not easily mapped to FLASH offsets due to intervening block and + * data headers. + * + * Input Parameters: + * volume - Describes the current volume + * entry - Describes the open inode + * fpos - The desired file position + * blkentry - Describes the block entry that we are positioned in + * + ****************************************************************************/ + +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("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 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; +} + +/**************************************************************************** + * Public Functions + ****************************************************************************/ +/**************************************************************************** + * Name: nxffs_read + * + * Description: + * This is an implementation of the NuttX standard file system read + * method. + * + ****************************************************************************/ + +ssize_t nxffs_read(FAR struct file *filep, FAR char *buffer, size_t buflen) +{ + FAR struct nxffs_volume_s *volume; + FAR struct nxffs_ofile_s *ofile; + struct nxffs_blkentry_s blkentry; + ssize_t total; + size_t available; + size_t readsize; + int ret; + + fvdbg("Read %d bytes from 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 */ + + ofile = (FAR struct nxffs_ofile_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("sem_wait failed: %d\n", ret); + goto errout; + } + + /* Check if the file was opened with read access */ + + if ((ofile->oflags & O_RDOK) == 0) + { + fdbg("File not open for read access\n"); + ret = -EACCES; + goto errout_with_semaphore; + } + + /* Loop until all bytes have been read */ + + for (total = 0; total < buflen; ) + { + /* Don't seek past the end of the file */ + + if (filep->f_pos >= ofile->entry.datlen) + { + /* Return the partial read */ + + filep->f_pos = ofile->entry.datlen; + break; + } + + /* Seek to the current file offset */ + + ret = nxffs_rdseek(volume, &ofile->entry, filep->f_pos, &blkentry); + if (ret < 0) + { + fdbg("nxffs_rdseek failed: %d\n", -ret); + ret = -EACCES; + goto errout_with_semaphore; + } + + /* How many bytes are available at this offset */ + + available = blkentry.datlen - blkentry.foffset; + + /* Don't read more than we need to */ + + readsize = buflen - total; + if (readsize > available) + { + readsize = available; + } + + /* Read data from that file offset */ + + memcpy(&buffer[total], &volume->cache[volume->iooffset], readsize); + + /* Update the file offset */ + + filep->f_pos += readsize; + total += readsize; + } + + sem_post(&volume->exclsem); + return total; + +errout_with_semaphore: + sem_post(&volume->exclsem); +errout: + return (ssize_t)ret; +} + +/**************************************************************************** + * 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. + * + ****************************************************************************/ + +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) + { + fvdbg("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; +} + +/**************************************************************************** + * 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. + * + ****************************************************************************/ + +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 the the block containing the data block header is in the cache */ + + nxffs_ioseek(volume, offset); + ret = nxffs_rdcache(volume, volume->ioblock); + if (ret < 0) + { + fvdbg("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("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("CRC failure\n"); + return -EIO; + } + + /* Looks good! Return the data length and success */ + + *datlen = dlen; + return OK; +} + + + |