/**************************************************************************** * fs/nxffs/nxffs_read.c * * Copyright (C) 2011 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #include #include #include #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; }