diff options
Diffstat (limited to 'nuttx/fs/nxffs/nxffs_read.c')
| -rw-r--r-- | nuttx/fs/nxffs/nxffs_read.c | 201 |
1 files changed, 199 insertions, 2 deletions
diff --git a/nuttx/fs/nxffs/nxffs_read.c b/nuttx/fs/nxffs/nxffs_read.c index d8c2e9567..3648c1314 100644 --- a/nuttx/fs/nxffs/nxffs_read.c +++ b/nuttx/fs/nxffs/nxffs_read.c @@ -43,6 +43,7 @@ #include <string.h> #include <fcntl.h> +#include <crc32.h> #include <assert.h> #include <errno.h> #include <debug.h> @@ -69,6 +70,178 @@ ****************************************************************************/ /**************************************************************************** + * Name: nxffs_rdblkhdr + * + * Description: + * Read the dataa block header at this offset. Called only from nxffs_nextblock(). + * + * 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 negater errno value is returned + * indicating the nature of the failure. + * + ****************************************************************************/ + +static int nxffs_rdblkhdr(FAR struct nxffs_volume_s *volume, off_t offset, + FAR size_t *datlen) +{ + struct nxffs_data_s blkhdr; + uint32_t ecrc; + uint32_t crc; + uint16_t doffset; + uint16_t dlen; + int ret; + + /* Read the header at the FLASH offset */ + + nxffs_ioseek(volume, offset); + ret = nxffs_rddata(volume, (FAR uint8_t *)&blkhdr, SIZEOF_NXFFS_DATA_HDR); + if (ret < 0) + { + fdbg("Failed to read data block header, offset %d: %d\n", offset, -ret); + return -EIO; + } + doffset = volume->iooffset; + + /* Extract the data length */ + + dlen = nxffs_rdle16(blkhdr.datlen); + 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_wrle16(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; +} + +/**************************************************************************** + * Name: nxffs_nextblock + * + * Description: + * Search for the next valid data block starting at the provided FLASH offset. + * + * Input Parameters: + * volume - Describes the NXFFS volume. + * offset - The FLASH memory offset to begin searching. + * 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 size_t *datlen) +{ + 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); + 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]) + { + nmagic = 0; + } + else if (nmagic < NXFFS_MAGICSIZE - 1) + { + nmagic++; + } + + /* We have found the magic sequence in the FLASH data that may + * indicate the beginning of an NXFFS data block. + */ + + else + { + ret = nxffs_rdblkhdr(volume, offset, datlen); + if (ret == OK) + { + fdbg("Found a valid fileheader\n"); + return OK; + } + + /* False alarm.. keep looking */ + + nmagic = 0; + } + } + } + + /* We won't get here, but to keep some compilers happy: */ + + return -ENOENT; +} + +/**************************************************************************** * Name: nxffs_rdseek * * Description: @@ -88,8 +261,32 @@ static ssize_t nxffs_rdseek(FAR struct nxffs_volume_s *volume, FAR struct nxffs_entry_s *entry, off_t fpos) { -#warning "Missing Logic" - return 0; + size_t datlen = 0; + size_t blklen = 0; + off_t offset = fpos; + int ret; + + /* Loop until we read the data block containing the desired position */ + + do + { + /* Get the data offset at the start of the next data block */ + + datlen += blklen; + + /* Get the length of the next data block */ + + ret = nxffs_nextblock(volume, offset, &blklen); + if (ret < 0) + { + fdbg("nxffs_nextblock failed: %d\n", -ret); + return ret; + } + } + while (datlen <= fpos && datlen + blklen > fpos); + + volume->iooffset += (fpos - datlen); + return OK; } /**************************************************************************** |