fs_fat32util.c

這是一個實時嵌入式作業系統 實作了MCS51 ARM等MCU

void fat_putuint16(ubyte *ptr, uint16 value16)
{
  ubyte *val = (ubyte*)&value16;
#ifdef CONFIG_ENDIAN_BIG
  /* The bytes always have to be swapped if the target is big-endian */

  ptr[0] = val[1];
  ptr[1] = val[0];
#else
  /* Byte-by-byte transfer is still necessary if the address is un-aligned */

  ptr[0] = val[0];
  ptr[1] = val[1];
#endif
}

/****************************************************************************
 * Name: fat_putuint32
 ****************************************************************************/

void fat_putuint32(ubyte *ptr, uint32 value32)
{
  uint16 *val = (uint16*)&value32;
#ifdef CONFIG_ENDIAN_BIG
  /* The bytes always have to be swapped if the target is big-endian */

  fat_putuint16(&ptr[0], val[2]);
  fat_putuint16(&ptr[2], val[0]);
#else
  /* Byte-by-byte transfer is still necessary if the address is un-aligned */

  fat_putuint16(&ptr[0], val[0]);
  fat_putuint16(&ptr[2], val[2]);
#endif
}

/****************************************************************************
 * Name: fat_semtake
 ****************************************************************************/

void fat_semtake(struct fat_mountpt_s *fs)
{
  /* Take the semaphore (perhaps waiting) */

  while (sem_wait(&fs->fs_sem) != 0)
    {
      /* The only case that an error should occur here is if
       * the wait was awakened by a signal.
       */

      ASSERT(*get_errno_ptr() == EINTR);
    }
}

/****************************************************************************
 * Name: fat_semgive
 ****************************************************************************/

void fat_semgive(struct fat_mountpt_s *fs)
{
   sem_post(&fs->fs_sem);
}

/****************************************************************************
 * Name: fat_systime2fattime
 *
 * Desciption: Get the system time convertto a time and and date suitble
 * for writing into the FAT FS.
 *
 *    TIME in LS 16-bits:
 *      Bits 0:4   = 2 second count (0-29 representing 0-58 seconds)
 *      Bits 5-10  = minutes (0-59)
 *      Bits 11-15 = hours (0-23)
 *    DATE in MS 16-bits
 *      Bits 0:4   = Day of month (0-31)
 *      Bits 5:8   = Month of year (1-12)
 *      Bits 9:15  = Year from 1980 (0-127 representing 1980-2107)
 *
 ****************************************************************************/

uint32 fat_systime2fattime(void)
{
#warning "Time not implemented"
    return 0;
}

/****************************************************************************
 * Name: fat_fattime2systime
 *
 * Desciption: Convert FAT data and time to a system time_t
 *
 *    16-bit FAT time:
 *      Bits 0:4   = 2 second count (0-29 representing 0-58 seconds)
 *      Bits 5-10  = minutes (0-59)
 *      Bits 11-15 = hours (0-23)
 *    16-bit FAT date:
 *      Bits 0:4   = Day of month (0-31)
 *      Bits 5:8   = Month of year (1-12)
 *      Bits 9:15  = Year from 1980 (0-127 representing 1980-2107)
 *
 ****************************************************************************/

time_t fat_fattime2systime(uint16 fattime, uint16 fatdate)
{
#warning "Time not implemented"
    return 0;
}

/****************************************************************************
 * Name: fat_mount
 *
 * Desciption: This function is called only when the mountpoint is first
 *   established.  It initializes the mountpoint structure and verifies
 *   that a valid FAT32 filesystem is provided by the block driver.
 *
 *   The caller should hold the mountpoint semaphore
 *
 ****************************************************************************/

int fat_mount(struct fat_mountpt_s *fs, boolean writeable)
{
  FAR struct inode *inode;
  struct geometry geo;
  int ret;

  /* Assume that the mount is successful */

  fs->fs_mounted = TRUE;

  /* Check if there is media available */

  inode = fs->fs_blkdriver;
  if (!inode || !inode->u.i_bops || !inode->u.i_bops->geometry ||
      inode->u.i_bops->geometry(inode, &geo) != OK || !geo.geo_available)
    {
      ret = -ENODEV;
      goto errout;
    }

  /* Make sure that that the media is write-able (if write access is needed) */

  if (writeable && !geo.geo_writeenabled)
    {
      ret = -EACCES;
      goto errout;
    }

  /* Save the hardware geometry */

  fs->fs_hwsectorsize = geo.geo_sectorsize;
  fs->fs_hwnsectors   = geo.geo_nsectors;

  /* Allocate a buffer to hold one hardware sector */

  fs->fs_buffer = (ubyte*)malloc(fs->fs_hwsectorsize);
  if (!fs->fs_buffer)
    {
      ret = -ENOMEM;
      goto errout;
    }

  /* Search FAT boot record on the drive.  First check at sector zero.  This
   * could be either the boot record or a partition that refers to the boot
   * record.
   *
   * First read sector zero.  This will be the first access to the drive and a
   * likely failure point.
   */

  fs->fs_fatbase = 0;
  ret = fat_hwread(fs, fs->fs_buffer, 0, 1);
  if (ret < 0)
    {
      goto errout_with_buffer;
    }

  if (fat_checkbootrecord(fs) != OK)
    {
      /* The contents of sector 0 is not a boot record.  It could be a
       * partition, however.  Assume it is a partition and get the offset
       * into the partition table.  This table is at offset MBR_TABLE and is
       * indexed by 16x the partition number.  Here we support only
       * parition 0.
       */

      ubyte *partition = &fs->fs_buffer[MBR_TABLE + 0];

      /* Check if the partition exists and, if so, get the bootsector for that
       * partition and see if we can find the boot record there.
       */
 
      if (partition[4])
        {
          /* There appears to be a partition, get the sector number of the
           * partition (LBA)
           */

          fs->fs_fatbase = MBR_GETPARTSECTOR(&partition[8]);

          /* Read the new candidate boot sector */

          ret = fat_hwread(fs, fs->fs_buffer, fs->fs_fatbase, 1);
          if (ret < 0)
          {
              goto errout_with_buffer;
          }

          /* Check if this is a boot record */

          if (fat_checkbootrecord(fs) != OK)
            {
              goto errout_with_buffer;
            }
        }
    }

  /* We have what appears to be a valid FAT filesystem! Now read the
   * FSINFO sector (FAT32 only)
   */

  if (fs->fs_type == FSTYPE_FAT32)
  {
      ret = fat_checkfsinfo(fs);
      if (ret != OK)
      {
          goto errout_with_buffer;
      }
  }

  /* We did it! */

  fdbg("FAT%d:\n", fs->fs_type == 0 ? 12 : fs->fs_type == 1  ? 16 : 32);
  fdbg("\tHW  sector size:     %d\n", fs->fs_hwsectorsize);
  fdbg("\t    sectors:         %d\n", fs->fs_hwnsectors);
  fdbg("\tFAT reserved:        %d\n", fs->fs_fatresvdseccount);
  fdbg("\t    sectors:         %d\n", fs->fs_fattotsec);
  fdbg("\t    start sector:    %d\n", fs->fs_fatbase);
  fdbg("\t    root sector:     %d\n", fs->fs_rootbase);
  fdbg("\t    root entries:    %d\n", fs->fs_rootentcnt);
  fdbg("\t    data sector:     %d\n", fs->fs_database);
  fdbg("\t    FSINFO sector:   %d\n", fs->fs_fsinfo);
  fdbg("\t    Num FATs:        %d\n", fs->fs_fatnumfats);
  fdbg("\t    FAT sectors:     %d\n", fs->fs_nfatsects);
  fdbg("\t    sectors/cluster: %d\n", fs->fs_fatsecperclus);
  fdbg("\t    max clusters:    %d\n", fs->fs_nclusters);
  fdbg("\tFSI free count       %d\n", fs->fs_fsifreecount);
  fdbg("\t    next free        %d\n", fs->fs_fsinextfree);

  return OK;

 errout_with_buffer:
  free(fs->fs_buffer);
  fs->fs_buffer = 0;
 errout:
  fs->fs_mounted = FALSE;
  return ret;
}

/****************************************************************************
 * Name: fat_checkmount
 *
 * Desciption: Check if the mountpoint is still valid.
 *
 *   The caller should hold the mountpoint semaphore
 *
 ****************************************************************************/

int fat_checkmount(struct fat_mountpt_s *fs)
{
  /* If the fs_mounted flag is FALSE, then we have already handled the loss
   * of the mount.
   */

  if (fs && fs->fs_mounted)
    {
      struct fat_file_s *file;

      /* We still think the mount is healthy.  Check an see if this is
       * still the case
       */

      if (fs->fs_blkdriver)
        {
          struct inode *inode = fs->fs_blkdriver;
          if (inode && inode->u.i_bops && inode->u.i_bops->geometry)
            {
              struct geometry geo;
              int errcode = inode->u.i_bops->geometry(inode, &geo);
              if (errcode == OK && geo.geo_available && !geo.geo_mediachanged)
                {
                  return OK;
                }
            }
        }

      /* If we get here, the mount is NOT healthy */

      fs->fs_mounted = FALSE;

      /* Make sure that this is flagged in every opened file */

      for (file = fs->fs_head; file; file = file->ff_next)
        {
          file->ff_open = FALSE;
        }
    }
  return -ENODEV;
}

/****************************************************************************
 * Name: fat_hwread
 *
 * Desciption: Read the specified sector into the sector buffer
 *
 ****************************************************************************/

int fat_hwread(struct fat_mountpt_s *fs, ubyte *buffer,  size_t sector,
               unsigned int nsectors)
{
  int ret = -ENODEV;
  if (fs && fs->fs_blkdriver )
    {
      struct inode *inode = fs->fs_blkdriver;
      if (inode && inode->u.i_bops && inode->u.i_bops->read)
        {
          ssize_t nSectorsRead = inode->u.i_bops->read(inode, buffer,
                                                       sector, nsectors);
          if (nSectorsRead == nsectors)
            {
              ret = OK;
            }
          else if (nSectorsRead < 0)
            {
              ret = nSectorsRead;
            }
        }
    }
  return ret;
}

/****************************************************************************
 * Name: fat_hwwrite
 *
 * Desciption: Write the sector buffer to the specified sector
 *
 ****************************************************************************/

int fat_hwwrite(struct fat_mountpt_s *fs, ubyte *buffer, size_t sector,
                unsigned int nsectors)
{
  int ret = -ENODEV;
  if (fs && fs->fs_blkdriver )
    {
      struct inode *inode = fs->fs_blkdriver;
      if (inode && inode->u.i_bops && inode->u.i_bops->write)
        {
          ssize_t nSectorsWritten =
              inode->u.i_bops->write(inode, buffer, sector, nsectors);

          if (nSectorsWritten == nsectors)
            {
              ret = OK;
            }
          else if (nSectorsWritten < 0)
            {
              ret = nSectorsWritten;
            }
        }
    }
  return ret;
}

/****************************************************************************
 * Name: fat_cluster2sector
 *
 * Desciption: Convert a cluster number to a start sector number
 *
 ****************************************************************************/

ssize_t fat_cluster2sector(struct fat_mountpt_s *fs,  uint32 cluster )
{
  cluster -= 2;
  if (cluster >= fs->fs_nclusters - 2)
    {
       return -EINVAL;
    }
  return cluster * fs->fs_fatsecperclus + fs->fs_database;
}

/****************************************************************************
 * Name: fat_getcluster
 *
 * Desciption: Get the cluster start sector into the FAT.
 *
 * Return:  <0: error, 0:cluster unassigned, >=0: start sector of cluster
 *
 ****************************************************************************/

ssize_t fat_getcluster(struct fat_mountpt_s *fs, uint32 clusterno)
{
  /* Verify that the cluster number is within range */

  if (clusterno >= 2 && clusterno < fs->fs_nclusters)
    {
      /* Okay.. Read the next cluster from the FAT.  The way we will do
       * this depends on the type of FAT filesystm we are dealing with.
       */

      switch (fs->fs_type)
        {
          case FSTYPE_FAT12 :
            {
              size_t       fatsector;
              unsigned int fatoffset;
              unsigned int startsector;
              unsigned int fatindex;

              /* FAT12 is more complex because it has 12-bits (1.5 bytes)
               * per FAT entry. Get the offset to the first byte:
               */

              fatoffset = (clusterno * 3) / 2;
              fatsector = fs->fs_fatbase + SEC_NSECTORS(fs, fatoffset);

              /* Read the sector at this offset */

              if (fat_fscacheread(fs, fatsector) < 0)
                {
                  /* Read error */
                  break;
                }

              /* Get the first, LS byte of the cluster from the FAT */

              fatindex    = fatoffset & SEC_NDXMASK(fs);
              startsector = fs->fs_buffer[fatindex];

              /* With FAT12, the second byte of the cluster number may lie in
               * a different sector than the first byte.
               */

              fatindex++;
              if (fatindex >= fs->fs_hwsectorsize)
                {
                  fatsector++;
                  fatindex = 0;

                  if (fat_fscacheread(fs, fatsector) < 0)
                    {
                      /* Read error */
                      break;
                    }
                }

              /* Get the second, MS byte of the cluster for 16-bits.  The
               * does not depend on the endian-ness of the target, but only
               * on the fact that the byte stream is little-endian.
               */

              startsector |= (unsigned int)fs->fs_buffer[fatindex] << 8;

              /* Now, pick out the correct 12 bit cluster start sector value */

              if ((clusterno & 1) != 0)
                {
                  /* Odd.. take the MS 12-bits */