FatPkg/EnhancedFatDxe: Make the comments align with EDKIIcoding style

[mirror_edk2.git] / FatPkg / EnhancedFatDxe / FileSpace.c

/** @file\r
  Routines dealing with disk spaces and FAT table entries.\r
\r
Copyright (c) 2005 - 2013, Intel Corporation. All rights reserved.<BR>\r
This program and the accompanying materials are licensed and made available\r
under the terms and conditions of the BSD License which accompanies this\r
distribution. The full text of the license may be found at\r
http://opensource.org/licenses/bsd-license.php\r
\r
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
\r
\r
**/\r
\r
#include "Fat.h"\r
\r
\r
/**\r
\r
  Get the FAT entry of the volume, which is identified with the Index.\r
\r
  @param  Volume                - FAT file system volume.\r
  @param  Index                 - The index of the FAT entry of the volume.\r
\r
  @return The buffer of the FAT entry\r
\r
**/\r
STATIC\r
VOID *\r
FatLoadFatEntry (\r
  IN FAT_VOLUME       *Volume,\r
  IN UINTN            Index\r
  )\r
{\r
  UINTN       Pos;\r
  EFI_STATUS  Status;\r
\r
  if (Index > (Volume->MaxCluster + 1)) {\r
    Volume->FatEntryBuffer = (UINT32) -1;\r
    return &Volume->FatEntryBuffer;\r
  }\r
  //\r
  // Compute buffer position needed\r
  //\r
  switch (Volume->FatType) {\r
  case Fat12:\r
    Pos = FAT_POS_FAT12 (Index);\r
    break;\r
\r
  case Fat16:\r
    Pos = FAT_POS_FAT16 (Index);\r
    break;\r
\r
  default:\r
    Pos = FAT_POS_FAT32 (Index);\r
  }\r
  //\r
  // Set the position and read the buffer\r
  //\r
  Volume->FatEntryPos = Volume->FatPos + Pos;\r
  Status = FatDiskIo (\r
             Volume,\r
             ReadFat,\r
             Volume->FatEntryPos,\r
             Volume->FatEntrySize,\r
             &Volume->FatEntryBuffer,\r
             NULL\r
             );\r
  if (EFI_ERROR (Status)) {\r
    Volume->FatEntryBuffer = (UINT32) -1;\r
  }\r
\r
  return &Volume->FatEntryBuffer;\r
}\r
\r
/**\r
\r
  Get the FAT entry value of the volume, which is identified with the Index.\r
\r
  @param  Volume                - FAT file system volume.\r
  @param  Index                 - The index of the FAT entry of the volume.\r
\r
  @return  The value of the FAT entry.\r
\r
**/\r
STATIC\r
UINTN\r
FatGetFatEntry (\r
  IN FAT_VOLUME       *Volume,\r
  IN UINTN            Index\r
  )\r
{\r
  VOID    *Pos;\r
  UINT8   *En12;\r
  UINT16  *En16;\r
  UINT32  *En32;\r
  UINTN   Accum;\r
\r
  Pos = FatLoadFatEntry (Volume, Index);\r
\r
  if (Index > (Volume->MaxCluster + 1)) {\r
    return (UINTN) -1;\r
  }\r
\r
  switch (Volume->FatType) {\r
  case Fat12:\r
    En12   = Pos;\r
    Accum = En12[0] | (En12[1] << 8);\r
    Accum = FAT_ODD_CLUSTER_FAT12 (Index) ? (Accum >> 4) : (Accum & FAT_CLUSTER_MASK_FAT12);\r
    Accum = Accum | ((Accum >= FAT_CLUSTER_SPECIAL_FAT12) ? FAT_CLUSTER_SPECIAL_EXT : 0);\r
    break;\r
\r
  case Fat16:\r
    En16   = Pos;\r
    Accum = *En16;\r
    Accum = Accum | ((Accum >= FAT_CLUSTER_SPECIAL_FAT16) ? FAT_CLUSTER_SPECIAL_EXT : 0);\r
    break;\r
\r
  default:\r
    En32   = Pos;\r
    Accum = *En32 & FAT_CLUSTER_MASK_FAT32;\r
    Accum = Accum | ((Accum >= FAT_CLUSTER_SPECIAL_FAT32) ? FAT_CLUSTER_SPECIAL_EXT : 0);\r
  }\r
\r
  return Accum;\r
}\r
\r
/**\r
\r
  Set the FAT entry value of the volume, which is identified with the Index.\r
\r
  @param  Volume                - FAT file system volume.\r
  @param  Index                 - The index of the FAT entry of the volume.\r
  @param  Value                 - The new value of the FAT entry.\r
\r
  @retval EFI_SUCCESS           - Set the new FAT entry value sucessfully.\r
  @retval EFI_VOLUME_CORRUPTED  - The FAT type of the volume is error.\r
  @return other                 - An error occurred when operation the FAT entries.\r
\r
**/\r
STATIC\r
EFI_STATUS\r
FatSetFatEntry (\r
  IN FAT_VOLUME       *Volume,\r
  IN UINTN            Index,\r
  IN UINTN            Value\r
  )\r
{\r
  VOID        *Pos;\r
  UINT8       *En12;\r
  UINT16      *En16;\r
  UINT32      *En32;\r
  UINTN       Accum;\r
  EFI_STATUS  Status;\r
  UINTN       OriginalVal;\r
\r
  if (Index < FAT_MIN_CLUSTER) {\r
    return EFI_VOLUME_CORRUPTED;\r
  }\r
\r
  OriginalVal = FatGetFatEntry (Volume, Index);\r
  if (Value == FAT_CLUSTER_FREE && OriginalVal != FAT_CLUSTER_FREE) {\r
    Volume->FatInfoSector.FreeInfo.ClusterCount += 1;\r
    if (Index < Volume->FatInfoSector.FreeInfo.NextCluster) {\r
      Volume->FatInfoSector.FreeInfo.NextCluster = (UINT32) Index;\r
    }\r
  } else if (Value != FAT_CLUSTER_FREE && OriginalVal == FAT_CLUSTER_FREE) {\r
    if (Volume->FatInfoSector.FreeInfo.ClusterCount != 0) {\r
      Volume->FatInfoSector.FreeInfo.ClusterCount -= 1;\r
    }\r
  }\r
  //\r
  // Make sure the entry is in memory\r
  //\r
  Pos = FatLoadFatEntry (Volume, Index);\r
\r
  //\r
  // Update the value\r
  //\r
  switch (Volume->FatType) {\r
  case Fat12:\r
    En12   = Pos;\r
    Accum = En12[0] | (En12[1] << 8);\r
    Value = Value & FAT_CLUSTER_MASK_FAT12;\r
\r
    if (FAT_ODD_CLUSTER_FAT12 (Index)) {\r
      Accum = (Value << 4) | (Accum & 0xF);\r
    } else {\r
      Accum = Value | (Accum & FAT_CLUSTER_UNMASK_FAT12);\r
    }\r
\r
    En12[0]  = (UINT8) (Accum & 0xFF);\r
    En12[1]  = (UINT8) (Accum >> 8);\r
    break;\r
\r
  case Fat16:\r
    En16   = Pos;\r
    *En16  = (UINT16) Value;\r
    break;\r
\r
  default:\r
    En32   = Pos;\r
    *En32  = (*En32 & FAT_CLUSTER_UNMASK_FAT32) | (UINT32) (Value & FAT_CLUSTER_MASK_FAT32);\r
  }\r
  //\r
  // If the volume's dirty bit is not set, set it now\r
  //\r
  if (!Volume->FatDirty && Volume->FatType != Fat12) {\r
    Volume->FatDirty = TRUE;\r
    FatAccessVolumeDirty (Volume, WriteFat, &Volume->DirtyValue);\r
  }\r
  //\r
  // Write the updated fat entry value to the volume\r
  // The fat is the first fat, and other fat will be in sync\r
  // when the FAT cache flush back.\r
  //\r
  Status = FatDiskIo (\r
             Volume,\r
             WriteFat,\r
             Volume->FatEntryPos,\r
             Volume->FatEntrySize,\r
             &Volume->FatEntryBuffer,\r
             NULL\r
             );\r
  return Status;\r
}\r
\r
/**\r
\r
  Free the cluster clain.\r
\r
  @param  Volume                - FAT file system volume.\r
  @param  Cluster               - The first cluster of cluster chain.\r
\r
  @retval EFI_SUCCESS           - The cluster chain is freed successfully.\r
  @retval EFI_VOLUME_CORRUPTED  - There are errors in the file's clusters.\r
\r
**/\r
STATIC\r
EFI_STATUS\r
FatFreeClusters (\r
  IN FAT_VOLUME           *Volume,\r
  IN UINTN                Cluster\r
  )\r
{\r
  UINTN LastCluster;\r
\r
  while (!FAT_END_OF_FAT_CHAIN (Cluster)) {\r
    if (Cluster == FAT_CLUSTER_FREE || Cluster >= FAT_CLUSTER_SPECIAL) {\r
\r
      DEBUG ((EFI_D_INIT | EFI_D_ERROR, "FatShrinkEof: cluster chain corrupt\n"));\r
      return EFI_VOLUME_CORRUPTED;\r
    }\r
\r
    LastCluster = Cluster;\r
    Cluster     = FatGetFatEntry (Volume, Cluster);\r
    FatSetFatEntry (Volume, LastCluster, FAT_CLUSTER_FREE);\r
  }\r
\r
  return EFI_SUCCESS;\r
}\r
\r
/**\r
\r
  Allocate a free cluster and return the cluster index.\r
\r
  @param  Volume                - FAT file system volume.\r
\r
  @return The index of the free cluster\r
\r
**/\r
STATIC\r
UINTN\r
FatAllocateCluster (\r
  IN FAT_VOLUME   *Volume\r
  )\r
{\r
  UINTN Cluster;\r
\r
  //\r
  // Start looking at FatFreePos for the next unallocated cluster\r
  //\r
  if (Volume->DiskError) {\r
    return (UINTN) FAT_CLUSTER_LAST;\r
  }\r
\r
  for (;;) {\r
    //\r
    // If the end of the list, return no available cluster\r
    //\r
    if (Volume->FatInfoSector.FreeInfo.NextCluster > (Volume->MaxCluster + 1)) {\r
      if (Volume->FreeInfoValid && 0 < (INT32) (Volume->FatInfoSector.FreeInfo.ClusterCount)) {\r
        Volume->FreeInfoValid = FALSE;\r
      }\r
\r
      FatComputeFreeInfo (Volume);\r
      if (Volume->FatInfoSector.FreeInfo.NextCluster > (Volume->MaxCluster + 1)) {\r
        return (UINTN) FAT_CLUSTER_LAST;\r
      }\r
    }\r
\r
    Cluster = FatGetFatEntry (Volume, Volume->FatInfoSector.FreeInfo.NextCluster);\r
    if (Cluster == FAT_CLUSTER_FREE) {\r
      break;\r
    }\r
    //\r
    // Try the next cluster\r
    //\r
    Volume->FatInfoSector.FreeInfo.NextCluster += 1;\r
  }\r
\r
  Cluster = Volume->FatInfoSector.FreeInfo.NextCluster;\r
  Volume->FatInfoSector.FreeInfo.NextCluster += 1;\r
  return Cluster;\r
}\r
\r
/**\r
\r
  Count the number of clusters given a size.\r
\r
  @param  Volume                - The file system volume.\r
  @param  Size                  - The size in bytes.\r
\r
  @return The number of the clusters.\r
\r
**/\r
STATIC\r
UINTN\r
FatSizeToClusters (\r
  IN FAT_VOLUME       *Volume,\r
  IN UINTN            Size\r
  )\r
{\r
  UINTN Clusters;\r
\r
  Clusters = Size >> Volume->ClusterAlignment;\r
  if ((Size & (Volume->ClusterSize - 1)) > 0) {\r
    Clusters += 1;\r
  }\r
\r
  return Clusters;\r
}\r
\r
/**\r
\r
  Shrink the end of the open file base on the file size.\r
\r
  @param  OFile                 - The open file.\r
\r
  @retval EFI_SUCCESS           - Shrinked sucessfully.\r
  @retval EFI_VOLUME_CORRUPTED  - There are errors in the file's clusters.\r
\r
**/\r
EFI_STATUS\r
FatShrinkEof (\r
  IN FAT_OFILE            *OFile\r
  )\r
{\r
  FAT_VOLUME  *Volume;\r
  UINTN       NewSize;\r
  UINTN       CurSize;\r
  UINTN       Cluster;\r
  UINTN       LastCluster;\r
\r
  Volume  = OFile->Volume;\r
  ASSERT_VOLUME_LOCKED (Volume);\r
\r
  NewSize = FatSizeToClusters (Volume, OFile->FileSize);\r
\r
  //\r
  // Find the address of the last cluster\r
  //\r
  Cluster     = OFile->FileCluster;\r
  LastCluster = FAT_CLUSTER_FREE;\r
\r
  if (NewSize != 0) {\r
\r
    for (CurSize = 0; CurSize < NewSize; CurSize++) {\r
      if (Cluster == FAT_CLUSTER_FREE || Cluster >= FAT_CLUSTER_SPECIAL) {\r
\r
        DEBUG ((EFI_D_INIT | EFI_D_ERROR, "FatShrinkEof: cluster chain corrupt\n"));\r
        return EFI_VOLUME_CORRUPTED;\r
      }\r
\r
      LastCluster = Cluster;\r
      Cluster     = FatGetFatEntry (Volume, Cluster);\r
    }\r
\r
    FatSetFatEntry (Volume, LastCluster, (UINTN) FAT_CLUSTER_LAST);\r
\r
  } else {\r
    //\r
    // Check to see if the file is already completely truncated\r
    //\r
    if (Cluster == FAT_CLUSTER_FREE) {\r
      return EFI_SUCCESS;\r
    }\r
    //\r
    // The file is being completely truncated.\r
    //\r
    OFile->FileCluster      = FAT_CLUSTER_FREE;\r
  }\r
  //\r
  // Set CurrentCluster == FileCluster\r
  // to force a recalculation of Position related stuffs\r
  //\r
  OFile->FileCurrentCluster = OFile->FileCluster;\r
  OFile->FileLastCluster    = LastCluster;\r
  OFile->Dirty              = TRUE;\r
  //\r
  // Free the remaining cluster chain\r
  //\r
  return FatFreeClusters (Volume, Cluster);\r
}\r
\r
/**\r
\r
  Grow the end of the open file base on the NewSizeInBytes.\r
\r
  @param  OFile                 - The open file.\r
  @param  NewSizeInBytes        - The new size in bytes of the open file.\r
\r
  @retval EFI_SUCCESS           - The file is grown sucessfully.\r
  @retval EFI_UNSUPPORTED       - The file size is larger than 4GB.\r
  @retval EFI_VOLUME_CORRUPTED  - There are errors in the files' clusters.\r
  @retval EFI_VOLUME_FULL       - The volume is full and can not grow the file.\r
\r
**/\r
EFI_STATUS\r
FatGrowEof (\r
  IN FAT_OFILE            *OFile,\r
  IN UINT64               NewSizeInBytes\r
  )\r
{\r
  FAT_VOLUME  *Volume;\r
  EFI_STATUS  Status;\r
  UINTN       Cluster;\r
  UINTN       CurSize;\r
  UINTN       NewSize;\r
  UINTN       LastCluster;\r
  UINTN       NewCluster;\r
  UINTN       ClusterCount;\r
\r
  //\r
  // For FAT file system, the max file is 4GB.\r
  //\r
  if (NewSizeInBytes > 0x0FFFFFFFFL) {\r
    return EFI_UNSUPPORTED;\r
  }\r
\r
  Volume = OFile->Volume;\r
  ASSERT_VOLUME_LOCKED (Volume);\r
  //\r
  // If the file is already large enough, do nothing\r
  //\r
  CurSize = FatSizeToClusters (Volume, OFile->FileSize);\r
  NewSize = FatSizeToClusters (Volume, (UINTN) NewSizeInBytes);\r
\r
  if (CurSize < NewSize) {\r
    //\r
    // If we haven't found the files last cluster do it now\r
    //\r
    if ((OFile->FileCluster != 0) && (OFile->FileLastCluster == 0)) {\r
      Cluster       = OFile->FileCluster;\r
      ClusterCount  = 0;\r
\r
      while (!FAT_END_OF_FAT_CHAIN (Cluster)) {\r
        if (Cluster == FAT_CLUSTER_FREE || Cluster >= FAT_CLUSTER_SPECIAL) {\r
\r
          DEBUG (\r
            (EFI_D_INIT | EFI_D_ERROR,\r
            "FatGrowEof: cluster chain corrupt\n")\r
            );\r
          Status = EFI_VOLUME_CORRUPTED;\r
          goto Done;\r
        }\r
\r
        ClusterCount++;\r
        OFile->FileLastCluster  = Cluster;\r
        Cluster                 = FatGetFatEntry (Volume, Cluster);\r
      }\r
\r
      if (ClusterCount != CurSize) {\r
        DEBUG (\r
          (EFI_D_INIT | EFI_D_ERROR,\r
          "FatGrowEof: cluster chain size does not match file size\n")\r
          );\r
        Status = EFI_VOLUME_CORRUPTED;\r
        goto Done;\r
      }\r
\r
    }\r
    //\r
    // Loop until we've allocated enough space\r
    //\r
    LastCluster = OFile->FileLastCluster;\r
\r
    while (CurSize < NewSize) {\r
      NewCluster = FatAllocateCluster (Volume);\r
      if (FAT_END_OF_FAT_CHAIN (NewCluster)) {\r
        if (LastCluster != FAT_CLUSTER_FREE) {\r
          FatSetFatEntry (Volume, LastCluster, (UINTN) FAT_CLUSTER_LAST);\r
          OFile->FileLastCluster = LastCluster;\r
        }\r
\r
        Status = EFI_VOLUME_FULL;\r
        goto Done;\r
      }\r
\r
      if (LastCluster != 0) {\r
        FatSetFatEntry (Volume, LastCluster, NewCluster);\r
      } else {\r
        OFile->FileCluster        = NewCluster;\r
        OFile->FileCurrentCluster = NewCluster;\r
      }\r
\r
      LastCluster = NewCluster;\r
      CurSize += 1;\r
    }\r
    //\r
    // Terminate the cluster list\r
    //\r
    FatSetFatEntry (Volume, LastCluster, (UINTN) FAT_CLUSTER_LAST);\r
    OFile->FileLastCluster = LastCluster;\r
  }\r
\r
  OFile->FileSize = (UINTN) NewSizeInBytes;\r
  OFile->Dirty    = TRUE;\r
  return EFI_SUCCESS;\r
\r
Done:\r
  FatShrinkEof (OFile);\r
  return Status;\r
}\r
\r
/**\r
\r
  Seek OFile to requested position, and calculate the number of\r
  consecutive clusters from the position in the file\r
\r
  @param  OFile                 - The open file.\r
  @param  Position              - The file's position which will be accessed.\r
  @param  PosLimit              - The maximum length current reading/writing may access\r
\r
  @retval EFI_SUCCESS           - Set the info successfully.\r
  @retval EFI_VOLUME_CORRUPTED  - Cluster chain corrupt.\r
\r
**/\r
EFI_STATUS\r
FatOFilePosition (\r
  IN FAT_OFILE            *OFile,\r
  IN UINTN                Position,\r
  IN UINTN                PosLimit\r
  )\r
{\r
  FAT_VOLUME  *Volume;\r
  UINTN       ClusterSize;\r
  UINTN       Cluster;\r
  UINTN       StartPos;\r
  UINTN       Run;\r
\r
  Volume      = OFile->Volume;\r
  ClusterSize = Volume->ClusterSize;\r
\r
  ASSERT_VOLUME_LOCKED (Volume);\r
\r
  //\r
  // If this is the fixed root dir, then compute it's position\r
  // from it's fixed info in the fat bpb\r
  //\r
  if (OFile->IsFixedRootDir) {\r
    OFile->PosDisk  = Volume->RootPos + Position;\r
    Run             = OFile->FileSize - Position;\r
  } else {\r
    //\r
    // Run the file's cluster chain to find the current position\r
    // If possible, run from the current cluster rather than\r
    // start from beginning\r
    // Assumption: OFile->Position is always consistent with\r
    // OFile->FileCurrentCluster.\r
    // OFile->Position is not modified outside this function;\r
    // OFile->FileCurrentCluster is modified outside this function\r
    // to be the same as OFile->FileCluster\r
    // when OFile->FileCluster is updated, so make a check of this\r
    // and invalidate the original OFile->Position in this case\r
    //\r
    Cluster     = OFile->FileCurrentCluster;\r
    StartPos    = OFile->Position;\r
    if (Position < StartPos || OFile->FileCluster == Cluster) {\r
      StartPos  = 0;\r
      Cluster   = OFile->FileCluster;\r
    }\r
\r
    while (StartPos + ClusterSize <= Position) {\r
      StartPos += ClusterSize;\r
      if (Cluster == FAT_CLUSTER_FREE || (Cluster >= FAT_CLUSTER_SPECIAL)) {\r
        DEBUG ((EFI_D_INIT | EFI_D_ERROR, "FatOFilePosition:"" cluster chain corrupt\n"));\r
        return EFI_VOLUME_CORRUPTED;\r
      }\r
\r
      Cluster = FatGetFatEntry (Volume, Cluster);\r
    }\r
\r
    if (Cluster < FAT_MIN_CLUSTER) {\r
      return EFI_VOLUME_CORRUPTED;\r
    }\r
\r
    OFile->PosDisk            = Volume->FirstClusterPos +\r
                                LShiftU64 (Cluster - FAT_MIN_CLUSTER, Volume->ClusterAlignment) +\r
                                Position - StartPos;\r
    OFile->FileCurrentCluster = Cluster;\r
    OFile->Position           = StartPos;\r
\r
    //\r
    // Compute the number of consecutive clusters in the file\r
    //\r
    Run = StartPos + ClusterSize - Position;\r
    if (!FAT_END_OF_FAT_CHAIN (Cluster)) {\r
      while ((FatGetFatEntry (Volume, Cluster) == Cluster + 1) && Run < PosLimit) {\r
        Run     += ClusterSize;\r
        Cluster += 1;\r
      }\r
    }\r
  }\r
\r
  OFile->PosRem = Run;\r
  return EFI_SUCCESS;\r
}\r
\r
/**\r
\r
  Get the size of directory of the open file.\r
\r
  @param  Volume                - The File System Volume.\r
  @param  Cluster               - The Starting cluster.\r
\r
  @return The physical size of the file starting at the input cluster, if there is error in the\r
  cluster chain, the return value is 0.\r
\r
**/\r
UINTN\r
FatPhysicalDirSize (\r
  IN FAT_VOLUME            *Volume,\r
  IN UINTN                 Cluster\r
  )\r
{\r
  UINTN Size;\r
  ASSERT_VOLUME_LOCKED (Volume);\r
  //\r
  // Run the cluster chain for the OFile\r
  //\r
  Size = 0;\r
  //\r
  // N.B. ".." directories on some media do not contain a starting\r
  // cluster.  In the case of "." or ".." we don't need the size anyway.\r
  //\r
  if (Cluster != 0) {\r
    while (!FAT_END_OF_FAT_CHAIN (Cluster)) {\r
      if (Cluster == FAT_CLUSTER_FREE || Cluster >= FAT_CLUSTER_SPECIAL) {\r
        DEBUG (\r
          (EFI_D_INIT | EFI_D_ERROR,\r
          "FATDirSize: cluster chain corrupt\n")\r
          );\r
        return 0;\r
      }\r
\r
      Size += Volume->ClusterSize;\r
      Cluster = FatGetFatEntry (Volume, Cluster);\r
    }\r
  }\r
\r
  return Size;\r
}\r
\r
/**\r
\r
  Get the physical size of a file on the disk.\r
\r
  @param  Volume                - The file system volume.\r
  @param  RealSize              - The real size of a file.\r
\r
  @return The physical size of a file on the disk.\r
\r
**/\r
UINT64\r
FatPhysicalFileSize (\r
  IN FAT_VOLUME            *Volume,\r
  IN UINTN                 RealSize\r
  )\r
{\r
  UINTN   ClusterSizeMask;\r
  UINT64  PhysicalSize;\r
  ClusterSizeMask = Volume->ClusterSize - 1;\r
  PhysicalSize    = (RealSize + ClusterSizeMask) & (~((UINT64) ClusterSizeMask));\r
  return PhysicalSize;\r
}\r
\r
/**\r
\r
  Update the free cluster info of FatInfoSector of the volume.\r
\r
  @param  Volume                - FAT file system volume.\r
\r
**/\r
VOID\r
FatComputeFreeInfo (\r
  IN FAT_VOLUME *Volume\r
  )\r
{\r
  UINTN Index;\r
\r
  //\r
  // If we don't have valid info, compute it now\r
  //\r
  if (!Volume->FreeInfoValid) {\r
\r
    Volume->FreeInfoValid                        = TRUE;\r
    Volume->FatInfoSector.FreeInfo.ClusterCount  = 0;\r
    for (Index = Volume->MaxCluster + 1; Index >= FAT_MIN_CLUSTER; Index--) {\r
      if (Volume->DiskError) {\r
        break;\r
      }\r
\r
      if (FatGetFatEntry (Volume, Index) == FAT_CLUSTER_FREE) {\r
        Volume->FatInfoSector.FreeInfo.ClusterCount += 1;\r
        Volume->FatInfoSector.FreeInfo.NextCluster = (UINT32) Index;\r
      }\r
    }\r
\r
    Volume->FatInfoSector.Signature          = FAT_INFO_SIGNATURE;\r
    Volume->FatInfoSector.InfoBeginSignature = FAT_INFO_BEGIN_SIGNATURE;\r
    Volume->FatInfoSector.InfoEndSignature   = FAT_INFO_END_SIGNATURE;\r
  }\r
}\r