FileSystemOperations.c

Go to the documentation of this file.

 
#include "Udf.h"
 
//
// Vendor-Defined Device Path GUID for UDF file system
//
EFI_GUID  gUdfDevPathGuid = EFI_UDF_DEVICE_PATH_GUID;
 
EFI_STATUS
FindAnchorVolumeDescriptorPointer (
  IN   EFI_BLOCK_IO_PROTOCOL                 *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL                  *DiskIo,
  OUT  UDF_ANCHOR_VOLUME_DESCRIPTOR_POINTER  *AnchorPoint
  )
{
  EFI_STATUS          Status;
  UINT32              BlockSize;
  EFI_LBA             EndLBA;
  EFI_LBA             DescriptorLBAs[4];
  UINTN               Index;
  UDF_DESCRIPTOR_TAG  *DescriptorTag;
 
  BlockSize         = BlockIo->Media->BlockSize;
  EndLBA            = BlockIo->Media->LastBlock;
  DescriptorLBAs[0] = 256;
  DescriptorLBAs[1] = EndLBA - 256;
  DescriptorLBAs[2] = EndLBA;
  DescriptorLBAs[3] = 512;
 
  for (Index = 0; Index < ARRAY_SIZE (DescriptorLBAs); Index++) {
    Status = DiskIo->ReadDisk (
                       DiskIo,
                       BlockIo->Media->MediaId,
                       MultU64x32 (DescriptorLBAs[Index], BlockSize),
                       sizeof (UDF_ANCHOR_VOLUME_DESCRIPTOR_POINTER),
                       (VOID *)AnchorPoint
                       );
    if (EFI_ERROR (Status)) {
      return Status;
    }
 
    DescriptorTag = &AnchorPoint->DescriptorTag;
 
    //
    // Check if read LBA has a valid AVDP descriptor.
    //
    if (DescriptorTag->TagIdentifier == UdfAnchorVolumeDescriptorPointer) {
      return EFI_SUCCESS;
    }
  }
 
  //
  // No AVDP found.
  //
  return EFI_VOLUME_CORRUPTED;
}
 
EFI_STATUS
StartMainVolumeDescriptorSequence (
  IN   EFI_BLOCK_IO_PROTOCOL                 *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL                  *DiskIo,
  IN   UDF_ANCHOR_VOLUME_DESCRIPTOR_POINTER  *AnchorPoint,
  OUT  UDF_VOLUME_INFO                       *Volume
  )
{
  EFI_STATUS          Status;
  UINT32              BlockSize;
  UDF_EXTENT_AD       *ExtentAd;
  EFI_LBA             SeqStartBlock;
  EFI_LBA             SeqEndBlock;
  BOOLEAN             StopSequence;
  VOID                *Buffer;
  UDF_DESCRIPTOR_TAG  *DescriptorTag;
  UINT32              LogicalBlockSize;
 
  BlockSize = BlockIo->Media->BlockSize;
  ExtentAd  = &AnchorPoint->MainVolumeDescriptorSequenceExtent;
 
  //
  // Allocate buffer for reading disk blocks
  //
  Buffer = AllocateZeroPool ((UINTN)BlockSize);
  if (Buffer == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  //
  // The logical partition created by Partition driver is relative to the main
  // VDS extent location, so we start the Main Volume Descriptor Sequence at
  // LBA 0.
  //
  // We don't need to check again if we have valid Volume Descriptors here since
  // Partition driver already did.
  //
  SeqStartBlock = 0;
  SeqEndBlock   = SeqStartBlock + DivU64x32 (
                                    (UINT64)ExtentAd->ExtentLength,
                                    BlockSize
                                    );
  StopSequence = FALSE;
  for ( ; SeqStartBlock < SeqEndBlock && !StopSequence; SeqStartBlock++) {
    //
    // Read disk block
    //
    Status = BlockIo->ReadBlocks (
                        BlockIo,
                        BlockIo->Media->MediaId,
                        SeqStartBlock,
                        BlockSize,
                        Buffer
                        );
    if (EFI_ERROR (Status)) {
      goto Out_Free;
    }
 
    DescriptorTag = Buffer;
 
    switch (DescriptorTag->TagIdentifier) {
      case UdfPartitionDescriptor:
        //
        // Save Partition Descriptor
        //
        CopyMem (&Volume->PartitionDesc, Buffer, sizeof (Volume->PartitionDesc));
        break;
 
      case UdfLogicalVolumeDescriptor:
        //
        // Save Logical Volume Descriptor
        //
        CopyMem (&Volume->LogicalVolDesc, Buffer, sizeof (Volume->LogicalVolDesc));
        break;
 
      case UdfTerminatingDescriptor:
        StopSequence = TRUE;
        break;
 
      default:
        ;
    }
  }
 
  //
  // Determine FE (File Entry) size
  //
  LogicalBlockSize = Volume->LogicalVolDesc.LogicalBlockSize;
  if (LogicalBlockSize >= UDF_LOGICAL_SECTOR_SIZE) {
    Volume->FileEntrySize = (UINTN)LogicalBlockSize;
  } else {
    Volume->FileEntrySize = UDF_LOGICAL_SECTOR_SIZE;
  }
 
  Status = EFI_SUCCESS;
 
Out_Free:
  //
  // Free block read buffer
  //
  FreePool (Buffer);
 
  return Status;
}
 
UDF_PARTITION_DESCRIPTOR *
GetPdFromLongAd (
  IN UDF_VOLUME_INFO                 *Volume,
  IN UDF_LONG_ALLOCATION_DESCRIPTOR  *LongAd
  )
{
  UDF_LOGICAL_VOLUME_DESCRIPTOR  *LogicalVolDesc;
  UINT16                         PartitionNum;
 
  LogicalVolDesc = &Volume->LogicalVolDesc;
 
  switch (LogicalVolDesc->DomainIdentifier.Suffix.Domain.UdfRevision) {
    case 0x0102:
    case 0x0150:
    case 0x0200:
    case 0x0201:
    case 0x0250:
    case 0x0260:
      //
      // UDF 1.02 specification:
      //
      // There shall be exactly one prevailing Logical Volume Descriptor recorded
      // per Volume Set. The Partition Maps field shall contain only Type 1
      // Partition Maps.
      //
      // UDF 1.50 through 2.60 specs say:
      //
      // For the purpose of interchange partition maps shall be limited to
      // Partition Map type 1, except type 2 maps as described in the document.
      //
      // NOTE: Only one Type 1 (Physical) Partition is supported. It has been
      // checked already in Partition driver for existence of a single Type 1
      // Partition map. Hence, the 'PartitionReferenceNumber' field (the index
      // used to access Partition Maps data within the Logical Volume Descriptor)
      // in the Long Allocation Descriptor should be 0 to indicate there is only
      // one partition.
      //
      if (LongAd->ExtentLocation.PartitionReferenceNumber != 0) {
        return NULL;
      }
 
      //
      // Since only one partition, get the first one directly.
      //
      PartitionNum = *(UINT16 *)((UINTN)&LogicalVolDesc->PartitionMaps[4]);
      break;
 
    default:
      //
      // Unsupported UDF revision
      //
      return NULL;
  }
 
  //
  // Check if partition number matches Partition Descriptor found in Main Volume
  // Descriptor Sequence.
  //
  if (Volume->PartitionDesc.PartitionNumber == PartitionNum) {
    return &Volume->PartitionDesc;
  }
 
  return NULL;
}
 
EFI_STATUS
GetLongAdLsn (
  IN  UDF_VOLUME_INFO                 *Volume,
  IN  UDF_LONG_ALLOCATION_DESCRIPTOR  *LongAd,
  OUT UINT64                          *Lsn
  )
{
  UDF_PARTITION_DESCRIPTOR  *PartitionDesc;
 
  PartitionDesc = GetPdFromLongAd (Volume, LongAd);
  if (PartitionDesc == NULL) {
    DEBUG ((
      DEBUG_ERROR,
      "%a: Fail to get the Partition Descriptor from the given Long Allocation Descriptor.\n",
      __func__
      ));
    return EFI_UNSUPPORTED;
  }
 
  *Lsn = (UINT64)PartitionDesc->PartitionStartingLocation -
         Volume->MainVdsStartLocation +
         LongAd->ExtentLocation.LogicalBlockNumber;
 
  return EFI_SUCCESS;
}
 
UINT64
GetShortAdLsn (
  IN UDF_VOLUME_INFO                  *Volume,
  IN UDF_PARTITION_DESCRIPTOR         *PartitionDesc,
  IN UDF_SHORT_ALLOCATION_DESCRIPTOR  *ShortAd
  )
{
  return (UINT64)PartitionDesc->PartitionStartingLocation -
         Volume->MainVdsStartLocation + ShortAd->ExtentPosition;
}
 
EFI_STATUS
FindFileSetDescriptor (
  IN   EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL   *DiskIo,
  IN   UDF_VOLUME_INFO        *Volume
  )
{
  EFI_STATUS                     Status;
  UINT64                         Lsn;
  UDF_LOGICAL_VOLUME_DESCRIPTOR  *LogicalVolDesc;
  UDF_DESCRIPTOR_TAG             *DescriptorTag;
 
  LogicalVolDesc = &Volume->LogicalVolDesc;
  Status         = GetLongAdLsn (Volume, &LogicalVolDesc->LogicalVolumeContentsUse, &Lsn);
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  //
  // As per UDF 2.60 specification:
  //
  // There shall be exactly one File Set Descriptor recorded per Logical
  // Volume.
  //
  // Read disk block
  //
  Status = DiskIo->ReadDisk (
                     DiskIo,
                     BlockIo->Media->MediaId,
                     MultU64x32 (Lsn, LogicalVolDesc->LogicalBlockSize),
                     sizeof (Volume->FileSetDesc),
                     &Volume->FileSetDesc
                     );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  DescriptorTag = &Volume->FileSetDesc.DescriptorTag;
 
  //
  // Check if read block is a File Set Descriptor
  //
  if (DescriptorTag->TagIdentifier != UdfFileSetDescriptor) {
    return EFI_VOLUME_CORRUPTED;
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ReadVolumeFileStructure (
  IN   EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL   *DiskIo,
  OUT  UDF_VOLUME_INFO        *Volume
  )
{
  EFI_STATUS                            Status;
  UDF_ANCHOR_VOLUME_DESCRIPTOR_POINTER  AnchorPoint;
  UDF_EXTENT_AD                         *ExtentAd;
 
  //
  // Find Anchor Volume Descriptor Pointer
  //
  Status = FindAnchorVolumeDescriptorPointer (
             BlockIo,
             DiskIo,
             &AnchorPoint
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  //
  // Save Main VDS start block number
  //
  ExtentAd = &AnchorPoint.MainVolumeDescriptorSequenceExtent;
 
  Volume->MainVdsStartLocation = (UINT64)ExtentAd->ExtentLocation;
 
  //
  // Start Main Volume Descriptor Sequence.
  //
  Status = StartMainVolumeDescriptorSequence (
             BlockIo,
             DiskIo,
             &AnchorPoint,
             Volume
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  return Status;
}
 
UINT64
GetFidDescriptorLength (
  IN UDF_FILE_IDENTIFIER_DESCRIPTOR  *FileIdentifierDesc
  )
{
  return (UINT64)(
                  (INTN)((OFFSET_OF (UDF_FILE_IDENTIFIER_DESCRIPTOR, Data[0]) + 3 +
                          FileIdentifierDesc->LengthOfFileIdentifier +
                          FileIdentifierDesc->LengthOfImplementationUse) >> 2) << 2
                  );
}
 
VOID
DuplicateFid (
  IN   UDF_FILE_IDENTIFIER_DESCRIPTOR  *FileIdentifierDesc,
  OUT  UDF_FILE_IDENTIFIER_DESCRIPTOR  **NewFileIdentifierDesc
  )
{
  *NewFileIdentifierDesc =
    (UDF_FILE_IDENTIFIER_DESCRIPTOR *)AllocateCopyPool (
                                        (UINTN)GetFidDescriptorLength (FileIdentifierDesc),
                                        FileIdentifierDesc
                                        );
}
 
VOID
DuplicateFe (
  IN   EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN   UDF_VOLUME_INFO        *Volume,
  IN   VOID                   *FileEntry,
  OUT  VOID                   **NewFileEntry
  )
{
  *NewFileEntry = AllocateCopyPool (Volume->FileEntrySize, FileEntry);
}
 
EFI_STATUS
GetFileEntryData (
  IN   VOID    *FileEntryData,
  IN   UINTN   FileEntrySize,
  OUT  VOID    **Data,
  OUT  UINT64  *Length
  )
{
  UDF_DESCRIPTOR_TAG       *DescriptorTag;
  UDF_EXTENDED_FILE_ENTRY  *ExtendedFileEntry;
  UDF_FILE_ENTRY           *FileEntry;
 
  DescriptorTag = FileEntryData;
 
  if (DescriptorTag->TagIdentifier == UdfExtendedFileEntry) {
    ExtendedFileEntry = (UDF_EXTENDED_FILE_ENTRY *)FileEntryData;
 
    *Length = ExtendedFileEntry->InformationLength;
    *Data   = (VOID *)((UINT8 *)ExtendedFileEntry->Data +
                       ExtendedFileEntry->LengthOfExtendedAttributes);
  } else if (DescriptorTag->TagIdentifier == UdfFileEntry) {
    FileEntry = (UDF_FILE_ENTRY *)FileEntryData;
 
    *Length = FileEntry->InformationLength;
    *Data   = (VOID *)((UINT8 *)FileEntry->Data +
                       FileEntry->LengthOfExtendedAttributes);
  }
 
  if ((*Length > FileEntrySize) ||
      ((UINTN)FileEntryData > (UINTN)(*Data)) ||
      ((UINTN)(*Data) - (UINTN)FileEntryData > FileEntrySize - *Length))
  {
    return EFI_VOLUME_CORRUPTED;
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
GetAdsInformation (
  IN   VOID    *FileEntryData,
  IN   UINTN   FileEntrySize,
  OUT  VOID    **AdsData,
  OUT  UINT64  *Length
  )
{
  UDF_DESCRIPTOR_TAG       *DescriptorTag;
  UDF_EXTENDED_FILE_ENTRY  *ExtendedFileEntry;
  UDF_FILE_ENTRY           *FileEntry;
 
  DescriptorTag = FileEntryData;
 
  if (DescriptorTag->TagIdentifier == UdfExtendedFileEntry) {
    ExtendedFileEntry = (UDF_EXTENDED_FILE_ENTRY *)FileEntryData;
 
    *Length  = ExtendedFileEntry->LengthOfAllocationDescriptors;
    *AdsData = (VOID *)((UINT8 *)ExtendedFileEntry->Data +
                        ExtendedFileEntry->LengthOfExtendedAttributes);
  } else if (DescriptorTag->TagIdentifier == UdfFileEntry) {
    FileEntry = (UDF_FILE_ENTRY *)FileEntryData;
 
    *Length  = FileEntry->LengthOfAllocationDescriptors;
    *AdsData = (VOID *)((UINT8 *)FileEntry->Data +
                        FileEntry->LengthOfExtendedAttributes);
  }
 
  if ((*Length > FileEntrySize) ||
      ((UINTN)FileEntryData > (UINTN)(*AdsData)) ||
      ((UINTN)(*AdsData) - (UINTN)FileEntryData > FileEntrySize - *Length))
  {
    return EFI_VOLUME_CORRUPTED;
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
GetLongAdFromAds (
  IN      VOID                            *Data,
  IN OUT  UINT64                          *Offset,
  IN      UINT64                          Length,
  OUT     UDF_LONG_ALLOCATION_DESCRIPTOR  **FoundLongAd
  )
{
  UDF_LONG_ALLOCATION_DESCRIPTOR  *LongAd;
  UDF_EXTENT_FLAGS                ExtentFlags;
 
  for ( ; ;) {
    if (*Offset >= Length) {
      //
      // No more Long Allocation Descriptors.
      //
      return EFI_DEVICE_ERROR;
    }
 
    LongAd =
      (UDF_LONG_ALLOCATION_DESCRIPTOR *)((UINT8 *)Data + *Offset);
 
    //
    // If it's either an indirect AD (Extended Alllocation Descriptor) or an
    // allocated AD, then return it.
    //
    ExtentFlags = GET_EXTENT_FLAGS (LongAdsSequence, LongAd);
    if ((ExtentFlags == ExtentIsNextExtent) ||
        (ExtentFlags == ExtentRecordedAndAllocated))
    {
      break;
    }
 
    //
    // This AD is either not recorded but allocated, or not recorded and not
    // allocated. Skip it.
    //
    *Offset += AD_LENGTH (LongAdsSequence);
  }
 
  *FoundLongAd = LongAd;
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
GetShortAdFromAds (
  IN      VOID                             *Data,
  IN OUT  UINT64                           *Offset,
  IN      UINT64                           Length,
  OUT     UDF_SHORT_ALLOCATION_DESCRIPTOR  **FoundShortAd
  )
{
  UDF_SHORT_ALLOCATION_DESCRIPTOR  *ShortAd;
  UDF_EXTENT_FLAGS                 ExtentFlags;
 
  for ( ; ;) {
    if (*Offset >= Length) {
      //
      // No more Short Allocation Descriptors.
      //
      return EFI_DEVICE_ERROR;
    }
 
    ShortAd =
      (UDF_SHORT_ALLOCATION_DESCRIPTOR *)((UINT8 *)Data + *Offset);
 
    //
    // If it's either an indirect AD (Extended Alllocation Descriptor) or an
    // allocated AD, then return it.
    //
    ExtentFlags = GET_EXTENT_FLAGS (ShortAdsSequence, ShortAd);
    if ((ExtentFlags == ExtentIsNextExtent) ||
        (ExtentFlags == ExtentRecordedAndAllocated))
    {
      break;
    }
 
    //
    // This AD is either not recorded but allocated, or not recorded and not
    // allocated. Skip it.
    //
    *Offset += AD_LENGTH (ShortAdsSequence);
  }
 
  *FoundShortAd = ShortAd;
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
GetAllocationDescriptor (
  IN      UDF_FE_RECORDING_FLAGS  RecordingFlags,
  IN      VOID                    *Data,
  IN OUT  UINT64                  *Offset,
  IN      UINT64                  Length,
  OUT     VOID                    **FoundAd
  )
{
  if (RecordingFlags == LongAdsSequence) {
    return GetLongAdFromAds (
             Data,
             Offset,
             Length,
             (UDF_LONG_ALLOCATION_DESCRIPTOR **)FoundAd
             );
  } else if (RecordingFlags == ShortAdsSequence) {
    return GetShortAdFromAds (
             Data,
             Offset,
             Length,
             (UDF_SHORT_ALLOCATION_DESCRIPTOR **)FoundAd
             );
  }
 
  //
  // Code should never reach here.
  //
  ASSERT (FALSE);
  return EFI_DEVICE_ERROR;
}
 
EFI_STATUS
GetAllocationDescriptorLsn (
  IN  UDF_FE_RECORDING_FLAGS          RecordingFlags,
  IN  UDF_VOLUME_INFO                 *Volume,
  IN  UDF_LONG_ALLOCATION_DESCRIPTOR  *ParentIcb,
  IN  VOID                            *Ad,
  OUT UINT64                          *Lsn
  )
{
  UDF_PARTITION_DESCRIPTOR  *PartitionDesc;
 
  if (RecordingFlags == LongAdsSequence) {
    return GetLongAdLsn (Volume, (UDF_LONG_ALLOCATION_DESCRIPTOR *)Ad, Lsn);
  } else if (RecordingFlags == ShortAdsSequence) {
    PartitionDesc = GetPdFromLongAd (Volume, ParentIcb);
    if (PartitionDesc == NULL) {
      return EFI_UNSUPPORTED;
    }
 
    *Lsn = GetShortAdLsn (
             Volume,
             PartitionDesc,
             (UDF_SHORT_ALLOCATION_DESCRIPTOR *)Ad
             );
    return EFI_SUCCESS;
  }
 
  //
  // Code should never reach here.
  //
  ASSERT (FALSE);
  return EFI_UNSUPPORTED;
}
 
EFI_STATUS
GetAedAdsOffset (
  IN   EFI_BLOCK_IO_PROTOCOL           *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL            *DiskIo,
  IN   UDF_VOLUME_INFO                 *Volume,
  IN   UDF_LONG_ALLOCATION_DESCRIPTOR  *ParentIcb,
  IN   UDF_FE_RECORDING_FLAGS          RecordingFlags,
  IN   VOID                            *Ad,
  OUT  UINT64                          *Offset,
  OUT  UINT64                          *Length
  )
{
  EFI_STATUS                        Status;
  UINT32                            ExtentLength;
  UINT64                            Lsn;
  VOID                              *Data;
  UINT32                            LogicalBlockSize;
  UDF_ALLOCATION_EXTENT_DESCRIPTOR  *AllocExtDesc;
  UDF_DESCRIPTOR_TAG                *DescriptorTag;
 
  ExtentLength = GET_EXTENT_LENGTH (RecordingFlags, Ad);
  Status       = GetAllocationDescriptorLsn (
                   RecordingFlags,
                   Volume,
                   ParentIcb,
                   Ad,
                   &Lsn
                   );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  Data = AllocatePool (ExtentLength);
  if (Data == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  LogicalBlockSize = Volume->LogicalVolDesc.LogicalBlockSize;
 
  //
  // Read extent.
  //
  Status = DiskIo->ReadDisk (
                     DiskIo,
                     BlockIo->Media->MediaId,
                     MultU64x32 (Lsn, LogicalBlockSize),
                     ExtentLength,
                     Data
                     );
  if (EFI_ERROR (Status)) {
    goto Exit;
  }
 
  AllocExtDesc = (UDF_ALLOCATION_EXTENT_DESCRIPTOR *)Data;
 
  DescriptorTag = &AllocExtDesc->DescriptorTag;
 
  //
  // Check if read extent contains a valid tag identifier for AED.
  //
  if (DescriptorTag->TagIdentifier != UdfAllocationExtentDescriptor) {
    Status = EFI_VOLUME_CORRUPTED;
    goto Exit;
  }
 
  //
  // Get AED's block offset and its length.
  //
  *Offset = MultU64x32 (Lsn, LogicalBlockSize) +
            sizeof (UDF_ALLOCATION_EXTENT_DESCRIPTOR);
  *Length = AllocExtDesc->LengthOfAllocationDescriptors;
 
Exit:
  FreePool (Data);
 
  return Status;
}
 
EFI_STATUS
GetAedAdsData (
  IN   EFI_BLOCK_IO_PROTOCOL           *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL            *DiskIo,
  IN   UDF_VOLUME_INFO                 *Volume,
  IN   UDF_LONG_ALLOCATION_DESCRIPTOR  *ParentIcb,
  IN   UDF_FE_RECORDING_FLAGS          RecordingFlags,
  IN   VOID                            *Ad,
  OUT  VOID                            **Data,
  OUT  UINT64                          *Length
  )
{
  EFI_STATUS  Status;
  UINT64      Offset;
 
  //
  // Get AED's offset + length.
  //
  Status = GetAedAdsOffset (
             BlockIo,
             DiskIo,
             Volume,
             ParentIcb,
             RecordingFlags,
             Ad,
             &Offset,
             Length
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  //
  // Allocate buffer to read in AED's data.
  //
  *Data = AllocatePool ((UINTN)(*Length));
  if (*Data == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  return DiskIo->ReadDisk (
                   DiskIo,
                   BlockIo->Media->MediaId,
                   Offset,
                   (UINTN)(*Length),
                   *Data
                   );
}
 
EFI_STATUS
GrowUpBufferToNextAd (
  IN      UDF_FE_RECORDING_FLAGS  RecordingFlags,
  IN      VOID                    *Ad,
  IN OUT  VOID                    **Buffer,
  IN      UINT64                  Length
  )
{
  UINT32  ExtentLength;
 
  ExtentLength = GET_EXTENT_LENGTH (RecordingFlags, Ad);
 
  if (*Buffer == NULL) {
    *Buffer = AllocatePool (ExtentLength);
    if (*Buffer == NULL) {
      return EFI_OUT_OF_RESOURCES;
    }
  } else {
    *Buffer = ReallocatePool ((UINTN)Length, (UINTN)(Length + ExtentLength), *Buffer);
    if (*Buffer == NULL) {
      return EFI_OUT_OF_RESOURCES;
    }
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ReadFile (
  IN      EFI_BLOCK_IO_PROTOCOL           *BlockIo,
  IN      EFI_DISK_IO_PROTOCOL            *DiskIo,
  IN      UDF_VOLUME_INFO                 *Volume,
  IN      UDF_LONG_ALLOCATION_DESCRIPTOR  *ParentIcb,
  IN      VOID                            *FileEntryData,
  IN OUT  UDF_READ_FILE_INFO              *ReadFileInfo
  )
{
  EFI_STATUS              Status;
  UINT32                  LogicalBlockSize;
  VOID                    *Data;
  VOID                    *DataBak;
  UINT64                  Length;
  VOID                    *Ad;
  UINT64                  AdOffset;
  UINT64                  Lsn;
  BOOLEAN                 DoFreeAed;
  UINT64                  FilePosition;
  UINT64                  Offset;
  UINT64                  DataOffset;
  UINT64                  BytesLeft;
  UINT64                  DataLength;
  BOOLEAN                 FinishedSeeking;
  UINT32                  ExtentLength;
  UDF_FE_RECORDING_FLAGS  RecordingFlags;
 
  LogicalBlockSize = Volume->LogicalVolDesc.LogicalBlockSize;
  DoFreeAed        = FALSE;
 
  //
  // set BytesLeft to suppress incorrect compiler/analyzer warnings
  //
  BytesLeft       = 0;
  DataOffset      = 0;
  FilePosition    = 0;
  FinishedSeeking = FALSE;
  Data            = NULL;
 
  switch (ReadFileInfo->Flags) {
    case ReadFileGetFileSize:
    case ReadFileAllocateAndRead:
      //
      // Initialise ReadFileInfo structure for either getting file size, or
      // reading file's recorded data.
      //
      ReadFileInfo->ReadLength = 0;
      ReadFileInfo->FileData   = NULL;
      break;
    case ReadFileSeekAndRead:
      //
      // About to seek a file and/or read its data.
      //
      Length = ReadFileInfo->FileSize - ReadFileInfo->FilePosition;
      if (ReadFileInfo->FileDataSize > Length) {
        //
        // About to read beyond the EOF -- truncate it.
        //
        ReadFileInfo->FileDataSize = Length;
      }
 
      //
      // Initialise data to start seeking and/or reading a file.
      //
      BytesLeft       = ReadFileInfo->FileDataSize;
      DataOffset      = 0;
      FilePosition    = 0;
      FinishedSeeking = FALSE;
 
      break;
  }
 
  RecordingFlags = GET_FE_RECORDING_FLAGS (FileEntryData);
  switch (RecordingFlags) {
    case InlineData:
      //
      // There are no extents for this FE/EFE. All data is inline.
      //
      Status = GetFileEntryData (FileEntryData, Volume->FileEntrySize, &Data, &Length);
      if (EFI_ERROR (Status)) {
        return Status;
      }
 
      if (ReadFileInfo->Flags == ReadFileGetFileSize) {
        ReadFileInfo->ReadLength = Length;
      } else if (ReadFileInfo->Flags == ReadFileAllocateAndRead) {
        //
        // Allocate buffer for starting read data.
        //
        ReadFileInfo->FileData = AllocatePool ((UINTN)Length);
        if (ReadFileInfo->FileData == NULL) {
          return EFI_OUT_OF_RESOURCES;
        }
 
        //
        // Read all inline data into ReadFileInfo->FileData
        //
        CopyMem (ReadFileInfo->FileData, Data, (UINTN)Length);
        ReadFileInfo->ReadLength = Length;
      } else if (ReadFileInfo->Flags == ReadFileSeekAndRead) {
        //
        // If FilePosition is non-zero, seek file to FilePosition, read
        // FileDataSize bytes and then updates FilePosition.
        //
        CopyMem (
          ReadFileInfo->FileData,
          (VOID *)((UINT8 *)Data + ReadFileInfo->FilePosition),
          (UINTN)ReadFileInfo->FileDataSize
          );
 
        ReadFileInfo->FilePosition += ReadFileInfo->FileDataSize;
      } else {
        ASSERT (FALSE);
        return EFI_INVALID_PARAMETER;
      }
 
      Status = EFI_SUCCESS;
      break;
 
    case LongAdsSequence:
    case ShortAdsSequence:
      //
      // This FE/EFE contains a run of Allocation Descriptors. Get data + size
      // for start reading them out.
      //
      Status = GetAdsInformation (FileEntryData, Volume->FileEntrySize, &Data, &Length);
      if (EFI_ERROR (Status)) {
        return Status;
      }
 
      AdOffset = 0;
 
      for ( ; ;) {
        //
        // Read AD.
        //
        Status = GetAllocationDescriptor (
                   RecordingFlags,
                   Data,
                   &AdOffset,
                   Length,
                   &Ad
                   );
        if (Status == EFI_DEVICE_ERROR) {
          Status = EFI_SUCCESS;
          goto Done;
        }
 
        //
        // Check if AD is an indirect AD. If so, read Allocation Extent
        // Descriptor and its extents (ADs).
        //
        if (GET_EXTENT_FLAGS (RecordingFlags, Ad) == ExtentIsNextExtent) {
          DataBak = Data;
          Status  = GetAedAdsData (
                      BlockIo,
                      DiskIo,
                      Volume,
                      ParentIcb,
                      RecordingFlags,
                      Ad,
                      &Data,
                      &Length
                      );
 
          if (!DoFreeAed) {
            DoFreeAed = TRUE;
          } else {
            FreePool (DataBak);
          }
 
          if (EFI_ERROR (Status)) {
            goto Error_Get_Aed;
          }
 
          ASSERT (Data != NULL);
 
          AdOffset = 0;
          continue;
        }
 
        ExtentLength = GET_EXTENT_LENGTH (RecordingFlags, Ad);
 
        Status = GetAllocationDescriptorLsn (
                   RecordingFlags,
                   Volume,
                   ParentIcb,
                   Ad,
                   &Lsn
                   );
        if (EFI_ERROR (Status)) {
          goto Done;
        }
 
        switch (ReadFileInfo->Flags) {
          case ReadFileGetFileSize:
            ReadFileInfo->ReadLength += ExtentLength;
            break;
          case ReadFileAllocateAndRead:
            //
            // Increase FileData (if necessary) to read next extent.
            //
            Status = GrowUpBufferToNextAd (
                       RecordingFlags,
                       Ad,
                       &ReadFileInfo->FileData,
                       ReadFileInfo->ReadLength
                       );
            if (EFI_ERROR (Status)) {
              goto Error_Alloc_Buffer_To_Next_Ad;
            }
 
            //
            // Read extent's data into FileData.
            //
            Status = DiskIo->ReadDisk (
                               DiskIo,
                               BlockIo->Media->MediaId,
                               MultU64x32 (Lsn, LogicalBlockSize),
                               ExtentLength,
                               (VOID *)((UINT8 *)ReadFileInfo->FileData +
                                        ReadFileInfo->ReadLength)
                               );
            if (EFI_ERROR (Status)) {
              goto Error_Read_Disk_Blk;
            }
 
            ReadFileInfo->ReadLength += ExtentLength;
            break;
          case ReadFileSeekAndRead:
            //
            // Seek file first before reading in its data.
            //
            if (FinishedSeeking) {
              Offset = 0;
              goto Skip_File_Seek;
            }
 
            if (FilePosition + ExtentLength < ReadFileInfo->FilePosition) {
              FilePosition += ExtentLength;
              goto Skip_Ad;
            }
 
            if (FilePosition + ExtentLength > ReadFileInfo->FilePosition) {
              Offset = ReadFileInfo->FilePosition - FilePosition;
            } else {
              Offset = 0;
            }
 
            //
            // Done with seeking file. Start reading its data.
            //
            FinishedSeeking = TRUE;
 
Skip_File_Seek:
            //
            // Make sure we don't read more data than really wanted.
            //
            if (ExtentLength - Offset > BytesLeft) {
              DataLength = BytesLeft;
            } else {
              DataLength = ExtentLength - Offset;
            }
 
            //
            // Read extent's data into FileData.
            //
            Status = DiskIo->ReadDisk (
                               DiskIo,
                               BlockIo->Media->MediaId,
                               Offset + MultU64x32 (Lsn, LogicalBlockSize),
                               (UINTN)DataLength,
                               (VOID *)((UINT8 *)ReadFileInfo->FileData +
                                        DataOffset)
                               );
            if (EFI_ERROR (Status)) {
              goto Error_Read_Disk_Blk;
            }
 
            //
            // Update current file's position.
            //
            DataOffset                 += DataLength;
            ReadFileInfo->FilePosition += DataLength;
 
            BytesLeft -= DataLength;
            if (BytesLeft == 0) {
              //
              // There is no more file data to read.
              //
              Status = EFI_SUCCESS;
              goto Done;
            }
 
            break;
        }
 
Skip_Ad:
        //
        // Point to the next AD (extent).
        //
        AdOffset += AD_LENGTH (RecordingFlags);
      }
 
      break;
    case ExtendedAdsSequence:
      // FIXME: Not supported. Got no volume with it, yet.
      ASSERT (FALSE);
      Status = EFI_UNSUPPORTED;
      break;
 
    default:
      //
      // A flag value reserved by the ECMA-167 standard (3rd Edition - June
      // 1997); 14.6 ICB Tag; 14.6.8 Flags (RBP 18); was found.
      //
      Status = EFI_UNSUPPORTED;
      break;
  }
 
Done:
  if (DoFreeAed) {
    FreePool (Data);
  }
 
  return Status;
 
Error_Read_Disk_Blk:
Error_Alloc_Buffer_To_Next_Ad:
  if (ReadFileInfo->Flags != ReadFileSeekAndRead) {
    FreePool (ReadFileInfo->FileData);
  }
 
  if (DoFreeAed) {
    FreePool (Data);
  }
 
Error_Get_Aed:
  return Status;
}
 
EFI_STATUS
InternalFindFile (
  IN   EFI_BLOCK_IO_PROTOCOL           *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL            *DiskIo,
  IN   UDF_VOLUME_INFO                 *Volume,
  IN   CHAR16                          *FileName,
  IN   UDF_FILE_INFO                   *Parent,
  IN   UDF_LONG_ALLOCATION_DESCRIPTOR  *Icb,
  OUT  UDF_FILE_INFO                   *File
  )
{
  EFI_STATUS                      Status;
  UDF_FILE_IDENTIFIER_DESCRIPTOR  *FileIdentifierDesc;
  UDF_READ_DIRECTORY_INFO         ReadDirInfo;
  BOOLEAN                         Found;
  CHAR16                          FoundFileName[UDF_FILENAME_LENGTH];
  VOID                            *CompareFileEntry;
 
  //
  // Check if both Parent->FileIdentifierDesc and Icb are NULL.
  //
  if ((Parent->FileIdentifierDesc == NULL) && (Icb == NULL)) {
    return EFI_INVALID_PARAMETER;
  }
 
  //
  // Check if parent file is really directory.
  //
  if (FE_ICB_FILE_TYPE (Parent->FileEntry) != UdfFileEntryDirectory) {
    return EFI_NOT_FOUND;
  }
 
  //
  // If FileName is current file or working directory, just duplicate Parent's
  // FE/EFE and FID descriptors.
  //
  if (StrCmp (FileName, L".") == 0) {
    if (Parent->FileIdentifierDesc == NULL) {
      return EFI_INVALID_PARAMETER;
    }
 
    DuplicateFe (BlockIo, Volume, Parent->FileEntry, &File->FileEntry);
    if (File->FileEntry == NULL) {
      return EFI_OUT_OF_RESOURCES;
    }
 
    DuplicateFid (Parent->FileIdentifierDesc, &File->FileIdentifierDesc);
    if (File->FileIdentifierDesc == NULL) {
      FreePool (File->FileEntry);
      return EFI_OUT_OF_RESOURCES;
    }
 
    return EFI_SUCCESS;
  }
 
  //
  // Start directory listing.
  //
  ZeroMem ((VOID *)&ReadDirInfo, sizeof (UDF_READ_DIRECTORY_INFO));
  Found = FALSE;
 
  for ( ; ;) {
    Status = ReadDirectoryEntry (
               BlockIo,
               DiskIo,
               Volume,
               (Parent->FileIdentifierDesc != NULL) ?
               &Parent->FileIdentifierDesc->Icb :
               Icb,
               Parent->FileEntry,
               &ReadDirInfo,
               &FileIdentifierDesc
               );
    if (EFI_ERROR (Status)) {
      if (Status == EFI_DEVICE_ERROR) {
        Status = EFI_NOT_FOUND;
      }
 
      break;
    }
 
    //
    // After calling function ReadDirectoryEntry(), if 'FileIdentifierDesc' is
    // NULL, then the 'Status' must be EFI_OUT_OF_RESOURCES. Hence, if the code
    // reaches here, 'FileIdentifierDesc' must be not NULL.
    //
    // The ASSERT here is for addressing a false positive NULL pointer
    // dereference issue raised from static analysis.
    //
    ASSERT (FileIdentifierDesc != NULL);
 
    if (FileIdentifierDesc->FileCharacteristics & PARENT_FILE) {
      //
      // This FID contains the location (FE/EFE) of the parent directory of this
      // directory (Parent), and if FileName is either ".." or "\\", then it's
      // the expected FID.
      //
      if ((StrCmp (FileName, L"..") == 0) || (StrCmp (FileName, L"\\") == 0)) {
        Found = TRUE;
        break;
      }
    } else {
      Status = GetFileNameFromFid (FileIdentifierDesc, ARRAY_SIZE (FoundFileName), FoundFileName);
      if (EFI_ERROR (Status)) {
        break;
      }
 
      if (StrCmp (FileName, FoundFileName) == 0) {
        //
        // FID has been found. Prepare to find its respective FE/EFE.
        //
        Found = TRUE;
        break;
      }
    }
 
    FreePool ((VOID *)FileIdentifierDesc);
  }
 
  if (ReadDirInfo.DirectoryData != NULL) {
    //
    // Free all allocated resources for the directory listing.
    //
    FreePool (ReadDirInfo.DirectoryData);
  }
 
  if (Found) {
    Status = EFI_SUCCESS;
 
    File->FileIdentifierDesc = FileIdentifierDesc;
 
    //
    // If the requested file is root directory, then the FE/EFE was already
    // retrieved in UdfOpenVolume() function, thus no need to find it again.
    //
    // Otherwise, find FE/EFE from the respective FID.
    //
    if (StrCmp (FileName, L"\\") != 0) {
      Status = FindFileEntry (
                 BlockIo,
                 DiskIo,
                 Volume,
                 &FileIdentifierDesc->Icb,
                 &CompareFileEntry
                 );
      if (EFI_ERROR (Status)) {
        goto Error_Find_Fe;
      }
 
      //
      // Make sure that both Parent's FE/EFE and found FE/EFE are not equal.
      //
      if (CompareMem (
            (VOID *)Parent->FileEntry,
            (VOID *)CompareFileEntry,
            Volume->FileEntrySize
            ) != 0)
      {
        File->FileEntry = CompareFileEntry;
      } else {
        FreePool ((VOID *)FileIdentifierDesc);
        FreePool ((VOID *)CompareFileEntry);
        Status = EFI_NOT_FOUND;
      }
    }
  }
 
  return Status;
 
Error_Find_Fe:
  FreePool ((VOID *)FileIdentifierDesc);
 
  return Status;
}
 
EFI_STATUS
ReadUdfVolumeInformation (
  IN   EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL   *DiskIo,
  OUT  UDF_VOLUME_INFO        *Volume
  )
{
  EFI_STATUS  Status;
 
  //
  // Read all necessary UDF volume information and keep it private to the driver
  //
  Status = ReadVolumeFileStructure (
             BlockIo,
             DiskIo,
             Volume
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  //
  // Find File Set Descriptor
  //
  Status = FindFileSetDescriptor (BlockIo, DiskIo, Volume);
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  return Status;
}
 
EFI_STATUS
FindRootDirectory (
  IN   EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL   *DiskIo,
  IN   UDF_VOLUME_INFO        *Volume,
  OUT  UDF_FILE_INFO          *File
  )
{
  EFI_STATUS     Status;
  UDF_FILE_INFO  Parent;
 
  Status = FindFileEntry (
             BlockIo,
             DiskIo,
             Volume,
             &Volume->FileSetDesc.RootDirectoryIcb,
             &File->FileEntry
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  Parent.FileEntry          = File->FileEntry;
  Parent.FileIdentifierDesc = NULL;
 
  Status = FindFile (
             BlockIo,
             DiskIo,
             Volume,
             L"\\",
             NULL,
             &Parent,
             &Volume->FileSetDesc.RootDirectoryIcb,
             File
             );
  if (EFI_ERROR (Status)) {
    FreePool (File->FileEntry);
  }
 
  return Status;
}
 
EFI_STATUS
FindFileEntry (
  IN   EFI_BLOCK_IO_PROTOCOL           *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL            *DiskIo,
  IN   UDF_VOLUME_INFO                 *Volume,
  IN   UDF_LONG_ALLOCATION_DESCRIPTOR  *Icb,
  OUT  VOID                            **FileEntry
  )
{
  EFI_STATUS          Status;
  UINT64              Lsn;
  UINT32              LogicalBlockSize;
  UDF_DESCRIPTOR_TAG  *DescriptorTag;
  VOID                *ReadBuffer;
 
  Status = GetLongAdLsn (Volume, Icb, &Lsn);
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  LogicalBlockSize = Volume->LogicalVolDesc.LogicalBlockSize;
 
  ReadBuffer = AllocateZeroPool (Volume->FileEntrySize);
  if (ReadBuffer == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  //
  // Read extent.
  //
  Status = DiskIo->ReadDisk (
                     DiskIo,
                     BlockIo->Media->MediaId,
                     MultU64x32 (Lsn, LogicalBlockSize),
                     Volume->FileEntrySize,
                     ReadBuffer
                     );
  if (EFI_ERROR (Status)) {
    goto Error_Read_Disk_Blk;
  }
 
  DescriptorTag = ReadBuffer;
 
  //
  // Check if the read extent contains a valid Tag Identifier for the expected
  // FE/EFE.
  //
  if ((DescriptorTag->TagIdentifier != UdfFileEntry) &&
      (DescriptorTag->TagIdentifier != UdfExtendedFileEntry))
  {
    Status = EFI_VOLUME_CORRUPTED;
    goto Error_Invalid_Fe;
  }
 
  *FileEntry = ReadBuffer;
  return EFI_SUCCESS;
 
Error_Invalid_Fe:
Error_Read_Disk_Blk:
  FreePool (ReadBuffer);
 
  return Status;
}
 
EFI_STATUS
FindFile (
  IN   EFI_BLOCK_IO_PROTOCOL           *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL            *DiskIo,
  IN   UDF_VOLUME_INFO                 *Volume,
  IN   CHAR16                          *FilePath,
  IN   UDF_FILE_INFO                   *Root,
  IN   UDF_FILE_INFO                   *Parent,
  IN   UDF_LONG_ALLOCATION_DESCRIPTOR  *Icb,
  OUT  UDF_FILE_INFO                   *File
  )
{
  EFI_STATUS     Status;
  CHAR16         FileName[UDF_FILENAME_LENGTH];
  CHAR16         *FileNamePointer;
  UDF_FILE_INFO  PreviousFile;
  VOID           *FileEntry;
 
  Status = EFI_NOT_FOUND;
 
  CopyMem ((VOID *)&PreviousFile, (VOID *)Parent, sizeof (UDF_FILE_INFO));
  while (*FilePath != L'\0') {
    FileNamePointer = FileName;
    while (*FilePath != L'\0' && *FilePath != L'\\') {
      if ((((UINTN)FileNamePointer - (UINTN)FileName) / sizeof (CHAR16)) >=
          (ARRAY_SIZE (FileName) - 1))
      {
        return EFI_NOT_FOUND;
      }
 
      *FileNamePointer++ = *FilePath++;
    }
 
    *FileNamePointer = L'\0';
    if (FileName[0] == L'\0') {
      //
      // Open root directory.
      //
      if (Root == NULL) {
        //
        // There is no file found for the root directory yet. So, find only its
        // FID by now.
        //
        // See UdfOpenVolume() function.
        //
        Status = InternalFindFile (
                   BlockIo,
                   DiskIo,
                   Volume,
                   L"\\",
                   &PreviousFile,
                   Icb,
                   File
                   );
      } else {
        //
        // We've already a file pointer (Root) for the root directory. Duplicate
        // its FE/EFE and FID descriptors.
        //
        Status = EFI_SUCCESS;
        DuplicateFe (BlockIo, Volume, Root->FileEntry, &File->FileEntry);
        if (File->FileEntry == NULL) {
          Status = EFI_OUT_OF_RESOURCES;
        } else {
          //
          // File->FileEntry is not NULL.
          //
          DuplicateFid (Root->FileIdentifierDesc, &File->FileIdentifierDesc);
          if (File->FileIdentifierDesc == NULL) {
            FreePool (File->FileEntry);
            Status = EFI_OUT_OF_RESOURCES;
          }
        }
      }
    } else {
      //
      // No root directory. Find filename from the current directory.
      //
      Status = InternalFindFile (
                 BlockIo,
                 DiskIo,
                 Volume,
                 FileName,
                 &PreviousFile,
                 Icb,
                 File
                 );
    }
 
    if (EFI_ERROR (Status)) {
      return Status;
    }
 
    //
    // If the found file is a symlink, then find its respective FE/EFE and
    // FID descriptors.
    //
    if (FE_ICB_FILE_TYPE (File->FileEntry) == UdfFileEntrySymlink) {
      FreePool ((VOID *)File->FileIdentifierDesc);
 
      FileEntry = File->FileEntry;
 
      Status = ResolveSymlink (
                 BlockIo,
                 DiskIo,
                 Volume,
                 &PreviousFile,
                 FileEntry,
                 File
                 );
 
      FreePool (FileEntry);
 
      if (EFI_ERROR (Status)) {
        return Status;
      }
    }
 
    if (CompareMem (
          (VOID *)&PreviousFile,
          (VOID *)Parent,
          sizeof (UDF_FILE_INFO)
          ) != 0)
    {
      CleanupFileInformation (&PreviousFile);
    }
 
    CopyMem ((VOID *)&PreviousFile, (VOID *)File, sizeof (UDF_FILE_INFO));
    if ((*FilePath != L'\0') && (*FilePath == L'\\')) {
      FilePath++;
    }
  }
 
  return Status;
}
 
EFI_STATUS
ReadDirectoryEntry (
  IN      EFI_BLOCK_IO_PROTOCOL           *BlockIo,
  IN      EFI_DISK_IO_PROTOCOL            *DiskIo,
  IN      UDF_VOLUME_INFO                 *Volume,
  IN      UDF_LONG_ALLOCATION_DESCRIPTOR  *ParentIcb,
  IN      VOID                            *FileEntryData,
  IN OUT  UDF_READ_DIRECTORY_INFO         *ReadDirInfo,
  OUT     UDF_FILE_IDENTIFIER_DESCRIPTOR  **FoundFid
  )
{
  EFI_STATUS                      Status;
  UDF_READ_FILE_INFO              ReadFileInfo;
  UDF_FILE_IDENTIFIER_DESCRIPTOR  *FileIdentifierDesc;
 
  if (ReadDirInfo->DirectoryData == NULL) {
    //
    // The directory's recorded data has not been read yet. So let's cache it
    // into memory and the next calls won't need to read it again.
    //
    ReadFileInfo.Flags = ReadFileAllocateAndRead;
 
    Status = ReadFile (
               BlockIo,
               DiskIo,
               Volume,
               ParentIcb,
               FileEntryData,
               &ReadFileInfo
               );
    if (EFI_ERROR (Status)) {
      return Status;
    }
 
    //
    // Fill in ReadDirInfo structure with the read directory's data information.
    //
    ReadDirInfo->DirectoryData   = ReadFileInfo.FileData;
    ReadDirInfo->DirectoryLength = ReadFileInfo.ReadLength;
  }
 
  do {
    if (ReadDirInfo->FidOffset >= ReadDirInfo->DirectoryLength) {
      //
      // There are no longer FIDs for this directory. By returning
      // EFI_DEVICE_ERROR to the callee will indicate end of directory
      // listening.
      //
      return EFI_DEVICE_ERROR;
    }
 
    //
    // Get FID for this entry.
    //
    FileIdentifierDesc = GET_FID_FROM_ADS (
                           ReadDirInfo->DirectoryData,
                           ReadDirInfo->FidOffset
                           );
    //
    // Update FidOffset to point to next FID.
    //
    ReadDirInfo->FidOffset += GetFidDescriptorLength (FileIdentifierDesc);
  } while (FileIdentifierDesc->FileCharacteristics & DELETED_FILE);
 
  DuplicateFid (FileIdentifierDesc, FoundFid);
  if (*FoundFid == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
GetFileNameFromFid (
  IN   UDF_FILE_IDENTIFIER_DESCRIPTOR  *FileIdentifierDesc,
  IN   UINTN                           CharMax,
  OUT  CHAR16                          *FileName
  )
{
  UINT8   *OstaCompressed;
  UINT8   CompressionId;
  UINT8   Length;
  UINTN   Index;
  CHAR16  *FileNameBak;
 
  if (CharMax == 0) {
    return EFI_BUFFER_TOO_SMALL;
  }
 
  OstaCompressed =
    (UINT8 *)(
              (UINT8 *)FileIdentifierDesc->Data +
              FileIdentifierDesc->LengthOfImplementationUse
              );
 
  CompressionId = OstaCompressed[0];
  if (!IS_VALID_COMPRESSION_ID (CompressionId)) {
    return EFI_VOLUME_CORRUPTED;
  }
 
  FileNameBak = FileName;
 
  //
  // Decode filename.
  //
  Length = FileIdentifierDesc->LengthOfFileIdentifier;
  if (CompressionId == 16) {
    if (((UINTN)Length >> 1) > CharMax) {
      return EFI_BUFFER_TOO_SMALL;
    }
  } else {
    if ((Length != 0) && ((UINTN)Length - 1 > CharMax)) {
      return EFI_BUFFER_TOO_SMALL;
    }
  }
 
  for (Index = 1; Index < Length; Index++) {
    if (CompressionId == 16) {
      *FileName = OstaCompressed[Index++] << 8;
    } else {
      *FileName = 0;
    }
 
    if (Index < Length) {
      *FileName |= (CHAR16)(OstaCompressed[Index]);
    }
 
    FileName++;
  }
 
  Index = ((UINTN)FileName - (UINTN)FileNameBak) / sizeof (CHAR16);
  if (Index > CharMax - 1) {
    Index = CharMax - 1;
  }
 
  FileNameBak[Index] = L'\0';
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
ResolveSymlink (
  IN   EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL   *DiskIo,
  IN   UDF_VOLUME_INFO        *Volume,
  IN   UDF_FILE_INFO          *Parent,
  IN   VOID                   *FileEntryData,
  OUT  UDF_FILE_INFO          *File
  )
{
  EFI_STATUS          Status;
  UDF_READ_FILE_INFO  ReadFileInfo;
  UINT8               *Data;
  UINT64              Length;
  UINT8               *EndData;
  UDF_PATH_COMPONENT  *PathComp;
  UINT8               PathCompLength;
  CHAR16              FileName[UDF_FILENAME_LENGTH];
  CHAR16              *Char;
  UINTN               Index;
  UINT8               CompressionId;
  UDF_FILE_INFO       PreviousFile;
  BOOLEAN             NotParent;
  BOOLEAN             NotFile;
 
  ZeroMem ((VOID *)File, sizeof (UDF_FILE_INFO));
 
  //
  // Symlink files on UDF volumes do not contain so much data other than
  // Path Components which resolves to real filenames, so it's OK to read in
  // all its data here -- usually the data will be inline with the FE/EFE for
  // lower filenames.
  //
  ReadFileInfo.Flags = ReadFileAllocateAndRead;
 
  Status = ReadFile (
             BlockIo,
             DiskIo,
             Volume,
             &Parent->FileIdentifierDesc->Icb,
             FileEntryData,
             &ReadFileInfo
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  Length = ReadFileInfo.ReadLength;
 
  Data    = (UINT8 *)ReadFileInfo.FileData;
  EndData = Data + Length;
 
  CopyMem ((VOID *)&PreviousFile, (VOID *)Parent, sizeof (UDF_FILE_INFO));
 
  for ( ; ;) {
    PathComp = (UDF_PATH_COMPONENT *)Data;
 
    PathCompLength = PathComp->LengthOfComponentIdentifier;
 
    switch (PathComp->ComponentType) {
      case 1:
      //
      // This Path Component specifies the root directory hierarchy subject to
      // agreement between the originator and recipient of the medium. Skip it.
      //
      // Fall through.
      //
      case 2:
        //
        // "\\." of the current directory. Read next Path Component.
        //
        goto Next_Path_Component;
      case 3:
        //
        // ".." (parent directory). Go to it.
        //
        CopyMem ((VOID *)FileName, L"..", 6);
        break;
      case 4:
        //
        // "." (current file). Duplicate both FE/EFE and FID of this file.
        //
        DuplicateFe (BlockIo, Volume, PreviousFile.FileEntry, &File->FileEntry);
        if (File->FileEntry == NULL) {
          Status = EFI_OUT_OF_RESOURCES;
          goto Error_Find_File;
        }
 
        DuplicateFid (
          PreviousFile.FileIdentifierDesc,
          &File->FileIdentifierDesc
          );
        if (File->FileIdentifierDesc == NULL) {
          FreePool (File->FileEntry);
          Status = EFI_OUT_OF_RESOURCES;
          goto Error_Find_File;
        }
 
        goto Next_Path_Component;
      case 5:
        //
        // This Path Component identifies an object, either a file or a
        // directory or an alias.
        //
        // Decode it from the compressed data in ComponentIdentifier and find
        // respective path.
        //
        CompressionId = PathComp->ComponentIdentifier[0];
        if (!IS_VALID_COMPRESSION_ID (CompressionId)) {
          return EFI_VOLUME_CORRUPTED;
        }
 
        if ((UINTN)PathComp->ComponentIdentifier + PathCompLength > (UINTN)EndData) {
          return EFI_VOLUME_CORRUPTED;
        }
 
        Char = FileName;
        for (Index = 1; Index < PathCompLength; Index++) {
          if (CompressionId == 16) {
            *Char = *(UINT8 *)((UINT8 *)PathComp->ComponentIdentifier +
                               Index) << 8;
            Index++;
          } else {
            if (Index > ARRAY_SIZE (FileName)) {
              return EFI_UNSUPPORTED;
            }
 
            *Char = 0;
          }
 
          if (Index < Length) {
            *Char |= (CHAR16)(*(UINT8 *)((UINT8 *)PathComp->ComponentIdentifier + Index));
          }
 
          Char++;
        }
 
        Index = ((UINTN)Char - (UINTN)FileName) / sizeof (CHAR16);
        if (Index > ARRAY_SIZE (FileName) - 1) {
          Index = ARRAY_SIZE (FileName) - 1;
        }
 
        FileName[Index] = L'\0';
        break;
      default:
        //
        // According to the ECMA-167 standard (3rd Edition - June 1997), Section
        // 14.16.1.1, all other values are reserved.
        //
        Status = EFI_VOLUME_CORRUPTED;
        goto Error_Find_File;
    }
 
    //
    // Find file from the read filename in symlink's file data.
    //
    Status = InternalFindFile (
               BlockIo,
               DiskIo,
               Volume,
               FileName,
               &PreviousFile,
               NULL,
               File
               );
    if (EFI_ERROR (Status)) {
      goto Error_Find_File;
    }
 
Next_Path_Component:
    Data += sizeof (UDF_PATH_COMPONENT) + PathCompLength;
    if (Data >= EndData) {
      break;
    }
 
    //
    // Check the content in the file info pointed by File.
    //
    if ((File->FileEntry == NULL) || (File->FileIdentifierDesc == NULL)) {
      Status = EFI_VOLUME_CORRUPTED;
      goto Error_Find_File;
    }
 
    NotParent = (CompareMem (
                   (VOID *)&PreviousFile,
                   (VOID *)Parent,
                   sizeof (UDF_FILE_INFO)
                   ) != 0);
    NotFile = (CompareMem (
                 (VOID *)&PreviousFile,
                 (VOID *)File,
                 sizeof (UDF_FILE_INFO)
                 ) != 0);
 
    if (NotParent && NotFile) {
      CleanupFileInformation (&PreviousFile);
    }
 
    if (NotFile) {
      CopyMem ((VOID *)&PreviousFile, (VOID *)File, sizeof (UDF_FILE_INFO));
    }
  }
 
  //
  // Unmap the symlink file.
  //
  FreePool (ReadFileInfo.FileData);
 
  //
  // Check the content in the resolved file info.
  //
  if ((File->FileEntry == NULL) || (File->FileIdentifierDesc == NULL)) {
    return EFI_VOLUME_CORRUPTED;
  }
 
  return EFI_SUCCESS;
 
Error_Find_File:
  if (CompareMem (
        (VOID *)&PreviousFile,
        (VOID *)Parent,
        sizeof (UDF_FILE_INFO)
        ) != 0)
  {
    CleanupFileInformation (&PreviousFile);
  }
 
  FreePool (ReadFileInfo.FileData);
 
  return Status;
}
 
VOID
CleanupFileInformation (
  IN UDF_FILE_INFO  *File
  )
{
  if (File->FileEntry != NULL) {
    FreePool (File->FileEntry);
  }
 
  if (File->FileIdentifierDesc != NULL) {
    FreePool ((VOID *)File->FileIdentifierDesc);
  }
 
  ZeroMem ((VOID *)File, sizeof (UDF_FILE_INFO));
}
 
EFI_STATUS
GetFileSize (
  IN   EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL   *DiskIo,
  IN   UDF_VOLUME_INFO        *Volume,
  IN   UDF_FILE_INFO          *File,
  OUT  UINT64                 *Size
  )
{
  EFI_STATUS          Status;
  UDF_READ_FILE_INFO  ReadFileInfo;
 
  ReadFileInfo.Flags = ReadFileGetFileSize;
 
  Status = ReadFile (
             BlockIo,
             DiskIo,
             Volume,
             &File->FileIdentifierDesc->Icb,
             File->FileEntry,
             &ReadFileInfo
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  *Size = ReadFileInfo.ReadLength;
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
SetFileInfo (
  IN      UDF_FILE_INFO  *File,
  IN      UINT64         FileSize,
  IN      CHAR16         *FileName,
  IN OUT  UINTN          *BufferSize,
  OUT     VOID           *Buffer
  )
{
  UINTN                    FileInfoLength;
  EFI_FILE_INFO            *FileInfo;
  UDF_FILE_ENTRY           *FileEntry;
  UDF_EXTENDED_FILE_ENTRY  *ExtendedFileEntry;
  UDF_DESCRIPTOR_TAG       *DescriptorTag;
 
  //
  // Calculate the needed size for the EFI_FILE_INFO structure.
  //
  FileInfoLength = sizeof (EFI_FILE_INFO) + ((FileName != NULL) ?
                                             StrSize (FileName) :
                                             sizeof (CHAR16));
  if (*BufferSize < FileInfoLength) {
    //
    // The given Buffer has no size enough for EFI_FILE_INFO structure.
    //
    *BufferSize = FileInfoLength;
    return EFI_BUFFER_TOO_SMALL;
  }
 
  //
  // Buffer now contains room enough to store EFI_FILE_INFO structure.
  // Now, fill it in with all necessary information about the file.
  //
  FileInfo             = (EFI_FILE_INFO *)Buffer;
  FileInfo->Size       = FileInfoLength;
  FileInfo->Attribute &= ~EFI_FILE_VALID_ATTR;
  FileInfo->Attribute |= EFI_FILE_READ_ONLY;
 
  if (IS_FID_DIRECTORY_FILE (File->FileIdentifierDesc)) {
    FileInfo->Attribute |= EFI_FILE_DIRECTORY;
  } else if (IS_FID_NORMAL_FILE (File->FileIdentifierDesc)) {
    FileInfo->Attribute |= EFI_FILE_ARCHIVE;
  }
 
  if (IS_FID_HIDDEN_FILE (File->FileIdentifierDesc)) {
    FileInfo->Attribute |= EFI_FILE_HIDDEN;
  }
 
  DescriptorTag = File->FileEntry;
 
  if (DescriptorTag->TagIdentifier == UdfFileEntry) {
    FileEntry = (UDF_FILE_ENTRY *)File->FileEntry;
 
    //
    // Check if FE has the system attribute set.
    //
    if (FileEntry->IcbTag.Flags & (1 << 10)) {
      FileInfo->Attribute |= EFI_FILE_SYSTEM;
    }
 
    FileInfo->FileSize     = FileSize;
    FileInfo->PhysicalSize = FileSize;
 
    FileInfo->CreateTime.Year       = FileEntry->AccessTime.Year;
    FileInfo->CreateTime.Month      = FileEntry->AccessTime.Month;
    FileInfo->CreateTime.Day        = FileEntry->AccessTime.Day;
    FileInfo->CreateTime.Hour       = FileEntry->AccessTime.Hour;
    FileInfo->CreateTime.Minute     = FileEntry->AccessTime.Minute;
    FileInfo->CreateTime.Second     = FileEntry->AccessTime.Second;
    FileInfo->CreateTime.Nanosecond =
      FileEntry->AccessTime.HundredsOfMicroseconds;
 
    FileInfo->LastAccessTime.Year =
      FileEntry->AccessTime.Year;
    FileInfo->LastAccessTime.Month =
      FileEntry->AccessTime.Month;
    FileInfo->LastAccessTime.Day =
      FileEntry->AccessTime.Day;
    FileInfo->LastAccessTime.Hour =
      FileEntry->AccessTime.Hour;
    FileInfo->LastAccessTime.Minute =
      FileEntry->AccessTime.Minute;
    FileInfo->LastAccessTime.Second =
      FileEntry->AccessTime.Second;
    FileInfo->LastAccessTime.Nanosecond =
      FileEntry->AccessTime.HundredsOfMicroseconds;
  } else if (DescriptorTag->TagIdentifier == UdfExtendedFileEntry) {
    ExtendedFileEntry = (UDF_EXTENDED_FILE_ENTRY *)File->FileEntry;
 
    //
    // Check if EFE has the system attribute set.
    //
    if (ExtendedFileEntry->IcbTag.Flags & (1 << 10)) {
      FileInfo->Attribute |= EFI_FILE_SYSTEM;
    }
 
    FileInfo->FileSize     = FileSize;
    FileInfo->PhysicalSize = FileSize;
 
    FileInfo->CreateTime.Year       = ExtendedFileEntry->CreationTime.Year;
    FileInfo->CreateTime.Month      = ExtendedFileEntry->CreationTime.Month;
    FileInfo->CreateTime.Day        = ExtendedFileEntry->CreationTime.Day;
    FileInfo->CreateTime.Hour       = ExtendedFileEntry->CreationTime.Hour;
    FileInfo->CreateTime.Minute     = ExtendedFileEntry->CreationTime.Second;
    FileInfo->CreateTime.Second     = ExtendedFileEntry->CreationTime.Second;
    FileInfo->CreateTime.Nanosecond =
      ExtendedFileEntry->AccessTime.HundredsOfMicroseconds;
 
    FileInfo->LastAccessTime.Year =
      ExtendedFileEntry->AccessTime.Year;
    FileInfo->LastAccessTime.Month =
      ExtendedFileEntry->AccessTime.Month;
    FileInfo->LastAccessTime.Day =
      ExtendedFileEntry->AccessTime.Day;
    FileInfo->LastAccessTime.Hour =
      ExtendedFileEntry->AccessTime.Hour;
    FileInfo->LastAccessTime.Minute =
      ExtendedFileEntry->AccessTime.Minute;
    FileInfo->LastAccessTime.Second =
      ExtendedFileEntry->AccessTime.Second;
    FileInfo->LastAccessTime.Nanosecond =
      ExtendedFileEntry->AccessTime.HundredsOfMicroseconds;
  }
 
  FileInfo->CreateTime.TimeZone     = EFI_UNSPECIFIED_TIMEZONE;
  FileInfo->CreateTime.Daylight     = EFI_TIME_ADJUST_DAYLIGHT;
  FileInfo->LastAccessTime.TimeZone = EFI_UNSPECIFIED_TIMEZONE;
  FileInfo->LastAccessTime.Daylight = EFI_TIME_ADJUST_DAYLIGHT;
 
  CopyMem (
    (VOID *)&FileInfo->ModificationTime,
    (VOID *)&FileInfo->LastAccessTime,
    sizeof (EFI_TIME)
    );
 
  if (FileName != NULL) {
    StrCpyS (FileInfo->FileName, StrLen (FileName) + 1, FileName);
  } else {
    FileInfo->FileName[0] = '\0';
  }
 
  *BufferSize = FileInfoLength;
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
GetVolumeLabel (
  IN   UDF_VOLUME_INFO  *Volume,
  IN   UINTN            CharMax,
  OUT  CHAR16           *String
  )
{
  UDF_FILE_SET_DESCRIPTOR  *FileSetDesc;
  UINTN                    Index;
  UINT8                    *OstaCompressed;
  UINT8                    CompressionId;
  CHAR16                   *StringBak;
 
  FileSetDesc = &Volume->FileSetDesc;
 
  OstaCompressed = &FileSetDesc->LogicalVolumeIdentifier[0];
 
  CompressionId = OstaCompressed[0];
  if (!IS_VALID_COMPRESSION_ID (CompressionId)) {
    return EFI_VOLUME_CORRUPTED;
  }
 
  StringBak = String;
  for (Index = 1; Index < 128; Index++) {
    if (CompressionId == 16) {
      if ((Index >> 1) > CharMax) {
        return EFI_BUFFER_TOO_SMALL;
      }
 
      *String = *(UINT8 *)(OstaCompressed + Index) << 8;
      Index++;
    } else {
      if (Index > CharMax) {
        return EFI_BUFFER_TOO_SMALL;
      }
 
      *String = 0;
    }
 
    if (Index < 128) {
      *String |= (CHAR16)(*(UINT8 *)(OstaCompressed + Index));
    }
 
    //
    // Unlike FID Identifiers, Logical Volume Identifier is stored in a
    // NULL-terminated OSTA compressed format, so we must check for the NULL
    // character.
    //
    if (*String == L'\0') {
      break;
    }
 
    String++;
  }
 
  Index = ((UINTN)String - (UINTN)StringBak) / sizeof (CHAR16);
  if (Index > CharMax - 1) {
    Index = CharMax - 1;
  }
 
  StringBak[Index] = L'\0';
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
GetVolumeSize (
  IN   EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN   EFI_DISK_IO_PROTOCOL   *DiskIo,
  IN   UDF_VOLUME_INFO        *Volume,
  OUT  UINT64                 *VolumeSize,
  OUT  UINT64                 *FreeSpaceSize
  )
{
  EFI_STATUS                     Status;
  UDF_LOGICAL_VOLUME_DESCRIPTOR  *LogicalVolDesc;
  UDF_EXTENT_AD                  *ExtentAd;
  UINT64                         Lsn;
  UINT32                         LogicalBlockSize;
  UDF_LOGICAL_VOLUME_INTEGRITY   *LogicalVolInt;
  UDF_DESCRIPTOR_TAG             *DescriptorTag;
  UINTN                          Index;
  UINTN                          Length;
  UINT32                         LsnsNo;
 
  LogicalVolDesc = &Volume->LogicalVolDesc;
 
  ExtentAd = &LogicalVolDesc->IntegritySequenceExtent;
 
  if ((ExtentAd->ExtentLength == 0) ||
      (ExtentAd->ExtentLength < sizeof (UDF_LOGICAL_VOLUME_INTEGRITY)))
  {
    return EFI_VOLUME_CORRUPTED;
  }
 
  LogicalVolInt = AllocatePool (ExtentAd->ExtentLength);
  if (LogicalVolInt == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }
 
  //
  // Get location of Logical Volume Integrity Descriptor
  //
  Lsn = (UINT64)ExtentAd->ExtentLocation - Volume->MainVdsStartLocation;
 
  LogicalBlockSize = LogicalVolDesc->LogicalBlockSize;
 
  //
  // Read disk block
  //
  Status = DiskIo->ReadDisk (
                     DiskIo,
                     BlockIo->Media->MediaId,
                     MultU64x32 (Lsn, LogicalBlockSize),
                     ExtentAd->ExtentLength,
                     LogicalVolInt
                     );
  if (EFI_ERROR (Status)) {
    goto Out_Free;
  }
 
  DescriptorTag = &LogicalVolInt->DescriptorTag;
 
  //
  // Check if read block is a Logical Volume Integrity Descriptor
  //
  if (DescriptorTag->TagIdentifier != UdfLogicalVolumeIntegrityDescriptor) {
    Status = EFI_VOLUME_CORRUPTED;
    goto Out_Free;
  }
 
  if ((LogicalVolInt->NumberOfPartitions > MAX_UINT32 / sizeof (UINT32) / 2) ||
      (LogicalVolInt->NumberOfPartitions * sizeof (UINT32) * 2 >
       ExtentAd->ExtentLength - sizeof (UDF_LOGICAL_VOLUME_INTEGRITY)))
  {
    Status = EFI_VOLUME_CORRUPTED;
    goto Out_Free;
  }
 
  *VolumeSize    = 0;
  *FreeSpaceSize = 0;
 
  Length = LogicalVolInt->NumberOfPartitions;
  for (Index = 0; Index < Length; Index += sizeof (UINT32)) {
    LsnsNo = *(UINT32 *)((UINT8 *)LogicalVolInt->Data + Index);
    //
    // Check if size is not specified
    //
    if (LsnsNo == 0xFFFFFFFFUL) {
      continue;
    }
 
    //
    // Accumulate free space size
    //
    *FreeSpaceSize += MultU64x32 ((UINT64)LsnsNo, LogicalBlockSize);
  }
 
  Length = LogicalVolInt->NumberOfPartitions * sizeof (UINT32) * 2;
  for ( ; Index < Length; Index += sizeof (UINT32)) {
    LsnsNo = *(UINT32 *)((UINT8 *)LogicalVolInt->Data + Index);
    //
    // Check if size is not specified
    //
    if (LsnsNo == 0xFFFFFFFFUL) {
      continue;
    }
 
    //
    // Accumulate used volume space
    //
    *VolumeSize += MultU64x32 ((UINT64)LsnsNo, LogicalBlockSize);
  }
 
  Status = EFI_SUCCESS;
 
Out_Free:
  //
  // Free Logical Volume Integrity Descriptor
  //
  FreePool (LogicalVolInt);
 
  return Status;
}
 
EFI_STATUS
ReadFileData (
  IN      EFI_BLOCK_IO_PROTOCOL  *BlockIo,
  IN      EFI_DISK_IO_PROTOCOL   *DiskIo,
  IN      UDF_VOLUME_INFO        *Volume,
  IN      UDF_FILE_INFO          *File,
  IN      UINT64                 FileSize,
  IN OUT  UINT64                 *FilePosition,
  IN OUT  VOID                   *Buffer,
  IN OUT  UINT64                 *BufferSize
  )
{
  EFI_STATUS          Status;
  UDF_READ_FILE_INFO  ReadFileInfo;
 
  ReadFileInfo.Flags        = ReadFileSeekAndRead;
  ReadFileInfo.FilePosition = *FilePosition;
  ReadFileInfo.FileData     = Buffer;
  ReadFileInfo.FileDataSize = *BufferSize;
  ReadFileInfo.FileSize     = FileSize;
 
  Status = ReadFile (
             BlockIo,
             DiskIo,
             Volume,
             &File->FileIdentifierDesc->Icb,
             File->FileEntry,
             &ReadFileInfo
             );
  if (EFI_ERROR (Status)) {
    return Status;
  }
 
  *BufferSize   = ReadFileInfo.FileDataSize;
  *FilePosition = ReadFileInfo.FilePosition;
 
  return EFI_SUCCESS;
}
 
EFI_STATUS
SupportUdfFileSystem (
  IN EFI_DRIVER_BINDING_PROTOCOL  *This,
  IN EFI_HANDLE                   ControllerHandle
  )
{
  EFI_STATUS                Status;
  EFI_DEVICE_PATH_PROTOCOL  *DevicePath;
  EFI_DEVICE_PATH_PROTOCOL  *DevicePathNode;
  EFI_DEVICE_PATH_PROTOCOL  *LastDevicePathNode;
  EFI_GUID                  *VendorDefinedGuid;
 
  //
  // Open Device Path protocol on ControllerHandle
  //
  Status = gBS->OpenProtocol (
                  ControllerHandle,
                  &gEfiDevicePathProtocolGuid,
                  (VOID **)&DevicePath,
                  This->DriverBindingHandle,
                  ControllerHandle,
                  EFI_OPEN_PROTOCOL_GET_PROTOCOL
                  );
  if (EFI_ERROR (Status)) {
    return EFI_UNSUPPORTED;
  }
 
  Status = EFI_UNSUPPORTED;
 
  //
  // Get last Device Path node
  //
  LastDevicePathNode = NULL;
  DevicePathNode     = DevicePath;
  while (!IsDevicePathEnd (DevicePathNode)) {
    LastDevicePathNode = DevicePathNode;
    DevicePathNode     = NextDevicePathNode (DevicePathNode);
  }
 
  //
  // Check if last Device Path node contains a Vendor-Defined Media Device Path
  // of an UDF file system.
  //
  if ((LastDevicePathNode != NULL) &&
      (DevicePathType (LastDevicePathNode) == MEDIA_DEVICE_PATH) &&
      (DevicePathSubType (LastDevicePathNode) == MEDIA_VENDOR_DP))
  {
    VendorDefinedGuid = (EFI_GUID *)((UINTN)LastDevicePathNode +
                                     OFFSET_OF (VENDOR_DEVICE_PATH, Guid));
    if (CompareGuid (VendorDefinedGuid, &gUdfDevPathGuid)) {
      Status = EFI_SUCCESS;
    }
  }
 
  //
  // Close Device Path protocol on ControllerHandle
  //
  gBS->CloseProtocol (
         ControllerHandle,
         &gEfiDevicePathProtocolGuid,
         This->DriverBindingHandle,
         ControllerHandle
         );
 
  return Status;
}