FatPkg/EnhancedFatDxe/DirectoryCache.c

/** @file
  Functions for directory cache operation.

Copyright (c) 2005, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials are licensed and made available
under the terms and conditions of the BSD License which accompanies this
distribution. The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.


**/

#include "Fat.h"

/**

  Free the directory structure and release the memory.

  @param  ODir                  - The directory to be freed.

**/
STATIC
VOID
FatFreeODir (
  IN FAT_ODIR    *ODir
  )
{
  FAT_DIRENT  *DirEnt;

  //
  // Release Directory Entry Nodes
  //
  while (!IsListEmpty (&ODir->ChildList)) {
    DirEnt = DIRENT_FROM_LINK (ODir->ChildList.ForwardLink);
    RemoveEntryList (&DirEnt->Link);
    //
    // Make sure the OFile has been closed
    //
    ASSERT (DirEnt->OFile == NULL);
    FatFreeDirEnt (DirEnt);
  }

  FreePool (ODir);
}

/**

  Allocate the directory structure.

  @param  OFile                   - The corresponding OFile.

**/
STATIC
FAT_ODIR *
FatAllocateODir (
  IN FAT_OFILE   *OFile
  )
{
  FAT_ODIR  *ODir;

  ODir = AllocateZeroPool (sizeof (FAT_ODIR));
  if (ODir != NULL) {
    //
    // Initialize the directory entry list
    //
    ODir->Signature = FAT_ODIR_SIGNATURE;
    InitializeListHead (&ODir->ChildList);
    ODir->CurrentCursor = &ODir->ChildList;
  }

  return ODir;
}

/**

  Discard the directory structure when an OFile will be freed.
  Volume will cache this directory if the OFile does not represent a deleted file.

  @param  OFile                 - The OFile whose directory structure is to be discarded.

**/
VOID
FatDiscardODir (
  IN FAT_OFILE    *OFile
  )
{
  FAT_ODIR    *ODir;
  FAT_VOLUME  *Volume;

  Volume  = OFile->Volume;
  ODir    = OFile->ODir;
  if (!OFile->DirEnt->Invalid) {
    //
    // If OFile does not represent a deleted file, then we will cache the directory
    // We use OFile's first cluster as the directory's tag
    //
    ODir->DirCacheTag = OFile->FileCluster;
    InsertHeadList (&Volume->DirCacheList, &ODir->DirCacheLink);
    if (Volume->DirCacheCount == FAT_MAX_DIR_CACHE_COUNT) {
      //
      // Replace the least recent used directory
      //
      ODir = ODIR_FROM_DIRCACHELINK (Volume->DirCacheList.BackLink);
      RemoveEntryList (&ODir->DirCacheLink);
    } else {
      //
      // No need to find a replace
      //
      Volume->DirCacheCount++;
      ODir = NULL;
    }
  }
  //
  // Release ODir Structure
  //
  if (ODir != NULL) {
    FatFreeODir (ODir);
  }
}

/**


  Request the directory structure when an OFile is newly generated.
  If the directory structure is cached by volume, then just return this directory;
  Otherwise, allocate a new one for OFile.

  @param  OFile                 - The OFile which requests directory structure.

**/
VOID
FatRequestODir (
  IN FAT_OFILE    *OFile
  )
{
  UINTN           DirCacheTag;
  FAT_VOLUME      *Volume;
  FAT_ODIR        *ODir;
  FAT_ODIR        *CurrentODir;
  LIST_ENTRY      *CurrentODirLink;

  Volume      = OFile->Volume;
  ODir        = NULL;
  DirCacheTag = OFile->FileCluster;
  for (CurrentODirLink  = Volume->DirCacheList.ForwardLink;
       CurrentODirLink != &Volume->DirCacheList;
       CurrentODirLink  = CurrentODirLink->ForwardLink
      ) {
    CurrentODir = ODIR_FROM_DIRCACHELINK (CurrentODirLink);
    if (CurrentODir->DirCacheTag == DirCacheTag) {
      RemoveEntryList (&CurrentODir->DirCacheLink);
      Volume->DirCacheCount--;
      ODir = CurrentODir;
      break;
    }
  }

  if (ODir == NULL) {
    //
    // This directory is not cached, then allocate a new one
    //
    ODir = FatAllocateODir (OFile);
  }

  OFile->ODir = ODir;
}

/**

  Clean up all the cached directory structures when the volume is going to be abandoned.

  @param  Volume                - FAT file system volume.

**/
VOID
FatCleanupODirCache (
  IN FAT_VOLUME         *Volume
  )
{
  FAT_ODIR  *ODir;
  while (Volume->DirCacheCount > 0) {
    ODir = ODIR_FROM_DIRCACHELINK (Volume->DirCacheList.BackLink);
    RemoveEntryList (&ODir->DirCacheLink);
    FatFreeODir (ODir);
    Volume->DirCacheCount--;
  }
}