/*++

Copyright (c) 2005, Intel Corporation
All rights reserved. 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.


Module Name:

  DirectoryCache.c

Abstract:

  Functions for directory cache operation

Revision History

--*/

#include "Fat.h"

STATIC
VOID
FatFreeODir (
  IN FAT_ODIR    *ODir
  )
/*++

Routine Description:

  Free the directory structure and release the memory.

Arguments:

  ODir                  - The directory to be freed.

Returns:

  None.

--*/
{
  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);
}

STATIC
FAT_ODIR *
FatAllocateODir (
  IN FAT_OFILE   *OFile
  )
/*++

Routine Description:

  Allocate the directory structure.

Arguments:

  OFile                   - The corresponding OFile.

Returns:

  None.

--*/
{
  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;
}

VOID
FatDiscardODir (
  IN FAT_OFILE    *OFile
  )
/*++

Routine Description:

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

Arguments:

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

Returns:

  None.

--*/
{
  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);
  }
}

VOID
FatRequestODir (
  IN FAT_OFILE    *OFile
  )
/*++

Routine Description:

  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.

Arguments:

  OFile                 - The OFile which requests directory structure.

Returns:

  None.

--*/
{
  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;
}

VOID
FatCleanupODirCache (
  IN FAT_VOLUME         *Volume
  )
/*++

Routine Description:

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

Arguments:

  Volume                - FAT file system volume.

Returns:

  None.

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