FatPkg/EnhancedFatDxe/DirectoryCache.c

   1 /** @file
   2   Functions for directory cache operation.
   3
   4 Copyright (c) 2005, Intel Corporation. All rights reserved.<BR>
   5 SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7
   8 **/
   9
  10 #include "Fat.h"
  11
  12 /**
  13
  14   Free the directory structure and release the memory.
  15
  16   @param  ODir                  - The directory to be freed.
  17
  18 **/
  19 STATIC
  20 VOID
  21 FatFreeODir (
  22   IN FAT_ODIR  *ODir
  23   )
  24 {
  25   FAT_DIRENT  *DirEnt;
  26
  27   //
  28   // Release Directory Entry Nodes
  29   //
  30   while (!IsListEmpty (&ODir->ChildList)) {
  31     DirEnt = DIRENT_FROM_LINK (ODir->ChildList.ForwardLink);
  32     RemoveEntryList (&DirEnt->Link);
  33     //
  34     // Make sure the OFile has been closed
  35     //
  36     ASSERT (DirEnt->OFile == NULL);
  37     FatFreeDirEnt (DirEnt);
  38   }
  39
  40   FreePool (ODir);
  41 }
  42
  43 /**
  44
  45   Allocate the directory structure.
  46
  47   @param  OFile                   - The corresponding OFile.
  48
  49 **/
  50 STATIC
  51 FAT_ODIR *
  52 FatAllocateODir (
  53   IN FAT_OFILE  *OFile
  54   )
  55 {
  56   FAT_ODIR  *ODir;
  57
  58   ODir = AllocateZeroPool (sizeof (FAT_ODIR));
  59   if (ODir != NULL) {
  60     //
  61     // Initialize the directory entry list
  62     //
  63     ODir->Signature = FAT_ODIR_SIGNATURE;
  64     InitializeListHead (&ODir->ChildList);
  65     ODir->CurrentCursor = &ODir->ChildList;
  66   }
  67
  68   return ODir;
  69 }
  70
  71 /**
  72
  73   Discard the directory structure when an OFile will be freed.
  74   Volume will cache this directory if the OFile does not represent a deleted file.
  75
  76   @param  OFile                 - The OFile whose directory structure is to be discarded.
  77
  78 **/
  79 VOID
  80 FatDiscardODir (
  81   IN FAT_OFILE  *OFile
  82   )
  83 {
  84   FAT_ODIR    *ODir;
  85   FAT_VOLUME  *Volume;
  86
  87   Volume = OFile->Volume;
  88   ODir   = OFile->ODir;
  89   if (!OFile->DirEnt->Invalid) {
  90     //
  91     // If OFile does not represent a deleted file, then we will cache the directory
  92     // We use OFile's first cluster as the directory's tag
  93     //
  94     ODir->DirCacheTag = OFile->FileCluster;
  95     InsertHeadList (&Volume->DirCacheList, &ODir->DirCacheLink);
  96     if (Volume->DirCacheCount == FAT_MAX_DIR_CACHE_COUNT) {
  97       //
  98       // Replace the least recent used directory
  99       //
 100       ODir = ODIR_FROM_DIRCACHELINK (Volume->DirCacheList.BackLink);
 101       RemoveEntryList (&ODir->DirCacheLink);
 102     } else {
 103       //
 104       // No need to find a replace
 105       //
 106       Volume->DirCacheCount++;
 107       ODir = NULL;
 108     }
 109   }
 110
 111   //
 112   // Release ODir Structure
 113   //
 114   if (ODir != NULL) {
 115     FatFreeODir (ODir);
 116   }
 117 }
 118
 119 /**
 120
 121
 122   Request the directory structure when an OFile is newly generated.
 123   If the directory structure is cached by volume, then just return this directory;
 124   Otherwise, allocate a new one for OFile.
 125
 126   @param  OFile                 - The OFile which requests directory structure.
 127
 128 **/
 129 VOID
 130 FatRequestODir (
 131   IN FAT_OFILE  *OFile
 132   )
 133 {
 134   UINTN       DirCacheTag;
 135   FAT_VOLUME  *Volume;
 136   FAT_ODIR    *ODir;
 137   FAT_ODIR    *CurrentODir;
 138   LIST_ENTRY  *CurrentODirLink;
 139
 140   Volume      = OFile->Volume;
 141   ODir        = NULL;
 142   DirCacheTag = OFile->FileCluster;
 143   for (CurrentODirLink  = Volume->DirCacheList.ForwardLink;
 144        CurrentODirLink != &Volume->DirCacheList;
 145        CurrentODirLink  = CurrentODirLink->ForwardLink
 146        )
 147   {
 148     CurrentODir = ODIR_FROM_DIRCACHELINK (CurrentODirLink);
 149     if (CurrentODir->DirCacheTag == DirCacheTag) {
 150       RemoveEntryList (&CurrentODir->DirCacheLink);
 151       Volume->DirCacheCount--;
 152       ODir = CurrentODir;
 153       break;
 154     }
 155   }
 156
 157   if (ODir == NULL) {
 158     //
 159     // This directory is not cached, then allocate a new one
 160     //
 161     ODir = FatAllocateODir (OFile);
 162   }
 163
 164   OFile->ODir = ODir;
 165 }
 166
 167 /**
 168
 169   Clean up all the cached directory structures when the volume is going to be abandoned.
 170
 171   @param  Volume                - FAT file system volume.
 172
 173 **/
 174 VOID
 175 FatCleanupODirCache (
 176   IN FAT_VOLUME  *Volume
 177   )
 178 {
 179   FAT_ODIR  *ODir;
 180
 181   while (Volume->DirCacheCount > 0) {
 182     ODir = ODIR_FROM_DIRCACHELINK (Volume->DirCacheList.BackLink);
 183     RemoveEntryList (&ODir->DirCacheLink);
 184     FatFreeODir (ODir);
 185     Volume->DirCacheCount--;
 186   }
 187 }