FatPkg/EnhancedFatDxe/DirectoryCache.c

   1 /** @file
   2   Functions for directory cache operation.
   3
   4 Copyright (c) 2005, Intel Corporation. All rights reserved.<BR>
   5 This program and the accompanying materials are licensed and made available
   6 under the terms and conditions of the BSD License which accompanies this
   7 distribution. The full text of the license may be found at
   8 http://opensource.org/licenses/bsd-license.php
   9
  10 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13
  14 **/
  15
  16 #include "Fat.h"
  17
  18 /**
  19
  20   Free the directory structure and release the memory.
  21
  22   @param  ODir                  - The directory to be freed.
  23
  24 **/
  25 STATIC
  26 VOID
  27 FatFreeODir (
  28   IN FAT_ODIR    *ODir
  29   )
  30 {
  31   FAT_DIRENT  *DirEnt;
  32
  33   //
  34   // Release Directory Entry Nodes
  35   //
  36   while (!IsListEmpty (&ODir->ChildList)) {
  37     DirEnt = DIRENT_FROM_LINK (ODir->ChildList.ForwardLink);
  38     RemoveEntryList (&DirEnt->Link);
  39     //
  40     // Make sure the OFile has been closed
  41     //
  42     ASSERT (DirEnt->OFile == NULL);
  43     FatFreeDirEnt (DirEnt);
  44   }
  45
  46   FreePool (ODir);
  47 }
  48
  49 /**
  50
  51   Allocate the directory structure.
  52
  53   @param  OFile                   - The corresponding OFile.
  54
  55 **/
  56 STATIC
  57 FAT_ODIR *
  58 FatAllocateODir (
  59   IN FAT_OFILE   *OFile
  60   )
  61 {
  62   FAT_ODIR  *ODir;
  63
  64   ODir = AllocateZeroPool (sizeof (FAT_ODIR));
  65   if (ODir != NULL) {
  66     //
  67     // Initialize the directory entry list
  68     //
  69     ODir->Signature = FAT_ODIR_SIGNATURE;
  70     InitializeListHead (&ODir->ChildList);
  71     ODir->CurrentCursor = &ODir->ChildList;
  72   }
  73
  74   return ODir;
  75 }
  76
  77 /**
  78
  79   Discard the directory structure when an OFile will be freed.
  80   Volume will cache this directory if the OFile does not represent a deleted file.
  81
  82   @param  OFile                 - The OFile whose directory structure is to be discarded.
  83
  84 **/
  85 VOID
  86 FatDiscardODir (
  87   IN FAT_OFILE    *OFile
  88   )
  89 {
  90   FAT_ODIR    *ODir;
  91   FAT_VOLUME  *Volume;
  92
  93   Volume  = OFile->Volume;
  94   ODir    = OFile->ODir;
  95   if (!OFile->DirEnt->Invalid) {
  96     //
  97     // If OFile does not represent a deleted file, then we will cache the directory
  98     // We use OFile's first cluster as the directory's tag
  99     //
 100     ODir->DirCacheTag = OFile->FileCluster;
 101     InsertHeadList (&Volume->DirCacheList, &ODir->DirCacheLink);
 102     if (Volume->DirCacheCount == FAT_MAX_DIR_CACHE_COUNT) {
 103       //
 104       // Replace the least recent used directory
 105       //
 106       ODir = ODIR_FROM_DIRCACHELINK (Volume->DirCacheList.BackLink);
 107       RemoveEntryList (&ODir->DirCacheLink);
 108     } else {
 109       //
 110       // No need to find a replace
 111       //
 112       Volume->DirCacheCount++;
 113       ODir = NULL;
 114     }
 115   }
 116   //
 117   // Release ODir Structure
 118   //
 119   if (ODir != NULL) {
 120     FatFreeODir (ODir);
 121   }
 122 }
 123
 124 /**
 125
 126
 127   Request the directory structure when an OFile is newly generated.
 128   If the directory structure is cached by volume, then just return this directory;
 129   Otherwise, allocate a new one for OFile.
 130
 131   @param  OFile                 - The OFile which requests directory structure.
 132
 133 **/
 134 VOID
 135 FatRequestODir (
 136   IN FAT_OFILE    *OFile
 137   )
 138 {
 139   UINTN           DirCacheTag;
 140   FAT_VOLUME      *Volume;
 141   FAT_ODIR        *ODir;
 142   FAT_ODIR        *CurrentODir;
 143   LIST_ENTRY      *CurrentODirLink;
 144
 145   Volume      = OFile->Volume;
 146   ODir        = NULL;
 147   DirCacheTag = OFile->FileCluster;
 148   for (CurrentODirLink  = Volume->DirCacheList.ForwardLink;
 149        CurrentODirLink != &Volume->DirCacheList;
 150        CurrentODirLink  = CurrentODirLink->ForwardLink
 151       ) {
 152     CurrentODir = ODIR_FROM_DIRCACHELINK (CurrentODirLink);
 153     if (CurrentODir->DirCacheTag == DirCacheTag) {
 154       RemoveEntryList (&CurrentODir->DirCacheLink);
 155       Volume->DirCacheCount--;
 156       ODir = CurrentODir;
 157       break;
 158     }
 159   }
 160
 161   if (ODir == NULL) {
 162     //
 163     // This directory is not cached, then allocate a new one
 164     //
 165     ODir = FatAllocateODir (OFile);
 166   }
 167
 168   OFile->ODir = ODir;
 169 }
 170
 171 /**
 172
 173   Clean up all the cached directory structures when the volume is going to be abandoned.
 174
 175   @param  Volume                - FAT file system volume.
 176
 177 **/
 178 VOID
 179 FatCleanupODirCache (
 180   IN FAT_VOLUME         *Volume
 181   )
 182 {
 183   FAT_ODIR  *ODir;
 184   while (Volume->DirCacheCount > 0) {
 185     ODir = ODIR_FROM_DIRCACHELINK (Volume->DirCacheList.BackLink);
 186     RemoveEntryList (&ODir->DirCacheLink);
 187     FatFreeODir (ODir);
 188     Volume->DirCacheCount--;
 189   }
 190 }