FatPkg/EnhancedFatDxe/Hash.c

/** @file
  Hash table operations.

Copyright (c) 2005 - 2015, 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"

/**

  Get hash value for long name.

  @param  LongNameString        - The long name string to be hashed.

  @return HashValue.

**/
STATIC
UINT32
FatHashLongName (
  IN CHAR16   *LongNameString
  )
{
  UINT32  HashValue;
  CHAR16  UpCasedLongFileName[EFI_PATH_STRING_LENGTH];
  StrnCpyS (
    UpCasedLongFileName,
    ARRAY_SIZE (UpCasedLongFileName),
    LongNameString,
    ARRAY_SIZE (UpCasedLongFileName) - 1
    );
  FatStrUpr (UpCasedLongFileName);
  gBS->CalculateCrc32 (UpCasedLongFileName, StrSize (UpCasedLongFileName), &HashValue);
  return (HashValue & HASH_TABLE_MASK);
}

/**

  Get hash value for short name.

  @param  ShortNameString       - The short name string to be hashed.

  @return HashValue

**/
STATIC
UINT32
FatHashShortName (
  IN CHAR8   *ShortNameString
  )
{
  UINT32  HashValue;
  gBS->CalculateCrc32 (ShortNameString, FAT_NAME_LEN, &HashValue);
  return (HashValue & HASH_TABLE_MASK);
}

/**

  Search the long name hash table for the directory entry.

  @param  ODir                  - The directory to be searched.
  @param  LongNameString        - The long name string to search.

  @return The previous long name hash node of the directory entry.

**/
FAT_DIRENT **
FatLongNameHashSearch (
  IN FAT_ODIR       *ODir,
  IN CHAR16         *LongNameString
  )
{
  FAT_DIRENT  **PreviousHashNode;
  for (PreviousHashNode   = &ODir->LongNameHashTable[FatHashLongName (LongNameString)];
       *PreviousHashNode != NULL;
       PreviousHashNode   = &(*PreviousHashNode)->LongNameForwardLink
      ) {
    if (FatStriCmp (LongNameString, (*PreviousHashNode)->FileString) == 0) {
      break;
    }
  }

  return PreviousHashNode;
}

/**

  Search the short name hash table for the directory entry.

  @param  ODir                  - The directory to be searched.
  @param  ShortNameString       - The short name string to search.

  @return The previous short name hash node of the directory entry.

**/
FAT_DIRENT **
FatShortNameHashSearch (
  IN FAT_ODIR      *ODir,
  IN CHAR8         *ShortNameString
  )
{
  FAT_DIRENT  **PreviousHashNode;
  for (PreviousHashNode   = &ODir->ShortNameHashTable[FatHashShortName (ShortNameString)];
       *PreviousHashNode != NULL;
       PreviousHashNode   = &(*PreviousHashNode)->ShortNameForwardLink
      ) {
    if (CompareMem (ShortNameString, (*PreviousHashNode)->Entry.FileName, FAT_NAME_LEN) == 0) {
      break;
    }
  }

  return PreviousHashNode;
}

/**

  Insert directory entry to hash table.

  @param  ODir                  - The parent directory.
  @param  DirEnt                - The directory entry node.

**/
VOID
FatInsertToHashTable (
  IN FAT_ODIR     *ODir,
  IN FAT_DIRENT   *DirEnt
  )
{
  FAT_DIRENT  **HashTable;
  UINT32      HashTableIndex;

  //
  // Insert hash table index for short name
  //
  HashTableIndex                = FatHashShortName (DirEnt->Entry.FileName);
  HashTable                     = ODir->ShortNameHashTable;
  DirEnt->ShortNameForwardLink  = HashTable[HashTableIndex];
  HashTable[HashTableIndex]     = DirEnt;
  //
  // Insert hash table index for long name
  //
  HashTableIndex                = FatHashLongName (DirEnt->FileString);
  HashTable                     = ODir->LongNameHashTable;
  DirEnt->LongNameForwardLink   = HashTable[HashTableIndex];
  HashTable[HashTableIndex]     = DirEnt;
}

/**

  Delete directory entry from hash table.

  @param  ODir                  - The parent directory.
  @param  DirEnt                - The directory entry node.

**/
VOID
FatDeleteFromHashTable (
  IN FAT_ODIR     *ODir,
  IN FAT_DIRENT   *DirEnt
  )
{
  *FatShortNameHashSearch (ODir, DirEnt->Entry.FileName) = DirEnt->ShortNameForwardLink;
  *FatLongNameHashSearch (ODir, DirEnt->FileString)      = DirEnt->LongNameForwardLink;
}