UefiLib.c

/** @file
  The UEFI Library provides functions and macros that simplify the development of
  UEFI Drivers and UEFI Applications.  These functions and macros help manage EFI
  events, build simple locks utilizing EFI Task Priority Levels (TPLs), install
  EFI Driver Model related protocols, manage Unicode string tables for UEFI Drivers,
  and print messages on the console output and standard error devices.

  Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "UefiLibInternal.h"

/**
  Empty constructor function that is required to resolve dependencies between
  libraries.

    ** DO NOT REMOVE **

  @param  ImageHandle   The firmware allocated handle for the EFI image.
  @param  SystemTable   A pointer to the EFI System Table.

  @retval EFI_SUCCESS   The constructor executed correctly.

**/
EFI_STATUS
EFIAPI
UefiLibConstructor (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  return EFI_SUCCESS;
}

/**
  Compare whether two names of languages are identical.

  @param  Language1 Name of language 1.
  @param  Language2 Name of language 2.

  @retval TRUE      Language 1 and language 2 are the same.
  @retval FALSE     Language 1 and language 2 are not the same.

**/
BOOLEAN
CompareIso639LanguageCode (
  IN CONST CHAR8  *Language1,
  IN CONST CHAR8  *Language2
  )
{
  UINT32  Name1;
  UINT32  Name2;

  Name1 = ReadUnaligned24 ((CONST UINT32 *)Language1);
  Name2 = ReadUnaligned24 ((CONST UINT32 *)Language2);

  return (BOOLEAN)(Name1 == Name2);
}

/**
  Retrieves a pointer to the system configuration table from the EFI System Table
  based on a specified GUID.

  This function searches the list of configuration tables stored in the EFI System Table
  for a table with a GUID that matches TableGuid.  If a match is found, then a pointer to
  the configuration table is returned in Table., and EFI_SUCCESS is returned. If a matching GUID
  is not found, then EFI_NOT_FOUND is returned.
  If TableGuid is NULL, then ASSERT().
  If Table is NULL, then ASSERT().

  @param  TableGuid       The pointer to table's GUID type.
  @param  Table           The pointer to the table associated with TableGuid in the EFI System Table.

  @retval EFI_SUCCESS     A configuration table matching TableGuid was found.
  @retval EFI_NOT_FOUND   A configuration table matching TableGuid could not be found.

**/
EFI_STATUS
EFIAPI
EfiGetSystemConfigurationTable (
  IN  EFI_GUID  *TableGuid,
  OUT VOID      **Table
  )
{
  EFI_SYSTEM_TABLE  *SystemTable;
  UINTN             Index;

  ASSERT (TableGuid != NULL);
  ASSERT (Table != NULL);

  SystemTable = gST;
  *Table      = NULL;
  for (Index = 0; Index < SystemTable->NumberOfTableEntries; Index++) {
    if (CompareGuid (TableGuid, &(SystemTable->ConfigurationTable[Index].VendorGuid))) {
      *Table = SystemTable->ConfigurationTable[Index].VendorTable;
      return EFI_SUCCESS;
    }
  }

  return EFI_NOT_FOUND;
}

/**
  Creates and returns a notification event and registers that event with all the protocol
  instances specified by ProtocolGuid.

  This function causes the notification function to be executed for every protocol of type
  ProtocolGuid instance that exists in the system when this function is invoked. If there are
  no instances of ProtocolGuid in the handle database at the time this function is invoked,
  then the notification function is still executed one time. In addition, every time a protocol
  of type ProtocolGuid instance is installed or reinstalled, the notification function is also
  executed. This function returns the notification event that was created.
  If ProtocolGuid is NULL, then ASSERT().
  If NotifyTpl is not a legal TPL value, then ASSERT().
  If NotifyFunction is NULL, then ASSERT().
  If Registration is NULL, then ASSERT().


  @param  ProtocolGuid    Supplies GUID of the protocol upon whose installation the event is fired.
  @param  NotifyTpl       Supplies the task priority level of the event notifications.
  @param  NotifyFunction  Supplies the function to notify when the event is signaled.
  @param  NotifyContext   The context parameter to pass to NotifyFunction.
  @param  Registration    A pointer to a memory location to receive the registration value.
                          This value is passed to LocateHandle() to obtain new handles that
                          have been added that support the ProtocolGuid-specified protocol.

  @return The notification event that was created.

**/
EFI_EVENT
EFIAPI
EfiCreateProtocolNotifyEvent (
  IN  EFI_GUID          *ProtocolGuid,
  IN  EFI_TPL           NotifyTpl,
  IN  EFI_EVENT_NOTIFY  NotifyFunction,
  IN  VOID              *NotifyContext   OPTIONAL,
  OUT VOID              **Registration
  )
{
  EFI_STATUS  Status;
  EFI_EVENT   Event;

  ASSERT (ProtocolGuid != NULL);
  ASSERT (NotifyFunction != NULL);
  ASSERT (Registration != NULL);

  //
  // Create the event
  //

  Status = gBS->CreateEvent (
                  EVT_NOTIFY_SIGNAL,
                  NotifyTpl,
                  NotifyFunction,
                  NotifyContext,
                  &Event
                  );
  ASSERT_EFI_ERROR (Status);

  //
  // Register for protocol notifications on this event
  //

  Status = gBS->RegisterProtocolNotify (
                  ProtocolGuid,
                  Event,
                  Registration
                  );

  ASSERT_EFI_ERROR (Status);

  //
  // Kick the event so we will perform an initial pass of
  // current installed drivers
  //

  gBS->SignalEvent (Event);
  return Event;
}

/**
  Creates a named event that can be signaled with EfiNamedEventSignal().

  This function creates an event using NotifyTpl, NoifyFunction, and NotifyContext.
  This event is signaled with EfiNamedEventSignal(). This provides the ability for one or more
  listeners on the same event named by the GUID specified by Name.
  If Name is NULL, then ASSERT().
  If NotifyTpl is not a legal TPL value, then ASSERT().
  If NotifyFunction is NULL, then ASSERT().

  @param  Name                  Supplies the GUID name of the event.
  @param  NotifyTpl             Supplies the task priority level of the event notifications.
  @param  NotifyFunction        Supplies the function to notify when the event is signaled.
  @param  NotifyContext         The context parameter to pass to NotifyFunction.
  @param  Registration          A pointer to a memory location to receive the registration value.

  @retval EFI_SUCCESS           A named event was created.
  @retval EFI_OUT_OF_RESOURCES  There are not enough resource to create the named event.

**/
EFI_STATUS
EFIAPI
EfiNamedEventListen (
  IN CONST EFI_GUID    *Name,
  IN EFI_TPL           NotifyTpl,
  IN EFI_EVENT_NOTIFY  NotifyFunction,
  IN CONST VOID        *NotifyContext   OPTIONAL,
  OUT VOID             *Registration OPTIONAL
  )
{
  EFI_STATUS  Status;
  EFI_EVENT   Event;
  VOID        *RegistrationLocal;

  ASSERT (Name != NULL);
  ASSERT (NotifyFunction != NULL);
  ASSERT (NotifyTpl <= TPL_HIGH_LEVEL);

  //
  // Create event
  //
  Status = gBS->CreateEvent (
                  EVT_NOTIFY_SIGNAL,
                  NotifyTpl,
                  NotifyFunction,
                  (VOID *)NotifyContext,
                  &Event
                  );
  ASSERT_EFI_ERROR (Status);

  //
  // The Registration is not optional to RegisterProtocolNotify().
  // To make it optional to EfiNamedEventListen(), may need to substitute with a local.
  //
  if (Registration != NULL) {
    RegistrationLocal = Registration;
  } else {
    RegistrationLocal = &RegistrationLocal;
  }

  //
  // Register for an installation of protocol interface
  //

  Status = gBS->RegisterProtocolNotify (
                  (EFI_GUID *)Name,
                  Event,
                  RegistrationLocal
                  );
  ASSERT_EFI_ERROR (Status);

  return Status;
}

/**
  Signals a named event created with EfiNamedEventListen().

  This function signals the named event specified by Name. The named event must have been
  created with EfiNamedEventListen().
  If Name is NULL, then ASSERT().

  @param  Name                  Supplies the GUID name of the event.

  @retval EFI_SUCCESS           A named event was signaled.
  @retval EFI_OUT_OF_RESOURCES  There are not enough resource to signal the named event.

**/
EFI_STATUS
EFIAPI
EfiNamedEventSignal (
  IN CONST EFI_GUID  *Name
  )
{
  EFI_STATUS  Status;
  EFI_HANDLE  Handle;

  ASSERT (Name != NULL);

  Handle = NULL;
  Status = gBS->InstallProtocolInterface (
                  &Handle,
                  (EFI_GUID *)Name,
                  EFI_NATIVE_INTERFACE,
                  NULL
                  );
  ASSERT_EFI_ERROR (Status);

  Status = gBS->UninstallProtocolInterface (
                  Handle,
                  (EFI_GUID *)Name,
                  NULL
                  );
  ASSERT_EFI_ERROR (Status);

  return Status;
}

/**
  Signals an event group by placing a new event in the group temporarily and
  signaling it.

  @param[in] EventGroup          Supplies the unique identifier of the event
                                 group to signal.

  @retval EFI_SUCCESS            The event group was signaled successfully.
  @retval EFI_INVALID_PARAMETER  EventGroup is NULL.
  @return                        Error codes that report problems about event
                                 creation or signaling.
**/
EFI_STATUS
EFIAPI
EfiEventGroupSignal (
  IN CONST EFI_GUID  *EventGroup
  )
{
  EFI_STATUS  Status;
  EFI_EVENT   Event;

  if (EventGroup == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  Status = gBS->CreateEventEx (
                  EVT_NOTIFY_SIGNAL,
                  TPL_CALLBACK,
                  EfiEventEmptyFunction,
                  NULL,
                  EventGroup,
                  &Event
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = gBS->SignalEvent (Event);
  gBS->CloseEvent (Event);

  return Status;
}

/**
  An empty function that can be used as NotifyFunction parameter of
  CreateEvent() or CreateEventEx().

  @param Event              Event whose notification function is being invoked.
  @param Context            The pointer to the notification function's context,
                            which is implementation-dependent.

**/
VOID
EFIAPI
EfiEventEmptyFunction (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  )
{
}

/**
  Returns the current TPL.

  This function returns the current TPL.  There is no EFI service to directly
  retrieve the current TPL. Instead, the RaiseTPL() function is used to raise
  the TPL to TPL_HIGH_LEVEL.  This will return the current TPL.  The TPL level
  can then immediately be restored back to the current TPL level with a call
  to RestoreTPL().

  @return The current TPL.

**/
EFI_TPL
EFIAPI
EfiGetCurrentTpl (
  VOID
  )
{
  EFI_TPL  Tpl;

  Tpl = gBS->RaiseTPL (TPL_HIGH_LEVEL);
  gBS->RestoreTPL (Tpl);

  return Tpl;
}

/**
  Initializes a basic mutual exclusion lock.

  This function initializes a basic mutual exclusion lock to the released state
  and returns the lock.  Each lock provides mutual exclusion access at its task
  priority level.  Since there is no preemption or multiprocessor support in EFI,
  acquiring the lock only consists of raising to the locks TPL.
  If Lock is NULL, then ASSERT().
  If Priority is not a valid TPL value, then ASSERT().

  @param  Lock       A pointer to the lock data structure to initialize.
  @param  Priority   EFI TPL is associated with the lock.

  @return The lock.

**/
EFI_LOCK *
EFIAPI
EfiInitializeLock (
  IN OUT EFI_LOCK  *Lock,
  IN EFI_TPL       Priority
  )
{
  ASSERT (Lock != NULL);
  ASSERT (Priority <= TPL_HIGH_LEVEL);

  Lock->Tpl      = Priority;
  Lock->OwnerTpl = TPL_APPLICATION;
  Lock->Lock     = EfiLockReleased;
  return Lock;
}

/**
  Acquires ownership of a lock.

  This function raises the system's current task priority level to the task
  priority level of the mutual exclusion lock.  Then, it places the lock in the
  acquired state.
  If Lock is NULL, then ASSERT().
  If Lock is not initialized, then ASSERT().
  If Lock is already in the acquired state, then ASSERT().

  @param  Lock              A pointer to the lock to acquire.

**/
VOID
EFIAPI
EfiAcquireLock (
  IN EFI_LOCK  *Lock
  )
{
  ASSERT (Lock != NULL);
  ASSERT (Lock->Lock == EfiLockReleased);

  Lock->OwnerTpl = gBS->RaiseTPL (Lock->Tpl);
  Lock->Lock     = EfiLockAcquired;
}

/**
  Acquires ownership of a lock.

  This function raises the system's current task priority level to the task priority
  level of the mutual exclusion lock.  Then, it attempts to place the lock in the acquired state.
  If the lock is already in the acquired state, then EFI_ACCESS_DENIED is returned.
  Otherwise, EFI_SUCCESS is returned.
  If Lock is NULL, then ASSERT().
  If Lock is not initialized, then ASSERT().

  @param  Lock              A pointer to the lock to acquire.

  @retval EFI_SUCCESS       The lock was acquired.
  @retval EFI_ACCESS_DENIED The lock could not be acquired because it is already owned.

**/
EFI_STATUS
EFIAPI
EfiAcquireLockOrFail (
  IN EFI_LOCK  *Lock
  )
{
  ASSERT (Lock != NULL);
  ASSERT (Lock->Lock != EfiLockUninitialized);

  if (Lock->Lock == EfiLockAcquired) {
    //
    // Lock is already owned, so bail out
    //
    return EFI_ACCESS_DENIED;
  }

  Lock->OwnerTpl = gBS->RaiseTPL (Lock->Tpl);

  Lock->Lock = EfiLockAcquired;

  return EFI_SUCCESS;
}

/**
  Releases ownership of a lock.

  This function transitions a mutual exclusion lock from the acquired state to
  the released state, and restores the system's task priority level to its
  previous level.
  If Lock is NULL, then ASSERT().
  If Lock is not initialized, then ASSERT().
  If Lock is already in the released state, then ASSERT().

  @param  Lock  A pointer to the lock to release.

**/
VOID
EFIAPI
EfiReleaseLock (
  IN EFI_LOCK  *Lock
  )
{
  EFI_TPL  Tpl;

  ASSERT (Lock != NULL);
  ASSERT (Lock->Lock == EfiLockAcquired);

  Tpl = Lock->OwnerTpl;

  Lock->Lock = EfiLockReleased;

  gBS->RestoreTPL (Tpl);
}

/**
  Tests whether a controller handle is being managed by a specific driver.

  This function tests whether the driver specified by DriverBindingHandle is
  currently managing the controller specified by ControllerHandle.  This test
  is performed by evaluating if the the protocol specified by ProtocolGuid is
  present on ControllerHandle and is was opened by DriverBindingHandle with an
  attribute of EFI_OPEN_PROTOCOL_BY_DRIVER.
  If ProtocolGuid is NULL, then ASSERT().

  @param  ControllerHandle     A handle for a controller to test.
  @param  DriverBindingHandle  Specifies the driver binding handle for the
                               driver.
  @param  ProtocolGuid         Specifies the protocol that the driver specified
                               by DriverBindingHandle opens in its Start()
                               function.

  @retval EFI_SUCCESS          ControllerHandle is managed by the driver
                               specified by DriverBindingHandle.
  @retval EFI_UNSUPPORTED      ControllerHandle is not managed by the driver
                               specified by DriverBindingHandle.

**/
EFI_STATUS
EFIAPI
EfiTestManagedDevice (
  IN CONST EFI_HANDLE  ControllerHandle,
  IN CONST EFI_HANDLE  DriverBindingHandle,
  IN CONST EFI_GUID    *ProtocolGuid
  )
{
  EFI_STATUS  Status;
  VOID        *ManagedInterface;

  ASSERT (ProtocolGuid != NULL);

  Status = gBS->OpenProtocol (
                  ControllerHandle,
                  (EFI_GUID *)ProtocolGuid,
                  &ManagedInterface,
                  DriverBindingHandle,
                  ControllerHandle,
                  EFI_OPEN_PROTOCOL_BY_DRIVER
                  );
  if (!EFI_ERROR (Status)) {
    gBS->CloseProtocol (
           ControllerHandle,
           (EFI_GUID *)ProtocolGuid,
           DriverBindingHandle,
           ControllerHandle
           );
    return EFI_UNSUPPORTED;
  }

  if (Status != EFI_ALREADY_STARTED) {
    return EFI_UNSUPPORTED;
  }

  return EFI_SUCCESS;
}

/**
  Tests whether a child handle is a child device of the controller.

  This function tests whether ChildHandle is one of the children of
  ControllerHandle.  This test is performed by checking to see if the protocol
  specified by ProtocolGuid is present on ControllerHandle and opened by
  ChildHandle with an attribute of EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER.
  If ProtocolGuid is NULL, then ASSERT().

  @param  ControllerHandle     A handle for a (parent) controller to test.
  @param  ChildHandle          A child handle to test.
  @param  ProtocolGuid         Supplies the protocol that the child controller
                               opens on its parent controller.

  @retval EFI_SUCCESS          ChildHandle is a child of the ControllerHandle.
  @retval EFI_UNSUPPORTED      ChildHandle is not a child of the
                               ControllerHandle.

**/
EFI_STATUS
EFIAPI
EfiTestChildHandle (
  IN CONST EFI_HANDLE  ControllerHandle,
  IN CONST EFI_HANDLE  ChildHandle,
  IN CONST EFI_GUID    *ProtocolGuid
  )
{
  EFI_STATUS                           Status;
  EFI_OPEN_PROTOCOL_INFORMATION_ENTRY  *OpenInfoBuffer;
  UINTN                                EntryCount;
  UINTN                                Index;

  ASSERT (ProtocolGuid != NULL);

  //
  // Retrieve the list of agents that are consuming the specific protocol
  // on ControllerHandle.
  //
  Status = gBS->OpenProtocolInformation (
                  ControllerHandle,
                  (EFI_GUID *)ProtocolGuid,
                  &OpenInfoBuffer,
                  &EntryCount
                  );
  if (EFI_ERROR (Status)) {
    return EFI_UNSUPPORTED;
  }

  //
  // Inspect if ChildHandle is one of the agents.
  //
  Status = EFI_UNSUPPORTED;
  for (Index = 0; Index < EntryCount; Index++) {
    if ((OpenInfoBuffer[Index].ControllerHandle == ChildHandle) &&
        ((OpenInfoBuffer[Index].Attributes & EFI_OPEN_PROTOCOL_BY_CHILD_CONTROLLER) != 0))
    {
      Status = EFI_SUCCESS;
      break;
    }
  }

  FreePool (OpenInfoBuffer);
  return Status;
}

/**
  This function checks the supported languages list for a target language,
  This only supports RFC 4646 Languages.

  @param  SupportedLanguages  The supported languages
  @param  TargetLanguage      The target language

  @retval Returns EFI_SUCCESS if the language is supported,
          EFI_UNSUPPORTED otherwise
**/
EFI_STATUS
EFIAPI
IsLanguageSupported (
  IN CONST CHAR8  *SupportedLanguages,
  IN CONST CHAR8  *TargetLanguage
  )
{
  UINTN  Index;

  while (*SupportedLanguages != 0) {
    for (Index = 0; SupportedLanguages[Index] != 0 && SupportedLanguages[Index] != ';'; Index++) {
    }

    if ((AsciiStrnCmp (SupportedLanguages, TargetLanguage, Index) == 0) && (TargetLanguage[Index] == 0)) {
      return EFI_SUCCESS;
    }

    SupportedLanguages += Index;
    for ( ; *SupportedLanguages != 0 && *SupportedLanguages == ';'; SupportedLanguages++) {
    }
  }

  return EFI_UNSUPPORTED;
}

/**
  This function looks up a Unicode string in UnicodeStringTable.

  If Language is a member of SupportedLanguages and a Unicode string is found in
  UnicodeStringTable that matches the language code specified by Language, then it
  is returned in UnicodeString.

  @param  Language                A pointer to the ISO 639-2 language code for the
                                  Unicode string to look up and return.
  @param  SupportedLanguages      A pointer to the set of ISO 639-2 language codes
                                  that the Unicode string table supports.  Language
                                  must be a member of this set.
  @param  UnicodeStringTable      A pointer to the table of Unicode strings.
  @param  UnicodeString           A pointer to the Unicode string from UnicodeStringTable
                                  that matches the language specified by Language.

  @retval EFI_SUCCESS             The Unicode string that matches the language
                                  specified by Language was found
                                  in the table of Unicode strings UnicodeStringTable,
                                  and it was returned in UnicodeString.
  @retval EFI_INVALID_PARAMETER   Language is NULL.
  @retval EFI_INVALID_PARAMETER   UnicodeString is NULL.
  @retval EFI_UNSUPPORTED         SupportedLanguages is NULL.
  @retval EFI_UNSUPPORTED         UnicodeStringTable is NULL.
  @retval EFI_UNSUPPORTED         The language specified by Language is not a
                                  member of SupportedLanguages.
  @retval EFI_UNSUPPORTED         The language specified by Language is not
                                  supported by UnicodeStringTable.

**/
EFI_STATUS
EFIAPI
LookupUnicodeString (
  IN CONST CHAR8                     *Language,
  IN CONST CHAR8                     *SupportedLanguages,
  IN CONST EFI_UNICODE_STRING_TABLE  *UnicodeStringTable,
  OUT CHAR16                         **UnicodeString
  )
{
  //
  // Make sure the parameters are valid
  //
  if ((Language == NULL) || (UnicodeString == NULL)) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // If there are no supported languages, or the Unicode String Table is empty, then the
  // Unicode String specified by Language is not supported by this Unicode String Table
  //
  if ((SupportedLanguages == NULL) || (UnicodeStringTable == NULL)) {
    return EFI_UNSUPPORTED;
  }

  //
  // Make sure Language is in the set of Supported Languages
  //
  while (*SupportedLanguages != 0) {
    if (CompareIso639LanguageCode (Language, SupportedLanguages)) {
      //
      // Search the Unicode String Table for the matching Language specifier
      //
      while (UnicodeStringTable->Language != NULL) {
        if (CompareIso639LanguageCode (Language, UnicodeStringTable->Language)) {
          //
          // A matching string was found, so return it
          //
          *UnicodeString = UnicodeStringTable->UnicodeString;
          return EFI_SUCCESS;
        }

        UnicodeStringTable++;
      }

      return EFI_UNSUPPORTED;
    }

    SupportedLanguages += 3;
  }

  return EFI_UNSUPPORTED;
}

/**
  This function looks up a Unicode string in UnicodeStringTable.

  If Language is a member of SupportedLanguages and a Unicode string is found in
  UnicodeStringTable that matches the language code specified by Language, then
  it is returned in UnicodeString.

  @param  Language             A pointer to an ASCII string containing the ISO 639-2 or the
                               RFC 4646 language code for the Unicode string to look up and
                               return. If Iso639Language is TRUE, then this ASCII string is
                               not assumed to be Null-terminated, and only the first three
                               characters are used. If Iso639Language is FALSE, then this ASCII
                               string must be Null-terminated.
  @param  SupportedLanguages   A pointer to a Null-terminated ASCII string that contains a
                               set of ISO 639-2 or RFC 4646 language codes that the Unicode
                               string table supports.  Language must be a member of this set.
                               If Iso639Language is TRUE, then this string contains one or more
                               ISO 639-2 language codes with no separator characters. If Iso639Language
                               is FALSE, then is string contains one or more RFC 4646 language
                               codes separated by ';'.
  @param  UnicodeStringTable   A pointer to the table of Unicode strings. Type EFI_UNICODE_STRING_TABLE
                               is defined in "Related Definitions".
  @param  UnicodeString        A pointer to the Null-terminated Unicode string from UnicodeStringTable
                               that matches the language specified by Language.
  @param  Iso639Language       Specifies the supported language code format. If it is TRUE, then
                               Language and SupportedLanguages follow ISO 639-2 language code format.
                               Otherwise, they follow RFC 4646 language code format.


  @retval  EFI_SUCCESS            The Unicode string that matches the language specified by Language
                                  was found in the table of Unicode strings UnicodeStringTable, and
                                  it was returned in UnicodeString.
  @retval  EFI_INVALID_PARAMETER  Language is NULL.
  @retval  EFI_INVALID_PARAMETER  UnicodeString is NULL.
  @retval  EFI_UNSUPPORTED        SupportedLanguages is NULL.
  @retval  EFI_UNSUPPORTED        UnicodeStringTable is NULL.
  @retval  EFI_UNSUPPORTED        The language specified by Language is not a member of SupportedLanguages.
  @retval  EFI_UNSUPPORTED        The language specified by Language is not supported by UnicodeStringTable.

**/
EFI_STATUS
EFIAPI
LookupUnicodeString2 (
  IN CONST CHAR8                     *Language,
  IN CONST CHAR8                     *SupportedLanguages,
  IN CONST EFI_UNICODE_STRING_TABLE  *UnicodeStringTable,
  OUT CHAR16                         **UnicodeString,
  IN BOOLEAN                         Iso639Language
  )
{
  BOOLEAN  Found;
  UINTN    Index;
  CHAR8    *LanguageString;

  //
  // Make sure the parameters are valid
  //
  if ((Language == NULL) || (UnicodeString == NULL)) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // If there are no supported languages, or the Unicode String Table is empty, then the
  // Unicode String specified by Language is not supported by this Unicode String Table
  //
  if ((SupportedLanguages == NULL) || (UnicodeStringTable == NULL)) {
    return EFI_UNSUPPORTED;
  }

  //
  // Make sure Language is in the set of Supported Languages
  //
  Found = FALSE;
  if (Iso639Language) {
    while (*SupportedLanguages != 0) {
      if (CompareIso639LanguageCode (Language, SupportedLanguages)) {
        Found = TRUE;
        break;
      }

      SupportedLanguages += 3;
    }
  } else {
    Found = !IsLanguageSupported (SupportedLanguages, Language);
  }

  //
  // If Language is not a member of SupportedLanguages, then return EFI_UNSUPPORTED
  //
  if (!Found) {
    return EFI_UNSUPPORTED;
  }

  //
  // Search the Unicode String Table for the matching Language specifier
  //
  while (UnicodeStringTable->Language != NULL) {
    LanguageString = UnicodeStringTable->Language;
    while (0 != *LanguageString) {
      for (Index = 0; LanguageString[Index] != 0 && LanguageString[Index] != ';'; Index++) {
      }

      if (AsciiStrnCmp (LanguageString, Language, Index) == 0) {
        *UnicodeString = UnicodeStringTable->UnicodeString;
        return EFI_SUCCESS;
      }

      LanguageString += Index;
      for (Index = 0; LanguageString[Index] != 0 && LanguageString[Index] == ';'; Index++) {
      }
    }

    UnicodeStringTable++;
  }

  return EFI_UNSUPPORTED;
}

/**
  This function adds a Unicode string to UnicodeStringTable.

  If Language is a member of SupportedLanguages then UnicodeString is added to
  UnicodeStringTable.  New buffers are allocated for both Language and
  UnicodeString.  The contents of Language and UnicodeString are copied into
  these new buffers.  These buffers are automatically freed when
  FreeUnicodeStringTable() is called.

  @param  Language                A pointer to the ISO 639-2 language code for the Unicode
                                  string to add.
  @param  SupportedLanguages      A pointer to the set of ISO 639-2 language codes
                                  that the Unicode string table supports.
                                  Language must be a member of this set.
  @param  UnicodeStringTable      A pointer to the table of Unicode strings.
  @param  UnicodeString           A pointer to the Unicode string to add.

  @retval EFI_SUCCESS             The Unicode string that matches the language
                                  specified by Language was found in the table of
                                  Unicode strings UnicodeStringTable, and it was
                                  returned in UnicodeString.
  @retval EFI_INVALID_PARAMETER   Language is NULL.
  @retval EFI_INVALID_PARAMETER   UnicodeString is NULL.
  @retval EFI_INVALID_PARAMETER   UnicodeString is an empty string.
  @retval EFI_UNSUPPORTED         SupportedLanguages is NULL.
  @retval EFI_ALREADY_STARTED     A Unicode string with language Language is
                                  already present in UnicodeStringTable.
  @retval EFI_OUT_OF_RESOURCES    There is not enough memory to add another
                                  Unicode string to UnicodeStringTable.
  @retval EFI_UNSUPPORTED         The language specified by Language is not a
                                  member of SupportedLanguages.

**/
EFI_STATUS
EFIAPI
AddUnicodeString (
  IN     CONST CHAR8               *Language,
  IN     CONST CHAR8               *SupportedLanguages,
  IN OUT EFI_UNICODE_STRING_TABLE  **UnicodeStringTable,
  IN     CONST CHAR16              *UnicodeString
  )
{
  UINTN                     NumberOfEntries;
  EFI_UNICODE_STRING_TABLE  *OldUnicodeStringTable;
  EFI_UNICODE_STRING_TABLE  *NewUnicodeStringTable;
  UINTN                     UnicodeStringLength;

  //
  // Make sure the parameter are valid
  //
  if ((Language == NULL) || (UnicodeString == NULL) || (UnicodeStringTable == NULL)) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // If there are no supported languages, then a Unicode String can not be added
  //
  if (SupportedLanguages == NULL) {
    return EFI_UNSUPPORTED;
  }

  //
  // If the Unicode String is empty, then a Unicode String can not be added
  //
  if (UnicodeString[0] == 0) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // Make sure Language is a member of SupportedLanguages
  //
  while (*SupportedLanguages != 0) {
    if (CompareIso639LanguageCode (Language, SupportedLanguages)) {
      //
      // Determine the size of the Unicode String Table by looking for a NULL Language entry
      //
      NumberOfEntries = 0;
      if (*UnicodeStringTable != NULL) {
        OldUnicodeStringTable = *UnicodeStringTable;
        while (OldUnicodeStringTable->Language != NULL) {
          if (CompareIso639LanguageCode (Language, OldUnicodeStringTable->Language)) {
            return EFI_ALREADY_STARTED;
          }

          OldUnicodeStringTable++;
          NumberOfEntries++;
        }
      }

      //
      // Allocate space for a new Unicode String Table.  It must hold the current number of
      // entries, plus 1 entry for the new Unicode String, plus 1 entry for the end of table
      // marker
      //
      NewUnicodeStringTable = AllocatePool ((NumberOfEntries + 2) * sizeof (EFI_UNICODE_STRING_TABLE));
      if (NewUnicodeStringTable == NULL) {
        return EFI_OUT_OF_RESOURCES;
      }

      //
      // If the current Unicode String Table contains any entries, then copy them to the
      // newly allocated Unicode String Table.
      //
      if (*UnicodeStringTable != NULL) {
        CopyMem (
          NewUnicodeStringTable,
          *UnicodeStringTable,
          NumberOfEntries * sizeof (EFI_UNICODE_STRING_TABLE)
          );
      }

      //
      // Allocate space for a copy of the Language specifier
      //
      NewUnicodeStringTable[NumberOfEntries].Language = AllocateCopyPool (3, Language);
      if (NewUnicodeStringTable[NumberOfEntries].Language == NULL) {
        FreePool (NewUnicodeStringTable);
        return EFI_OUT_OF_RESOURCES;
      }

      //
      // Compute the length of the Unicode String
      //
      for (UnicodeStringLength = 0; UnicodeString[UnicodeStringLength] != 0; UnicodeStringLength++) {
      }

      //
      // Allocate space for a copy of the Unicode String
      //
      NewUnicodeStringTable[NumberOfEntries].UnicodeString = AllocateCopyPool (
                                                               (UnicodeStringLength + 1) * sizeof (CHAR16),
                                                               UnicodeString
                                                               );
      if (NewUnicodeStringTable[NumberOfEntries].UnicodeString == NULL) {
        FreePool (NewUnicodeStringTable[NumberOfEntries].Language);
        FreePool (NewUnicodeStringTable);
        return EFI_OUT_OF_RESOURCES;
      }

      //
      // Mark the end of the Unicode String Table
      //
      NewUnicodeStringTable[NumberOfEntries + 1].Language      = NULL;
      NewUnicodeStringTable[NumberOfEntries + 1].UnicodeString = NULL;

      //
      // Free the old Unicode String Table
      //
      if (*UnicodeStringTable != NULL) {
        FreePool (*UnicodeStringTable);
      }

      //
      // Point UnicodeStringTable at the newly allocated Unicode String Table
      //
      *UnicodeStringTable = NewUnicodeStringTable;

      return EFI_SUCCESS;
    }

    SupportedLanguages += 3;
  }

  return EFI_UNSUPPORTED;
}

/**
  This function adds the Null-terminated Unicode string specified by UnicodeString
  to UnicodeStringTable.

  If Language is a member of SupportedLanguages then UnicodeString is added to
  UnicodeStringTable.  New buffers are allocated for both Language and UnicodeString.
  The contents of Language and UnicodeString are copied into these new buffers.
  These buffers are automatically freed when EfiLibFreeUnicodeStringTable() is called.

  @param  Language            A pointer to an ASCII string containing the ISO 639-2 or
                              the RFC 4646 language code for the Unicode string to add.
                              If Iso639Language is TRUE, then this ASCII string is not
                              assumed to be Null-terminated, and only the first three
                              chacters are used. If Iso639Language is FALSE, then this
                              ASCII string must be Null-terminated.
  @param  SupportedLanguages  A pointer to a Null-terminated ASCII string that contains
                              a set of ISO 639-2 or RFC 4646 language codes that the Unicode
                              string table supports.  Language must be a member of this set.
                              If Iso639Language is TRUE, then this string contains one or more
                              ISO 639-2 language codes with no separator characters.
                              If Iso639Language is FALSE, then is string contains one or more
                              RFC 4646 language codes separated by ';'.
  @param  UnicodeStringTable  A pointer to the table of Unicode strings. Type EFI_UNICODE_STRING_TABLE
                              is defined in "Related Definitions".
  @param  UnicodeString       A pointer to the Unicode string to add.
  @param  Iso639Language      Specifies the supported language code format. If it is TRUE,
                              then Language and SupportedLanguages follow ISO 639-2 language code format.
                              Otherwise, they follow RFC 4646 language code format.

  @retval EFI_SUCCESS            The Unicode string that matches the language specified by
                                 Language was found in the table of Unicode strings UnicodeStringTable,
                                 and it was returned in UnicodeString.
  @retval EFI_INVALID_PARAMETER  Language is NULL.
  @retval EFI_INVALID_PARAMETER  UnicodeString is NULL.
  @retval EFI_INVALID_PARAMETER  UnicodeString is an empty string.
  @retval EFI_UNSUPPORTED        SupportedLanguages is NULL.
  @retval EFI_ALREADY_STARTED    A Unicode string with language Language is already present in
                                 UnicodeStringTable.
  @retval EFI_OUT_OF_RESOURCES   There is not enough memory to add another Unicode string UnicodeStringTable.
  @retval EFI_UNSUPPORTED        The language specified by Language is not a member of SupportedLanguages.

**/
EFI_STATUS
EFIAPI
AddUnicodeString2 (
  IN     CONST CHAR8               *Language,
  IN     CONST CHAR8               *SupportedLanguages,
  IN OUT EFI_UNICODE_STRING_TABLE  **UnicodeStringTable,
  IN     CONST CHAR16              *UnicodeString,
  IN     BOOLEAN                   Iso639Language
  )
{
  UINTN                     NumberOfEntries;
  EFI_UNICODE_STRING_TABLE  *OldUnicodeStringTable;
  EFI_UNICODE_STRING_TABLE  *NewUnicodeStringTable;
  UINTN                     UnicodeStringLength;
  BOOLEAN                   Found;
  UINTN                     Index;
  CHAR8                     *LanguageString;

  //
  // Make sure the parameter are valid
  //
  if ((Language == NULL) || (UnicodeString == NULL) || (UnicodeStringTable == NULL)) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // If there are no supported languages, then a Unicode String can not be added
  //
  if (SupportedLanguages == NULL) {
    return EFI_UNSUPPORTED;
  }

  //
  // If the Unicode String is empty, then a Unicode String can not be added
  //
  if (UnicodeString[0] == 0) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // Make sure Language is a member of SupportedLanguages
  //
  Found = FALSE;
  if (Iso639Language) {
    while (*SupportedLanguages != 0) {
      if (CompareIso639LanguageCode (Language, SupportedLanguages)) {
        Found = TRUE;
        break;
      }

      SupportedLanguages += 3;
    }
  } else {
    Found = !IsLanguageSupported (SupportedLanguages, Language);
  }

  //
  // If Language is not a member of SupportedLanguages, then return EFI_UNSUPPORTED
  //
  if (!Found) {
    return EFI_UNSUPPORTED;
  }

  //
  // Determine the size of the Unicode String Table by looking for a NULL Language entry
  //
  NumberOfEntries = 0;
  if (*UnicodeStringTable != NULL) {
    OldUnicodeStringTable = *UnicodeStringTable;
    while (OldUnicodeStringTable->Language != NULL) {
      LanguageString = OldUnicodeStringTable->Language;

      while (*LanguageString != 0) {
        for (Index = 0; LanguageString[Index] != 0 && LanguageString[Index] != ';'; Index++) {
        }

        if (AsciiStrnCmp (Language, LanguageString, Index) == 0) {
          return EFI_ALREADY_STARTED;
        }

        LanguageString += Index;
        for ( ; *LanguageString != 0 && *LanguageString == ';'; LanguageString++) {
        }
      }

      OldUnicodeStringTable++;
      NumberOfEntries++;
    }
  }

  //
  // Allocate space for a new Unicode String Table.  It must hold the current number of
  // entries, plus 1 entry for the new Unicode String, plus 1 entry for the end of table
  // marker
  //
  NewUnicodeStringTable = AllocatePool ((NumberOfEntries + 2) * sizeof (EFI_UNICODE_STRING_TABLE));
  if (NewUnicodeStringTable == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  //
  // If the current Unicode String Table contains any entries, then copy them to the
  // newly allocated Unicode String Table.
  //
  if (*UnicodeStringTable != NULL) {
    CopyMem (
      NewUnicodeStringTable,
      *UnicodeStringTable,
      NumberOfEntries * sizeof (EFI_UNICODE_STRING_TABLE)
      );
  }

  //
  // Allocate space for a copy of the Language specifier
  //
  NewUnicodeStringTable[NumberOfEntries].Language = AllocateCopyPool (AsciiStrSize (Language), Language);
  if (NewUnicodeStringTable[NumberOfEntries].Language == NULL) {
    FreePool (NewUnicodeStringTable);
    return EFI_OUT_OF_RESOURCES;
  }

  //
  // Compute the length of the Unicode String
  //
  for (UnicodeStringLength = 0; UnicodeString[UnicodeStringLength] != 0; UnicodeStringLength++) {
  }

  //
  // Allocate space for a copy of the Unicode String
  //
  NewUnicodeStringTable[NumberOfEntries].UnicodeString = AllocateCopyPool (StrSize (UnicodeString), UnicodeString);
  if (NewUnicodeStringTable[NumberOfEntries].UnicodeString == NULL) {
    FreePool (NewUnicodeStringTable[NumberOfEntries].Language);
    FreePool (NewUnicodeStringTable);
    return EFI_OUT_OF_RESOURCES;
  }

  //
  // Mark the end of the Unicode String Table
  //
  NewUnicodeStringTable[NumberOfEntries + 1].Language      = NULL;
  NewUnicodeStringTable[NumberOfEntries + 1].UnicodeString = NULL;

  //
  // Free the old Unicode String Table
  //
  if (*UnicodeStringTable != NULL) {
    FreePool (*UnicodeStringTable);
  }

  //
  // Point UnicodeStringTable at the newly allocated Unicode String Table
  //
  *UnicodeStringTable = NewUnicodeStringTable;

  return EFI_SUCCESS;
}

/**
  This function frees the table of Unicode strings in UnicodeStringTable.

  If UnicodeStringTable is NULL, then EFI_SUCCESS is returned.
  Otherwise, each language code, and each Unicode string in the Unicode string
  table are freed, and EFI_SUCCESS is returned.

  @param  UnicodeStringTable  A pointer to the table of Unicode strings.

  @retval EFI_SUCCESS         The Unicode string table was freed.

**/
EFI_STATUS
EFIAPI
FreeUnicodeStringTable (
  IN EFI_UNICODE_STRING_TABLE  *UnicodeStringTable
  )
{
  UINTN  Index;

  //
  // If the Unicode String Table is NULL, then it is already freed
  //
  if (UnicodeStringTable == NULL) {
    return EFI_SUCCESS;
  }

  //
  // Loop through the Unicode String Table until we reach the end of table marker
  //
  for (Index = 0; UnicodeStringTable[Index].Language != NULL; Index++) {
    //
    // Free the Language string from the Unicode String Table
    //
    FreePool (UnicodeStringTable[Index].Language);

    //
    // Free the Unicode String from the Unicode String Table
    //
    if (UnicodeStringTable[Index].UnicodeString != NULL) {
      FreePool (UnicodeStringTable[Index].UnicodeString);
    }
  }

  //
  // Free the Unicode String Table itself
  //
  FreePool (UnicodeStringTable);

  return EFI_SUCCESS;
}

/**
  Returns the status whether get the variable success. The function retrieves
  variable  through the UEFI Runtime Service GetVariable().  The
  returned buffer is allocated using AllocatePool().  The caller is responsible
  for freeing this buffer with FreePool().

  If Name  is NULL, then ASSERT().
  If Guid  is NULL, then ASSERT().
  If Value is NULL, then ASSERT().

  @param[in]  Name  The pointer to a Null-terminated Unicode string.
  @param[in]  Guid  The pointer to an EFI_GUID structure
  @param[out] Value The buffer point saved the variable info.
  @param[out] Size  The buffer size of the variable.

  @return EFI_OUT_OF_RESOURCES      Allocate buffer failed.
  @return EFI_SUCCESS               Find the specified variable.
  @return Others Errors             Return errors from call to gRT->GetVariable.

**/
EFI_STATUS
EFIAPI
GetVariable2 (
  IN CONST CHAR16    *Name,
  IN CONST EFI_GUID  *Guid,
  OUT VOID           **Value,
  OUT UINTN          *Size OPTIONAL
  )
{
  EFI_STATUS  Status;
  UINTN       BufferSize;

  ASSERT (Name != NULL && Guid != NULL && Value != NULL);

  //
  // Try to get the variable size.
  //
  BufferSize = 0;
  *Value     = NULL;
  if (Size != NULL) {
    *Size = 0;
  }

  Status = gRT->GetVariable ((CHAR16 *)Name, (EFI_GUID *)Guid, NULL, &BufferSize, *Value);
  if (Status != EFI_BUFFER_TOO_SMALL) {
    return Status;
  }

  //
  // Allocate buffer to get the variable.
  //
  *Value = AllocatePool (BufferSize);
  ASSERT (*Value != NULL);
  if (*Value == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  //
  // Get the variable data.
  //
  Status = gRT->GetVariable ((CHAR16 *)Name, (EFI_GUID *)Guid, NULL, &BufferSize, *Value);
  if (EFI_ERROR (Status)) {
    FreePool (*Value);
    *Value = NULL;
  }

  if (Size != NULL) {
    *Size = BufferSize;
  }

  return Status;
}

/** Return the attributes of the variable.

  Returns the status whether get the variable success. The function retrieves
  variable  through the UEFI Runtime Service GetVariable().  The
  returned buffer is allocated using AllocatePool().  The caller is responsible
  for freeing this buffer with FreePool().  The attributes are returned if
  the caller provides a valid Attribute parameter.

  If Name  is NULL, then ASSERT().
  If Guid  is NULL, then ASSERT().
  If Value is NULL, then ASSERT().

  @param[in]  Name  The pointer to a Null-terminated Unicode string.
  @param[in]  Guid  The pointer to an EFI_GUID structure
  @param[out] Value The buffer point saved the variable info.
  @param[out] Size  The buffer size of the variable.
  @param[out] Attr  The pointer to the variable attributes as found in var store

  @retval EFI_OUT_OF_RESOURCES      Allocate buffer failed.
  @retval EFI_SUCCESS               Find the specified variable.
  @retval Others Errors             Return errors from call to gRT->GetVariable.

**/
EFI_STATUS
EFIAPI
GetVariable3 (
  IN CONST CHAR16    *Name,
  IN CONST EFI_GUID  *Guid,
  OUT VOID           **Value,
  OUT UINTN          *Size OPTIONAL,
  OUT UINT32         *Attr OPTIONAL
  )
{
  EFI_STATUS  Status;
  UINTN       BufferSize;

  ASSERT (Name != NULL && Guid != NULL && Value != NULL);

  //
  // Try to get the variable size.
  //
  BufferSize = 0;
  *Value     = NULL;
  if (Size != NULL) {
    *Size = 0;
  }

  if (Attr != NULL) {
    *Attr = 0;
  }

  Status = gRT->GetVariable ((CHAR16 *)Name, (EFI_GUID *)Guid, Attr, &BufferSize, *Value);
  if (Status != EFI_BUFFER_TOO_SMALL) {
    return Status;
  }

  //
  // Allocate buffer to get the variable.
  //
  *Value = AllocatePool (BufferSize);
  ASSERT (*Value != NULL);
  if (*Value == NULL) {
    return EFI_OUT_OF_RESOURCES;
  }

  //
  // Get the variable data.
  //
  Status = gRT->GetVariable ((CHAR16 *)Name, (EFI_GUID *)Guid, Attr, &BufferSize, *Value);
  if (EFI_ERROR (Status)) {
    FreePool (*Value);
    *Value = NULL;
  }

  if (Size != NULL) {
    *Size = BufferSize;
  }

  return Status;
}

/**
  Returns a pointer to an allocated buffer that contains the contents of a
  variable retrieved through the UEFI Runtime Service GetVariable().  This
  function always uses the EFI_GLOBAL_VARIABLE GUID to retrieve variables.
  The returned buffer is allocated using AllocatePool().  The caller is
  responsible for freeing this buffer with FreePool().

  If Name is NULL, then ASSERT().
  If Value is NULL, then ASSERT().

  @param[in]  Name  The pointer to a Null-terminated Unicode string.
  @param[out] Value The buffer point saved the variable info.
  @param[out] Size  The buffer size of the variable.

  @return EFI_OUT_OF_RESOURCES      Allocate buffer failed.
  @return EFI_SUCCESS               Find the specified variable.
  @return Others Errors             Return errors from call to gRT->GetVariable.

**/
EFI_STATUS
EFIAPI
GetEfiGlobalVariable2 (
  IN CONST CHAR16  *Name,
  OUT VOID         **Value,
  OUT UINTN        *Size OPTIONAL
  )
{
  return GetVariable2 (Name, &gEfiGlobalVariableGuid, Value, Size);
}

/**
  Returns a pointer to an allocated buffer that contains the best matching language
  from a set of supported languages.

  This function supports both ISO 639-2 and RFC 4646 language codes, but language
  code types may not be mixed in a single call to this function.  The language
  code returned is allocated using AllocatePool().  The caller is responsible for
  freeing the allocated buffer using FreePool().  This function supports a variable
  argument list that allows the caller to pass in a prioritized list of language
  codes to test against all the language codes in SupportedLanguages.

  If SupportedLanguages is NULL, then ASSERT().

  @param[in]  SupportedLanguages  A pointer to a Null-terminated ASCII string that
                                  contains a set of language codes in the format
                                  specified by Iso639Language.
  @param[in]  Iso639Language      If not zero, then all language codes are assumed to be
                                  in ISO 639-2 format.  If zero, then all language
                                  codes are assumed to be in RFC 4646 language format
  @param[in]  ...                 A variable argument list that contains pointers to
                                  Null-terminated ASCII strings that contain one or more
                                  language codes in the format specified by Iso639Language.
                                  The first language code from each of these language
                                  code lists is used to determine if it is an exact or
                                  close match to any of the language codes in
                                  SupportedLanguages.  Close matches only apply to RFC 4646
                                  language codes, and the matching algorithm from RFC 4647
                                  is used to determine if a close match is present.  If
                                  an exact or close match is found, then the matching
                                  language code from SupportedLanguages is returned.  If
                                  no matches are found, then the next variable argument
                                  parameter is evaluated.  The variable argument list
                                  is terminated by a NULL.

  @retval NULL   The best matching language could not be found in SupportedLanguages.
  @retval NULL   There are not enough resources available to return the best matching
                 language.
  @retval Other  A pointer to a Null-terminated ASCII string that is the best matching
                 language in SupportedLanguages.

**/
CHAR8 *
EFIAPI
GetBestLanguage (
  IN CONST CHAR8  *SupportedLanguages,
  IN UINTN        Iso639Language,
  ...
  )
{
  VA_LIST      Args;
  CHAR8        *Language;
  UINTN        CompareLength;
  UINTN        LanguageLength;
  CONST CHAR8  *Supported;
  CHAR8        *BestLanguage;

  ASSERT (SupportedLanguages != NULL);

  VA_START (Args, Iso639Language);
  while ((Language = VA_ARG (Args, CHAR8 *)) != NULL) {
    //
    // Default to ISO 639-2 mode
    //
    CompareLength  = 3;
    LanguageLength = MIN (3, AsciiStrLen (Language));

    //
    // If in RFC 4646 mode, then determine the length of the first RFC 4646 language code in Language
    //
    if (Iso639Language == 0) {
      for (LanguageLength = 0; Language[LanguageLength] != 0 && Language[LanguageLength] != ';'; LanguageLength++) {
      }
    }

    //
    // Trim back the length of Language used until it is empty
    //
    while (LanguageLength > 0) {
      //
      // Loop through all language codes in SupportedLanguages
      //
      for (Supported = SupportedLanguages; *Supported != '\0'; Supported += CompareLength) {
        //
        // In RFC 4646 mode, then Loop through all language codes in SupportedLanguages
        //
        if (Iso639Language == 0) {
          //
          // Skip ';' characters in Supported
          //
          for ( ; *Supported != '\0' && *Supported == ';'; Supported++) {
          }

          //
          // Determine the length of the next language code in Supported
          //
          for (CompareLength = 0; Supported[CompareLength] != 0 && Supported[CompareLength] != ';'; CompareLength++) {
          }

          //
          // If Language is longer than the Supported, then skip to the next language
          //
          if (LanguageLength > CompareLength) {
            continue;
          }
        }

        //
        // See if the first LanguageLength characters in Supported match Language
        //
        if (AsciiStrnCmp (Supported, Language, LanguageLength) == 0) {
          VA_END (Args);
          //
          // Allocate, copy, and return the best matching language code from SupportedLanguages
          //
          BestLanguage = AllocateZeroPool (CompareLength + 1);
          if (BestLanguage == NULL) {
            return NULL;
          }

          return CopyMem (BestLanguage, Supported, CompareLength);
        }
      }

      if (Iso639Language != 0) {
        //
        // If ISO 639 mode, then each language can only be tested once
        //
        LanguageLength = 0;
      } else {
        //
        // If RFC 4646 mode, then trim Language from the right to the next '-' character
        //
        for (LanguageLength--; LanguageLength > 0 && Language[LanguageLength] != '-'; LanguageLength--) {
        }
      }
    }
  }

  VA_END (Args);

  //
  // No matches were found
  //
  return NULL;
}

/**
  Returns an array of protocol instance that matches the given protocol.

  @param[in]  Protocol      Provides the protocol to search for.
  @param[out] NoProtocols   The number of protocols returned in Buffer.
  @param[out] Buffer        A pointer to the buffer to return the requested
                            array of protocol instances that match Protocol.
                            The returned buffer is allocated using
                            EFI_BOOT_SERVICES.AllocatePool().  The caller is
                            responsible for freeing this buffer with
                            EFI_BOOT_SERVICES.FreePool().

  @retval EFI_SUCCESS            The array of protocols was returned in Buffer,
                                 and the number of protocols in Buffer was
                                 returned in NoProtocols.
  @retval EFI_NOT_FOUND          No protocols found.
  @retval EFI_OUT_OF_RESOURCES   There is not enough pool memory to store the
                                 matching results.
  @retval EFI_INVALID_PARAMETER  Protocol is NULL.
  @retval EFI_INVALID_PARAMETER  NoProtocols is NULL.
  @retval EFI_INVALID_PARAMETER  Buffer is NULL.

**/
EFI_STATUS
EFIAPI
EfiLocateProtocolBuffer (
  IN  EFI_GUID  *Protocol,
  OUT UINTN     *NoProtocols,
  OUT VOID      ***Buffer
  )
{
  EFI_STATUS  Status;
  UINTN       NoHandles;
  EFI_HANDLE  *HandleBuffer;
  UINTN       Index;

  //
  // Check input parameters
  //
  if ((Protocol == NULL) || (NoProtocols == NULL) || (Buffer == NULL)) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // Initialze output parameters
  //
  *NoProtocols = 0;
  *Buffer      = NULL;

  //
  // Retrieve the array of handles that support Protocol
  //
  Status = gBS->LocateHandleBuffer (
                  ByProtocol,
                  Protocol,
                  NULL,
                  &NoHandles,
                  &HandleBuffer
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  //
  // Allocate array of protocol instances
  //
  Status = gBS->AllocatePool (
                  EfiBootServicesData,
                  NoHandles * sizeof (VOID *),
                  (VOID **)Buffer
                  );
  if (EFI_ERROR (Status)) {
    //
    // Free the handle buffer
    //
    gBS->FreePool (HandleBuffer);
    return EFI_OUT_OF_RESOURCES;
  }

  ZeroMem (*Buffer, NoHandles * sizeof (VOID *));

  //
  // Lookup Protocol on each handle in HandleBuffer to fill in the array of
  // protocol instances.  Handle case where protocol instance was present when
  // LocateHandleBuffer() was called, but is not present when HandleProtocol()
  // is called.
  //
  for (Index = 0, *NoProtocols = 0; Index < NoHandles; Index++) {
    Status = gBS->HandleProtocol (
                    HandleBuffer[Index],
                    Protocol,
                    &((*Buffer)[*NoProtocols])
                    );
    if (!EFI_ERROR (Status)) {
      (*NoProtocols)++;
    }
  }

  //
  // Free the handle buffer
  //
  gBS->FreePool (HandleBuffer);

  //
  // Make sure at least one protocol instance was found
  //
  if (*NoProtocols == 0) {
    gBS->FreePool (*Buffer);
    *Buffer = NULL;
    return EFI_NOT_FOUND;
  }

  return EFI_SUCCESS;
}

/**
  Open or create a file or directory, possibly creating the chain of
  directories leading up to the directory.

  EfiOpenFileByDevicePath() first locates EFI_SIMPLE_FILE_SYSTEM_PROTOCOL on
  FilePath, and opens the root directory of that filesystem with
  EFI_SIMPLE_FILE_SYSTEM_PROTOCOL.OpenVolume().

  On the remaining device path, the longest initial sequence of
  FILEPATH_DEVICE_PATH nodes is node-wise traversed with
  EFI_FILE_PROTOCOL.Open().

  (As a consequence, if OpenMode includes EFI_FILE_MODE_CREATE, and Attributes
  includes EFI_FILE_DIRECTORY, and each FILEPATH_DEVICE_PATH specifies a single
  pathname component, then EfiOpenFileByDevicePath() ensures that the specified
  series of subdirectories exist on return.)

  The EFI_FILE_PROTOCOL identified by the last FILEPATH_DEVICE_PATH node is
  output to the caller; intermediate EFI_FILE_PROTOCOL instances are closed. If
  there are no FILEPATH_DEVICE_PATH nodes past the node that identifies the
  filesystem, then the EFI_FILE_PROTOCOL of the root directory of the
  filesystem is output to the caller. If a device path node that is different
  from FILEPATH_DEVICE_PATH is encountered relative to the filesystem, the
  traversal is stopped with an error, and a NULL EFI_FILE_PROTOCOL is output.

  @param[in,out] FilePath  On input, the device path to the file or directory
                           to open or create. The caller is responsible for
                           ensuring that the device path pointed-to by FilePath
                           is well-formed. On output, FilePath points one past
                           the last node in the original device path that has
                           been successfully processed. FilePath is set on
                           output even if EfiOpenFileByDevicePath() returns an
                           error.

  @param[out] File         On error, File is set to NULL. On success, File is
                           set to the EFI_FILE_PROTOCOL of the root directory
                           of the filesystem, if there are no
                           FILEPATH_DEVICE_PATH nodes in FilePath; otherwise,
                           File is set to the EFI_FILE_PROTOCOL identified by
                           the last node in FilePath.

  @param[in] OpenMode      The OpenMode parameter to pass to
                           EFI_FILE_PROTOCOL.Open().

  @param[in] Attributes    The Attributes parameter to pass to
                           EFI_FILE_PROTOCOL.Open().

  @retval EFI_SUCCESS            The file or directory has been opened or
                                 created.

  @retval EFI_INVALID_PARAMETER  FilePath is NULL; or File is NULL; or FilePath
                                 contains a device path node, past the node
                                 that identifies
                                 EFI_SIMPLE_FILE_SYSTEM_PROTOCOL, that is not a
                                 FILEPATH_DEVICE_PATH node.

  @retval EFI_OUT_OF_RESOURCES   Memory allocation failed.

  @return                        Error codes propagated from the
                                 LocateDevicePath() and OpenProtocol() boot
                                 services, and from the
                                 EFI_SIMPLE_FILE_SYSTEM_PROTOCOL.OpenVolume()
                                 and EFI_FILE_PROTOCOL.Open() member functions.
**/
EFI_STATUS
EFIAPI
EfiOpenFileByDevicePath (
  IN OUT EFI_DEVICE_PATH_PROTOCOL  **FilePath,
  OUT    EFI_FILE_PROTOCOL         **File,
  IN     UINT64                    OpenMode,
  IN     UINT64                    Attributes
  )
{
  EFI_STATUS                       Status;
  EFI_HANDLE                       FileSystemHandle;
  EFI_SIMPLE_FILE_SYSTEM_PROTOCOL  *FileSystem;
  EFI_FILE_PROTOCOL                *LastFile;
  FILEPATH_DEVICE_PATH             *FilePathNode;
  CHAR16                           *AlignedPathName;
  CHAR16                           *PathName;
  EFI_FILE_PROTOCOL                *NextFile;

  if (File == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  *File = NULL;

  if (FilePath == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  //
  // Look up the filesystem.
  //
  Status = gBS->LocateDevicePath (
                  &gEfiSimpleFileSystemProtocolGuid,
                  FilePath,
                  &FileSystemHandle
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  Status = gBS->OpenProtocol (
                  FileSystemHandle,
                  &gEfiSimpleFileSystemProtocolGuid,
                  (VOID **)&FileSystem,
                  gImageHandle,
                  NULL,
                  EFI_OPEN_PROTOCOL_GET_PROTOCOL
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  //
  // Open the root directory of the filesystem. After this operation succeeds,
  // we have to release LastFile on error.
  //
  Status = FileSystem->OpenVolume (FileSystem, &LastFile);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  //
  // Traverse the device path nodes relative to the filesystem.
  //
  while (!IsDevicePathEnd (*FilePath)) {
    if ((DevicePathType (*FilePath) != MEDIA_DEVICE_PATH) ||
        (DevicePathSubType (*FilePath) != MEDIA_FILEPATH_DP))
    {
      Status = EFI_INVALID_PARAMETER;
      goto CloseLastFile;
    }

    FilePathNode = (FILEPATH_DEVICE_PATH *)*FilePath;

    //
    // FilePathNode->PathName may be unaligned, and the UEFI specification
    // requires pointers that are passed to protocol member functions to be
    // aligned. Create an aligned copy of the pathname if necessary.
    //
    if ((UINTN)FilePathNode->PathName % sizeof *FilePathNode->PathName == 0) {
      AlignedPathName = NULL;
      PathName        = FilePathNode->PathName;
    } else {
      AlignedPathName = AllocateCopyPool (
                          (DevicePathNodeLength (FilePathNode) -
                           SIZE_OF_FILEPATH_DEVICE_PATH),
                          FilePathNode->PathName
                          );
      if (AlignedPathName == NULL) {
        Status = EFI_OUT_OF_RESOURCES;
        goto CloseLastFile;
      }

      PathName = AlignedPathName;
    }

    //
    // Open or create the file corresponding to the next pathname fragment.
    //
    Status = LastFile->Open (
                         LastFile,
                         &NextFile,
                         PathName,
                         OpenMode,
                         Attributes
                         );

    //
    // Release any AlignedPathName on both error and success paths; PathName is
    // no longer needed.
    //
    if (AlignedPathName != NULL) {
      FreePool (AlignedPathName);
    }

    if (EFI_ERROR (Status)) {
      goto CloseLastFile;
    }

    //
    // Advance to the next device path node.
    //
    LastFile->Close (LastFile);
    LastFile  = NextFile;
    *FilePath = NextDevicePathNode (FilePathNode);
  }

  *File = LastFile;
  return EFI_SUCCESS;

CloseLastFile:
  LastFile->Close (LastFile);

  //
  // We are on the error path; we must have set an error Status for returning
  // to the caller.
  //
  ASSERT (EFI_ERROR (Status));
  return Status;
}