ArmPkg/BaseMemoryLibStm: implement new IsZeroBuffer() API function

BaseMemoryLib has recently been extended with an API function
IsZeroBuffer(), so copy the default implementation into BaseMemoryLibStm
as well.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

ArmPkg/Library/BaseMemoryLibStm/BaseMemoryLibStm.inf

@@ -45,6 +45,7 @@
   SetMem16Wrapper.c
   SetMemWrapper.c
   CopyMemWrapper.c
+  IsZeroBufferWrapper.c
   MemLibGeneric.c
   MemLibGuid.c
   MemLibInternals.h

ArmPkg/Library/BaseMemoryLibStm/IsZeroBufferWrapper.c

@@ -0,0 +1,54 @@
+/** @file
+  Implementation of IsZeroBuffer function.
+
+  The following BaseMemoryLib instances contain the same copy of this file:
+
+    BaseMemoryLib
+    BaseMemoryLibMmx
+    BaseMemoryLibSse2
+    BaseMemoryLibRepStr
+    BaseMemoryLibOptDxe
+    BaseMemoryLibOptPei
+    PeiMemoryLib
+    UefiMemoryLib
+
+  Copyright (c) 2016, 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 "MemLibInternals.h"
+
+/**
+  Checks if the contents of a buffer are all zeros.
+
+  This function checks whether the contents of a buffer are all zeros. If the
+  contents are all zeros, return TRUE. Otherwise, return FALSE.
+
+  If Length > 0 and Buffer is NULL, then ASSERT().
+  If Length is greater than (MAX_ADDRESS - Buffer + 1), then ASSERT().
+
+  @param  Buffer      The pointer to the buffer to be checked.
+  @param  Length      The size of the buffer (in bytes) to be checked.
+
+  @retval TRUE        Contents of the buffer are all zeros.
+  @retval FALSE       Contents of the buffer are not all zeros.
+
+**/
+BOOLEAN
+EFIAPI
+IsZeroBuffer (
+  IN CONST VOID  *Buffer,
+  IN UINTN       Length
+  )
+{
+  ASSERT (!(Buffer == NULL && Length > 0));
+  ASSERT ((Length - 1) <= (MAX_ADDRESS - (UINTN)Buffer));
+  return InternalMemIsZeroBuffer (Buffer, Length);
+}

ArmPkg/Library/BaseMemoryLibStm/MemLibGeneric.c

@@ -262,3 +262,32 @@ InternalMemScanMem64 (
   } while (--Length != 0);
   return NULL;
 }
+
+/**
+  Checks whether the contents of a buffer are all zeros.
+
+  @param  Buffer  The pointer to the buffer to be checked.
+  @param  Length  The size of the buffer (in bytes) to be checked.
+
+  @retval TRUE    Contents of the buffer are all zeros.
+  @retval FALSE   Contents of the buffer are not all zeros.
+
+**/
+BOOLEAN
+EFIAPI
+InternalMemIsZeroBuffer (
+  IN CONST VOID  *Buffer,
+  IN UINTN       Length
+  )
+{
+  CONST UINT8 *BufferData;
+  UINTN       Index;
+
+  BufferData = Buffer;
+  for (Index = 0; Index < Length; Index++) {
+    if (BufferData[Index] != 0) {
+      return FALSE;
+    }
+  }
+  return TRUE;
+}

ArmPkg/Library/BaseMemoryLibStm/MemLibInternals.h

@@ -231,4 +231,21 @@ InternalMemScanMem64 (
   IN      UINT64                    Value
   );
 
+/**
+  Checks whether the contents of a buffer are all zeros.
+
+  @param  Buffer  The pointer to the buffer to be checked.
+  @param  Length  The size of the buffer (in bytes) to be checked.
+
+  @retval TRUE    Contents of the buffer are all zeros.
+  @retval FALSE   Contents of the buffer are not all zeros.
+
+**/
+BOOLEAN
+EFIAPI
+InternalMemIsZeroBuffer (
+  IN CONST VOID  *Buffer,
+  IN UINTN       Length
+  );
+
 #endif