ShellPkg: Add AcpiViewCommandLib

The UefiShellAcpiViewCommandLib is converted from NULL library to a
named library so that it may be used in modules other than shell.
The library interface exposes the main method for to AcpiView
functionality as well as a helper method to dump a buffer to a file.

The Shell module is still built by pulling UefiShellAcpiViewCommandLib
as a NULL library to preserve the modularity of shell builds.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Zhichao Gao <zhichao.gao@intel.com>
Reviewed-by: Zhichao Gao <zhichao.gao@intel.com>
Signed-off-by: Tomas Pilar <tomas.pilar@arm.com>

ShellPkg/Include/Library/AcpiViewCommandLib.h

@@ -0,0 +1,46 @@
+/** @file
+  Library providing 'acpiview' functionality to display and
+  validate installed ACPI tables.
+
+  Copyright (c) 2016 - 2020, ARM Limited. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#ifndef ACPI_VIEW_COMMAND_LIB_H_
+#define ACPI_VIEW_COMMAND_LIB_H_
+
+/**
+  Dump a buffer to a file. Print error message if a file cannot be created.
+
+  @param[in] FileName   The filename that shall be created to contain the buffer.
+  @param[in] Buffer     Pointer to buffer that shall be dumped.
+  @param[in] BufferSize The size of buffer to be dumped in bytes.
+
+  @return The number of bytes that were written
+**/
+UINTN
+EFIAPI
+ShellDumpBufferToFile (
+  IN CONST CHAR16* FileNameBuffer,
+  IN CONST VOID*   Buffer,
+  IN CONST UINTN   BufferSize
+  );
+
+/**
+  Display and validate ACPI tables.
+
+  @param[in] ImageHandle  Handle to the Image (NULL if internal).
+  @param[in] SystemTable  Pointer to the System Table (NULL if internal).
+
+  @retval SHELL_INVALID_PARAMETER The command line invocation could not be parsed.
+  @retval SHELL_NOT_FOUND         The command failed.
+  @retval SHELL_SUCCESS           The command was successful.
+**/
+SHELL_STATUS
+EFIAPI
+ShellCommandRunAcpiView (
+  IN EFI_HANDLE        ImageHandle,
+  IN EFI_SYSTEM_TABLE  *SystemTable
+  );
+
+#endif // UEFI_SHELL_ACPIVIEW_COMMAND_LIB_H_