[edk2-platforms][PATCH v4 2/2] Ext4Pkg: Add base containing record macro for EXT4_FILE

["Savva Mitrofanov" <savvamtr@gmail.com>]

We shouldn't use direct casts, because in the future it could break
the code, so using BASE_CR would be safe against possible structure
changes and rearrangements

Cc: Marvin Häuser <mhaeuser@posteo.de>
Cc: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Vitaly Cheptsov <vit9696@protonmail.com>
Signed-off-by: Savva Mitrofanov <savvamtr@gmail.com>
---
 Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h |  2 ++
 Features/Ext4Pkg/Ext4Dxe/File.c    | 16 ++++++++--------
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
index c1df9d1149e4..1e63e6282fa5 100644
--- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
+++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
@@ -382,6 +382,8 @@ struct _Ext4File {
   EXT4_DENTRY           *Dentry;
 };
 
+#define EXT4_FILE_FROM_THIS(This)  BASE_CR ((This), EXT4_FILE, Protocol)
+
 #define EXT4_FILE_FROM_OPEN_FILES_NODE(Node)                                   \
   BASE_CR(Node, EXT4_FILE, OpenFilesListNode)
 
diff --git a/Features/Ext4Pkg/Ext4Dxe/File.c b/Features/Ext4Pkg/Ext4Dxe/File.c
index ae9230d6422b..b1744ad56c98 100644
--- a/Features/Ext4Pkg/Ext4Dxe/File.c
+++ b/Features/Ext4Pkg/Ext4Dxe/File.c
@@ -562,7 +562,7 @@ Ext4Open (
   EXT4_FILE   *FoundFile;
   EXT4_FILE   *Source;
 
-  Source = (EXT4_FILE *)This;
+  Source = EXT4_FILE_FROM_THIS (This);
 
   //
   // Reset SymLoops counter
@@ -599,7 +599,7 @@ Ext4Close (
   IN EFI_FILE_PROTOCOL  *This
   )
 {
-  return Ext4CloseInternal ((EXT4_FILE *)This);
+  return Ext4CloseInternal (EXT4_FILE_FROM_THIS (This));
 }
 
 /**
@@ -680,7 +680,7 @@ Ext4ReadFile (
   EXT4_PARTITION  *Partition;
   EFI_STATUS      Status;
 
-  File      = (EXT4_FILE *)This;
+  File      = EXT4_FILE_FROM_THIS (This);
   Partition = File->Partition;
 
   ASSERT (Ext4FileIsOpenable (File));
@@ -731,7 +731,7 @@ Ext4WriteFile (
 {
   EXT4_FILE  *File;
 
-  File = (EXT4_FILE *)This;
+  File = EXT4_FILE_FROM_THIS (This);
 
   if (!(File->OpenMode & EFI_FILE_MODE_WRITE)) {
     return EFI_ACCESS_DENIED;
@@ -761,7 +761,7 @@ Ext4GetPosition (
 {
   EXT4_FILE  *File;
 
-  File = (EXT4_FILE *)This;
+  File = EXT4_FILE_FROM_THIS (This);
 
   if (Ext4FileIsDir (File)) {
     return EFI_UNSUPPORTED;
@@ -794,7 +794,7 @@ Ext4SetPosition (
 {
   EXT4_FILE  *File;
 
-  File = (EXT4_FILE *)This;
+  File = EXT4_FILE_FROM_THIS (This);
 
   // Only seeks to 0 (so it resets the ReadDir operation) are allowed
   if (Ext4FileIsDir (File) && (Position != 0)) {
@@ -1062,7 +1062,7 @@ Ext4GetInfo (
   EXT4_FILE       *File;
   EXT4_PARTITION  *Partition;
 
-  File      = (EXT4_FILE *)This;
+  File      = EXT4_FILE_FROM_THIS (This);
   Partition = File->Partition;
 
   if (CompareGuid (InformationType, &gEfiFileInfoGuid)) {
@@ -1179,7 +1179,7 @@ Ext4SetInfo (
   EXT4_FILE       *File;
   EXT4_PARTITION  *Partition;
 
-  File      = (EXT4_FILE *)This;
+  File      = EXT4_FILE_FROM_THIS (This);
   Partition = File->Partition;
 
   if (Partition->ReadOnly) {
-- 
2.37.1