From a3b6740302459c24a3d406bf86442af035956c27 Mon Sep 17 00:00:00 2001
From: Qian Qian <qiqian82@gmail.com>
Date: Fri, 31 Mar 2023 15:00:49 +0800
Subject: [PATCH] align buffer at 64-byte boundary so that memcpy can take
 advantage of simd

---
 dokan/dokan.c | 4 ++--
 sys/public.h  | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/dokan/dokan.c b/dokan/dokan.c
index ee205a81..5624c01c 100644
--- a/dokan/dokan.c
+++ b/dokan/dokan.c
@@ -1366,8 +1366,8 @@ VOID DOKANAPI DokanMapKernelToUserCreateFileFlags(
 }
 
 VOID DOKANAPI DokanInit() {
-  // ensure 64-bit alignment
-  assert(FIELD_OFFSET(EVENT_INFORMATION, Buffer) % 8 == 0);
+  // ensure 64-byte alignment, memcpy runs much faster on 64-byte aligned buffer on moden CPU
+  static_assert(FIELD_OFFSET(EVENT_INFORMATION, Buffer) % 64 == 0, "alignment error");
 
   // this is not as safe as a critical section so to some degree we rely on
   // the user to do the right thing
diff --git a/sys/public.h b/sys/public.h
index b7c74be6..1b967404 100644
--- a/sys/public.h
+++ b/sys/public.h
@@ -388,6 +388,7 @@ typedef struct _EVENT_INFORMATION {
   ULONG64 Context;
   ULONG BufferLength;
   ULONG PullEventTimeoutMs;
+  UCHAR Padding[24]; // ensure buffer is 64-byte aligned
   UCHAR Buffer[DOKAN_EVENT_INFO_MIN_BUFFER_SIZE];
 } EVENT_INFORMATION, *PEVENT_INFORMATION;