From 466d14a9e099644decb093168bbcf1e07295cf21 Mon Sep 17 00:00:00 2001
From: Nuno Cruces <ncruces@users.noreply.github.com>
Date: Fri, 8 Nov 2024 13:02:19 +0000
Subject: [PATCH] Fix, speed.

---
 vfs/shm_copy.go    |  7 +++++--
 vfs/shm_dotlk.go   |  8 ++++----
 vfs/shm_windows.go | 10 +++++-----
 3 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/vfs/shm_copy.go b/vfs/shm_copy.go
index 7a25052..e6007aa 100644
--- a/vfs/shm_copy.go
+++ b/vfs/shm_copy.go
@@ -31,7 +31,10 @@ const (
 //
 // https://sqlite.org/walformat.html#the_wal_index_file_format
 
-func (s *vfsShm) shmAcquire() {
+func (s *vfsShm) shmAcquire(ptr *_ErrorCode) {
+	if ptr != nil && *ptr != _OK {
+		return
+	}
 	if len(s.ptrs) == 0 || shmUnmodified(s.shadow[0][:], s.shared[0][:]) {
 		return
 	}
@@ -69,7 +72,7 @@ func (s *vfsShm) shmRelease() {
 
 func (s *vfsShm) shmBarrier() {
 	s.Lock()
-	s.shmAcquire()
+	s.shmAcquire(nil)
 	s.shmRelease()
 	s.Unlock()
 }
diff --git a/vfs/shm_dotlk.go b/vfs/shm_dotlk.go
index ce22a36..4c7f47d 100644
--- a/vfs/shm_dotlk.go
+++ b/vfs/shm_dotlk.go
@@ -112,7 +112,7 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 
 	s.Lock()
 	defer s.Unlock()
-	defer s.shmAcquire()
+	defer s.shmAcquire(nil)
 
 	// Extend shared memory.
 	if int(id) >= len(s.shared) {
@@ -125,7 +125,6 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 	// Allocate shadow memory.
 	if int(id) >= len(s.shadow) {
 		s.shadow = append(s.shadow, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shadow)+1)...)
-		s.shadow[0][4] = 1 // force invalidation
 	}
 
 	// Allocate local memory.
@@ -141,16 +140,17 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 		s.ptrs = append(s.ptrs, uint32(s.stack[0]))
 	}
 
+	s.shadow[0][4] = 1
 	return s.ptrs[id], _OK
 }
 
-func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
+func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) (rc _ErrorCode) {
 	s.Lock()
 	defer s.Unlock()
 
 	switch {
 	case flags&_SHM_LOCK != 0:
-		defer s.shmAcquire()
+		defer s.shmAcquire(&rc)
 	case flags&_SHM_EXCLUSIVE != 0:
 		s.shmRelease()
 	}
diff --git a/vfs/shm_windows.go b/vfs/shm_windows.go
index 156f862..374d491 100644
--- a/vfs/shm_windows.go
+++ b/vfs/shm_windows.go
@@ -64,7 +64,7 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 	return osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
 }
 
-func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (uint32, _ErrorCode) {
+func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, extend bool) (_ uint32, rc _ErrorCode) {
 	// Ensure size is a multiple of the OS page size.
 	if size != _WALINDEX_PGSZ || (windows.Getpagesize()-1)&_WALINDEX_PGSZ != 0 {
 		return 0, _IOERR_SHMMAP
@@ -78,7 +78,7 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 		return 0, rc
 	}
 
-	defer s.shmAcquire()
+	defer s.shmAcquire(&rc)
 
 	// Check if file is big enough.
 	o, err := s.Seek(0, io.SeekEnd)
@@ -107,7 +107,6 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 	// Allocate shadow memory.
 	if int(id) >= len(s.shadow) {
 		s.shadow = append(s.shadow, make([][_WALINDEX_PGSZ]byte, int(id)-len(s.shadow)+1)...)
-		s.shadow[0][4] = 1 // force invalidation
 	}
 
 	// Allocate local memory.
@@ -123,10 +122,11 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 		s.ptrs = append(s.ptrs, uint32(s.stack[0]))
 	}
 
+	s.shadow[0][4] = 1
 	return s.ptrs[id], _OK
 }
 
-func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
+func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) (rc _ErrorCode) {
 	var timeout time.Duration
 	if s.blocking {
 		timeout = time.Millisecond
@@ -134,7 +134,7 @@ func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
 
 	switch {
 	case flags&_SHM_LOCK != 0:
-		defer s.shmAcquire()
+		defer s.shmAcquire(&rc)
 	case flags&_SHM_EXCLUSIVE != 0:
 		s.shmRelease()
 	}