From 2c582a1d66bc0f1b3fca93c26623118482f7a7b2 Mon Sep 17 00:00:00 2001
From: Nuno Cruces <ncruces@users.noreply.github.com>
Date: Tue, 5 Aug 2025 14:15:21 +0100
Subject: [PATCH] VFS improvements.

---
 ext/serdes/serdes.go      |  2 +-
 ext/serdes/serdes_test.go |  2 +-
 util/vfsutil/slice.go     | 14 ++++++++++----
 util/vfsutil/wrap.go      |  8 ++++++++
 vfs/readervfs/reader.go   | 25 +++++++++++++++----------
 5 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/ext/serdes/serdes.go b/ext/serdes/serdes.go
index f138c82..648b868 100644
--- a/ext/serdes/serdes.go
+++ b/ext/serdes/serdes.go
@@ -59,7 +59,7 @@ func (sliceVFS) Open(name string, flags vfs.OpenFlag) (vfs.File, vfs.OpenFlag, e
 }
 
 func (sliceVFS) Delete(name string, dirSync bool) error {
-	// notest // OPEN_MEMORY
+	// notest // no journals to delete
 	return sqlite3.IOERR_DELETE
 }
 
diff --git a/ext/serdes/serdes_test.go b/ext/serdes/serdes_test.go
index 29eda28..8f128a4 100644
--- a/ext/serdes/serdes_test.go
+++ b/ext/serdes/serdes_test.go
@@ -29,7 +29,7 @@ func Test_wal(t *testing.T) {
 
 	compareDBs(t, data, walDB)
 
-	err = serdes.Deserialize(db, "main", walDB)
+	err = serdes.Deserialize(db, "temp", walDB)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/util/vfsutil/slice.go b/util/vfsutil/slice.go
index 4a1f547..b0fbe99 100644
--- a/util/vfsutil/slice.go
+++ b/util/vfsutil/slice.go
@@ -69,20 +69,26 @@ func (*SliceFile) Close() error { return nil }
 func (*SliceFile) Sync(flags vfs.SyncFlag) error { return nil }
 
 // Lock implements [vfs.File].
-func (*SliceFile) Lock(lock vfs.LockLevel) error { return nil }
+func (*SliceFile) Lock(lock vfs.LockLevel) error {
+	// notest // not concurrency safe
+	return sqlite3.IOERR_LOCK
+}
 
 // Unlock implements [vfs.File].
-func (*SliceFile) Unlock(lock vfs.LockLevel) error { return nil }
+func (*SliceFile) Unlock(lock vfs.LockLevel) error {
+	// notest // not concurrency safe
+	return sqlite3.IOERR_UNLOCK
+}
 
 // CheckReservedLock implements [vfs.File].
 func (*SliceFile) CheckReservedLock() (bool, error) {
-	// notest // OPEN_MEMORY
+	// notest // not concurrency safe
 	return false, sqlite3.IOERR_CHECKRESERVEDLOCK
 }
 
 // SectorSize implements [vfs.File].
 func (*SliceFile) SectorSize() int {
-	// notest // IOCAP_POWERSAFE_OVERWRITE
+	// notest // safe default
 	return 0
 }
 
diff --git a/util/vfsutil/wrap.go b/util/vfsutil/wrap.go
index b51a404..ad96547 100644
--- a/util/vfsutil/wrap.go
+++ b/util/vfsutil/wrap.go
@@ -22,6 +22,14 @@ func UnwrapFile[T vfs.File](f vfs.File) (_ T, _ bool) {
 	}
 }
 
+// WrapOpen helps wrap [vfs.VFS].
+func WrapOpen(f vfs.VFS, name string, flags vfs.OpenFlag) (file vfs.File, _ vfs.OpenFlag, err error) {
+	if f, ok := f.(vfs.VFSFilename); name == "" && ok {
+		return f.OpenFilename(nil, flags)
+	}
+	return f.Open(name, flags)
+}
+
 // WrapOpenFilename helps wrap [vfs.VFSFilename].
 func WrapOpenFilename(f vfs.VFS, name *vfs.Filename, flags vfs.OpenFlag) (file vfs.File, _ vfs.OpenFlag, err error) {
 	if f, ok := f.(vfs.VFSFilename); ok {
diff --git a/vfs/readervfs/reader.go b/vfs/readervfs/reader.go
index 043951d..4312744 100644
--- a/vfs/readervfs/reader.go
+++ b/vfs/readervfs/reader.go
@@ -3,14 +3,19 @@ package readervfs
 import (
 	"github.com/ncruces/go-sqlite3"
 	"github.com/ncruces/go-sqlite3/util/ioutil"
+	"github.com/ncruces/go-sqlite3/util/vfsutil"
 	"github.com/ncruces/go-sqlite3/vfs"
 )
 
 type readerVFS struct{}
 
 func (readerVFS) Open(name string, flags vfs.OpenFlag) (vfs.File, vfs.OpenFlag, error) {
+	// Temp journals, as used by the sorter, use SliceFile.
+	if flags&vfs.OPEN_TEMP_JOURNAL != 0 {
+		return &vfsutil.SliceFile{}, flags | vfs.OPEN_MEMORY, nil
+	}
+	// Refuse to open all other file types.
 	if flags&vfs.OPEN_MAIN_DB == 0 {
-		// notest
 		return nil, flags, sqlite3.CANTOPEN
 	}
 	readerMtx.RLock()
@@ -22,12 +27,12 @@ func (readerVFS) Open(name string, flags vfs.OpenFlag) (vfs.File, vfs.OpenFlag,
 }
 
 func (readerVFS) Delete(name string, dirSync bool) error {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return sqlite3.IOERR_DELETE
 }
 
 func (readerVFS) Access(name string, flag vfs.AccessFlag) (bool, error) {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return false, sqlite3.IOERR_ACCESS
 }
 
@@ -42,37 +47,37 @@ func (readerFile) Close() error {
 }
 
 func (readerFile) WriteAt(b []byte, off int64) (n int, err error) {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return 0, sqlite3.IOERR_WRITE
 }
 
 func (readerFile) Truncate(size int64) error {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return sqlite3.IOERR_TRUNCATE
 }
 
 func (readerFile) Sync(flag vfs.SyncFlag) error {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return sqlite3.IOERR_FSYNC
 }
 
 func (readerFile) Lock(lock vfs.LockLevel) error {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return sqlite3.IOERR_LOCK
 }
 
 func (readerFile) Unlock(lock vfs.LockLevel) error {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return sqlite3.IOERR_UNLOCK
 }
 
 func (readerFile) CheckReservedLock() (bool, error) {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return false, sqlite3.IOERR_CHECKRESERVEDLOCK
 }
 
 func (readerFile) SectorSize() int {
-	// notest
+	// notest // IOCAP_IMMUTABLE
 	return 0
 }