More VFS API.

2026-01-12 05:59:14 +00:00 · 2023-05-17 14:04:00 +01:00
parent f6a887dd1c
commit c94cdaf720
6 changed files with 292 additions and 106 deletions
--- a/const.go
+++ b/const.go
@@ -143,28 +143,17 @@ const (
 type OpenFlag uint32

 const (
-	OPEN_READONLY      OpenFlag = 0x00000001 /* Ok for sqlite3_open_v2() */
-	OPEN_READWRITE     OpenFlag = 0x00000002 /* Ok for sqlite3_open_v2() */
-	OPEN_CREATE        OpenFlag = 0x00000004 /* Ok for sqlite3_open_v2() */
-	OPEN_DELETEONCLOSE OpenFlag = 0x00000008 /* VFS only */
-	OPEN_EXCLUSIVE     OpenFlag = 0x00000010 /* VFS only */
-	OPEN_AUTOPROXY     OpenFlag = 0x00000020 /* VFS only */
-	OPEN_URI           OpenFlag = 0x00000040 /* Ok for sqlite3_open_v2() */
-	OPEN_MEMORY        OpenFlag = 0x00000080 /* Ok for sqlite3_open_v2() */
-	OPEN_MAIN_DB       OpenFlag = 0x00000100 /* VFS only */
-	OPEN_TEMP_DB       OpenFlag = 0x00000200 /* VFS only */
-	OPEN_TRANSIENT_DB  OpenFlag = 0x00000400 /* VFS only */
-	OPEN_MAIN_JOURNAL  OpenFlag = 0x00000800 /* VFS only */
-	OPEN_TEMP_JOURNAL  OpenFlag = 0x00001000 /* VFS only */
-	OPEN_SUBJOURNAL    OpenFlag = 0x00002000 /* VFS only */
-	OPEN_SUPER_JOURNAL OpenFlag = 0x00004000 /* VFS only */
-	OPEN_NOMUTEX       OpenFlag = 0x00008000 /* Ok for sqlite3_open_v2() */
-	OPEN_FULLMUTEX     OpenFlag = 0x00010000 /* Ok for sqlite3_open_v2() */
-	OPEN_SHAREDCACHE   OpenFlag = 0x00020000 /* Ok for sqlite3_open_v2() */
-	OPEN_PRIVATECACHE  OpenFlag = 0x00040000 /* Ok for sqlite3_open_v2() */
-	OPEN_WAL           OpenFlag = 0x00080000 /* VFS only */
-	OPEN_NOFOLLOW      OpenFlag = 0x01000000 /* Ok for sqlite3_open_v2() */
-	OPEN_EXRESCODE     OpenFlag = 0x02000000 /* Extended result codes */
+	OPEN_READONLY     OpenFlag = 0x00000001 /* Ok for sqlite3_open_v2() */
+	OPEN_READWRITE    OpenFlag = 0x00000002 /* Ok for sqlite3_open_v2() */
+	OPEN_CREATE       OpenFlag = 0x00000004 /* Ok for sqlite3_open_v2() */
+	OPEN_URI          OpenFlag = 0x00000040 /* Ok for sqlite3_open_v2() */
+	OPEN_MEMORY       OpenFlag = 0x00000080 /* Ok for sqlite3_open_v2() */
+	OPEN_NOMUTEX      OpenFlag = 0x00008000 /* Ok for sqlite3_open_v2() */
+	OPEN_FULLMUTEX    OpenFlag = 0x00010000 /* Ok for sqlite3_open_v2() */
+	OPEN_SHAREDCACHE  OpenFlag = 0x00020000 /* Ok for sqlite3_open_v2() */
+	OPEN_PRIVATECACHE OpenFlag = 0x00040000 /* Ok for sqlite3_open_v2() */
+	OPEN_NOFOLLOW     OpenFlag = 0x01000000 /* Ok for sqlite3_open_v2() */
+	OPEN_EXRESCODE    OpenFlag = 0x02000000 /* Extended result codes */
 )

 // PrepareFlag is a flag that can be passed to [Conn.PrepareFlags].
--- a/internal/vfs/const.go
+++ b/internal/vfs/const.go
@@ -1,6 +1,9 @@
 package vfs

+import "github.com/ncruces/go-sqlite3/sqlite3vfs"
+
 const (
+	_MAX_STRING          = 512 // Used for short strings: names, error messages…
 	_MAX_PATHNAME        = 512
 	_DEFAULT_SECTOR_SIZE = 4096
 )
@@ -59,93 +62,59 @@ const (
 )

 // https://www.sqlite.org/c3ref/c_open_autoproxy.html
-type _OpenFlag uint32
+type _OpenFlag = sqlite3vfs.OpenFlag

 const (
-	_OPEN_READONLY      _OpenFlag = 0x00000001 /* Ok for sqlite3_open_v2() */
-	_OPEN_READWRITE     _OpenFlag = 0x00000002 /* Ok for sqlite3_open_v2() */
-	_OPEN_CREATE        _OpenFlag = 0x00000004 /* Ok for sqlite3_open_v2() */
-	_OPEN_DELETEONCLOSE _OpenFlag = 0x00000008 /* VFS only */
-	_OPEN_EXCLUSIVE     _OpenFlag = 0x00000010 /* VFS only */
-	_OPEN_AUTOPROXY     _OpenFlag = 0x00000020 /* VFS only */
-	_OPEN_URI           _OpenFlag = 0x00000040 /* Ok for sqlite3_open_v2() */
-	_OPEN_MEMORY        _OpenFlag = 0x00000080 /* Ok for sqlite3_open_v2() */
-	_OPEN_MAIN_DB       _OpenFlag = 0x00000100 /* VFS only */
-	_OPEN_TEMP_DB       _OpenFlag = 0x00000200 /* VFS only */
-	_OPEN_TRANSIENT_DB  _OpenFlag = 0x00000400 /* VFS only */
-	_OPEN_MAIN_JOURNAL  _OpenFlag = 0x00000800 /* VFS only */
-	_OPEN_TEMP_JOURNAL  _OpenFlag = 0x00001000 /* VFS only */
-	_OPEN_SUBJOURNAL    _OpenFlag = 0x00002000 /* VFS only */
-	_OPEN_SUPER_JOURNAL _OpenFlag = 0x00004000 /* VFS only */
-	_OPEN_NOMUTEX       _OpenFlag = 0x00008000 /* Ok for sqlite3_open_v2() */
-	_OPEN_FULLMUTEX     _OpenFlag = 0x00010000 /* Ok for sqlite3_open_v2() */
-	_OPEN_SHAREDCACHE   _OpenFlag = 0x00020000 /* Ok for sqlite3_open_v2() */
-	_OPEN_PRIVATECACHE  _OpenFlag = 0x00040000 /* Ok for sqlite3_open_v2() */
-	_OPEN_WAL           _OpenFlag = 0x00080000 /* VFS only */
-	_OPEN_NOFOLLOW      _OpenFlag = 0x01000000 /* Ok for sqlite3_open_v2() */
-	_OPEN_EXRESCODE     _OpenFlag = 0x02000000 /* Extended result codes */
+	_OPEN_READONLY      = sqlite3vfs.OPEN_READONLY
+	_OPEN_READWRITE     = sqlite3vfs.OPEN_READWRITE
+	_OPEN_CREATE        = sqlite3vfs.OPEN_CREATE
+	_OPEN_DELETEONCLOSE = sqlite3vfs.OPEN_DELETEONCLOSE
+	_OPEN_EXCLUSIVE     = sqlite3vfs.OPEN_EXCLUSIVE
+	_OPEN_AUTOPROXY     = sqlite3vfs.OPEN_AUTOPROXY
+	_OPEN_URI           = sqlite3vfs.OPEN_URI
+	_OPEN_MEMORY        = sqlite3vfs.OPEN_MEMORY
+	_OPEN_MAIN_DB       = sqlite3vfs.OPEN_MAIN_DB
+	_OPEN_TEMP_DB       = sqlite3vfs.OPEN_TEMP_DB
+	_OPEN_TRANSIENT_DB  = sqlite3vfs.OPEN_TRANSIENT_DB
+	_OPEN_MAIN_JOURNAL  = sqlite3vfs.OPEN_MAIN_JOURNAL
+	_OPEN_TEMP_JOURNAL  = sqlite3vfs.OPEN_TEMP_JOURNAL
+	_OPEN_SUBJOURNAL    = sqlite3vfs.OPEN_SUBJOURNAL
+	_OPEN_SUPER_JOURNAL = sqlite3vfs.OPEN_SUPER_JOURNAL
+	_OPEN_NOMUTEX       = sqlite3vfs.OPEN_NOMUTEX
+	_OPEN_FULLMUTEX     = sqlite3vfs.OPEN_FULLMUTEX
+	_OPEN_SHAREDCACHE   = sqlite3vfs.OPEN_SHAREDCACHE
+	_OPEN_PRIVATECACHE  = sqlite3vfs.OPEN_PRIVATECACHE
+	_OPEN_WAL           = sqlite3vfs.OPEN_WAL
+	_OPEN_NOFOLLOW      = sqlite3vfs.OPEN_NOFOLLOW
 )

 // https://www.sqlite.org/c3ref/c_access_exists.html
-type _AccessFlag uint32
+type _AccessFlag = sqlite3vfs.AccessFlag

 const (
-	_ACCESS_EXISTS    _AccessFlag = 0
-	_ACCESS_READWRITE _AccessFlag = 1 /* Used by PRAGMA temp_store_directory */
-	_ACCESS_READ      _AccessFlag = 2 /* Unused */
+	_ACCESS_EXISTS    = sqlite3vfs.ACCESS_EXISTS
+	_ACCESS_READWRITE = sqlite3vfs.ACCESS_READWRITE
+	_ACCESS_READ      = sqlite3vfs.ACCESS_READ
 )

 // https://www.sqlite.org/c3ref/c_sync_dataonly.html
-type _SyncFlag uint32
+type _SyncFlag = sqlite3vfs.SyncFlag

 const (
-	_SYNC_NORMAL   _SyncFlag = 0x00002
-	_SYNC_FULL     _SyncFlag = 0x00003
-	_SYNC_DATAONLY _SyncFlag = 0x00010
+	_SYNC_NORMAL   = sqlite3vfs.SYNC_NORMAL
+	_SYNC_FULL     = sqlite3vfs.SYNC_FULL
+	_SYNC_DATAONLY = sqlite3vfs.SYNC_DATAONLY
 )

 // https://www.sqlite.org/c3ref/c_lock_exclusive.html
-type _LockLevel uint32
+type _LockLevel = sqlite3vfs.LockLevel

 const (
-	// No locks are held on the database.
-	// The database may be neither read nor written.
-	// Any internally cached data is considered suspect and subject to
-	// verification against the database file before being used.
-	// Other processes can read or write the database as their own locking
-	// states permit.
-	// This is the default state.
-	_LOCK_NONE _LockLevel = 0 /* xUnlock() only */
-
-	// The database may be read but not written.
-	// Any number of processes can hold SHARED locks at the same time,
-	// hence there can be many simultaneous readers.
-	// But no other thread or process is allowed to write to the database file
-	// while one or more SHARED locks are active.
-	_LOCK_SHARED _LockLevel = 1 /* xLock() or xUnlock() */
-
-	// A RESERVED lock means that the process is planning on writing to the
-	// database file at some point in the future but that it is currently just
-	// reading from the file.
-	// Only a single RESERVED lock may be active at one time,
-	// though multiple SHARED locks can coexist with a single RESERVED lock.
-	// RESERVED differs from PENDING in that new SHARED locks can be acquired
-	// while there is a RESERVED lock.
-	_LOCK_RESERVED _LockLevel = 2 /* xLock() only */
-
-	// A PENDING lock means that the process holding the lock wants to write to
-	// the database as soon as possible and is just waiting on all current
-	// SHARED locks to clear so that it can get an EXCLUSIVE lock.
-	// No new SHARED locks are permitted against the database if a PENDING lock
-	// is active, though existing SHARED locks are allowed to continue.
-	_LOCK_PENDING _LockLevel = 3 /* internal use only */
-
-	// An EXCLUSIVE lock is needed in order to write to the database file.
-	// Only one EXCLUSIVE lock is allowed on the file and no other locks of any
-	// kind are allowed to coexist with an EXCLUSIVE lock.
-	// In order to maximize concurrency, SQLite works to minimize the amount of
-	// time that EXCLUSIVE locks are held.
-	_LOCK_EXCLUSIVE _LockLevel = 4 /* xLock() only */
+	_LOCK_NONE      = sqlite3vfs.LOCK_NONE
+	_LOCK_SHARED    = sqlite3vfs.LOCK_SHARED
+	_LOCK_RESERVED  = sqlite3vfs.LOCK_RESERVED
+	_LOCK_PENDING   = sqlite3vfs.LOCK_PENDING
+	_LOCK_EXCLUSIVE = sqlite3vfs.LOCK_EXCLUSIVE
 )

 // https://www.sqlite.org/c3ref/c_fcntl_begin_atomic_write.html
--- a/internal/vfs/vfs.go
+++ b/internal/vfs/vfs.go
@@ -12,6 +12,7 @@ import (
 	"time"

 	"github.com/ncruces/go-sqlite3/internal/util"
+	"github.com/ncruces/go-sqlite3/sqlite3vfs"
 	"github.com/ncruces/julianday"
 	"github.com/tetratelabs/wazero"
 	"github.com/tetratelabs/wazero/api"
@@ -64,6 +65,10 @@ func (vfs *vfsState) Close() error {
 }

 func vfsFind(ctx context.Context, mod api.Module, zVfsName uint32) uint32 {
+	name := util.ReadString(mod, zVfsName, _MAX_STRING)
+	if sqlite3vfs.Find(name) != nil {
+		return 1
+	}
 	return 0
 }

@@ -113,10 +118,29 @@ func vfsCurrentTime64(ctx context.Context, mod api.Module, pVfs, piNow uint32) _
 }

 func vfsFullPathname(ctx context.Context, mod api.Module, pVfs, zRelative, nFull, zFull uint32) _ErrorCode {
+	vfs := getVFS(mod, pVfs)
 	rel := util.ReadString(mod, zRelative, _MAX_PATHNAME)
-	abs, err := filepath.Abs(rel)
-	if err != nil {
-		return _CANTOPEN_FULLPATH
+
+	var abs string
+	var symlink bool
+	if vfs != nil {
+		p, err := vfs.FullPathname(rel)
+		if err != nil {
+			return _CANTOPEN_FULLPATH
+		}
+		abs = p
+	} else {
+		p, err := filepath.Abs(rel)
+		if err != nil {
+			return _CANTOPEN_FULLPATH
+		}
+		s, err := os.Lstat(p)
+		if err == nil {
+			symlink = s.Mode()&fs.ModeSymlink != 0
+		} else if !errors.Is(err, fs.ErrNotExist) {
+			return _CANTOPEN_FULLPATH
+		}
+		abs = p
 	}

 	size := uint64(len(abs) + 1)
@@ -127,15 +151,10 @@ func vfsFullPathname(ctx context.Context, mod api.Module, pVfs, zRelative, nFull
 	mem[len(abs)] = 0
 	copy(mem, abs)

-	if fi, err := os.Lstat(abs); err == nil {
-		if fi.Mode()&fs.ModeSymlink != 0 {
-			return _OK_SYMLINK
-		}
-		return _OK
-	} else if errors.Is(err, fs.ErrNotExist) {
-		return _OK
+	if symlink {
+		return _OK_SYMLINK
 	}
-	return _CANTOPEN_FULLPATH
+	return _OK
 }

 func vfsDelete(ctx context.Context, mod api.Module, pVfs, zPath, syncDir uint32) _ErrorCode {
@@ -192,6 +211,8 @@ func vfsAccess(ctx context.Context, mod api.Module, pVfs, zPath uint32, flags _A
 }

 func vfsOpen(ctx context.Context, mod api.Module, pVfs, zName, pFile uint32, flags _OpenFlag, pOutFlags uint32) _ErrorCode {
+	vfs := getVFS(mod, pVfs)
+
 	var oflags int
 	if flags&_OPEN_EXCLUSIVE != 0 {
 		oflags |= os.O_EXCL
@@ -207,11 +228,17 @@ func vfsOpen(ctx context.Context, mod api.Module, pVfs, zName, pFile uint32, fla
 	}

 	var err error
+	var name string
 	var f *os.File
-	if zName == 0 {
+	if zName != 0 {
+		name = util.ReadString(mod, zName, _MAX_PATHNAME)
+	}
+	switch {
+	case vfs != nil:
+		_, flags, err = vfs.Open(name, flags)
+	case name == "":
 		f, err = os.CreateTemp("", "*.db")
-	} else {
-		name := util.ReadString(mod, zName, _MAX_PATHNAME)
+	default:
 		f, err = osOpenFile(name, oflags, 0666)
 	}
 	if err != nil {
@@ -393,3 +420,11 @@ func vfsFileMoved(ctx context.Context, mod api.Module, pFile, pResOut uint32) _E
 	util.WriteUint32(mod, pResOut, res)
 	return _OK
 }
+
+func getVFS(mod api.Module, pVfs uint32) sqlite3vfs.VFS {
+	if pVfs == 0 {
+		return nil
+	}
+	name := util.ReadString(mod, util.ReadUint32(mod, pVfs+16), _MAX_STRING)
+	return sqlite3vfs.Find(name)
+}
--- a/sqlite3vfs/const.go
+++ b/sqlite3vfs/const.go
@@ -0,0 +1,98 @@
+package sqlite3vfs
+
+// OpenFlag is a flag for the [VFS.Open] method.
+//
+// https://www.sqlite.org/c3ref/c_open_autoproxy.html
+type OpenFlag uint32
+
+const (
+	OPEN_READONLY      OpenFlag = 0x00000001 /* Ok for sqlite3_open_v2() */
+	OPEN_READWRITE     OpenFlag = 0x00000002 /* Ok for sqlite3_open_v2() */
+	OPEN_CREATE        OpenFlag = 0x00000004 /* Ok for sqlite3_open_v2() */
+	OPEN_DELETEONCLOSE OpenFlag = 0x00000008 /* VFS only */
+	OPEN_EXCLUSIVE     OpenFlag = 0x00000010 /* VFS only */
+	OPEN_AUTOPROXY     OpenFlag = 0x00000020 /* VFS only */
+	OPEN_URI           OpenFlag = 0x00000040 /* Ok for sqlite3_open_v2() */
+	OPEN_MEMORY        OpenFlag = 0x00000080 /* Ok for sqlite3_open_v2() */
+	OPEN_MAIN_DB       OpenFlag = 0x00000100 /* VFS only */
+	OPEN_TEMP_DB       OpenFlag = 0x00000200 /* VFS only */
+	OPEN_TRANSIENT_DB  OpenFlag = 0x00000400 /* VFS only */
+	OPEN_MAIN_JOURNAL  OpenFlag = 0x00000800 /* VFS only */
+	OPEN_TEMP_JOURNAL  OpenFlag = 0x00001000 /* VFS only */
+	OPEN_SUBJOURNAL    OpenFlag = 0x00002000 /* VFS only */
+	OPEN_SUPER_JOURNAL OpenFlag = 0x00004000 /* VFS only */
+	OPEN_NOMUTEX       OpenFlag = 0x00008000 /* Ok for sqlite3_open_v2() */
+	OPEN_FULLMUTEX     OpenFlag = 0x00010000 /* Ok for sqlite3_open_v2() */
+	OPEN_SHAREDCACHE   OpenFlag = 0x00020000 /* Ok for sqlite3_open_v2() */
+	OPEN_PRIVATECACHE  OpenFlag = 0x00040000 /* Ok for sqlite3_open_v2() */
+	OPEN_WAL           OpenFlag = 0x00080000 /* VFS only */
+	OPEN_NOFOLLOW      OpenFlag = 0x01000000 /* Ok for sqlite3_open_v2() */
+)
+
+// AccessFlag is a flag for the [VFS.Access] method.
+//
+// https://www.sqlite.org/c3ref/c_access_exists.html
+type AccessFlag uint32
+
+const (
+	ACCESS_EXISTS    AccessFlag = 0
+	ACCESS_READWRITE AccessFlag = 1 /* Used by PRAGMA temp_store_directory */
+	ACCESS_READ      AccessFlag = 2 /* Unused */
+)
+
+// SyncFlag is a flag for the [File.Sync] method.
+//
+// https://www.sqlite.org/c3ref/c_sync_dataonly.html
+type SyncFlag uint32
+
+const (
+	SYNC_NORMAL   SyncFlag = 0x00002
+	SYNC_FULL     SyncFlag = 0x00003
+	SYNC_DATAONLY SyncFlag = 0x00010
+)
+
+// LockLevel is a value used with [File.Lock] and [File.Unlock] methods.
+//
+// https://www.sqlite.org/c3ref/c_lock_exclusive.html
+type LockLevel uint32
+
+const (
+	// No locks are held on the database.
+	// The database may be neither read nor written.
+	// Any internally cached data is considered suspect and subject to
+	// verification against the database file before being used.
+	// Other processes can read or write the database as their own locking
+	// states permit.
+	// This is the default state.
+	LOCK_NONE LockLevel = 0 /* xUnlock() only */
+
+	// The database may be read but not written.
+	// Any number of processes can hold SHARED locks at the same time,
+	// hence there can be many simultaneous readers.
+	// But no other thread or process is allowed to write to the database file
+	// while one or more SHARED locks are active.
+	LOCK_SHARED LockLevel = 1 /* xLock() or xUnlock() */
+
+	// A RESERVED lock means that the process is planning on writing to the
+	// database file at some point in the future but that it is currently just
+	// reading from the file.
+	// Only a single RESERVED lock may be active at one time,
+	// though multiple SHARED locks can coexist with a single RESERVED lock.
+	// RESERVED differs from PENDING in that new SHARED locks can be acquired
+	// while there is a RESERVED lock.
+	LOCK_RESERVED LockLevel = 2 /* xLock() only */
+
+	// A PENDING lock means that the process holding the lock wants to write to
+	// the database as soon as possible and is just waiting on all current
+	// SHARED locks to clear so that it can get an EXCLUSIVE lock.
+	// No new SHARED locks are permitted against the database if a PENDING lock
+	// is active, though existing SHARED locks are allowed to continue.
+	LOCK_PENDING LockLevel = 3 /* internal use only */
+
+	// An EXCLUSIVE lock is needed in order to write to the database file.
+	// Only one EXCLUSIVE lock is allowed on the file and no other locks of any
+	// kind are allowed to coexist with an EXCLUSIVE lock.
+	// In order to maximize concurrency, SQLite works to minimize the amount of
+	// time that EXCLUSIVE locks are held.
+	LOCK_EXCLUSIVE LockLevel = 4 /* xLock() only */
+)
--- a/sqlite3vfs/vfs.go
+++ b/sqlite3vfs/vfs.go
@@ -0,0 +1,49 @@
+package sqlite3vfs
+
+import "sync"
+
+type VFS interface {
+	Open(name string, flags OpenFlag) (File, OpenFlag, error)
+	Delete(name string, dirSync bool) error
+	Access(name string, flags AccessFlag) (bool, error)
+	FullPathname(name string) (string, error)
+}
+
+type File interface {
+	Close() error
+	ReadAt(p []byte, off int64) (n int, err error)
+	WriteAt(p []byte, off int64) (n int, err error)
+	Truncate(size int64) error
+	Sync(flag SyncFlag) error
+	FileSize() (int64, error)
+	Lock(elock LockLevel) error
+	Unlock(elock LockLevel) error
+	CheckReservedLock() (bool, error)
+	SectorSize() int64
+}
+
+var (
+	vfsRegistry    map[string]VFS
+	vfsRegistryMtx sync.Mutex
+)
+
+func Find(name string) VFS {
+	vfsRegistryMtx.Lock()
+	defer vfsRegistryMtx.Unlock()
+	return vfsRegistry[name]
+}
+
+func Register(name string, vfs VFS) {
+	vfsRegistryMtx.Lock()
+	defer vfsRegistryMtx.Unlock()
+	if vfsRegistry == nil {
+		vfsRegistry = map[string]VFS{}
+	}
+	vfsRegistry[name] = vfs
+}
+
+func Unregister(name string) {
+	vfsRegistryMtx.Lock()
+	defer vfsRegistryMtx.Unlock()
+	delete(vfsRegistry, name)
+}
--- a/sqlite3vfs/vfs_api_test.go
+++ b/sqlite3vfs/vfs_api_test.go
@@ -0,0 +1,46 @@
+package sqlite3vfs_test
+
+import (
+	"testing"
+
+	"github.com/ncruces/go-sqlite3"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	"github.com/ncruces/go-sqlite3/sqlite3vfs"
+)
+
+type testVFS struct {
+	*testing.T
+}
+
+func (t testVFS) Open(name string, flags sqlite3vfs.OpenFlag) (sqlite3vfs.File, sqlite3vfs.OpenFlag, error) {
+	t.Log("Open", name, flags)
+	t.SkipNow()
+	return nil, flags, nil
+}
+
+func (testVFS) Delete(name string, dirSync bool) error {
+	panic("unimplemented")
+}
+
+func (testVFS) Access(name string, flags sqlite3vfs.AccessFlag) (bool, error) {
+	panic("unimplemented")
+}
+
+func (t testVFS) FullPathname(name string) (string, error) {
+	t.Log("FullPathname", name)
+	return name, nil
+}
+
+func TestRegister(t *testing.T) {
+	vfs := testVFS{t}
+	sqlite3vfs.Register("foo", vfs)
+	defer sqlite3vfs.Unregister("foo")
+
+	defer func() { _ = recover() }()
+
+	conn, err := sqlite3.Open("file:file.db?vfs=foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+}