[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/ncruces/go-sqlite3/vfs/file.go

@@ -0,0 +1,217 @@
+package vfs
+
+import (
+	"errors"
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"runtime"
+	"syscall"
+
+	"github.com/ncruces/go-sqlite3/util/osutil"
+)
+
+type vfsOS struct{}
+
+func (vfsOS) FullPathname(path string) (string, error) {
+	path, err := filepath.Abs(path)
+	if err != nil {
+		return "", err
+	}
+	fi, err := os.Lstat(path)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return path, nil
+		}
+		return "", err
+	}
+	if fi.Mode()&fs.ModeSymlink != 0 {
+		err = _OK_SYMLINK
+	}
+	return path, err
+}
+
+func (vfsOS) Delete(path string, syncDir bool) error {
+	err := os.Remove(path)
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return _IOERR_DELETE_NOENT
+		}
+		return err
+	}
+	if runtime.GOOS != "windows" && syncDir {
+		f, err := os.Open(filepath.Dir(path))
+		if err != nil {
+			return _OK
+		}
+		defer f.Close()
+		err = osSync(f, false, false)
+		if err != nil {
+			return _IOERR_DIR_FSYNC
+		}
+	}
+	return nil
+}
+
+func (vfsOS) Access(name string, flags AccessFlag) (bool, error) {
+	err := osAccess(name, flags)
+	if flags == ACCESS_EXISTS {
+		if errors.Is(err, fs.ErrNotExist) {
+			return false, nil
+		}
+	} else {
+		if errors.Is(err, fs.ErrPermission) {
+			return false, nil
+		}
+	}
+	return err == nil, err
+}
+
+func (vfsOS) Open(name string, flags OpenFlag) (File, OpenFlag, error) {
+	return nil, 0, _CANTOPEN
+}
+
+func (vfsOS) OpenFilename(name *Filename, flags OpenFlag) (File, OpenFlag, error) {
+	var oflags int
+	if flags&OPEN_EXCLUSIVE != 0 {
+		oflags |= os.O_EXCL
+	}
+	if flags&OPEN_CREATE != 0 {
+		oflags |= os.O_CREATE
+	}
+	if flags&OPEN_READONLY != 0 {
+		oflags |= os.O_RDONLY
+	}
+	if flags&OPEN_READWRITE != 0 {
+		oflags |= os.O_RDWR
+	}
+
+	var err error
+	var f *os.File
+	if name == nil {
+		f, err = os.CreateTemp("", "*.db")
+	} else {
+		f, err = osutil.OpenFile(name.String(), oflags, 0666)
+	}
+	if err != nil {
+		if errors.Is(err, syscall.EISDIR) {
+			return nil, flags, _CANTOPEN_ISDIR
+		}
+		return nil, flags, err
+	}
+
+	if modeof := name.URIParameter("modeof"); modeof != "" {
+		if err = osSetMode(f, modeof); err != nil {
+			f.Close()
+			return nil, flags, _IOERR_FSTAT
+		}
+	}
+	if flags&OPEN_DELETEONCLOSE != 0 {
+		os.Remove(f.Name())
+	}
+
+	file := vfsFile{
+		File:     f,
+		psow:     true,
+		readOnly: flags&OPEN_READONLY != 0,
+		syncDir: runtime.GOOS != "windows" &&
+			flags&(OPEN_CREATE) != 0 &&
+			flags&(OPEN_MAIN_JOURNAL|OPEN_SUPER_JOURNAL|OPEN_WAL) != 0,
+		shm: NewSharedMemory(name.String()+"-shm", flags),
+	}
+	return &file, flags, nil
+}
+
+type vfsFile struct {
+	*os.File
+	shm      SharedMemory
+	lock     LockLevel
+	readOnly bool
+	keepWAL  bool
+	syncDir  bool
+	psow     bool
+}
+
+var (
+	// Ensure these interfaces are implemented:
+	_ FileLockState          = &vfsFile{}
+	_ FileHasMoved           = &vfsFile{}
+	_ FileSizeHint           = &vfsFile{}
+	_ FilePersistentWAL      = &vfsFile{}
+	_ FilePowersafeOverwrite = &vfsFile{}
+)
+
+func (f *vfsFile) Close() error {
+	if f.shm != nil {
+		f.shm.Close()
+	}
+	return f.File.Close()
+}
+
+func (f *vfsFile) Sync(flags SyncFlag) error {
+	dataonly := (flags & SYNC_DATAONLY) != 0
+	fullsync := (flags & 0x0f) == SYNC_FULL
+
+	err := osSync(f.File, fullsync, dataonly)
+	if err != nil {
+		return err
+	}
+	if runtime.GOOS != "windows" && f.syncDir {
+		f.syncDir = false
+		d, err := os.Open(filepath.Dir(f.File.Name()))
+		if err != nil {
+			return nil
+		}
+		defer d.Close()
+		err = osSync(d, false, false)
+		if err != nil {
+			return _IOERR_DIR_FSYNC
+		}
+	}
+	return nil
+}
+
+func (f *vfsFile) Size() (int64, error) {
+	return f.Seek(0, io.SeekEnd)
+}
+
+func (f *vfsFile) SectorSize() int {
+	return _DEFAULT_SECTOR_SIZE
+}
+
+func (f *vfsFile) DeviceCharacteristics() DeviceCharacteristic {
+	var res DeviceCharacteristic
+	if osBatchAtomic(f.File) {
+		res |= IOCAP_BATCH_ATOMIC
+	}
+	if f.psow {
+		res |= IOCAP_POWERSAFE_OVERWRITE
+	}
+	return res
+}
+
+func (f *vfsFile) SizeHint(size int64) error {
+	return osAllocate(f.File, size)
+}
+
+func (f *vfsFile) HasMoved() (bool, error) {
+	fi, err := f.Stat()
+	if err != nil {
+		return false, err
+	}
+	pi, err := os.Stat(f.Name())
+	if err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			return true, nil
+		}
+		return false, err
+	}
+	return !os.SameFile(fi, pi), nil
+}
+
+func (f *vfsFile) LockState() LockLevel            { return f.lock }
+func (f *vfsFile) PowersafeOverwrite() bool        { return f.psow }
+func (f *vfsFile) PersistentWAL() bool             { return f.keepWAL }
+func (f *vfsFile) SetPowersafeOverwrite(psow bool) { f.psow = psow }
+func (f *vfsFile) SetPersistentWAL(keepWAL bool)   { f.keepWAL = keepWAL }