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e82a7e3dfa
As foretold by the prophecy, "once the database refactor is merged, then shall appear a request to propagate errors from the store known throughout the land as the NamedspacedKV, and it shall be good".
253 lines
5.2 KiB
Go
253 lines
5.2 KiB
Go
// Copyright (C) 2016 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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package fs
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import (
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"time"
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)
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// The database is where we store the virtual mtimes
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type database interface {
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Bytes(key string) (data []byte, ok bool, err error)
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PutBytes(key string, data []byte) error
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Delete(key string) error
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}
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// The MtimeFS is a filesystem with nanosecond mtime precision, regardless
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// of what shenanigans the underlying filesystem gets up to. A nil MtimeFS
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// just does the underlying operations with no additions.
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type MtimeFS struct {
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Filesystem
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chtimes func(string, time.Time, time.Time) error
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db database
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caseInsensitive bool
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}
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type MtimeFSOption func(*MtimeFS)
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func WithCaseInsensitivity(v bool) MtimeFSOption {
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return func(f *MtimeFS) {
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f.caseInsensitive = v
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}
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}
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func NewMtimeFS(underlying Filesystem, db database, options ...MtimeFSOption) *MtimeFS {
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f := &MtimeFS{
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Filesystem: underlying,
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chtimes: underlying.Chtimes, // for mocking it out in the tests
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db: db,
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}
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for _, opt := range options {
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opt(f)
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}
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return f
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}
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func (f *MtimeFS) Chtimes(name string, atime, mtime time.Time) error {
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if f == nil {
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return f.chtimes(name, atime, mtime)
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}
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// Do a normal Chtimes call, don't care if it succeeds or not.
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f.chtimes(name, atime, mtime)
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// Stat the file to see what happened. Here we *do* return an error,
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// because it might be "does not exist" or similar.
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info, err := f.Filesystem.Lstat(name)
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if err != nil {
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return err
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}
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f.save(name, info.ModTime(), mtime)
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return nil
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}
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func (f *MtimeFS) Stat(name string) (FileInfo, error) {
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info, err := f.Filesystem.Stat(name)
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if err != nil {
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return nil, err
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}
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real, virtual, err := f.load(name)
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if err != nil {
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return nil, err
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}
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if real == info.ModTime() {
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info = mtimeFileInfo{
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FileInfo: info,
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mtime: virtual,
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}
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}
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return info, nil
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}
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func (f *MtimeFS) Lstat(name string) (FileInfo, error) {
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info, err := f.Filesystem.Lstat(name)
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if err != nil {
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return nil, err
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}
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real, virtual, err := f.load(name)
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if err != nil {
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return nil, err
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}
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if real == info.ModTime() {
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info = mtimeFileInfo{
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FileInfo: info,
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mtime: virtual,
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}
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}
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return info, nil
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}
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func (f *MtimeFS) Walk(root string, walkFn WalkFunc) error {
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return f.Filesystem.Walk(root, func(path string, info FileInfo, err error) error {
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if info != nil {
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real, virtual, loadErr := f.load(path)
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if loadErr != nil && err == nil {
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// The iterator gets to deal with the error
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err = loadErr
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}
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if real == info.ModTime() {
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info = mtimeFileInfo{
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FileInfo: info,
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mtime: virtual,
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}
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}
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}
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return walkFn(path, info, err)
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})
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}
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func (f *MtimeFS) Create(name string) (File, error) {
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fd, err := f.Filesystem.Create(name)
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if err != nil {
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return nil, err
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}
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return &mtimeFile{fd, f}, nil
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}
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func (f *MtimeFS) Open(name string) (File, error) {
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fd, err := f.Filesystem.Open(name)
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if err != nil {
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return nil, err
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}
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return &mtimeFile{fd, f}, nil
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}
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func (f *MtimeFS) OpenFile(name string, flags int, mode FileMode) (File, error) {
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fd, err := f.Filesystem.OpenFile(name, flags, mode)
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if err != nil {
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return nil, err
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}
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return &mtimeFile{fd, f}, nil
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}
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// "real" is the on disk timestamp
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// "virtual" is what want the timestamp to be
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func (f *MtimeFS) save(name string, real, virtual time.Time) {
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if f.caseInsensitive {
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name = UnicodeLowercase(name)
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}
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if real.Equal(virtual) {
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// If the virtual time and the real on disk time are equal we don't
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// need to store anything.
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f.db.Delete(name)
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return
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}
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mtime := dbMtime{
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real: real,
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virtual: virtual,
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}
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bs, _ := mtime.Marshal() // Can't fail
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f.db.PutBytes(name, bs)
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}
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func (f *MtimeFS) load(name string) (real, virtual time.Time, err error) {
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if f.caseInsensitive {
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name = UnicodeLowercase(name)
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}
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data, exists, err := f.db.Bytes(name)
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if err != nil {
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return time.Time{}, time.Time{}, err
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} else if !exists {
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return time.Time{}, time.Time{}, nil
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}
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var mtime dbMtime
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if err := mtime.Unmarshal(data); err != nil {
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return time.Time{}, time.Time{}, err
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}
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return mtime.real, mtime.virtual, nil
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}
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// The mtimeFileInfo is an os.FileInfo that lies about the ModTime().
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type mtimeFileInfo struct {
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FileInfo
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mtime time.Time
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}
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func (m mtimeFileInfo) ModTime() time.Time {
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return m.mtime
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}
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type mtimeFile struct {
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File
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fs *MtimeFS
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}
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func (f *mtimeFile) Stat() (FileInfo, error) {
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info, err := f.File.Stat()
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if err != nil {
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return nil, err
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}
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real, virtual, err := f.fs.load(f.Name())
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if err != nil {
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return nil, err
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}
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if real == info.ModTime() {
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info = mtimeFileInfo{
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FileInfo: info,
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mtime: virtual,
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}
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}
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return info, nil
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}
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// The dbMtime is our database representation
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type dbMtime struct {
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real time.Time
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virtual time.Time
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}
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func (t *dbMtime) Marshal() ([]byte, error) {
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bs0, _ := t.real.MarshalBinary()
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bs1, _ := t.virtual.MarshalBinary()
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return append(bs0, bs1...), nil
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}
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func (t *dbMtime) Unmarshal(bs []byte) error {
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if err := t.real.UnmarshalBinary(bs[:len(bs)/2]); err != nil {
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return err
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}
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if err := t.virtual.UnmarshalBinary(bs[len(bs)/2:]); err != nil {
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return err
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}
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return nil
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}
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