137 lines
2.9 KiB
Go
137 lines
2.9 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 http://mozilla.org/MPL/2.0/.
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package fs
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import (
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"os"
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"time"
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"github.com/syncthing/syncthing/lib/osutil"
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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)
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PutBytes(key string, data []byte)
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Delete(key string)
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}
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// variable so that we can mock it for testing
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var osChtimes = os.Chtimes
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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.
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type MtimeFS struct {
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db database
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}
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func NewMtimeFS(db database) *MtimeFS {
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return &MtimeFS{
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db: db,
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}
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}
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func (f *MtimeFS) Chtimes(name string, atime, mtime time.Time) error {
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// Do a normal Chtimes call, don't care if it succeeds or not.
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osChtimes(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. osutil.Lstat is the
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// souped up version to account for Android breakage.
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info, err := osutil.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) Lstat(name string) (os.FileInfo, error) {
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info, err := osutil.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 := f.load(name)
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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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// "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 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) {
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data, exists := f.db.Bytes(name)
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if !exists {
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return
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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
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}
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return mtime.real, mtime.virtual
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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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os.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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// 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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