606 lines
17 KiB
Go
606 lines
17 KiB
Go
// Copyright (c) 2014-2018 The Notify Authors. All rights reserved.
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// Use of this source code is governed by the MIT license that can be
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// found in the LICENSE file.
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// +build windows
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package notify
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import (
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"errors"
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"runtime"
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"sync"
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"sync/atomic"
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"syscall"
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"unsafe"
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)
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// readBufferSize defines the size of an array in which read statuses are stored.
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// The buffer have to be DWORD-aligned and, if notify is used in monitoring a
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// directory over the network, its size must not be greater than 64KB. Each of
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// watched directories uses its own buffer for storing events.
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const readBufferSize = 4096
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// Since all operations which go through the Windows completion routine are done
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// asynchronously, filter may set one of the constants below. They were defined
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// in order to distinguish whether current folder should be re-registered in
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// ReadDirectoryChangesW function or some control operations need to be executed.
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const (
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stateRewatch uint32 = 1 << (28 + iota)
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stateUnwatch
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stateCPClose
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)
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// Filter used in current implementation was split into four segments:
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// - bits 0-11 store ReadDirectoryChangesW filters,
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// - bits 12-19 store File notify actions,
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// - bits 20-27 store notify specific events and flags,
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// - bits 28-31 store states which are used in loop's FSM.
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// Constants below are used as masks to retrieve only specific filter parts.
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const (
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onlyNotifyChanges uint32 = 0x00000FFF
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onlyNGlobalEvents uint32 = 0x0FF00000
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onlyMachineStates uint32 = 0xF0000000
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)
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// grip represents a single watched directory. It stores the data required by
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// ReadDirectoryChangesW function. Only the filter, recursive, and handle members
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// may by modified by watcher implementation. Rest of the them have to remain
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// constant since they are used by Windows completion routine. This indicates that
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// grip can be removed only when all operations on the file handle are finished.
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type grip struct {
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handle syscall.Handle
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filter uint32
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recursive bool
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pathw []uint16
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buffer [readBufferSize]byte
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parent *watched
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ovlapped *overlappedEx
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}
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// overlappedEx stores information used in asynchronous input and output.
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// Additionally, overlappedEx contains a pointer to 'grip' item which is used in
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// order to gather the structure in which the overlappedEx object was created.
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type overlappedEx struct {
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syscall.Overlapped
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parent *grip
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}
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// newGrip creates a new file handle that can be used in overlapped operations.
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// Then, the handle is associated with I/O completion port 'cph' and its value
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// is stored in newly created 'grip' object.
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func newGrip(cph syscall.Handle, parent *watched, filter uint32) (*grip, error) {
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g := &grip{
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handle: syscall.InvalidHandle,
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filter: filter,
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recursive: parent.recursive,
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pathw: parent.pathw,
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parent: parent,
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ovlapped: &overlappedEx{},
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}
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if err := g.register(cph); err != nil {
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return nil, err
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}
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g.ovlapped.parent = g
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return g, nil
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}
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// NOTE : Thread safe
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func (g *grip) register(cph syscall.Handle) (err error) {
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if g.handle, err = syscall.CreateFile(
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&g.pathw[0],
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syscall.FILE_LIST_DIRECTORY,
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syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE|syscall.FILE_SHARE_DELETE,
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nil,
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syscall.OPEN_EXISTING,
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syscall.FILE_FLAG_BACKUP_SEMANTICS|syscall.FILE_FLAG_OVERLAPPED,
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0,
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); err != nil {
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return
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}
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if _, err = syscall.CreateIoCompletionPort(g.handle, cph, 0, 0); err != nil {
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syscall.CloseHandle(g.handle)
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return
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}
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return g.readDirChanges()
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}
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// readDirChanges tells the system to store file change information in grip's
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// buffer. Directory changes that occur between calls to this function are added
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// to the buffer and then, returned with the next call.
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func (g *grip) readDirChanges() error {
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handle := syscall.Handle(atomic.LoadUintptr((*uintptr)(&g.handle)))
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if handle == syscall.InvalidHandle {
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return nil // Handle was closed.
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}
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return syscall.ReadDirectoryChanges(
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handle,
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&g.buffer[0],
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uint32(unsafe.Sizeof(g.buffer)),
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g.recursive,
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encode(g.filter),
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nil,
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(*syscall.Overlapped)(unsafe.Pointer(g.ovlapped)),
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0,
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)
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}
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// encode transforms a generic filter, which contains platform independent and
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// implementation specific bit fields, to value that can be used as NotifyFilter
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// parameter in ReadDirectoryChangesW function.
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func encode(filter uint32) uint32 {
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e := Event(filter & (onlyNGlobalEvents | onlyNotifyChanges))
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if e&dirmarker != 0 {
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return uint32(FileNotifyChangeDirName)
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}
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if e&Create != 0 {
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e = (e ^ Create) | FileNotifyChangeFileName
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}
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if e&Remove != 0 {
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e = (e ^ Remove) | FileNotifyChangeFileName
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}
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if e&Write != 0 {
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e = (e ^ Write) | FileNotifyChangeAttributes | FileNotifyChangeSize |
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FileNotifyChangeCreation | FileNotifyChangeSecurity
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}
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if e&Rename != 0 {
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e = (e ^ Rename) | FileNotifyChangeFileName
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}
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return uint32(e)
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}
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// watched is made in order to check whether an action comes from a directory or
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// file. This approach requires two file handlers per single monitored folder. The
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// second grip handles actions which include creating or deleting a directory. If
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// these processes are not monitored, only the first grip is created.
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type watched struct {
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filter uint32
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recursive bool
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count uint8
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pathw []uint16
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digrip [2]*grip
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}
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// newWatched creates a new watched instance. It splits the filter variable into
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// two parts. The first part is responsible for watching all events which can be
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// created for a file in watched directory structure and the second one watches
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// only directory Create/Remove actions. If all operations succeed, the Create
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// message is sent to I/O completion port queue for further processing.
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func newWatched(cph syscall.Handle, filter uint32, recursive bool,
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path string) (wd *watched, err error) {
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wd = &watched{
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filter: filter,
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recursive: recursive,
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}
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if wd.pathw, err = syscall.UTF16FromString(path); err != nil {
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return
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}
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if err = wd.recreate(cph); err != nil {
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return
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}
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return wd, nil
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}
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// TODO : doc
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func (wd *watched) recreate(cph syscall.Handle) (err error) {
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filefilter := wd.filter &^ uint32(FileNotifyChangeDirName)
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if err = wd.updateGrip(0, cph, filefilter == 0, filefilter); err != nil {
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return
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}
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dirfilter := wd.filter & uint32(FileNotifyChangeDirName|Create|Remove)
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if err = wd.updateGrip(1, cph, dirfilter == 0, wd.filter|uint32(dirmarker)); err != nil {
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return
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}
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wd.filter &^= onlyMachineStates
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return
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}
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// TODO : doc
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func (wd *watched) updateGrip(idx int, cph syscall.Handle, reset bool,
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newflag uint32) (err error) {
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if reset {
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wd.digrip[idx] = nil
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} else {
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if wd.digrip[idx] == nil {
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if wd.digrip[idx], err = newGrip(cph, wd, newflag); err != nil {
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wd.closeHandle()
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return
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}
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} else {
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wd.digrip[idx].filter = newflag
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wd.digrip[idx].recursive = wd.recursive
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if err = wd.digrip[idx].register(cph); err != nil {
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wd.closeHandle()
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return
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}
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}
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wd.count++
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}
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return
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}
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// closeHandle closes handles that are stored in digrip array. Function always
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// tries to close all of the handlers before it exits, even when there are errors
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// returned from the operating system kernel.
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func (wd *watched) closeHandle() (err error) {
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for _, g := range wd.digrip {
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if g == nil {
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continue
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}
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for {
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handle := syscall.Handle(atomic.LoadUintptr((*uintptr)(&g.handle)))
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if handle == syscall.InvalidHandle {
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break // Already closed.
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}
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e := syscall.CloseHandle(handle)
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if e != nil && err == nil {
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err = e
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}
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// Set invalid handle even when CloseHandle fails. This will leak
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// the handle but, since we can't close it anyway, there won't be
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// any difference.
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if atomic.CompareAndSwapUintptr((*uintptr)(&g.handle),
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(uintptr)(handle), (uintptr)(syscall.InvalidHandle)) {
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break
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}
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}
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}
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return
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}
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// watcher implements Watcher interface. It stores a set of watched directories.
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// All operations which remove watched objects from map `m` must be performed in
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// loop goroutine since these structures are used internally by operating system.
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type readdcw struct {
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sync.Mutex
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m map[string]*watched
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cph syscall.Handle
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start bool
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wg sync.WaitGroup
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c chan<- EventInfo
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}
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// NewWatcher creates new non-recursive watcher backed by ReadDirectoryChangesW.
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func newWatcher(c chan<- EventInfo) watcher {
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r := &readdcw{
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m: make(map[string]*watched),
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cph: syscall.InvalidHandle,
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c: c,
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}
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runtime.SetFinalizer(r, func(r *readdcw) {
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if r.cph != syscall.InvalidHandle {
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syscall.CloseHandle(r.cph)
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}
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})
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return r
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}
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// Watch implements notify.Watcher interface.
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func (r *readdcw) Watch(path string, event Event) error {
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return r.watch(path, event, false)
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}
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// RecursiveWatch implements notify.RecursiveWatcher interface.
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func (r *readdcw) RecursiveWatch(path string, event Event) error {
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return r.watch(path, event, true)
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}
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// watch inserts a directory to the group of watched folders. If watched folder
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// already exists, function tries to rewatch it with new filters(NOT VALID). Moreover,
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// watch starts the main event loop goroutine when called for the first time.
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func (r *readdcw) watch(path string, event Event, recursive bool) error {
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if event&^(All|fileNotifyChangeAll) != 0 {
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return errors.New("notify: unknown event")
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}
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r.Lock()
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defer r.Unlock()
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if wd, ok := r.m[path]; ok {
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dbgprint("watch: already exists")
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wd.filter &^= stateUnwatch
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return nil
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}
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if err := r.lazyinit(); err != nil {
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return err
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}
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wd, err := newWatched(r.cph, uint32(event), recursive, path)
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if err != nil {
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return err
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}
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r.m[path] = wd
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dbgprint("watch: new watch added")
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return nil
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}
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// lazyinit creates an I/O completion port and starts the main event loop.
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func (r *readdcw) lazyinit() (err error) {
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invalid := uintptr(syscall.InvalidHandle)
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if atomic.LoadUintptr((*uintptr)(&r.cph)) == invalid {
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cph := syscall.InvalidHandle
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if cph, err = syscall.CreateIoCompletionPort(cph, 0, 0, 0); err != nil {
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return
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}
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r.cph, r.start = cph, true
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go r.loop()
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}
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return
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}
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// TODO(pknap) : doc
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func (r *readdcw) loop() {
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var n, key uint32
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var overlapped *syscall.Overlapped
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for {
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err := syscall.GetQueuedCompletionStatus(r.cph, &n, &key, &overlapped, syscall.INFINITE)
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if key == stateCPClose {
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r.Lock()
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handle := r.cph
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r.cph = syscall.InvalidHandle
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r.Unlock()
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syscall.CloseHandle(handle)
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r.wg.Done()
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return
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}
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if overlapped == nil {
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// TODO: check key == rewatch delete or 0(panic)
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continue
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}
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overEx := (*overlappedEx)(unsafe.Pointer(overlapped))
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if n != 0 {
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r.loopevent(n, overEx)
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if err = overEx.parent.readDirChanges(); err != nil {
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// TODO: error handling
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}
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}
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r.loopstate(overEx)
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}
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}
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// TODO(pknap) : doc
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func (r *readdcw) loopstate(overEx *overlappedEx) {
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r.Lock()
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defer r.Unlock()
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filter := overEx.parent.parent.filter
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if filter&onlyMachineStates == 0 {
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return
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}
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if overEx.parent.parent.count--; overEx.parent.parent.count == 0 {
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switch filter & onlyMachineStates {
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case stateRewatch:
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dbgprint("loopstate rewatch")
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overEx.parent.parent.recreate(r.cph)
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case stateUnwatch:
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dbgprint("loopstate unwatch")
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overEx.parent.parent.closeHandle()
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delete(r.m, syscall.UTF16ToString(overEx.parent.pathw))
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case stateCPClose:
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default:
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panic(`notify: windows loopstate logic error`)
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}
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}
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}
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// TODO(pknap) : doc
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func (r *readdcw) loopevent(n uint32, overEx *overlappedEx) {
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events := []*event{}
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var currOffset uint32
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for {
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raw := (*syscall.FileNotifyInformation)(unsafe.Pointer(&overEx.parent.buffer[currOffset]))
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name := syscall.UTF16ToString((*[syscall.MAX_LONG_PATH]uint16)(unsafe.Pointer(&raw.FileName))[:raw.FileNameLength>>1])
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events = append(events, &event{
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pathw: overEx.parent.pathw,
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filter: overEx.parent.filter,
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action: raw.Action,
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name: name,
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})
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if raw.NextEntryOffset == 0 {
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break
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}
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if currOffset += raw.NextEntryOffset; currOffset >= n {
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break
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}
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}
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r.send(events)
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}
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// TODO(pknap) : doc
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func (r *readdcw) send(es []*event) {
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for _, e := range es {
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var syse Event
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if e.e, syse = decode(e.filter, e.action); e.e == 0 && syse == 0 {
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continue
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}
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switch {
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case e.action == syscall.FILE_ACTION_MODIFIED:
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e.ftype = fTypeUnknown
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case e.filter&uint32(dirmarker) != 0:
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e.ftype = fTypeDirectory
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default:
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e.ftype = fTypeFile
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}
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switch {
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case e.e == 0:
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e.e = syse
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case syse != 0:
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r.c <- &event{
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pathw: e.pathw,
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name: e.name,
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ftype: e.ftype,
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action: e.action,
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filter: e.filter,
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e: syse,
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}
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}
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r.c <- e
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}
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}
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// Rewatch implements notify.Rewatcher interface.
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func (r *readdcw) Rewatch(path string, oldevent, newevent Event) error {
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return r.rewatch(path, uint32(oldevent), uint32(newevent), false)
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}
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// RecursiveRewatch implements notify.RecursiveRewatcher interface.
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func (r *readdcw) RecursiveRewatch(oldpath, newpath string, oldevent,
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newevent Event) error {
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if oldpath != newpath {
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if err := r.unwatch(oldpath); err != nil {
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return err
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}
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return r.watch(newpath, newevent, true)
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}
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return r.rewatch(newpath, uint32(oldevent), uint32(newevent), true)
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}
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// TODO : (pknap) doc.
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func (r *readdcw) rewatch(path string, oldevent, newevent uint32, recursive bool) (err error) {
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if Event(newevent)&^(All|fileNotifyChangeAll) != 0 {
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return errors.New("notify: unknown event")
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}
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var wd *watched
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r.Lock()
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defer r.Unlock()
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if wd, err = r.nonStateWatchedLocked(path); err != nil {
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return
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}
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if wd.filter&(onlyNotifyChanges|onlyNGlobalEvents) != oldevent {
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panic(`notify: windows re-watcher logic error`)
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}
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wd.filter = stateRewatch | newevent
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wd.recursive, recursive = recursive, wd.recursive
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if err = wd.closeHandle(); err != nil {
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wd.filter = oldevent
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wd.recursive = recursive
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return
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}
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return
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}
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// TODO : pknap
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func (r *readdcw) nonStateWatchedLocked(path string) (wd *watched, err error) {
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wd, ok := r.m[path]
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if !ok || wd == nil {
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err = errors.New(`notify: ` + path + ` path is unwatched`)
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return
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}
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if wd.filter&onlyMachineStates != 0 {
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err = errors.New(`notify: another re/unwatching operation in progress`)
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return
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}
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return
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}
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// Unwatch implements notify.Watcher interface.
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func (r *readdcw) Unwatch(path string) error {
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return r.unwatch(path)
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}
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// RecursiveUnwatch implements notify.RecursiveWatcher interface.
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func (r *readdcw) RecursiveUnwatch(path string) error {
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return r.unwatch(path)
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}
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// TODO : pknap
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func (r *readdcw) unwatch(path string) (err error) {
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var wd *watched
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r.Lock()
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defer r.Unlock()
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if wd, err = r.nonStateWatchedLocked(path); err != nil {
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return
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}
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wd.filter |= stateUnwatch
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dbgprint("unwatch: set unwatch state")
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if _, attrErr := syscall.GetFileAttributes(&wd.pathw[0]); attrErr != nil {
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for _, g := range wd.digrip {
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if g == nil {
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continue
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}
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dbgprint("unwatch: posting")
|
|
if err = syscall.PostQueuedCompletionStatus(r.cph, 0, 0, (*syscall.Overlapped)(unsafe.Pointer(g.ovlapped))); err != nil {
|
|
wd.filter &^= stateUnwatch
|
|
return
|
|
}
|
|
}
|
|
}
|
|
|
|
return
|
|
}
|
|
|
|
// Close resets the whole watcher object, closes all existing file descriptors,
|
|
// and sends stateCPClose state as completion key to the main watcher's loop.
|
|
func (r *readdcw) Close() (err error) {
|
|
r.Lock()
|
|
if !r.start {
|
|
r.Unlock()
|
|
return nil
|
|
}
|
|
for _, wd := range r.m {
|
|
wd.filter &^= onlyMachineStates
|
|
wd.filter |= stateCPClose
|
|
if e := wd.closeHandle(); e != nil && err == nil {
|
|
err = e
|
|
}
|
|
}
|
|
r.start = false
|
|
r.Unlock()
|
|
r.wg.Add(1)
|
|
if e := syscall.PostQueuedCompletionStatus(r.cph, 0, stateCPClose, nil); e != nil && err == nil {
|
|
return e
|
|
}
|
|
r.wg.Wait()
|
|
return
|
|
}
|
|
|
|
// decode creates a notify event from both non-raw filter and action which was
|
|
// returned from completion routine. Function may return Event(0) in case when
|
|
// filter was replaced by a new value which does not contain fields that are
|
|
// valid with passed action.
|
|
func decode(filter, action uint32) (Event, Event) {
|
|
switch action {
|
|
case syscall.FILE_ACTION_ADDED:
|
|
return gensys(filter, Create, FileActionAdded)
|
|
case syscall.FILE_ACTION_REMOVED:
|
|
return gensys(filter, Remove, FileActionRemoved)
|
|
case syscall.FILE_ACTION_MODIFIED:
|
|
return gensys(filter, Write, FileActionModified)
|
|
case syscall.FILE_ACTION_RENAMED_OLD_NAME:
|
|
return gensys(filter, Rename, FileActionRenamedOldName)
|
|
case syscall.FILE_ACTION_RENAMED_NEW_NAME:
|
|
return gensys(filter, Rename, FileActionRenamedNewName)
|
|
}
|
|
panic(`notify: cannot decode internal mask`)
|
|
}
|
|
|
|
// gensys decides whether the Windows action, system-independent event or both
|
|
// of them should be returned. Since the grip's filter may be atomically changed
|
|
// during watcher lifetime, it is possible that neither Windows nor notify masks
|
|
// are watched by the user when this function is called.
|
|
func gensys(filter uint32, ge, se Event) (gene, syse Event) {
|
|
isdir := filter&uint32(dirmarker) != 0
|
|
if isdir && filter&uint32(FileNotifyChangeDirName) != 0 ||
|
|
!isdir && filter&uint32(FileNotifyChangeFileName) != 0 ||
|
|
filter&uint32(fileNotifyChangeModified) != 0 {
|
|
syse = se
|
|
}
|
|
if filter&uint32(ge) != 0 {
|
|
gene = ge
|
|
}
|
|
return
|
|
}
|