diff options
Diffstat (limited to 'vendor/github.com/rjeczalik/notify/watcher_readdcw.go')
| -rw-r--r-- | vendor/github.com/rjeczalik/notify/watcher_readdcw.go | 574 |
1 files changed, 574 insertions, 0 deletions
diff --git a/vendor/github.com/rjeczalik/notify/watcher_readdcw.go b/vendor/github.com/rjeczalik/notify/watcher_readdcw.go new file mode 100644 index 000000000..5923bfdda --- /dev/null +++ b/vendor/github.com/rjeczalik/notify/watcher_readdcw.go @@ -0,0 +1,574 @@ +// Copyright (c) 2014-2015 The Notify Authors. All rights reserved. +// Use of this source code is governed by the MIT license that can be +// found in the LICENSE file. + +// +build windows + +package notify + +import ( + "errors" + "runtime" + "sync" + "sync/atomic" + "syscall" + "unsafe" +) + +// readBufferSize defines the size of an array in which read statuses are stored. +// The buffer have to be DWORD-aligned and, if notify is used in monitoring a +// directory over the network, its size must not be greater than 64KB. Each of +// watched directories uses its own buffer for storing events. +const readBufferSize = 4096 + +// Since all operations which go through the Windows completion routine are done +// asynchronously, filter may set one of the constants belor. They were defined +// in order to distinguish whether current folder should be re-registered in +// ReadDirectoryChangesW function or some control operations need to be executed. +const ( + stateRewatch uint32 = 1 << (28 + iota) + stateUnwatch + stateCPClose +) + +// Filter used in current implementation was split into four segments: +// - bits 0-11 store ReadDirectoryChangesW filters, +// - bits 12-19 store File notify actions, +// - bits 20-27 store notify specific events and flags, +// - bits 28-31 store states which are used in loop's FSM. +// Constants below are used as masks to retrieve only specific filter parts. +const ( + onlyNotifyChanges uint32 = 0x00000FFF + onlyNGlobalEvents uint32 = 0x0FF00000 + onlyMachineStates uint32 = 0xF0000000 +) + +// grip represents a single watched directory. It stores the data required by +// ReadDirectoryChangesW function. Only the filter, recursive, and handle members +// may by modified by watcher implementation. Rest of the them have to remain +// constant since they are used by Windows completion routine. This indicates that +// grip can be removed only when all operations on the file handle are finished. +type grip struct { + handle syscall.Handle + filter uint32 + recursive bool + pathw []uint16 + buffer [readBufferSize]byte + parent *watched + ovlapped *overlappedEx +} + +// overlappedEx stores information used in asynchronous input and output. +// Additionally, overlappedEx contains a pointer to 'grip' item which is used in +// order to gather the structure in which the overlappedEx object was created. +type overlappedEx struct { + syscall.Overlapped + parent *grip +} + +// newGrip creates a new file handle that can be used in overlapped operations. +// Then, the handle is associated with I/O completion port 'cph' and its value +// is stored in newly created 'grip' object. +func newGrip(cph syscall.Handle, parent *watched, filter uint32) (*grip, error) { + g := &grip{ + handle: syscall.InvalidHandle, + filter: filter, + recursive: parent.recursive, + pathw: parent.pathw, + parent: parent, + ovlapped: &overlappedEx{}, + } + if err := g.register(cph); err != nil { + return nil, err + } + g.ovlapped.parent = g + return g, nil +} + +// NOTE : Thread safe +func (g *grip) register(cph syscall.Handle) (err error) { + if g.handle, err = syscall.CreateFile( + &g.pathw[0], + syscall.FILE_LIST_DIRECTORY, + syscall.FILE_SHARE_READ|syscall.FILE_SHARE_WRITE|syscall.FILE_SHARE_DELETE, + nil, + syscall.OPEN_EXISTING, + syscall.FILE_FLAG_BACKUP_SEMANTICS|syscall.FILE_FLAG_OVERLAPPED, + 0, + ); err != nil { + return + } + if _, err = syscall.CreateIoCompletionPort(g.handle, cph, 0, 0); err != nil { + syscall.CloseHandle(g.handle) + return + } + return g.readDirChanges() +} + +// readDirChanges tells the system to store file change information in grip's +// buffer. Directory changes that occur between calls to this function are added +// to the buffer and then, returned with the next call. +func (g *grip) readDirChanges() error { + return syscall.ReadDirectoryChanges( + g.handle, + &g.buffer[0], + uint32(unsafe.Sizeof(g.buffer)), + g.recursive, + encode(g.filter), + nil, + (*syscall.Overlapped)(unsafe.Pointer(g.ovlapped)), + 0, + ) +} + +// encode transforms a generic filter, which contains platform independent and +// implementation specific bit fields, to value that can be used as NotifyFilter +// parameter in ReadDirectoryChangesW function. +func encode(filter uint32) uint32 { + e := Event(filter & (onlyNGlobalEvents | onlyNotifyChanges)) + if e&dirmarker != 0 { + return uint32(FileNotifyChangeDirName) + } + if e&Create != 0 { + e = (e ^ Create) | FileNotifyChangeFileName + } + if e&Remove != 0 { + e = (e ^ Remove) | FileNotifyChangeFileName + } + if e&Write != 0 { + e = (e ^ Write) | FileNotifyChangeAttributes | FileNotifyChangeSize | + FileNotifyChangeCreation | FileNotifyChangeSecurity + } + if e&Rename != 0 { + e = (e ^ Rename) | FileNotifyChangeFileName + } + return uint32(e) +} + +// watched is made in order to check whether an action comes from a directory or +// file. This approach requires two file handlers per single monitored folder. The +// second grip handles actions which include creating or deleting a directory. If +// these processes are not monitored, only the first grip is created. +type watched struct { + filter uint32 + recursive bool + count uint8 + pathw []uint16 + digrip [2]*grip +} + +// newWatched creates a new watched instance. It splits the filter variable into +// two parts. The first part is responsible for watching all events which can be +// created for a file in watched directory structure and the second one watches +// only directory Create/Remove actions. If all operations succeed, the Create +// message is sent to I/O completion port queue for further processing. +func newWatched(cph syscall.Handle, filter uint32, recursive bool, + path string) (wd *watched, err error) { + wd = &watched{ + filter: filter, + recursive: recursive, + } + if wd.pathw, err = syscall.UTF16FromString(path); err != nil { + return + } + if err = wd.recreate(cph); err != nil { + return + } + return wd, nil +} + +// TODO : doc +func (wd *watched) recreate(cph syscall.Handle) (err error) { + filefilter := wd.filter &^ uint32(FileNotifyChangeDirName) + if err = wd.updateGrip(0, cph, filefilter == 0, filefilter); err != nil { + return + } + dirfilter := wd.filter & uint32(FileNotifyChangeDirName|Create|Remove) + if err = wd.updateGrip(1, cph, dirfilter == 0, wd.filter|uint32(dirmarker)); err != nil { + return + } + wd.filter &^= onlyMachineStates + return +} + +// TODO : doc +func (wd *watched) updateGrip(idx int, cph syscall.Handle, reset bool, + newflag uint32) (err error) { + if reset { + wd.digrip[idx] = nil + } else { + if wd.digrip[idx] == nil { + if wd.digrip[idx], err = newGrip(cph, wd, newflag); err != nil { + wd.closeHandle() + return + } + } else { + wd.digrip[idx].filter = newflag + wd.digrip[idx].recursive = wd.recursive + if err = wd.digrip[idx].register(cph); err != nil { + wd.closeHandle() + return + } + } + wd.count++ + } + return +} + +// closeHandle closes handles that are stored in digrip array. Function always +// tries to close all of the handlers before it exits, even when there are errors +// returned from the operating system kernel. +func (wd *watched) closeHandle() (err error) { + for _, g := range wd.digrip { + if g != nil && g.handle != syscall.InvalidHandle { + switch suberr := syscall.CloseHandle(g.handle); { + case suberr == nil: + g.handle = syscall.InvalidHandle + case err == nil: + err = suberr + } + } + } + return +} + +// watcher implements Watcher interface. It stores a set of watched directories. +// All operations which remove watched objects from map `m` must be performed in +// loop goroutine since these structures are used internally by operating system. +type readdcw struct { + sync.Mutex + m map[string]*watched + cph syscall.Handle + start bool + wg sync.WaitGroup + c chan<- EventInfo +} + +// NewWatcher creates new non-recursive watcher backed by ReadDirectoryChangesW. +func newWatcher(c chan<- EventInfo) watcher { + r := &readdcw{ + m: make(map[string]*watched), + cph: syscall.InvalidHandle, + c: c, + } + runtime.SetFinalizer(r, func(r *readdcw) { + if r.cph != syscall.InvalidHandle { + syscall.CloseHandle(r.cph) + } + }) + return r +} + +// Watch implements notify.Watcher interface. +func (r *readdcw) Watch(path string, event Event) error { + return r.watch(path, event, false) +} + +// RecursiveWatch implements notify.RecursiveWatcher interface. +func (r *readdcw) RecursiveWatch(path string, event Event) error { + return r.watch(path, event, true) +} + +// watch inserts a directory to the group of watched folders. If watched folder +// already exists, function tries to rewatch it with new filters(NOT VALID). Moreover, +// watch starts the main event loop goroutine when called for the first time. +func (r *readdcw) watch(path string, event Event, recursive bool) (err error) { + if event&^(All|fileNotifyChangeAll) != 0 { + return errors.New("notify: unknown event") + } + r.Lock() + wd, ok := r.m[path] + r.Unlock() + if !ok { + if err = r.lazyinit(); err != nil { + return + } + r.Lock() + if wd, ok = r.m[path]; ok { + r.Unlock() + return + } + if wd, err = newWatched(r.cph, uint32(event), recursive, path); err != nil { + r.Unlock() + return + } + r.m[path] = wd + r.Unlock() + } + return nil +} + +// lazyinit creates an I/O completion port and starts the main event processing +// loop. This method uses Double-Checked Locking optimization. +func (r *readdcw) lazyinit() (err error) { + invalid := uintptr(syscall.InvalidHandle) + if atomic.LoadUintptr((*uintptr)(&r.cph)) == invalid { + r.Lock() + defer r.Unlock() + if atomic.LoadUintptr((*uintptr)(&r.cph)) == invalid { + cph := syscall.InvalidHandle + if cph, err = syscall.CreateIoCompletionPort(cph, 0, 0, 0); err != nil { + return + } + r.cph, r.start = cph, true + go r.loop() + } + } + return +} + +// TODO(pknap) : doc +func (r *readdcw) loop() { + var n, key uint32 + var overlapped *syscall.Overlapped + for { + err := syscall.GetQueuedCompletionStatus(r.cph, &n, &key, &overlapped, syscall.INFINITE) + if key == stateCPClose { + r.Lock() + handle := r.cph + r.cph = syscall.InvalidHandle + r.Unlock() + syscall.CloseHandle(handle) + r.wg.Done() + return + } + if overlapped == nil { + // TODO: check key == rewatch delete or 0(panic) + continue + } + overEx := (*overlappedEx)(unsafe.Pointer(overlapped)) + if n == 0 { + r.loopstate(overEx) + } else { + r.loopevent(n, overEx) + if err = overEx.parent.readDirChanges(); err != nil { + // TODO: error handling + } + } + } +} + +// TODO(pknap) : doc +func (r *readdcw) loopstate(overEx *overlappedEx) { + filter := atomic.LoadUint32(&overEx.parent.parent.filter) + if filter&onlyMachineStates == 0 { + return + } + if overEx.parent.parent.count--; overEx.parent.parent.count == 0 { + switch filter & onlyMachineStates { + case stateRewatch: + r.Lock() + overEx.parent.parent.recreate(r.cph) + r.Unlock() + case stateUnwatch: + r.Lock() + delete(r.m, syscall.UTF16ToString(overEx.parent.pathw)) + r.Unlock() + case stateCPClose: + default: + panic(`notify: windows loopstate logic error`) + } + } +} + +// TODO(pknap) : doc +func (r *readdcw) loopevent(n uint32, overEx *overlappedEx) { + events := []*event{} + var currOffset uint32 + for { + raw := (*syscall.FileNotifyInformation)(unsafe.Pointer(&overEx.parent.buffer[currOffset])) + name := syscall.UTF16ToString((*[syscall.MAX_LONG_PATH]uint16)(unsafe.Pointer(&raw.FileName))[:raw.FileNameLength>>1]) + events = append(events, &event{ + pathw: overEx.parent.pathw, + filter: overEx.parent.filter, + action: raw.Action, + name: name, + }) + if raw.NextEntryOffset == 0 { + break + } + if currOffset += raw.NextEntryOffset; currOffset >= n { + break + } + } + r.send(events) +} + +// TODO(pknap) : doc +func (r *readdcw) send(es []*event) { + for _, e := range es { + var syse Event + if e.e, syse = decode(e.filter, e.action); e.e == 0 && syse == 0 { + continue + } + switch { + case e.action == syscall.FILE_ACTION_MODIFIED: + e.ftype = fTypeUnknown + case e.filter&uint32(dirmarker) != 0: + e.ftype = fTypeDirectory + default: + e.ftype = fTypeFile + } + switch { + case e.e == 0: + e.e = syse + case syse != 0: + r.c <- &event{ + pathw: e.pathw, + name: e.name, + ftype: e.ftype, + action: e.action, + filter: e.filter, + e: syse, + } + } + r.c <- e + } +} + +// Rewatch implements notify.Rewatcher interface. +func (r *readdcw) Rewatch(path string, oldevent, newevent Event) error { + return r.rewatch(path, uint32(oldevent), uint32(newevent), false) +} + +// RecursiveRewatch implements notify.RecursiveRewatcher interface. +func (r *readdcw) RecursiveRewatch(oldpath, newpath string, oldevent, + newevent Event) error { + if oldpath != newpath { + if err := r.unwatch(oldpath); err != nil { + return err + } + return r.watch(newpath, newevent, true) + } + return r.rewatch(newpath, uint32(oldevent), uint32(newevent), true) +} + +// TODO : (pknap) doc. +func (r *readdcw) rewatch(path string, oldevent, newevent uint32, recursive bool) (err error) { + if Event(newevent)&^(All|fileNotifyChangeAll) != 0 { + return errors.New("notify: unknown event") + } + var wd *watched + r.Lock() + if wd, err = r.nonStateWatched(path); err != nil { + r.Unlock() + return + } + if wd.filter&(onlyNotifyChanges|onlyNGlobalEvents) != oldevent { + panic(`notify: windows re-watcher logic error`) + } + wd.filter = stateRewatch | newevent + wd.recursive, recursive = recursive, wd.recursive + if err = wd.closeHandle(); err != nil { + wd.filter = oldevent + wd.recursive = recursive + r.Unlock() + return + } + r.Unlock() + return +} + +// TODO : pknap +func (r *readdcw) nonStateWatched(path string) (wd *watched, err error) { + wd, ok := r.m[path] + if !ok || wd == nil { + err = errors.New(`notify: ` + path + ` path is unwatched`) + return + } + if filter := atomic.LoadUint32(&wd.filter); filter&onlyMachineStates != 0 { + err = errors.New(`notify: another re/unwatching operation in progress`) + return + } + return +} + +// Unwatch implements notify.Watcher interface. +func (r *readdcw) Unwatch(path string) error { + return r.unwatch(path) +} + +// RecursiveUnwatch implements notify.RecursiveWatcher interface. +func (r *readdcw) RecursiveUnwatch(path string) error { + return r.unwatch(path) +} + +// TODO : pknap +func (r *readdcw) unwatch(path string) (err error) { + var wd *watched + r.Lock() + if wd, err = r.nonStateWatched(path); err != nil { + r.Unlock() + return + } + wd.filter |= stateUnwatch + if err = wd.closeHandle(); err != nil { + wd.filter &^= stateUnwatch + r.Unlock() + return + } + r.Unlock() + 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 +} |