Line data Source code
1 : // Copyright 2012 The LevelDB-Go and Pebble Authors. All rights reserved. Use
2 : // of this source code is governed by a BSD-style license that can be found in
3 : // the LICENSE file.
4 :
5 : package vfs // import "github.com/cockroachdb/pebble/vfs"
6 :
7 : import (
8 : "bytes"
9 : "fmt"
10 : "io"
11 : "os"
12 : "path"
13 : "sort"
14 : "strings"
15 : "sync"
16 : "sync/atomic"
17 : "syscall"
18 : "time"
19 :
20 : "github.com/cockroachdb/errors"
21 : "github.com/cockroachdb/errors/oserror"
22 : "github.com/cockroachdb/pebble/internal/invariants"
23 : )
24 :
25 : const sep = "/"
26 :
27 : // NewMem returns a new memory-backed FS implementation.
28 2 : func NewMem() *MemFS {
29 2 : return &MemFS{
30 2 : root: newRootMemNode(),
31 2 : }
32 2 : }
33 :
34 : // NewStrictMem returns a "strict" memory-backed FS implementation. The behaviour is strict wrt
35 : // needing a Sync() call on files or directories for the state changes to be finalized. Any
36 : // changes that are not finalized are visible to reads until MemFS.ResetToSyncedState() is called,
37 : // at which point they are discarded and no longer visible.
38 : //
39 : // Expected usage:
40 : //
41 : // strictFS := NewStrictMem()
42 : // db := Open(..., &Options{FS: strictFS})
43 : // // Do and commit various operations.
44 : // ...
45 : // // Prevent any more changes to finalized state.
46 : // strictFS.SetIgnoreSyncs(true)
47 : // // This will finish any ongoing background flushes, compactions but none of these writes will
48 : // // be finalized since syncs are being ignored.
49 : // db.Close()
50 : // // Discard unsynced state.
51 : // strictFS.ResetToSyncedState()
52 : // // Allow changes to finalized state.
53 : // strictFS.SetIgnoreSyncs(false)
54 : // // Open the DB. This DB should have the same state as if the earlier strictFS operations and
55 : // // db.Close() were not called.
56 : // db := Open(..., &Options{FS: strictFS})
57 2 : func NewStrictMem() *MemFS {
58 2 : return &MemFS{
59 2 : root: newRootMemNode(),
60 2 : strict: true,
61 2 : }
62 2 : }
63 :
64 : // NewMemFile returns a memory-backed File implementation. The memory-backed
65 : // file takes ownership of data.
66 1 : func NewMemFile(data []byte) File {
67 1 : n := &memNode{}
68 1 : n.refs.Store(1)
69 1 : n.mu.data = data
70 1 : n.mu.modTime = time.Now()
71 1 : return &memFile{
72 1 : n: n,
73 1 : read: true,
74 1 : }
75 1 : }
76 :
77 : // MemFS implements FS.
78 : type MemFS struct {
79 : mu sync.Mutex
80 : root *memNode
81 :
82 : // lockFiles holds a map of open file locks. Presence in this map indicates
83 : // a file lock is currently held. Keys are strings holding the path of the
84 : // locked file. The stored value is untyped and unused; only presence of
85 : // the key within the map is significant.
86 : lockedFiles sync.Map
87 : strict bool
88 : ignoreSyncs bool
89 : // Windows has peculiar semantics with respect to hard links and deleting
90 : // open files. In tests meant to exercise this behavior, this flag can be
91 : // set to error if removing an open file.
92 : windowsSemantics bool
93 : }
94 :
95 : var _ FS = &MemFS{}
96 :
97 : // UseWindowsSemantics configures whether the MemFS implements Windows-style
98 : // semantics, in particular with respect to whether any of an open file's links
99 : // may be removed. Windows semantics default to off.
100 1 : func (y *MemFS) UseWindowsSemantics(windowsSemantics bool) {
101 1 : y.mu.Lock()
102 1 : defer y.mu.Unlock()
103 1 : y.windowsSemantics = windowsSemantics
104 1 : }
105 :
106 : // String dumps the contents of the MemFS.
107 1 : func (y *MemFS) String() string {
108 1 : y.mu.Lock()
109 1 : defer y.mu.Unlock()
110 1 :
111 1 : s := new(bytes.Buffer)
112 1 : y.root.dump(s, 0)
113 1 : return s.String()
114 1 : }
115 :
116 : // SetIgnoreSyncs sets the MemFS.ignoreSyncs field. See the usage comment with NewStrictMem() for
117 : // details.
118 1 : func (y *MemFS) SetIgnoreSyncs(ignoreSyncs bool) {
119 1 : y.mu.Lock()
120 1 : if !y.strict {
121 0 : // noop
122 0 : return
123 0 : }
124 1 : y.ignoreSyncs = ignoreSyncs
125 1 : y.mu.Unlock()
126 : }
127 :
128 : // ResetToSyncedState discards state in the FS that is not synced. See the usage comment with
129 : // NewStrictMem() for details.
130 1 : func (y *MemFS) ResetToSyncedState() {
131 1 : if !y.strict {
132 0 : // noop
133 0 : return
134 0 : }
135 1 : y.mu.Lock()
136 1 : y.root.resetToSyncedState()
137 1 : y.mu.Unlock()
138 : }
139 :
140 : // walk walks the directory tree for the fullname, calling f at each step. If
141 : // f returns an error, the walk will be aborted and return that same error.
142 : //
143 : // Each walk is atomic: y's mutex is held for the entire operation, including
144 : // all calls to f.
145 : //
146 : // dir is the directory at that step, frag is the name fragment, and final is
147 : // whether it is the final step. For example, walking "/foo/bar/x" will result
148 : // in 3 calls to f:
149 : // - "/", "foo", false
150 : // - "/foo/", "bar", false
151 : // - "/foo/bar/", "x", true
152 : //
153 : // Similarly, walking "/y/z/", with a trailing slash, will result in 3 calls to f:
154 : // - "/", "y", false
155 : // - "/y/", "z", false
156 : // - "/y/z/", "", true
157 2 : func (y *MemFS) walk(fullname string, f func(dir *memNode, frag string, final bool) error) error {
158 2 : y.mu.Lock()
159 2 : defer y.mu.Unlock()
160 2 :
161 2 : // For memfs, the current working directory is the same as the root directory,
162 2 : // so we strip off any leading "/"s to make fullname a relative path, and
163 2 : // the walk starts at y.root.
164 2 : for len(fullname) > 0 && fullname[0] == sep[0] {
165 2 : fullname = fullname[1:]
166 2 : }
167 2 : dir := y.root
168 2 :
169 2 : for {
170 2 : frag, remaining := fullname, ""
171 2 : i := strings.IndexRune(fullname, rune(sep[0]))
172 2 : final := i < 0
173 2 : if !final {
174 2 : frag, remaining = fullname[:i], fullname[i+1:]
175 2 : for len(remaining) > 0 && remaining[0] == sep[0] {
176 0 : remaining = remaining[1:]
177 0 : }
178 : }
179 2 : if err := f(dir, frag, final); err != nil {
180 1 : return err
181 1 : }
182 2 : if final {
183 2 : break
184 : }
185 2 : child := dir.children[frag]
186 2 : if child == nil {
187 2 : return &os.PathError{
188 2 : Op: "open",
189 2 : Path: fullname,
190 2 : Err: oserror.ErrNotExist,
191 2 : }
192 2 : }
193 2 : if !child.isDir {
194 1 : return &os.PathError{
195 1 : Op: "open",
196 1 : Path: fullname,
197 1 : Err: errors.New("not a directory"),
198 1 : }
199 1 : }
200 2 : dir, fullname = child, remaining
201 : }
202 2 : return nil
203 : }
204 :
205 : // Create implements FS.Create.
206 2 : func (y *MemFS) Create(fullname string) (File, error) {
207 2 : var ret *memFile
208 2 : err := y.walk(fullname, func(dir *memNode, frag string, final bool) error {
209 2 : if final {
210 2 : if frag == "" {
211 0 : return errors.New("pebble/vfs: empty file name")
212 0 : }
213 2 : n := &memNode{name: frag}
214 2 : dir.children[frag] = n
215 2 : ret = &memFile{
216 2 : n: n,
217 2 : fs: y,
218 2 : read: true,
219 2 : write: true,
220 2 : }
221 : }
222 2 : return nil
223 : })
224 2 : if err != nil {
225 1 : return nil, err
226 1 : }
227 2 : ret.n.refs.Add(1)
228 2 : return ret, nil
229 : }
230 :
231 : // Link implements FS.Link.
232 2 : func (y *MemFS) Link(oldname, newname string) error {
233 2 : var n *memNode
234 2 : err := y.walk(oldname, func(dir *memNode, frag string, final bool) error {
235 2 : if final {
236 2 : if frag == "" {
237 0 : return errors.New("pebble/vfs: empty file name")
238 0 : }
239 2 : n = dir.children[frag]
240 : }
241 2 : return nil
242 : })
243 2 : if err != nil {
244 0 : return err
245 0 : }
246 2 : if n == nil {
247 1 : return &os.LinkError{
248 1 : Op: "link",
249 1 : Old: oldname,
250 1 : New: newname,
251 1 : Err: oserror.ErrNotExist,
252 1 : }
253 1 : }
254 2 : return y.walk(newname, func(dir *memNode, frag string, final bool) error {
255 2 : if final {
256 2 : if frag == "" {
257 0 : return errors.New("pebble/vfs: empty file name")
258 0 : }
259 2 : if _, ok := dir.children[frag]; ok {
260 1 : return &os.LinkError{
261 1 : Op: "link",
262 1 : Old: oldname,
263 1 : New: newname,
264 1 : Err: oserror.ErrExist,
265 1 : }
266 1 : }
267 2 : dir.children[frag] = n
268 : }
269 2 : return nil
270 : })
271 : }
272 :
273 2 : func (y *MemFS) open(fullname string, openForWrite bool) (File, error) {
274 2 : var ret *memFile
275 2 : err := y.walk(fullname, func(dir *memNode, frag string, final bool) error {
276 2 : if final {
277 2 : if frag == "" {
278 2 : ret = &memFile{
279 2 : n: dir,
280 2 : fs: y,
281 2 : }
282 2 : return nil
283 2 : }
284 2 : if n := dir.children[frag]; n != nil {
285 2 : ret = &memFile{
286 2 : n: n,
287 2 : fs: y,
288 2 : read: true,
289 2 : write: openForWrite,
290 2 : }
291 2 : }
292 : }
293 2 : return nil
294 : })
295 2 : if err != nil {
296 2 : return nil, err
297 2 : }
298 2 : if ret == nil {
299 2 : return nil, &os.PathError{
300 2 : Op: "open",
301 2 : Path: fullname,
302 2 : Err: oserror.ErrNotExist,
303 2 : }
304 2 : }
305 2 : ret.n.refs.Add(1)
306 2 : return ret, nil
307 : }
308 :
309 : // Open implements FS.Open.
310 2 : func (y *MemFS) Open(fullname string, opts ...OpenOption) (File, error) {
311 2 : return y.open(fullname, false /* openForWrite */)
312 2 : }
313 :
314 : // OpenReadWrite implements FS.OpenReadWrite.
315 2 : func (y *MemFS) OpenReadWrite(fullname string, opts ...OpenOption) (File, error) {
316 2 : f, err := y.open(fullname, true /* openForWrite */)
317 2 : pathErr, ok := err.(*os.PathError)
318 2 : if ok && pathErr.Err == oserror.ErrNotExist {
319 2 : return y.Create(fullname)
320 2 : }
321 2 : return f, err
322 : }
323 :
324 : // OpenDir implements FS.OpenDir.
325 2 : func (y *MemFS) OpenDir(fullname string) (File, error) {
326 2 : return y.open(fullname, false /* openForWrite */)
327 2 : }
328 :
329 : // Remove implements FS.Remove.
330 2 : func (y *MemFS) Remove(fullname string) error {
331 2 : return y.walk(fullname, func(dir *memNode, frag string, final bool) error {
332 2 : if final {
333 2 : if frag == "" {
334 0 : return errors.New("pebble/vfs: empty file name")
335 0 : }
336 2 : child, ok := dir.children[frag]
337 2 : if !ok {
338 1 : return oserror.ErrNotExist
339 1 : }
340 2 : if y.windowsSemantics {
341 1 : // Disallow removal of open files/directories which implements
342 1 : // Windows semantics. This ensures that we don't regress in the
343 1 : // ordering of operations and try to remove a file while it is
344 1 : // still open.
345 1 : if n := child.refs.Load(); n > 0 {
346 1 : return oserror.ErrInvalid
347 1 : }
348 : }
349 2 : if len(child.children) > 0 {
350 1 : return errNotEmpty
351 1 : }
352 2 : delete(dir.children, frag)
353 : }
354 2 : return nil
355 : })
356 : }
357 :
358 : // RemoveAll implements FS.RemoveAll.
359 1 : func (y *MemFS) RemoveAll(fullname string) error {
360 1 : err := y.walk(fullname, func(dir *memNode, frag string, final bool) error {
361 1 : if final {
362 1 : if frag == "" {
363 0 : return errors.New("pebble/vfs: empty file name")
364 0 : }
365 1 : _, ok := dir.children[frag]
366 1 : if !ok {
367 1 : return nil
368 1 : }
369 1 : delete(dir.children, frag)
370 : }
371 1 : return nil
372 : })
373 : // Match os.RemoveAll which returns a nil error even if the parent
374 : // directories don't exist.
375 1 : if oserror.IsNotExist(err) {
376 1 : err = nil
377 1 : }
378 1 : return err
379 : }
380 :
381 : // Rename implements FS.Rename.
382 2 : func (y *MemFS) Rename(oldname, newname string) error {
383 2 : var n *memNode
384 2 : err := y.walk(oldname, func(dir *memNode, frag string, final bool) error {
385 2 : if final {
386 2 : if frag == "" {
387 0 : return errors.New("pebble/vfs: empty file name")
388 0 : }
389 2 : n = dir.children[frag]
390 2 : delete(dir.children, frag)
391 : }
392 2 : return nil
393 : })
394 2 : if err != nil {
395 0 : return err
396 0 : }
397 2 : if n == nil {
398 1 : return &os.PathError{
399 1 : Op: "open",
400 1 : Path: oldname,
401 1 : Err: oserror.ErrNotExist,
402 1 : }
403 1 : }
404 2 : return y.walk(newname, func(dir *memNode, frag string, final bool) error {
405 2 : if final {
406 2 : if frag == "" {
407 0 : return errors.New("pebble/vfs: empty file name")
408 0 : }
409 2 : dir.children[frag] = n
410 2 : n.name = frag
411 : }
412 2 : return nil
413 : })
414 : }
415 :
416 : // ReuseForWrite implements FS.ReuseForWrite.
417 1 : func (y *MemFS) ReuseForWrite(oldname, newname string) (File, error) {
418 1 : if err := y.Rename(oldname, newname); err != nil {
419 1 : return nil, err
420 1 : }
421 1 : f, err := y.Open(newname)
422 1 : if err != nil {
423 0 : return nil, err
424 0 : }
425 1 : y.mu.Lock()
426 1 : defer y.mu.Unlock()
427 1 :
428 1 : mf := f.(*memFile)
429 1 : mf.read = false
430 1 : mf.write = true
431 1 : return f, nil
432 : }
433 :
434 : // MkdirAll implements FS.MkdirAll.
435 2 : func (y *MemFS) MkdirAll(dirname string, perm os.FileMode) error {
436 2 : return y.walk(dirname, func(dir *memNode, frag string, final bool) error {
437 2 : if frag == "" {
438 1 : if final {
439 1 : return nil
440 1 : }
441 0 : return errors.New("pebble/vfs: empty file name")
442 : }
443 2 : child := dir.children[frag]
444 2 : if child == nil {
445 2 : dir.children[frag] = &memNode{
446 2 : name: frag,
447 2 : children: make(map[string]*memNode),
448 2 : isDir: true,
449 2 : }
450 2 : return nil
451 2 : }
452 2 : if !child.isDir {
453 0 : return &os.PathError{
454 0 : Op: "open",
455 0 : Path: dirname,
456 0 : Err: errors.New("not a directory"),
457 0 : }
458 0 : }
459 2 : return nil
460 : })
461 : }
462 :
463 : // Lock implements FS.Lock.
464 2 : func (y *MemFS) Lock(fullname string) (io.Closer, error) {
465 2 : // FS.Lock excludes other processes, but other processes cannot see this
466 2 : // process' memory. However some uses (eg, Cockroach tests) may open and
467 2 : // close the same MemFS-backed database multiple times. We want mutual
468 2 : // exclusion in this case too. See cockroachdb/cockroach#110645.
469 2 : _, loaded := y.lockedFiles.Swap(fullname, nil /* the value itself is insignificant */)
470 2 : if loaded {
471 1 : // This file lock has already been acquired. On unix, this results in
472 1 : // either EACCES or EAGAIN so we mimic.
473 1 : return nil, syscall.EAGAIN
474 1 : }
475 : // Otherwise, we successfully acquired the lock. Locks are visible in the
476 : // parent directory listing, and they also must be created under an existent
477 : // directory. Create the path so that we have the normal detection of
478 : // non-existent directory paths, and make the lock visible when listing
479 : // directory entries.
480 2 : f, err := y.Create(fullname)
481 2 : if err != nil {
482 1 : // "Release" the lock since we failed.
483 1 : y.lockedFiles.Delete(fullname)
484 1 : return nil, err
485 1 : }
486 2 : return &memFileLock{
487 2 : y: y,
488 2 : f: f,
489 2 : fullname: fullname,
490 2 : }, nil
491 : }
492 :
493 : // List implements FS.List.
494 2 : func (y *MemFS) List(dirname string) ([]string, error) {
495 2 : if !strings.HasSuffix(dirname, sep) {
496 2 : dirname += sep
497 2 : }
498 2 : var ret []string
499 2 : err := y.walk(dirname, func(dir *memNode, frag string, final bool) error {
500 2 : if final {
501 2 : if frag != "" {
502 0 : panic("unreachable")
503 : }
504 2 : ret = make([]string, 0, len(dir.children))
505 2 : for s := range dir.children {
506 2 : ret = append(ret, s)
507 2 : }
508 : }
509 2 : return nil
510 : })
511 2 : return ret, err
512 : }
513 :
514 : // Stat implements FS.Stat.
515 2 : func (y *MemFS) Stat(name string) (os.FileInfo, error) {
516 2 : f, err := y.Open(name)
517 2 : if err != nil {
518 2 : if pe, ok := err.(*os.PathError); ok {
519 2 : pe.Op = "stat"
520 2 : }
521 2 : return nil, err
522 : }
523 2 : defer f.Close()
524 2 : return f.Stat()
525 : }
526 :
527 : // PathBase implements FS.PathBase.
528 2 : func (*MemFS) PathBase(p string) string {
529 2 : // Note that MemFS uses forward slashes for its separator, hence the use of
530 2 : // path.Base, not filepath.Base.
531 2 : return path.Base(p)
532 2 : }
533 :
534 : // PathJoin implements FS.PathJoin.
535 2 : func (*MemFS) PathJoin(elem ...string) string {
536 2 : // Note that MemFS uses forward slashes for its separator, hence the use of
537 2 : // path.Join, not filepath.Join.
538 2 : return path.Join(elem...)
539 2 : }
540 :
541 : // PathDir implements FS.PathDir.
542 2 : func (*MemFS) PathDir(p string) string {
543 2 : // Note that MemFS uses forward slashes for its separator, hence the use of
544 2 : // path.Dir, not filepath.Dir.
545 2 : return path.Dir(p)
546 2 : }
547 :
548 : // GetDiskUsage implements FS.GetDiskUsage.
549 2 : func (*MemFS) GetDiskUsage(string) (DiskUsage, error) {
550 2 : return DiskUsage{}, ErrUnsupported
551 2 : }
552 :
553 : // memNode holds a file's data or a directory's children, and implements os.FileInfo.
554 : type memNode struct {
555 : name string
556 : isDir bool
557 : refs atomic.Int32
558 :
559 : // Mutable state.
560 : // - For a file: data, syncedDate, modTime: A file is only being mutated by a single goroutine,
561 : // but there can be concurrent readers e.g. DB.Checkpoint() which can read WAL or MANIFEST
562 : // files that are being written to. Additionally Sync() calls can be concurrent with writing.
563 : // - For a directory: children and syncedChildren. Concurrent writes are possible, and
564 : // these are protected using MemFS.mu.
565 : mu struct {
566 : sync.Mutex
567 : data []byte
568 : syncedData []byte
569 : modTime time.Time
570 : }
571 :
572 : children map[string]*memNode
573 : syncedChildren map[string]*memNode
574 : }
575 :
576 2 : func newRootMemNode() *memNode {
577 2 : return &memNode{
578 2 : name: "/", // set the name to match what file systems do
579 2 : children: make(map[string]*memNode),
580 2 : isDir: true,
581 2 : }
582 2 : }
583 :
584 1 : func (f *memNode) IsDir() bool {
585 1 : return f.isDir
586 1 : }
587 :
588 0 : func (f *memNode) ModTime() time.Time {
589 0 : f.mu.Lock()
590 0 : defer f.mu.Unlock()
591 0 : return f.mu.modTime
592 0 : }
593 :
594 0 : func (f *memNode) Mode() os.FileMode {
595 0 : if f.isDir {
596 0 : return os.ModeDir | 0755
597 0 : }
598 0 : return 0755
599 : }
600 :
601 1 : func (f *memNode) Name() string {
602 1 : return f.name
603 1 : }
604 :
605 2 : func (f *memNode) Size() int64 {
606 2 : f.mu.Lock()
607 2 : defer f.mu.Unlock()
608 2 : return int64(len(f.mu.data))
609 2 : }
610 :
611 0 : func (f *memNode) Sys() interface{} {
612 0 : return nil
613 0 : }
614 :
615 1 : func (f *memNode) dump(w *bytes.Buffer, level int) {
616 1 : if f.isDir {
617 1 : w.WriteString(" ")
618 1 : } else {
619 1 : f.mu.Lock()
620 1 : fmt.Fprintf(w, "%8d ", len(f.mu.data))
621 1 : f.mu.Unlock()
622 1 : }
623 1 : for i := 0; i < level; i++ {
624 1 : w.WriteString(" ")
625 1 : }
626 1 : w.WriteString(f.name)
627 1 : if !f.isDir {
628 1 : w.WriteByte('\n')
629 1 : return
630 1 : }
631 1 : if level > 0 { // deal with the fact that the root's name is already "/"
632 1 : w.WriteByte(sep[0])
633 1 : }
634 1 : w.WriteByte('\n')
635 1 : names := make([]string, 0, len(f.children))
636 1 : for name := range f.children {
637 1 : names = append(names, name)
638 1 : }
639 1 : sort.Strings(names)
640 1 : for _, name := range names {
641 1 : f.children[name].dump(w, level+1)
642 1 : }
643 : }
644 :
645 1 : func (f *memNode) resetToSyncedState() {
646 1 : if f.isDir {
647 1 : f.children = make(map[string]*memNode)
648 1 : for k, v := range f.syncedChildren {
649 1 : f.children[k] = v
650 1 : }
651 1 : for _, v := range f.children {
652 1 : v.resetToSyncedState()
653 1 : }
654 1 : } else {
655 1 : f.mu.Lock()
656 1 : f.mu.data = append([]byte(nil), f.mu.syncedData...)
657 1 : f.mu.Unlock()
658 1 : }
659 : }
660 :
661 : // memFile is a reader or writer of a node's data, and implements File.
662 : type memFile struct {
663 : n *memNode
664 : fs *MemFS // nil for a standalone memFile
665 : rpos int
666 : wpos int
667 : read, write bool
668 : }
669 :
670 : var _ File = (*memFile)(nil)
671 :
672 2 : func (f *memFile) Close() error {
673 2 : if n := f.n.refs.Add(-1); n < 0 {
674 0 : panic(fmt.Sprintf("pebble: close of unopened file: %d", n))
675 : }
676 2 : f.n = nil
677 2 : return nil
678 : }
679 :
680 2 : func (f *memFile) Read(p []byte) (int, error) {
681 2 : if !f.read {
682 0 : return 0, errors.New("pebble/vfs: file was not opened for reading")
683 0 : }
684 2 : if f.n.isDir {
685 0 : return 0, errors.New("pebble/vfs: cannot read a directory")
686 0 : }
687 2 : f.n.mu.Lock()
688 2 : defer f.n.mu.Unlock()
689 2 : if f.rpos >= len(f.n.mu.data) {
690 2 : return 0, io.EOF
691 2 : }
692 2 : n := copy(p, f.n.mu.data[f.rpos:])
693 2 : f.rpos += n
694 2 : return n, nil
695 : }
696 :
697 2 : func (f *memFile) ReadAt(p []byte, off int64) (int, error) {
698 2 : if !f.read {
699 0 : return 0, errors.New("pebble/vfs: file was not opened for reading")
700 0 : }
701 2 : if f.n.isDir {
702 0 : return 0, errors.New("pebble/vfs: cannot read a directory")
703 0 : }
704 2 : f.n.mu.Lock()
705 2 : defer f.n.mu.Unlock()
706 2 : if off >= int64(len(f.n.mu.data)) {
707 0 : return 0, io.EOF
708 0 : }
709 2 : n := copy(p, f.n.mu.data[off:])
710 2 : if n < len(p) {
711 1 : return n, io.EOF
712 1 : }
713 2 : return n, nil
714 : }
715 :
716 2 : func (f *memFile) Write(p []byte) (int, error) {
717 2 : if !f.write {
718 0 : return 0, errors.New("pebble/vfs: file was not created for writing")
719 0 : }
720 2 : if f.n.isDir {
721 0 : return 0, errors.New("pebble/vfs: cannot write a directory")
722 0 : }
723 2 : f.n.mu.Lock()
724 2 : defer f.n.mu.Unlock()
725 2 : f.n.mu.modTime = time.Now()
726 2 : if f.wpos+len(p) <= len(f.n.mu.data) {
727 2 : n := copy(f.n.mu.data[f.wpos:f.wpos+len(p)], p)
728 2 : if n != len(p) {
729 0 : panic("stuff")
730 : }
731 2 : } else {
732 2 : f.n.mu.data = append(f.n.mu.data[:f.wpos], p...)
733 2 : }
734 2 : f.wpos += len(p)
735 2 :
736 2 : if invariants.Enabled {
737 2 : // Mutate the input buffer to flush out bugs in Pebble which expect the
738 2 : // input buffer to be unmodified.
739 2 : for i := range p {
740 2 : p[i] ^= 0xff
741 2 : }
742 : }
743 2 : return len(p), nil
744 : }
745 :
746 2 : func (f *memFile) WriteAt(p []byte, ofs int64) (int, error) {
747 2 : if !f.write {
748 0 : return 0, errors.New("pebble/vfs: file was not created for writing")
749 0 : }
750 2 : if f.n.isDir {
751 0 : return 0, errors.New("pebble/vfs: cannot write a directory")
752 0 : }
753 2 : f.n.mu.Lock()
754 2 : defer f.n.mu.Unlock()
755 2 : f.n.mu.modTime = time.Now()
756 2 :
757 2 : for len(f.n.mu.data) < int(ofs)+len(p) {
758 2 : f.n.mu.data = append(f.n.mu.data, 0)
759 2 : }
760 :
761 2 : n := copy(f.n.mu.data[int(ofs):int(ofs)+len(p)], p)
762 2 : if n != len(p) {
763 0 : panic("stuff")
764 : }
765 :
766 2 : return len(p), nil
767 : }
768 :
769 2 : func (f *memFile) Prefetch(offset int64, length int64) error { return nil }
770 2 : func (f *memFile) Preallocate(offset, length int64) error { return nil }
771 :
772 2 : func (f *memFile) Stat() (os.FileInfo, error) {
773 2 : return f.n, nil
774 2 : }
775 :
776 2 : func (f *memFile) Sync() error {
777 2 : if f.fs != nil && f.fs.strict {
778 2 : f.fs.mu.Lock()
779 2 : defer f.fs.mu.Unlock()
780 2 : if f.fs.ignoreSyncs {
781 1 : return nil
782 1 : }
783 2 : if f.n.isDir {
784 2 : f.n.syncedChildren = make(map[string]*memNode)
785 2 : for k, v := range f.n.children {
786 2 : f.n.syncedChildren[k] = v
787 2 : }
788 2 : } else {
789 2 : f.n.mu.Lock()
790 2 : f.n.mu.syncedData = append([]byte(nil), f.n.mu.data...)
791 2 : f.n.mu.Unlock()
792 2 : }
793 : }
794 2 : return nil
795 : }
796 :
797 2 : func (f *memFile) SyncData() error {
798 2 : return f.Sync()
799 2 : }
800 :
801 0 : func (f *memFile) SyncTo(length int64) (fullSync bool, err error) {
802 0 : // NB: This SyncTo implementation lies, with its return values claiming it
803 0 : // synced the data up to `length`. When fullSync=false, SyncTo provides no
804 0 : // durability guarantees, so this can help surface bugs where we improperly
805 0 : // rely on SyncTo providing durability.
806 0 : return false, nil
807 0 : }
808 :
809 2 : func (f *memFile) Fd() uintptr {
810 2 : return InvalidFd
811 2 : }
812 :
813 : // Flush is a no-op and present only to prevent buffering at higher levels
814 : // (e.g. it prevents sstable.Writer from using a bufio.Writer).
815 1 : func (f *memFile) Flush() error {
816 1 : return nil
817 1 : }
818 :
819 : type memFileLock struct {
820 : y *MemFS
821 : f File
822 : fullname string
823 : }
824 :
825 2 : func (l *memFileLock) Close() error {
826 2 : if l.y == nil {
827 0 : return nil
828 0 : }
829 2 : l.y.lockedFiles.Delete(l.fullname)
830 2 : l.y = nil
831 2 : return l.f.Close()
832 : }
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