forked from OpenPrinting/ipp-usb
-
Notifications
You must be signed in to change notification settings - Fork 0
/
usbtransport.go
828 lines (689 loc) · 20.2 KB
/
usbtransport.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
/* ipp-usb - HTTP reverse proxy, backed by IPP-over-USB connection to device
*
* Copyright (C) 2020 and up by Alexander Pevzner ([email protected])
* See LICENSE for license terms and conditions
*
* USB transport for HTTP
*/
package main
import (
"bufio"
"bytes"
"context"
"fmt"
"io"
"io/ioutil"
"math"
"net/http"
"os"
"sort"
"strings"
"sync/atomic"
"time"
)
// UsbTransport implements HTTP transport functionality over USB
type UsbTransport struct {
addr UsbAddr // Device address
info UsbDeviceInfo // USB device info
log *Logger // Device's own logger
dev *UsbDevHandle // Underlying USB device
connPool chan *usbConn // Pool of idle connections
connList []*usbConn // List of all connections
connReleased chan struct{} // Signalled when connection released
shutdown chan struct{} // Closed by Shutdown()
connstate *usbConnState // Connections state tracker
quirks []Quirks // Device quirks
deadline time.Time // Deadline for requests
}
// NewUsbTransport creates new http.RoundTripper backed by IPP-over-USB
func NewUsbTransport(desc UsbDeviceDesc) (*UsbTransport, error) {
// Open the device
dev, err := UsbOpenDevice(desc)
if err != nil {
return nil, err
}
// Create UsbTransport
transport := &UsbTransport{
addr: desc.UsbAddr,
log: NewLogger(),
dev: dev,
connReleased: make(chan struct{}),
shutdown: make(chan struct{}),
}
// Obtain device info
transport.info, err = dev.UsbDeviceInfo()
if err != nil {
dev.Close()
return nil, err
}
transport.log.Cc(Console)
transport.log.ToDevFile(transport.info)
transport.log.SetLevels(Conf.LogDevice)
// Setup quirks
transport.quirks = Conf.Quirks.Get(transport.info.MfgAndProduct)
// Write device info to the log
log := transport.log.Begin().
Nl(LogDebug).
Debug(' ', "===============================").
Info('+', "%s: added %s", transport.addr, transport.info.ProductName).
Debug(' ', "Device info:").
Debug(' ', " Ident: %s", transport.info.Ident()).
Debug(' ', " Manufacturer: %s", transport.info.Manufacturer).
Debug(' ', " Product: %s", transport.info.ProductName).
Debug(' ', " SerialNumber: %s", transport.info.SerialNumber).
Debug(' ', " MfgAndProduct: %s", transport.info.MfgAndProduct).
Debug(' ', " BasicCaps: %s", transport.info.BasicCaps).
Nl(LogDebug)
log.Debug(' ', "Device quirks:")
for _, quirks := range transport.quirks {
log.Debug(' ', " from [%s] (%s)", quirks.Model, quirks.Origin)
log.Debug(' ', " blacklist = %v", quirks.Blacklist)
log.Debug(' ', " usb-max-interfaces = %v", quirks.UsbMaxInterfaces)
for name, value := range quirks.HttpHeaders {
log.Debug(' ', " http-%s = %q", strings.ToLower(name), value)
}
}
log.Nl(LogDebug)
transport.dumpUSBparams(log)
log.Nl(LogDebug)
log.Debug(' ', "USB interfaces:")
log.Debug(' ', " Config Interface Alt Class SubClass Proto")
for _, ifdesc := range desc.IfDescs {
prefix := byte(' ')
if ifdesc.IsIppOverUsb() {
prefix = '*'
}
log.Debug(prefix,
" %-3d %-3d %-3d %-3d %-3d %-3d",
ifdesc.Config, ifdesc.IfNum,
ifdesc.Alt, ifdesc.Class, ifdesc.SubClass, ifdesc.Proto)
}
log.Nl(LogDebug)
log.Commit()
var maxconn uint
// Check for blacklisted device
if len(transport.quirks) > 0 && transport.quirks[0].Blacklist {
err = ErrBlackListed
goto ERROR
}
// Configure the device
err = dev.Configure(desc)
if err != nil {
goto ERROR
}
// Open connections
maxconn = math.MaxUint32
for _, quirks := range transport.quirks {
if quirks.UsbMaxInterfaces != 0 {
maxconn = quirks.UsbMaxInterfaces
}
}
for i, ifaddr := range desc.IfAddrs {
var conn *usbConn
conn, err = transport.openUsbConn(i, ifaddr)
if err != nil {
goto ERROR
}
transport.connList = append(transport.connList, conn)
maxconn--
if maxconn == 0 {
break
}
}
transport.connPool = make(chan *usbConn, len(transport.connList))
transport.connstate = newUsbConnState(len(desc.IfAddrs))
for _, conn := range transport.connList {
transport.connPool <- conn
}
return transport, nil
// Error: cleanup and exit
ERROR:
for _, conn := range transport.connList {
conn.destroy()
}
dev.Close()
return nil, err
}
// Dump USB stack parameters to the UsbTransport's log
func (transport *UsbTransport) dumpUSBparams(log *LogMessage) {
const usbParamsDir = "/sys/module/usbcore/parameters"
// Obtain list of parameter names (file names)
dir, err := os.Open(usbParamsDir)
if err != nil {
return
}
files, err := dir.Readdirnames(-1)
dir.Close()
if err != nil {
return
}
sort.Strings(files)
if len(files) == 0 {
return
}
// Compute max width of parameter names
wid := 0
for _, file := range files {
if wid < len(file) {
wid = len(file)
}
}
wid++
// Write the table
log.Debug(' ', "USB stack parameters")
for _, file := range files {
p, _ := ioutil.ReadFile(usbParamsDir + "/" + file)
if p == nil {
p = []byte("-")
} else {
p = bytes.TrimSpace(p)
}
log.Debug(' ', " %*s %s", -wid, file+":", p)
}
}
// Get count of connections still in use
func (transport *UsbTransport) connInUse() int {
return cap(transport.connPool) - len(transport.connPool)
}
// SetDeadline sets the deadline for all requests, submitted
// via RoundTrip and RoundTripWithSession methods
//
// A deadline is an absolute time after which request processing
// will fail instead of blocking
//
// This is useful only at initialization time and if some requests
// were failed due to timeout, device reset is required, because
// at this case synchronization with device will probably be lost
//
// A zero value for t means no timeout
func (transport *UsbTransport) SetDeadline(t time.Time) {
transport.deadline = t
}
// DeadlineExpired reports if deadline previously set by SetDeadline()
// is already expired
func (transport *UsbTransport) DeadlineExpired() bool {
deadline := transport.deadline
return !deadline.IsZero() && time.Until(deadline) <= 0
}
// closeShutdownChan closes the transport.shutdown, which effectively
// disables connections allocation (usbConnGet will return ErrShutdown)
//
// This function can be safely called multiple times (only the first
// call closes the channel)
//
// Note, this function cannot be called simultaneously from
// different threads. However, it's not a problem, because it
// is only called from (*UsbTransport) Shutdown() and
// (*UsbTransport) Close(), and both of these functions are
// only called from the PnP thread context.
func (transport *UsbTransport) closeShutdownChan() {
select {
case <-transport.shutdown:
// Channel already closed
default:
close(transport.shutdown)
}
}
// Shutdown gracefully shuts down the transport. If provided
// context expires before shutdown completion, Shutdown
// returns the Context's error
func (transport *UsbTransport) Shutdown(ctx context.Context) error {
transport.closeShutdownChan()
for {
n := transport.connInUse()
if n == 0 {
break
}
transport.log.Info('-', "%s: shutdown: %d connections still in use",
transport.addr, n)
select {
case <-transport.connReleased:
case <-ctx.Done():
transport.log.Error('-', "%s: %s: shutdown timeout expired",
transport.addr, transport.info.ProductName)
return ctx.Err()
}
}
return nil
}
// Close the transport
func (transport *UsbTransport) Close(reset bool) {
// Reset the device, if required
if transport.connInUse() > 0 || reset {
transport.log.Info('-', "%s: resetting %s",
transport.addr, transport.info.ProductName)
transport.dev.Reset()
}
// Wait until all connections become inactive
transport.Shutdown(context.Background())
// Destroy all connections and close the USB device
for _, conn := range transport.connList {
conn.destroy()
}
transport.dev.Close()
transport.log.Info('-', "%s: removed %s",
transport.addr, transport.info.ProductName)
}
// Log returns device's own logger
func (transport *UsbTransport) Log() *Logger {
return transport.log
}
// UsbDeviceInfo returns USB device information for the device
// behind the transport
func (transport *UsbTransport) UsbDeviceInfo() UsbDeviceInfo {
return transport.info
}
// RoundTrip implements http.RoundTripper interface
func (transport *UsbTransport) RoundTrip(r *http.Request) (
*http.Response, error) {
session := int(atomic.AddInt32(&httpSessionID, 1)-1) % 1000
return transport.RoundTripWithSession(session, r)
}
// RoundTripWithSession executes a single HTTP transaction, returning
// a Response for the provided Request. Session number, for logging,
// provided as a separate parameter
func (transport *UsbTransport) RoundTripWithSession(session int,
rq *http.Request) (*http.Response, error) {
// Log the request
transport.log.HTTPRqParams(LogDebug, '>', session, rq)
// Prevent request from being canceled from outside
// We cannot do it on USB: closing USB connection
// doesn't drain buffered data that server is
// about to send to client
outreq := rq.WithContext(context.Background())
outreq.Cancel = nil
// Remove Expect: 100-continue, if any
outreq.Header.Del("Expect")
// Apply quirks
for _, quirks := range transport.quirks {
for name, value := range quirks.HttpHeaders {
if value != "" {
outreq.Header.Set(name, value)
} else {
outreq.Header.Del(name)
}
}
}
// Don't let Go's stdlib to add Connection: close header
// automatically
outreq.Close = false
// Add User-Agent, if missed. It is just cosmetic
if _, found := outreq.Header["User-Agent"]; !found {
outreq.Header["User-Agent"] = []string{"ipp-usb"}
}
// Wrap request body
if outreq.Body != nil {
outreq.Body = &usbRequestBodyWrapper{
log: transport.log,
session: session,
body: outreq.Body,
}
}
// Prepare to correctly handle HTTP transaction, in a case
// client drops request in a middle of reading body
switch {
case outreq.ContentLength <= 0:
// Nothing to do
case outreq.ContentLength < 16384:
// Body is small, prefetch it before sending to USB
buf := &bytes.Buffer{}
_, err := io.CopyN(buf, outreq.Body, outreq.ContentLength)
if err != nil {
return nil, err
}
outreq.Body.Close()
outreq.Body = ioutil.NopCloser(buf)
transport.log.HTTPDebug('>', session,
"body is small (%d bytes), prefetched before sending",
buf.Len())
default:
// Force chunked encoding, so if client drops request,
// we still be able to correctly handle HTTP transaction
transport.log.HTTPDebug('>', session,
"body is large (%d bytes), sending as chunked",
outreq.ContentLength)
outreq.ContentLength = -1
}
// Log request details
transport.log.Begin().
HTTPRequest(LogTraceHTTP, '>', session, outreq).
Commit()
// Allocate USB connection
conn, err := transport.usbConnGet(rq.Context())
if err != nil {
return nil, err
}
transport.log.HTTPDebug(' ', session, "connection %d allocated", conn.index)
// Send request and receive a response
err = outreq.Write(conn)
if err != nil {
transport.log.HTTPError('!', session, "%s", err)
conn.put()
return nil, err
}
resp, err := http.ReadResponse(conn.reader, outreq)
if err != nil {
transport.log.HTTPError('!', session, "%s", err)
conn.put()
return nil, err
}
// Wrap response body
resp.Body = &usbResponseBodyWrapper{
log: transport.log,
session: session,
body: resp.Body,
conn: conn,
}
// Log the response
if resp != nil {
transport.log.Begin().
HTTPRspStatus(LogDebug, '<', session, outreq, resp).
HTTPResponse(LogTraceHTTP, '<', session, resp).
Commit()
}
return resp, nil
}
// usbRequestBodyWrapper wraps http.Request.Body, adding
// data path instrumentation
type usbRequestBodyWrapper struct {
log *Logger // Device's logger
session int // HTTP session, for logging
count int // Total count of received bytes
body io.ReadCloser // Request.body
drained bool // EOF or error has been seen
}
// Read from usbRequestBodyWrapper
func (wrap *usbRequestBodyWrapper) Read(buf []byte) (int, error) {
n, err := wrap.body.Read(buf)
wrap.count += n
if err != nil {
wrap.log.HTTPDebug('>', wrap.session,
"request body: got %d bytes; %s", wrap.count, err)
err = io.EOF
wrap.drained = true
}
return n, err
}
// Close usbRequestBodyWrapper
func (wrap *usbRequestBodyWrapper) Close() error {
if !wrap.drained {
wrap.log.HTTPDebug('>', wrap.session,
"request body: got %d bytes; closed", wrap.count)
}
return wrap.body.Close()
}
// usbResponseBodyWrapper wraps http.Response.Body and guarantees
// that connection will be always drained before closed
type usbResponseBodyWrapper struct {
log *Logger // Device's logger
session int // HTTP session, for logging
body io.ReadCloser // Response.body
conn *usbConn // Underlying USB connection
count int // Total count of received bytes
drained bool // EOF or error has been seen
}
// Read from usbResponseBodyWrapper
func (wrap *usbResponseBodyWrapper) Read(buf []byte) (int, error) {
n, err := wrap.body.Read(buf)
wrap.count += n
if err != nil {
wrap.log.HTTPDebug('<', wrap.session,
"response body: got %d bytes; %s", wrap.count, err)
wrap.drained = true
}
return n, err
}
// Close usbResponseBodyWrapper
func (wrap *usbResponseBodyWrapper) Close() error {
// If EOF or error seen, we can close synchronously
if wrap.drained {
wrap.body.Close()
wrap.conn.put()
return nil
}
// Otherwise, we need to drain USB connection
wrap.log.HTTPDebug('<', wrap.session, "client has gone; draining response from USB")
go func() {
defer func() {
v := recover()
if v != nil {
Log.Panic(v)
}
}()
io.Copy(ioutil.Discard, wrap.body)
wrap.body.Close()
wrap.conn.put()
}()
return nil
}
// usbConn implements an USB connection
type usbConn struct {
transport *UsbTransport // Transport that owns the connection
index int // Connection index (for logging)
iface *UsbInterface // Underlying interface
reader *bufio.Reader // For http.ReadResponse
cntRecv int // Total bytes received
cntSent int // Total bytes sent
}
// Open usbConn
func (transport *UsbTransport) openUsbConn(
index int, ifaddr UsbIfAddr) (*usbConn, error) {
dev := transport.dev
transport.log.Debug(' ', "USB[%d]: open: %s", index, ifaddr)
// Initialize connection structure
conn := &usbConn{
transport: transport,
index: index,
}
conn.reader = bufio.NewReader(conn)
// Obtain interface
var err error
conn.iface, err = dev.OpenUsbInterface(ifaddr)
if err != nil {
goto ERROR
}
// Soft-reset interface
//
// Note, disabled for now, because it causes problems
// with EPSON ET-4750 (see #17)
//
// May be in a future we will enable it conditionally,
// for some printer models (based on quirks)
//
// err = conn.iface.SoftReset()
if err != nil {
// Don't treat it too seriously
transport.log.Info('?', "USB[%d]: SOFT_RESET: %s", index, err)
}
return conn, nil
// Error: cleanup and exit
ERROR:
transport.log.Error('!', "USB[%d]: %s", index, err)
if conn.iface != nil {
conn.iface.Close()
}
return nil, err
}
// Compute Recv/Send timeout
func (conn *usbConn) timeout() (tm time.Duration, expored bool) {
deadline := conn.transport.deadline
if deadline.IsZero() {
return
}
tm = time.Until(deadline)
return tm, tm <= 0
}
// Read from USB
func (conn *usbConn) Read(b []byte) (int, error) {
conn.transport.connstate.beginRead(conn)
defer conn.transport.connstate.doneRead(conn)
// Note, to avoid LIBUSB_TRANSFER_OVERFLOW errors
// from libusb, input buffer size must always
// be aligned by 1024 bytes for USB 3.0, 512 bytes
// for USB 2.0, so 1024 bytes alignment is safe for
// both
//
// However if caller requests less that 1024 bytes, we
// can't align here simply by shrinking the buffer,
// because it will result a zero-size buffer. At
// this case we assume caller knows what it is
// doing (actually bufio never behaves this way)
if n := len(b); n >= 1024 {
n &= ^1023
b = b[0:n]
}
backoff := time.Millisecond * 100
for {
tm, expired := conn.timeout()
if expired {
return 0, ErrInitTimedOut
}
n, err := conn.iface.Recv(b, tm)
conn.cntRecv += n
conn.transport.log.Add(LogTraceHTTP, '<',
"USB[%d]: read: wanted %d got %d total %d",
conn.index, len(b), n, conn.cntRecv)
conn.transport.log.HexDump(LogTraceUSB, '<', b[:n])
if err != nil {
conn.transport.log.Error('!',
"USB[%d]: recv: %s", conn.index, err)
}
if n != 0 || err != nil {
return n, err
}
conn.transport.log.Error('!',
"USB[%d]: zero-size read", conn.index)
time.Sleep(backoff)
backoff *= 2
if backoff > time.Millisecond*1000 {
backoff = time.Millisecond * 1000
}
}
}
// Write to USB
func (conn *usbConn) Write(b []byte) (int, error) {
conn.transport.connstate.beginWrite(conn)
defer conn.transport.connstate.doneWrite(conn)
tm, expired := conn.timeout()
if expired {
return 0, ErrInitTimedOut
}
n, err := conn.iface.Send(b, tm)
conn.cntSent += n
conn.transport.log.Add(LogTraceHTTP, '>',
"USB[%d]: write: wanted %d sent %d total %d",
conn.index, len(b), n, conn.cntSent)
conn.transport.log.HexDump(LogTraceUSB, '>', b[:n])
if err != nil {
conn.transport.log.Error('!',
"USB[%d]: send: %s", conn.index, err)
}
return n, err
}
// Allocate a connection
func (transport *UsbTransport) usbConnGet(ctx context.Context) (*usbConn, error) {
select {
case <-transport.shutdown:
return nil, ErrShutdown
case <-ctx.Done():
return nil, ctx.Err()
case conn := <-transport.connPool:
transport.connstate.gotConn(conn)
transport.log.Debug(' ', "USB[%d]: connection allocated, %s",
conn.index, transport.connstate)
return conn, nil
}
}
// Release the connection
func (conn *usbConn) put() {
transport := conn.transport
conn.reader.Reset(conn)
conn.cntRecv = 0
conn.cntSent = 0
transport.connstate.putConn(conn)
transport.log.Debug(' ', "USB[%d]: connection released, %s",
conn.index, transport.connstate)
transport.connPool <- conn
select {
case transport.connReleased <- struct{}{}:
default:
}
}
// Destroy USB connection
func (conn *usbConn) destroy() {
conn.transport.log.Debug(' ', "USB[%d]: closed", conn.index)
conn.iface.Close()
}
// usbConnState tracks connections state, for logging
type usbConnState struct {
alloc []int32 // Per-connection "allocated" flag
read []int32 // Per-connection "reading" flag
write []int32 // Per-connection "writing" flag
}
// newUsbConnState creates a new usbConnState for given
// number of connections
func newUsbConnState(cnt int) *usbConnState {
return &usbConnState{
alloc: make([]int32, cnt),
read: make([]int32, cnt),
write: make([]int32, cnt),
}
}
// gotConn notifies usbConnState, that connection is allocated
func (state *usbConnState) gotConn(conn *usbConn) {
atomic.AddInt32(&state.alloc[conn.index], 1)
}
// putConn notifies usbConnState, that connection is released
func (state *usbConnState) putConn(conn *usbConn) {
atomic.AddInt32(&state.alloc[conn.index], -1)
}
// beginRead notifies usbConnState, that read is started
func (state *usbConnState) beginRead(conn *usbConn) {
atomic.AddInt32(&state.read[conn.index], 1)
}
// doneRead notifies usbConnState, that read is done
func (state *usbConnState) doneRead(conn *usbConn) {
atomic.AddInt32(&state.read[conn.index], -1)
}
// beginWrite notifies usbConnState, that write is started
func (state *usbConnState) beginWrite(conn *usbConn) {
atomic.AddInt32(&state.write[conn.index], 1)
}
// doneWrite notifies usbConnState, that write is done
func (state *usbConnState) doneWrite(conn *usbConn) {
atomic.AddInt32(&state.write[conn.index], -1)
}
// String returns a string, representing connections state
func (state *usbConnState) String() string {
buf := make([]byte, 0, 64)
used := 0
for i := range state.alloc {
a := atomic.LoadInt32(&state.alloc[i])
r := atomic.LoadInt32(&state.read[i])
w := atomic.LoadInt32(&state.write[i])
if len(buf) != 0 {
buf = append(buf, ' ')
}
if a|r|w == 0 {
buf = append(buf, '-', '-', '-')
} else {
used++
if a != 0 {
buf = append(buf, 'a')
} else {
buf = append(buf, '-')
}
if r != 0 {
buf = append(buf, 'r')
} else {
buf = append(buf, '-')
}
if w != 0 {
buf = append(buf, 'w')
} else {
buf = append(buf, '-')
}
}
}
return fmt.Sprintf("%d in use: %s", used, buf)
}