Merge tag 'linux-user-for-7.1-pull-request' of https://gitlab.com/laurent_vivier...
[qemu.git] / migration / qemu-file.c
1 /*
2 * QEMU System Emulator
3 *
4 * Copyright (c) 2003-2008 Fabrice Bellard
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24 #include "qemu/osdep.h"
25 #include <zlib.h>
26 #include "qemu/error-report.h"
27 #include "qemu/iov.h"
28 #include "migration.h"
29 #include "qemu-file.h"
30 #include "trace.h"
31 #include "qapi/error.h"
32
33 #define IO_BUF_SIZE 32768
34 #define MAX_IOV_SIZE MIN_CONST(IOV_MAX, 64)
35
36 struct QEMUFile {
37 const QEMUFileOps *ops;
38 const QEMUFileHooks *hooks;
39 void *opaque;
40
41 int64_t bytes_xfer;
42 int64_t xfer_limit;
43
44 int64_t pos; /* start of buffer when writing, end of buffer
45 when reading */
46 int buf_index;
47 int buf_size; /* 0 when writing */
48 uint8_t buf[IO_BUF_SIZE];
49
50 DECLARE_BITMAP(may_free, MAX_IOV_SIZE);
51 struct iovec iov[MAX_IOV_SIZE];
52 unsigned int iovcnt;
53
54 int last_error;
55 Error *last_error_obj;
56 /* has the file has been shutdown */
57 bool shutdown;
58 /* Whether opaque points to a QIOChannel */
59 bool has_ioc;
60 };
61
62 /*
63 * Stop a file from being read/written - not all backing files can do this
64 * typically only sockets can.
65 */
66 int qemu_file_shutdown(QEMUFile *f)
67 {
68 int ret;
69
70 f->shutdown = true;
71 if (!f->ops->shut_down) {
72 return -ENOSYS;
73 }
74 ret = f->ops->shut_down(f->opaque, true, true, NULL);
75
76 if (!f->last_error) {
77 qemu_file_set_error(f, -EIO);
78 }
79 return ret;
80 }
81
82 /*
83 * Result: QEMUFile* for a 'return path' for comms in the opposite direction
84 * NULL if not available
85 */
86 QEMUFile *qemu_file_get_return_path(QEMUFile *f)
87 {
88 if (!f->ops->get_return_path) {
89 return NULL;
90 }
91 return f->ops->get_return_path(f->opaque);
92 }
93
94 bool qemu_file_mode_is_not_valid(const char *mode)
95 {
96 if (mode == NULL ||
97 (mode[0] != 'r' && mode[0] != 'w') ||
98 mode[1] != 'b' || mode[2] != 0) {
99 fprintf(stderr, "qemu_fopen: Argument validity check failed\n");
100 return true;
101 }
102
103 return false;
104 }
105
106 QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops, bool has_ioc)
107 {
108 QEMUFile *f;
109
110 f = g_new0(QEMUFile, 1);
111
112 f->opaque = opaque;
113 f->ops = ops;
114 f->has_ioc = has_ioc;
115 return f;
116 }
117
118
119 void qemu_file_set_hooks(QEMUFile *f, const QEMUFileHooks *hooks)
120 {
121 f->hooks = hooks;
122 }
123
124 /*
125 * Get last error for stream f with optional Error*
126 *
127 * Return negative error value if there has been an error on previous
128 * operations, return 0 if no error happened.
129 * Optional, it returns Error* in errp, but it may be NULL even if return value
130 * is not 0.
131 *
132 */
133 int qemu_file_get_error_obj(QEMUFile *f, Error **errp)
134 {
135 if (errp) {
136 *errp = f->last_error_obj ? error_copy(f->last_error_obj) : NULL;
137 }
138 return f->last_error;
139 }
140
141 /*
142 * Set the last error for stream f with optional Error*
143 */
144 void qemu_file_set_error_obj(QEMUFile *f, int ret, Error *err)
145 {
146 if (f->last_error == 0 && ret) {
147 f->last_error = ret;
148 error_propagate(&f->last_error_obj, err);
149 } else if (err) {
150 error_report_err(err);
151 }
152 }
153
154 /*
155 * Get last error for stream f
156 *
157 * Return negative error value if there has been an error on previous
158 * operations, return 0 if no error happened.
159 *
160 */
161 int qemu_file_get_error(QEMUFile *f)
162 {
163 return qemu_file_get_error_obj(f, NULL);
164 }
165
166 /*
167 * Set the last error for stream f
168 */
169 void qemu_file_set_error(QEMUFile *f, int ret)
170 {
171 qemu_file_set_error_obj(f, ret, NULL);
172 }
173
174 bool qemu_file_is_writable(QEMUFile *f)
175 {
176 return f->ops->writev_buffer;
177 }
178
179 static void qemu_iovec_release_ram(QEMUFile *f)
180 {
181 struct iovec iov;
182 unsigned long idx;
183
184 /* Find and release all the contiguous memory ranges marked as may_free. */
185 idx = find_next_bit(f->may_free, f->iovcnt, 0);
186 if (idx >= f->iovcnt) {
187 return;
188 }
189 iov = f->iov[idx];
190
191 /* The madvise() in the loop is called for iov within a continuous range and
192 * then reinitialize the iov. And in the end, madvise() is called for the
193 * last iov.
194 */
195 while ((idx = find_next_bit(f->may_free, f->iovcnt, idx + 1)) < f->iovcnt) {
196 /* check for adjacent buffer and coalesce them */
197 if (iov.iov_base + iov.iov_len == f->iov[idx].iov_base) {
198 iov.iov_len += f->iov[idx].iov_len;
199 continue;
200 }
201 if (qemu_madvise(iov.iov_base, iov.iov_len, QEMU_MADV_DONTNEED) < 0) {
202 error_report("migrate: madvise DONTNEED failed %p %zd: %s",
203 iov.iov_base, iov.iov_len, strerror(errno));
204 }
205 iov = f->iov[idx];
206 }
207 if (qemu_madvise(iov.iov_base, iov.iov_len, QEMU_MADV_DONTNEED) < 0) {
208 error_report("migrate: madvise DONTNEED failed %p %zd: %s",
209 iov.iov_base, iov.iov_len, strerror(errno));
210 }
211 memset(f->may_free, 0, sizeof(f->may_free));
212 }
213
214 /**
215 * Flushes QEMUFile buffer
216 *
217 * This will flush all pending data. If data was only partially flushed, it
218 * will set an error state.
219 */
220 void qemu_fflush(QEMUFile *f)
221 {
222 ssize_t ret = 0;
223 ssize_t expect = 0;
224 Error *local_error = NULL;
225
226 if (!qemu_file_is_writable(f)) {
227 return;
228 }
229
230 if (f->shutdown) {
231 return;
232 }
233 if (f->iovcnt > 0) {
234 expect = iov_size(f->iov, f->iovcnt);
235 ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt, f->pos,
236 &local_error);
237
238 qemu_iovec_release_ram(f);
239 }
240
241 if (ret >= 0) {
242 f->pos += ret;
243 }
244 /* We expect the QEMUFile write impl to send the full
245 * data set we requested, so sanity check that.
246 */
247 if (ret != expect) {
248 qemu_file_set_error_obj(f, ret < 0 ? ret : -EIO, local_error);
249 }
250 f->buf_index = 0;
251 f->iovcnt = 0;
252 }
253
254 void ram_control_before_iterate(QEMUFile *f, uint64_t flags)
255 {
256 int ret = 0;
257
258 if (f->hooks && f->hooks->before_ram_iterate) {
259 ret = f->hooks->before_ram_iterate(f, f->opaque, flags, NULL);
260 if (ret < 0) {
261 qemu_file_set_error(f, ret);
262 }
263 }
264 }
265
266 void ram_control_after_iterate(QEMUFile *f, uint64_t flags)
267 {
268 int ret = 0;
269
270 if (f->hooks && f->hooks->after_ram_iterate) {
271 ret = f->hooks->after_ram_iterate(f, f->opaque, flags, NULL);
272 if (ret < 0) {
273 qemu_file_set_error(f, ret);
274 }
275 }
276 }
277
278 void ram_control_load_hook(QEMUFile *f, uint64_t flags, void *data)
279 {
280 int ret = -EINVAL;
281
282 if (f->hooks && f->hooks->hook_ram_load) {
283 ret = f->hooks->hook_ram_load(f, f->opaque, flags, data);
284 if (ret < 0) {
285 qemu_file_set_error(f, ret);
286 }
287 } else {
288 /*
289 * Hook is a hook specifically requested by the source sending a flag
290 * that expects there to be a hook on the destination.
291 */
292 if (flags == RAM_CONTROL_HOOK) {
293 qemu_file_set_error(f, ret);
294 }
295 }
296 }
297
298 size_t ram_control_save_page(QEMUFile *f, ram_addr_t block_offset,
299 ram_addr_t offset, size_t size,
300 uint64_t *bytes_sent)
301 {
302 if (f->hooks && f->hooks->save_page) {
303 int ret = f->hooks->save_page(f, f->opaque, block_offset,
304 offset, size, bytes_sent);
305 if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
306 f->bytes_xfer += size;
307 }
308
309 if (ret != RAM_SAVE_CONTROL_DELAYED &&
310 ret != RAM_SAVE_CONTROL_NOT_SUPP) {
311 if (bytes_sent && *bytes_sent > 0) {
312 qemu_update_position(f, *bytes_sent);
313 } else if (ret < 0) {
314 qemu_file_set_error(f, ret);
315 }
316 }
317
318 return ret;
319 }
320
321 return RAM_SAVE_CONTROL_NOT_SUPP;
322 }
323
324 /*
325 * Attempt to fill the buffer from the underlying file
326 * Returns the number of bytes read, or negative value for an error.
327 *
328 * Note that it can return a partially full buffer even in a not error/not EOF
329 * case if the underlying file descriptor gives a short read, and that can
330 * happen even on a blocking fd.
331 */
332 static ssize_t qemu_fill_buffer(QEMUFile *f)
333 {
334 int len;
335 int pending;
336 Error *local_error = NULL;
337
338 assert(!qemu_file_is_writable(f));
339
340 pending = f->buf_size - f->buf_index;
341 if (pending > 0) {
342 memmove(f->buf, f->buf + f->buf_index, pending);
343 }
344 f->buf_index = 0;
345 f->buf_size = pending;
346
347 if (f->shutdown) {
348 return 0;
349 }
350
351 len = f->ops->get_buffer(f->opaque, f->buf + pending, f->pos,
352 IO_BUF_SIZE - pending, &local_error);
353 if (len > 0) {
354 f->buf_size += len;
355 f->pos += len;
356 } else if (len == 0) {
357 qemu_file_set_error_obj(f, -EIO, local_error);
358 } else if (len != -EAGAIN) {
359 qemu_file_set_error_obj(f, len, local_error);
360 } else {
361 error_free(local_error);
362 }
363
364 return len;
365 }
366
367 void qemu_update_position(QEMUFile *f, size_t size)
368 {
369 f->pos += size;
370 }
371
372 /** Closes the file
373 *
374 * Returns negative error value if any error happened on previous operations or
375 * while closing the file. Returns 0 or positive number on success.
376 *
377 * The meaning of return value on success depends on the specific backend
378 * being used.
379 */
380 int qemu_fclose(QEMUFile *f)
381 {
382 int ret;
383 qemu_fflush(f);
384 ret = qemu_file_get_error(f);
385
386 if (f->ops->close) {
387 int ret2 = f->ops->close(f->opaque, NULL);
388 if (ret >= 0) {
389 ret = ret2;
390 }
391 }
392 /* If any error was spotted before closing, we should report it
393 * instead of the close() return value.
394 */
395 if (f->last_error) {
396 ret = f->last_error;
397 }
398 error_free(f->last_error_obj);
399 g_free(f);
400 trace_qemu_file_fclose();
401 return ret;
402 }
403
404 /*
405 * Add buf to iovec. Do flush if iovec is full.
406 *
407 * Return values:
408 * 1 iovec is full and flushed
409 * 0 iovec is not flushed
410 *
411 */
412 static int add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,
413 bool may_free)
414 {
415 /* check for adjacent buffer and coalesce them */
416 if (f->iovcnt > 0 && buf == f->iov[f->iovcnt - 1].iov_base +
417 f->iov[f->iovcnt - 1].iov_len &&
418 may_free == test_bit(f->iovcnt - 1, f->may_free))
419 {
420 f->iov[f->iovcnt - 1].iov_len += size;
421 } else {
422 if (f->iovcnt >= MAX_IOV_SIZE) {
423 /* Should only happen if a previous fflush failed */
424 assert(f->shutdown || !qemu_file_is_writable(f));
425 return 1;
426 }
427 if (may_free) {
428 set_bit(f->iovcnt, f->may_free);
429 }
430 f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
431 f->iov[f->iovcnt++].iov_len = size;
432 }
433
434 if (f->iovcnt >= MAX_IOV_SIZE) {
435 qemu_fflush(f);
436 return 1;
437 }
438
439 return 0;
440 }
441
442 static void add_buf_to_iovec(QEMUFile *f, size_t len)
443 {
444 if (!add_to_iovec(f, f->buf + f->buf_index, len, false)) {
445 f->buf_index += len;
446 if (f->buf_index == IO_BUF_SIZE) {
447 qemu_fflush(f);
448 }
449 }
450 }
451
452 void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, size_t size,
453 bool may_free)
454 {
455 if (f->last_error) {
456 return;
457 }
458
459 f->bytes_xfer += size;
460 add_to_iovec(f, buf, size, may_free);
461 }
462
463 void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, size_t size)
464 {
465 size_t l;
466
467 if (f->last_error) {
468 return;
469 }
470
471 while (size > 0) {
472 l = IO_BUF_SIZE - f->buf_index;
473 if (l > size) {
474 l = size;
475 }
476 memcpy(f->buf + f->buf_index, buf, l);
477 f->bytes_xfer += l;
478 add_buf_to_iovec(f, l);
479 if (qemu_file_get_error(f)) {
480 break;
481 }
482 buf += l;
483 size -= l;
484 }
485 }
486
487 void qemu_put_byte(QEMUFile *f, int v)
488 {
489 if (f->last_error) {
490 return;
491 }
492
493 f->buf[f->buf_index] = v;
494 f->bytes_xfer++;
495 add_buf_to_iovec(f, 1);
496 }
497
498 void qemu_file_skip(QEMUFile *f, int size)
499 {
500 if (f->buf_index + size <= f->buf_size) {
501 f->buf_index += size;
502 }
503 }
504
505 /*
506 * Read 'size' bytes from file (at 'offset') without moving the
507 * pointer and set 'buf' to point to that data.
508 *
509 * It will return size bytes unless there was an error, in which case it will
510 * return as many as it managed to read (assuming blocking fd's which
511 * all current QEMUFile are)
512 */
513 size_t qemu_peek_buffer(QEMUFile *f, uint8_t **buf, size_t size, size_t offset)
514 {
515 ssize_t pending;
516 size_t index;
517
518 assert(!qemu_file_is_writable(f));
519 assert(offset < IO_BUF_SIZE);
520 assert(size <= IO_BUF_SIZE - offset);
521
522 /* The 1st byte to read from */
523 index = f->buf_index + offset;
524 /* The number of available bytes starting at index */
525 pending = f->buf_size - index;
526
527 /*
528 * qemu_fill_buffer might return just a few bytes, even when there isn't
529 * an error, so loop collecting them until we get enough.
530 */
531 while (pending < size) {
532 int received = qemu_fill_buffer(f);
533
534 if (received <= 0) {
535 break;
536 }
537
538 index = f->buf_index + offset;
539 pending = f->buf_size - index;
540 }
541
542 if (pending <= 0) {
543 return 0;
544 }
545 if (size > pending) {
546 size = pending;
547 }
548
549 *buf = f->buf + index;
550 return size;
551 }
552
553 /*
554 * Read 'size' bytes of data from the file into buf.
555 * 'size' can be larger than the internal buffer.
556 *
557 * It will return size bytes unless there was an error, in which case it will
558 * return as many as it managed to read (assuming blocking fd's which
559 * all current QEMUFile are)
560 */
561 size_t qemu_get_buffer(QEMUFile *f, uint8_t *buf, size_t size)
562 {
563 size_t pending = size;
564 size_t done = 0;
565
566 while (pending > 0) {
567 size_t res;
568 uint8_t *src;
569
570 res = qemu_peek_buffer(f, &src, MIN(pending, IO_BUF_SIZE), 0);
571 if (res == 0) {
572 return done;
573 }
574 memcpy(buf, src, res);
575 qemu_file_skip(f, res);
576 buf += res;
577 pending -= res;
578 done += res;
579 }
580 return done;
581 }
582
583 /*
584 * Read 'size' bytes of data from the file.
585 * 'size' can be larger than the internal buffer.
586 *
587 * The data:
588 * may be held on an internal buffer (in which case *buf is updated
589 * to point to it) that is valid until the next qemu_file operation.
590 * OR
591 * will be copied to the *buf that was passed in.
592 *
593 * The code tries to avoid the copy if possible.
594 *
595 * It will return size bytes unless there was an error, in which case it will
596 * return as many as it managed to read (assuming blocking fd's which
597 * all current QEMUFile are)
598 *
599 * Note: Since **buf may get changed, the caller should take care to
600 * keep a pointer to the original buffer if it needs to deallocate it.
601 */
602 size_t qemu_get_buffer_in_place(QEMUFile *f, uint8_t **buf, size_t size)
603 {
604 if (size < IO_BUF_SIZE) {
605 size_t res;
606 uint8_t *src = NULL;
607
608 res = qemu_peek_buffer(f, &src, size, 0);
609
610 if (res == size) {
611 qemu_file_skip(f, res);
612 *buf = src;
613 return res;
614 }
615 }
616
617 return qemu_get_buffer(f, *buf, size);
618 }
619
620 /*
621 * Peeks a single byte from the buffer; this isn't guaranteed to work if
622 * offset leaves a gap after the previous read/peeked data.
623 */
624 int qemu_peek_byte(QEMUFile *f, int offset)
625 {
626 int index = f->buf_index + offset;
627
628 assert(!qemu_file_is_writable(f));
629 assert(offset < IO_BUF_SIZE);
630
631 if (index >= f->buf_size) {
632 qemu_fill_buffer(f);
633 index = f->buf_index + offset;
634 if (index >= f->buf_size) {
635 return 0;
636 }
637 }
638 return f->buf[index];
639 }
640
641 int qemu_get_byte(QEMUFile *f)
642 {
643 int result;
644
645 result = qemu_peek_byte(f, 0);
646 qemu_file_skip(f, 1);
647 return result;
648 }
649
650 int64_t qemu_ftell_fast(QEMUFile *f)
651 {
652 int64_t ret = f->pos;
653 int i;
654
655 for (i = 0; i < f->iovcnt; i++) {
656 ret += f->iov[i].iov_len;
657 }
658
659 return ret;
660 }
661
662 int64_t qemu_ftell(QEMUFile *f)
663 {
664 qemu_fflush(f);
665 return f->pos;
666 }
667
668 int qemu_file_rate_limit(QEMUFile *f)
669 {
670 if (f->shutdown) {
671 return 1;
672 }
673 if (qemu_file_get_error(f)) {
674 return 1;
675 }
676 if (f->xfer_limit > 0 && f->bytes_xfer > f->xfer_limit) {
677 return 1;
678 }
679 return 0;
680 }
681
682 int64_t qemu_file_get_rate_limit(QEMUFile *f)
683 {
684 return f->xfer_limit;
685 }
686
687 void qemu_file_set_rate_limit(QEMUFile *f, int64_t limit)
688 {
689 f->xfer_limit = limit;
690 }
691
692 void qemu_file_reset_rate_limit(QEMUFile *f)
693 {
694 f->bytes_xfer = 0;
695 }
696
697 void qemu_file_update_transfer(QEMUFile *f, int64_t len)
698 {
699 f->bytes_xfer += len;
700 }
701
702 void qemu_put_be16(QEMUFile *f, unsigned int v)
703 {
704 qemu_put_byte(f, v >> 8);
705 qemu_put_byte(f, v);
706 }
707
708 void qemu_put_be32(QEMUFile *f, unsigned int v)
709 {
710 qemu_put_byte(f, v >> 24);
711 qemu_put_byte(f, v >> 16);
712 qemu_put_byte(f, v >> 8);
713 qemu_put_byte(f, v);
714 }
715
716 void qemu_put_be64(QEMUFile *f, uint64_t v)
717 {
718 qemu_put_be32(f, v >> 32);
719 qemu_put_be32(f, v);
720 }
721
722 unsigned int qemu_get_be16(QEMUFile *f)
723 {
724 unsigned int v;
725 v = qemu_get_byte(f) << 8;
726 v |= qemu_get_byte(f);
727 return v;
728 }
729
730 unsigned int qemu_get_be32(QEMUFile *f)
731 {
732 unsigned int v;
733 v = (unsigned int)qemu_get_byte(f) << 24;
734 v |= qemu_get_byte(f) << 16;
735 v |= qemu_get_byte(f) << 8;
736 v |= qemu_get_byte(f);
737 return v;
738 }
739
740 uint64_t qemu_get_be64(QEMUFile *f)
741 {
742 uint64_t v;
743 v = (uint64_t)qemu_get_be32(f) << 32;
744 v |= qemu_get_be32(f);
745 return v;
746 }
747
748 /* return the size after compression, or negative value on error */
749 static int qemu_compress_data(z_stream *stream, uint8_t *dest, size_t dest_len,
750 const uint8_t *source, size_t source_len)
751 {
752 int err;
753
754 err = deflateReset(stream);
755 if (err != Z_OK) {
756 return -1;
757 }
758
759 stream->avail_in = source_len;
760 stream->next_in = (uint8_t *)source;
761 stream->avail_out = dest_len;
762 stream->next_out = dest;
763
764 err = deflate(stream, Z_FINISH);
765 if (err != Z_STREAM_END) {
766 return -1;
767 }
768
769 return stream->next_out - dest;
770 }
771
772 /* Compress size bytes of data start at p and store the compressed
773 * data to the buffer of f.
774 *
775 * Since the file is dummy file with empty_ops, return -1 if f has no space to
776 * save the compressed data.
777 */
778 ssize_t qemu_put_compression_data(QEMUFile *f, z_stream *stream,
779 const uint8_t *p, size_t size)
780 {
781 ssize_t blen = IO_BUF_SIZE - f->buf_index - sizeof(int32_t);
782
783 if (blen < compressBound(size)) {
784 return -1;
785 }
786
787 blen = qemu_compress_data(stream, f->buf + f->buf_index + sizeof(int32_t),
788 blen, p, size);
789 if (blen < 0) {
790 return -1;
791 }
792
793 qemu_put_be32(f, blen);
794 add_buf_to_iovec(f, blen);
795 return blen + sizeof(int32_t);
796 }
797
798 /* Put the data in the buffer of f_src to the buffer of f_des, and
799 * then reset the buf_index of f_src to 0.
800 */
801
802 int qemu_put_qemu_file(QEMUFile *f_des, QEMUFile *f_src)
803 {
804 int len = 0;
805
806 if (f_src->buf_index > 0) {
807 len = f_src->buf_index;
808 qemu_put_buffer(f_des, f_src->buf, f_src->buf_index);
809 f_src->buf_index = 0;
810 f_src->iovcnt = 0;
811 }
812 return len;
813 }
814
815 /*
816 * Get a string whose length is determined by a single preceding byte
817 * A preallocated 256 byte buffer must be passed in.
818 * Returns: len on success and a 0 terminated string in the buffer
819 * else 0
820 * (Note a 0 length string will return 0 either way)
821 */
822 size_t qemu_get_counted_string(QEMUFile *f, char buf[256])
823 {
824 size_t len = qemu_get_byte(f);
825 size_t res = qemu_get_buffer(f, (uint8_t *)buf, len);
826
827 buf[res] = 0;
828
829 return res == len ? res : 0;
830 }
831
832 /*
833 * Put a string with one preceding byte containing its length. The length of
834 * the string should be less than 256.
835 */
836 void qemu_put_counted_string(QEMUFile *f, const char *str)
837 {
838 size_t len = strlen(str);
839
840 assert(len < 256);
841 qemu_put_byte(f, len);
842 qemu_put_buffer(f, (const uint8_t *)str, len);
843 }
844
845 /*
846 * Set the blocking state of the QEMUFile.
847 * Note: On some transports the OS only keeps a single blocking state for
848 * both directions, and thus changing the blocking on the main
849 * QEMUFile can also affect the return path.
850 */
851 void qemu_file_set_blocking(QEMUFile *f, bool block)
852 {
853 if (f->ops->set_blocking) {
854 f->ops->set_blocking(f->opaque, block, NULL);
855 }
856 }
857
858 /*
859 * Return the ioc object if it's a migration channel. Note: it can return NULL
860 * for callers passing in a non-migration qemufile. E.g. see qemu_fopen_bdrv()
861 * and its usage in e.g. load_snapshot(). So we need to check against NULL
862 * before using it. If without the check, migration_incoming_state_destroy()
863 * could fail for load_snapshot().
864 */
865 QIOChannel *qemu_file_get_ioc(QEMUFile *file)
866 {
867 return file->has_ioc ? QIO_CHANNEL(file->opaque) : NULL;
868 }