aboutsummaryrefslogtreecommitdiff
path: root/migration/qemu-file.c
blob: 6338d8e2ff532c6b0bebe12b867887386ddb42e6 (plain)
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
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
/*
 * QEMU System Emulator
 *
 * Copyright (c) 2003-2008 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#include "qemu/osdep.h"
#include <zlib.h>
#include "qemu/error-report.h"
#include "qemu/iov.h"
#include "migration.h"
#include "qemu-file.h"
#include "trace.h"
#include "qapi/error.h"

#define IO_BUF_SIZE 32768
#define MAX_IOV_SIZE MIN_CONST(IOV_MAX, 64)

struct QEMUFile {
    const QEMUFileOps *ops;
    const QEMUFileHooks *hooks;
    void *opaque;

    int64_t bytes_xfer;
    int64_t xfer_limit;

    int64_t pos; /* start of buffer when writing, end of buffer
                    when reading */
    int buf_index;
    int buf_size; /* 0 when writing */
    uint8_t buf[IO_BUF_SIZE];

    DECLARE_BITMAP(may_free, MAX_IOV_SIZE);
    struct iovec iov[MAX_IOV_SIZE];
    unsigned int iovcnt;

    int last_error;
    Error *last_error_obj;
    /* has the file has been shutdown */
    bool shutdown;
    /* Whether opaque points to a QIOChannel */
    bool has_ioc;
};

/*
 * Stop a file from being read/written - not all backing files can do this
 * typically only sockets can.
 */
int qemu_file_shutdown(QEMUFile *f)
{
    int ret;

    f->shutdown = true;
    if (!f->ops->shut_down) {
        return -ENOSYS;
    }
    ret = f->ops->shut_down(f->opaque, true, true, NULL);

    if (!f->last_error) {
        qemu_file_set_error(f, -EIO);
    }
    return ret;
}

/*
 * Result: QEMUFile* for a 'return path' for comms in the opposite direction
 *         NULL if not available
 */
QEMUFile *qemu_file_get_return_path(QEMUFile *f)
{
    if (!f->ops->get_return_path) {
        return NULL;
    }
    return f->ops->get_return_path(f->opaque);
}

bool qemu_file_mode_is_not_valid(const char *mode)
{
    if (mode == NULL ||
        (mode[0] != 'r' && mode[0] != 'w') ||
        mode[1] != 'b' || mode[2] != 0) {
        fprintf(stderr, "qemu_fopen: Argument validity check failed\n");
        return true;
    }

    return false;
}

QEMUFile *qemu_fopen_ops(void *opaque, const QEMUFileOps *ops, bool has_ioc)
{
    QEMUFile *f;

    f = g_new0(QEMUFile, 1);

    f->opaque = opaque;
    f->ops = ops;
    f->has_ioc = has_ioc;
    return f;
}


void qemu_file_set_hooks(QEMUFile *f, const QEMUFileHooks *hooks)
{
    f->hooks = hooks;
}

/*
 * Get last error for stream f with optional Error*
 *
 * Return negative error value if there has been an error on previous
 * operations, return 0 if no error happened.
 * Optional, it returns Error* in errp, but it may be NULL even if return value
 * is not 0.
 *
 */
int qemu_file_get_error_obj(QEMUFile *f, Error **errp)
{
    if (errp) {
        *errp = f->last_error_obj ? error_copy(f->last_error_obj) : NULL;
    }
    return f->last_error;
}

/*
 * Set the last error for stream f with optional Error*
 */
void qemu_file_set_error_obj(QEMUFile *f, int ret, Error *err)
{
    if (f->last_error == 0 && ret) {
        f->last_error = ret;
        error_propagate(&f->last_error_obj, err);
    } else if (err) {
        error_report_err(err);
    }
}

/*
 * Get last error for stream f
 *
 * Return negative error value if there has been an error on previous
 * operations, return 0 if no error happened.
 *
 */
int qemu_file_get_error(QEMUFile *f)
{
    return qemu_file_get_error_obj(f, NULL);
}

/*
 * Set the last error for stream f
 */
void qemu_file_set_error(QEMUFile *f, int ret)
{
    qemu_file_set_error_obj(f, ret, NULL);
}

bool qemu_file_is_writable(QEMUFile *f)
{
    return f->ops->writev_buffer;
}

static void qemu_iovec_release_ram(QEMUFile *f)
{
    struct iovec iov;
    unsigned long idx;

    /* Find and release all the contiguous memory ranges marked as may_free. */
    idx = find_next_bit(f->may_free, f->iovcnt, 0);
    if (idx >= f->iovcnt) {
        return;
    }
    iov = f->iov[idx];

    /* The madvise() in the loop is called for iov within a continuous range and
     * then reinitialize the iov. And in the end, madvise() is called for the
     * last iov.
     */
    while ((idx = find_next_bit(f->may_free, f->iovcnt, idx + 1)) < f->iovcnt) {
        /* check for adjacent buffer and coalesce them */
        if (iov.iov_base + iov.iov_len == f->iov[idx].iov_base) {
            iov.iov_len += f->iov[idx].iov_len;
            continue;
        }
        if (qemu_madvise(iov.iov_base, iov.iov_len, QEMU_MADV_DONTNEED) < 0) {
            error_report("migrate: madvise DONTNEED failed %p %zd: %s",
                         iov.iov_base, iov.iov_len, strerror(errno));
        }
        iov = f->iov[idx];
    }
    if (qemu_madvise(iov.iov_base, iov.iov_len, QEMU_MADV_DONTNEED) < 0) {
            error_report("migrate: madvise DONTNEED failed %p %zd: %s",
                         iov.iov_base, iov.iov_len, strerror(errno));
    }
    memset(f->may_free, 0, sizeof(f->may_free));
}

/**
 * Flushes QEMUFile buffer
 *
 * This will flush all pending data. If data was only partially flushed, it
 * will set an error state.
 */
void qemu_fflush(QEMUFile *f)
{
    ssize_t ret = 0;
    ssize_t expect = 0;
    Error *local_error = NULL;

    if (!qemu_file_is_writable(f)) {
        return;
    }

    if (f->shutdown) {
        return;
    }
    if (f->iovcnt > 0) {
        expect = iov_size(f->iov, f->iovcnt);
        ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt, f->pos,
                                    &local_error);

        qemu_iovec_release_ram(f);
    }

    if (ret >= 0) {
        f->pos += ret;
    }
    /* We expect the QEMUFile write impl to send the full
     * data set we requested, so sanity check that.
     */
    if (ret != expect) {
        qemu_file_set_error_obj(f, ret < 0 ? ret : -EIO, local_error);
    }
    f->buf_index = 0;
    f->iovcnt = 0;
}

void ram_control_before_iterate(QEMUFile *f, uint64_t flags)
{
    int ret = 0;

    if (f->hooks && f->hooks->before_ram_iterate) {
        ret = f->hooks->before_ram_iterate(f, f->opaque, flags, NULL);
        if (ret < 0) {
            qemu_file_set_error(f, ret);
        }
    }
}

void ram_control_after_iterate(QEMUFile *f, uint64_t flags)
{
    int ret = 0;

    if (f->hooks && f->hooks->after_ram_iterate) {
        ret = f->hooks->after_ram_iterate(f, f->opaque, flags, NULL);
        if (ret < 0) {
            qemu_file_set_error(f, ret);
        }
    }
}

void ram_control_load_hook(QEMUFile *f, uint64_t flags, void *data)
{
    int ret = -EINVAL;

    if (f->hooks && f->hooks->hook_ram_load) {
        ret = f->hooks->hook_ram_load(f, f->opaque, flags, data);
        if (ret < 0) {
            qemu_file_set_error(f, ret);
        }
    } else {
        /*
         * Hook is a hook specifically requested by the source sending a flag
         * that expects there to be a hook on the destination.
         */
        if (flags == RAM_CONTROL_HOOK) {
            qemu_file_set_error(f, ret);
        }
    }
}

size_t ram_control_save_page(QEMUFile *f, ram_addr_t block_offset,
                             ram_addr_t offset, size_t size,
                             uint64_t *bytes_sent)
{
    if (f->hooks && f->hooks->save_page) {
        int ret = f->hooks->save_page(f, f->opaque, block_offset,
                                      offset, size, bytes_sent);
        if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
            f->bytes_xfer += size;
        }

        if (ret != RAM_SAVE_CONTROL_DELAYED &&
            ret != RAM_SAVE_CONTROL_NOT_SUPP) {
            if (bytes_sent && *bytes_sent > 0) {
                qemu_update_position(f, *bytes_sent);
            } else if (ret < 0) {
                qemu_file_set_error(f, ret);
            }
        }

        return ret;
    }

    return RAM_SAVE_CONTROL_NOT_SUPP;
}

/*
 * Attempt to fill the buffer from the underlying file
 * Returns the number of bytes read, or negative value for an error.
 *
 * Note that it can return a partially full buffer even in a not error/not EOF
 * case if the underlying file descriptor gives a short read, and that can
 * happen even on a blocking fd.
 */
static ssize_t qemu_fill_buffer(QEMUFile *f)
{
    int len;
    int pending;
    Error *local_error = NULL;

    assert(!qemu_file_is_writable(f));

    pending = f->buf_size - f->buf_index;
    if (pending > 0) {
        memmove(f->buf, f->buf + f->buf_index, pending);
    }
    f->buf_index = 0;
    f->buf_size = pending;

    if (f->shutdown) {
        return 0;
    }

    len = f->ops->get_buffer(f->opaque, f->buf + pending, f->pos,
                             IO_BUF_SIZE - pending, &local_error);
    if (len > 0) {
        f->buf_size += len;
        f->pos += len;
    } else if (len == 0) {
        qemu_file_set_error_obj(f, -EIO, local_error);
    } else if (len != -EAGAIN) {
        qemu_file_set_error_obj(f, len, local_error);
    } else {
        error_free(local_error);
    }

    return len;
}

void qemu_update_position(QEMUFile *f, size_t size)
{
    f->pos += size;
}

/** Closes the file
 *
 * Returns negative error value if any error happened on previous operations or
 * while closing the file. Returns 0 or positive number on success.
 *
 * The meaning of return value on success depends on the specific backend
 * being used.
 */
int qemu_fclose(QEMUFile *f)
{
    int ret;
    qemu_fflush(f);
    ret = qemu_file_get_error(f);

    if (f->ops->close) {
        int ret2 = f->ops->close(f->opaque, NULL);
        if (ret >= 0) {
            ret = ret2;
        }
    }
    /* If any error was spotted before closing, we should report it
     * instead of the close() return value.
     */
    if (f->last_error) {
        ret = f->last_error;
    }
    error_free(f->last_error_obj);
    g_free(f);
    trace_qemu_file_fclose();
    return ret;
}

/*
 * Add buf to iovec. Do flush if iovec is full.
 *
 * Return values:
 * 1 iovec is full and flushed
 * 0 iovec is not flushed
 *
 */
static int add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,
                        bool may_free)
{
    /* check for adjacent buffer and coalesce them */
    if (f->iovcnt > 0 && buf == f->iov[f->iovcnt - 1].iov_base +
        f->iov[f->iovcnt - 1].iov_len &&
        may_free == test_bit(f->iovcnt - 1, f->may_free))
    {
        f->iov[f->iovcnt - 1].iov_len += size;
    } else {
        if (f->iovcnt >= MAX_IOV_SIZE) {
            /* Should only happen if a previous fflush failed */
            assert(f->shutdown || !qemu_file_is_writable(f));
            return 1;
        }
        if (may_free) {
            set_bit(f->iovcnt, f->may_free);
        }
        f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
        f->iov[f->iovcnt++].iov_len = size;
    }

    if (f->iovcnt >= MAX_IOV_SIZE) {
        qemu_fflush(f);
        return 1;
    }

    return 0;
}

static void add_buf_to_iovec(QEMUFile *f, size_t len)
{
    if (!add_to_iovec(f, f->buf + f->buf_index, len, false)) {
        f->buf_index += len;
        if (f->buf_index == IO_BUF_SIZE) {
            qemu_fflush(f);
        }
    }
}

void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, size_t size,
                           bool may_free)
{
    if (f->last_error) {
        return;
    }

    f->bytes_xfer += size;
    add_to_iovec(f, buf, size, may_free);
}

void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, size_t size)
{
    size_t l;

    if (f->last_error) {
        return;
    }

    while (size > 0) {
        l = IO_BUF_SIZE - f->buf_index;
        if (l > size) {
            l = size;
        }
        memcpy(f->buf + f->buf_index, buf, l);
        f->bytes_xfer += l;
        add_buf_to_iovec(f, l);
        if (qemu_file_get_error(f)) {
            break;
        }
        buf += l;
        size -= l;
    }
}

void qemu_put_byte(QEMUFile *f, int v)
{
    if (f->last_error) {
        return;
    }

    f->buf[f->buf_index] = v;
    f->bytes_xfer++;
    add_buf_to_iovec(f, 1);
}

void qemu_file_skip(QEMUFile *f, int size)
{
    if (f->buf_index + size <= f->buf_size) {
        f->buf_index += size;
    }
}

/*
 * Read 'size' bytes from file (at 'offset') without moving the
 * pointer and set 'buf' to point to that data.
 *
 * It will return size bytes unless there was an error, in which case it will
 * return as many as it managed to read (assuming blocking fd's which
 * all current QEMUFile are)
 */
size_t qemu_peek_buffer(QEMUFile *f, uint8_t **buf, size_t size, size_t offset)
{
    ssize_t pending;
    size_t index;

    assert(!qemu_file_is_writable(f));
    assert(offset < IO_BUF_SIZE);
    assert(size <= IO_BUF_SIZE - offset);

    /* The 1st byte to read from */
    index = f->buf_index + offset;
    /* The number of available bytes starting at index */
    pending = f->buf_size - index;

    /*
     * qemu_fill_buffer might return just a few bytes, even when there isn't
     * an error, so loop collecting them until we get enough.
     */
    while (pending < size) {
        int received = qemu_fill_buffer(f);

        if (received <= 0) {
            break;
        }

        index = f->buf_index + offset;
        pending = f->buf_size - index;
    }

    if (pending <= 0) {
        return 0;
    }
    if (size > pending) {
        size = pending;
    }

    *buf = f->buf + index;
    return size;
}

/*
 * Read 'size' bytes of data from the file into buf.
 * 'size' can be larger than the internal buffer.
 *
 * It will return size bytes unless there was an error, in which case it will
 * return as many as it managed to read (assuming blocking fd's which
 * all current QEMUFile are)
 */
size_t qemu_get_buffer(QEMUFile *f, uint8_t *buf, size_t size)
{
    size_t pending = size;
    size_t done = 0;

    while (pending > 0) {
        size_t res;
        uint8_t *src;

        res = qemu_peek_buffer(f, &src, MIN(pending, IO_BUF_SIZE), 0);
        if (res == 0) {
            return done;
        }
        memcpy(buf, src, res);
        qemu_file_skip(f, res);
        buf += res;
        pending -= res;
        done += res;
    }
    return done;
}

/*
 * Read 'size' bytes of data from the file.
 * 'size' can be larger than the internal buffer.
 *
 * The data:
 *   may be held on an internal buffer (in which case *buf is updated
 *     to point to it) that is valid until the next qemu_file operation.
 * OR
 *   will be copied to the *buf that was passed in.
 *
 * The code tries to avoid the copy if possible.
 *
 * It will return size bytes unless there was an error, in which case it will
 * return as many as it managed to read (assuming blocking fd's which
 * all current QEMUFile are)
 *
 * Note: Since **buf may get changed, the caller should take care to
 *       keep a pointer to the original buffer if it needs to deallocate it.
 */
size_t qemu_get_buffer_in_place(QEMUFile *f, uint8_t **buf, size_t size)
{
    if (size < IO_BUF_SIZE) {
        size_t res;
        uint8_t *src = NULL;

        res = qemu_peek_buffer(f, &src, size, 0);

        if (res == size) {
            qemu_file_skip(f, res);
            *buf = src;
            return res;
        }
    }

    return qemu_get_buffer(f, *buf, size);
}

/*
 * Peeks a single byte from the buffer; this isn't guaranteed to work if
 * offset leaves a gap after the previous read/peeked data.
 */
int qemu_peek_byte(QEMUFile *f, int offset)
{
    int index = f->buf_index + offset;

    assert(!qemu_file_is_writable(f));
    assert(offset < IO_BUF_SIZE);

    if (index >= f->buf_size) {
        qemu_fill_buffer(f);
        index = f->buf_index + offset;
        if (index >= f->buf_size) {
            return 0;
        }
    }
    return f->buf[index];
}

int qemu_get_byte(QEMUFile *f)
{
    int result;

    result = qemu_peek_byte(f, 0);
    qemu_file_skip(f, 1);
    return result;
}

int64_t qemu_ftell_fast(QEMUFile *f)
{
    int64_t ret = f->pos;
    int i;

    for (i = 0; i < f->iovcnt; i++) {
        ret += f->iov[i].iov_len;
    }

    return ret;
}

int64_t qemu_ftell(QEMUFile *f)
{
    qemu_fflush(f);
    return f->pos;
}

int qemu_file_rate_limit(QEMUFile *f)
{
    if (f->shutdown) {
        return 1;
    }
    if (qemu_file_get_error(f)) {
        return 1;
    }
    if (f->xfer_limit > 0 && f->bytes_xfer > f->xfer_limit) {
        return 1;
    }
    return 0;
}

int64_t qemu_file_get_rate_limit(QEMUFile *f)
{
    return f->xfer_limit;
}

void qemu_file_set_rate_limit(QEMUFile *f, int64_t limit)
{
    f->xfer_limit = limit;
}

void qemu_file_reset_rate_limit(QEMUFile *f)
{
    f->bytes_xfer = 0;
}

void qemu_file_update_transfer(QEMUFile *f, int64_t len)
{
    f->bytes_xfer += len;
}

void qemu_put_be16(QEMUFile *f, unsigned int v)
{
    qemu_put_byte(f, v >> 8);
    qemu_put_byte(f, v);
}

void qemu_put_be32(QEMUFile *f, unsigned int v)
{
    qemu_put_byte(f, v >> 24);
    qemu_put_byte(f, v >> 16);
    qemu_put_byte(f, v >> 8);
    qemu_put_byte(f, v);
}

void qemu_put_be64(QEMUFile *f, uint64_t v)
{
    qemu_put_be32(f, v >> 32);
    qemu_put_be32(f, v);
}

unsigned int qemu_get_be16(QEMUFile *f)
{
    unsigned int v;
    v = qemu_get_byte(f) << 8;
    v |= qemu_get_byte(f);
    return v;
}

unsigned int qemu_get_be32(QEMUFile *f)
{
    unsigned int v;
    v = (unsigned int)qemu_get_byte(f) << 24;
    v |= qemu_get_byte(f) << 16;
    v |= qemu_get_byte(f) << 8;
    v |= qemu_get_byte(f);
    return v;
}

uint64_t qemu_get_be64(QEMUFile *f)
{
    uint64_t v;
    v = (uint64_t)qemu_get_be32(f) << 32;
    v |= qemu_get_be32(f);
    return v;
}

/* return the size after compression, or negative value on error */
static int qemu_compress_data(z_stream *stream, uint8_t *dest, size_t dest_len,
                              const uint8_t *source, size_t source_len)
{
    int err;

    err = deflateReset(stream);
    if (err != Z_OK) {
        return -1;
    }

    stream->avail_in = source_len;
    stream->next_in = (uint8_t *)source;
    stream->avail_out = dest_len;
    stream->next_out = dest;

    err = deflate(stream, Z_FINISH);
    if (err != Z_STREAM_END) {
        return -1;
    }

    return stream->next_out - dest;
}

/* Compress size bytes of data start at p and store the compressed
 * data to the buffer of f.
 *
 * Since the file is dummy file with empty_ops, return -1 if f has no space to
 * save the compressed data.
 */
ssize_t qemu_put_compression_data(QEMUFile *f, z_stream *stream,
                                  const uint8_t *p, size_t size)
{
    ssize_t blen = IO_BUF_SIZE - f->buf_index - sizeof(int32_t);

    if (blen < compressBound(size)) {
        return -1;
    }

    blen = qemu_compress_data(stream, f->buf + f->buf_index + sizeof(int32_t),
                              blen, p, size);
    if (blen < 0) {
        return -1;
    }

    qemu_put_be32(f, blen);
    add_buf_to_iovec(f, blen);
    return blen + sizeof(int32_t);
}

/* Put the data in the buffer of f_src to the buffer of f_des, and
 * then reset the buf_index of f_src to 0.
 */

int qemu_put_qemu_file(QEMUFile *f_des, QEMUFile *f_src)
{
    int len = 0;

    if (f_src->buf_index > 0) {
        len = f_src->buf_index;
        qemu_put_buffer(f_des, f_src->buf, f_src->buf_index);
        f_src->buf_index = 0;
        f_src->iovcnt = 0;
    }
    return len;
}

/*
 * Get a string whose length is determined by a single preceding byte
 * A preallocated 256 byte buffer must be passed in.
 * Returns: len on success and a 0 terminated string in the buffer
 *          else 0
 *          (Note a 0 length string will return 0 either way)
 */
size_t qemu_get_counted_string(QEMUFile *f, char buf[256])
{
    size_t len = qemu_get_byte(f);
    size_t res = qemu_get_buffer(f, (uint8_t *)buf, len);

    buf[res] = 0;

    return res == len ? res : 0;
}

/*
 * Put a string with one preceding byte containing its length. The length of
 * the string should be less than 256.
 */
void qemu_put_counted_string(QEMUFile *f, const char *str)
{
    size_t len = strlen(str);

    assert(len < 256);
    qemu_put_byte(f, len);
    qemu_put_buffer(f, (const uint8_t *)str, len);
}

/*
 * Set the blocking state of the QEMUFile.
 * Note: On some transports the OS only keeps a single blocking state for
 *       both directions, and thus changing the blocking on the main
 *       QEMUFile can also affect the return path.
 */
void qemu_file_set_blocking(QEMUFile *f, bool block)
{
    if (f->ops->set_blocking) {
        f->ops->set_blocking(f->opaque, block, NULL);
    }
}

/*
 * Return the ioc object if it's a migration channel.  Note: it can return NULL
 * for callers passing in a non-migration qemufile.  E.g. see qemu_fopen_bdrv()
 * and its usage in e.g. load_snapshot().  So we need to check against NULL
 * before using it.  If without the check, migration_incoming_state_destroy()
 * could fail for load_snapshot().
 */
QIOChannel *qemu_file_get_ioc(QEMUFile *file)
{
    return file->has_ioc ? QIO_CHANNEL(file->opaque) : NULL;
}