1 | /* |
2 | * Helpers for getting linearized buffers from iov / filling buffers into iovs |
3 | * |
4 | * Copyright IBM, Corp. 2007, 2008 |
5 | * Copyright (C) 2010 Red Hat, Inc. |
6 | * |
7 | * Author(s): |
8 | * Anthony Liguori <aliguori@us.ibm.com> |
9 | * Amit Shah <amit.shah@redhat.com> |
10 | * Michael Tokarev <mjt@tls.msk.ru> |
11 | * |
12 | * This work is licensed under the terms of the GNU GPL, version 2. See |
13 | * the COPYING file in the top-level directory. |
14 | * |
15 | * Contributions after 2012-01-13 are licensed under the terms of the |
16 | * GNU GPL, version 2 or (at your option) any later version. |
17 | */ |
18 | |
19 | #include "qemu/osdep.h" |
20 | #include "qemu-common.h" |
21 | #include "qemu/iov.h" |
22 | #include "qemu/sockets.h" |
23 | #include "qemu/cutils.h" |
24 | |
25 | size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt, |
26 | size_t offset, const void *buf, size_t bytes) |
27 | { |
28 | size_t done; |
29 | unsigned int i; |
30 | for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) { |
31 | if (offset < iov[i].iov_len) { |
32 | size_t len = MIN(iov[i].iov_len - offset, bytes - done); |
33 | memcpy(iov[i].iov_base + offset, buf + done, len); |
34 | done += len; |
35 | offset = 0; |
36 | } else { |
37 | offset -= iov[i].iov_len; |
38 | } |
39 | } |
40 | assert(offset == 0); |
41 | return done; |
42 | } |
43 | |
44 | size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt, |
45 | size_t offset, void *buf, size_t bytes) |
46 | { |
47 | size_t done; |
48 | unsigned int i; |
49 | for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) { |
50 | if (offset < iov[i].iov_len) { |
51 | size_t len = MIN(iov[i].iov_len - offset, bytes - done); |
52 | memcpy(buf + done, iov[i].iov_base + offset, len); |
53 | done += len; |
54 | offset = 0; |
55 | } else { |
56 | offset -= iov[i].iov_len; |
57 | } |
58 | } |
59 | assert(offset == 0); |
60 | return done; |
61 | } |
62 | |
63 | size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt, |
64 | size_t offset, int fillc, size_t bytes) |
65 | { |
66 | size_t done; |
67 | unsigned int i; |
68 | for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) { |
69 | if (offset < iov[i].iov_len) { |
70 | size_t len = MIN(iov[i].iov_len - offset, bytes - done); |
71 | memset(iov[i].iov_base + offset, fillc, len); |
72 | done += len; |
73 | offset = 0; |
74 | } else { |
75 | offset -= iov[i].iov_len; |
76 | } |
77 | } |
78 | assert(offset == 0); |
79 | return done; |
80 | } |
81 | |
82 | size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt) |
83 | { |
84 | size_t len; |
85 | unsigned int i; |
86 | |
87 | len = 0; |
88 | for (i = 0; i < iov_cnt; i++) { |
89 | len += iov[i].iov_len; |
90 | } |
91 | return len; |
92 | } |
93 | |
94 | /* helper function for iov_send_recv() */ |
95 | static ssize_t |
96 | do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send) |
97 | { |
98 | #ifdef CONFIG_POSIX |
99 | ssize_t ret; |
100 | struct msghdr msg; |
101 | memset(&msg, 0, sizeof(msg)); |
102 | msg.msg_iov = iov; |
103 | msg.msg_iovlen = iov_cnt; |
104 | do { |
105 | ret = do_send |
106 | ? sendmsg(sockfd, &msg, 0) |
107 | : recvmsg(sockfd, &msg, 0); |
108 | } while (ret < 0 && errno == EINTR); |
109 | return ret; |
110 | #else |
111 | /* else send piece-by-piece */ |
112 | /*XXX Note: windows has WSASend() and WSARecv() */ |
113 | unsigned i = 0; |
114 | ssize_t ret = 0; |
115 | while (i < iov_cnt) { |
116 | ssize_t r = do_send |
117 | ? send(sockfd, iov[i].iov_base, iov[i].iov_len, 0) |
118 | : recv(sockfd, iov[i].iov_base, iov[i].iov_len, 0); |
119 | if (r > 0) { |
120 | ret += r; |
121 | } else if (!r) { |
122 | break; |
123 | } else if (errno == EINTR) { |
124 | continue; |
125 | } else { |
126 | /* else it is some "other" error, |
127 | * only return if there was no data processed. */ |
128 | if (ret == 0) { |
129 | ret = -1; |
130 | } |
131 | break; |
132 | } |
133 | i++; |
134 | } |
135 | return ret; |
136 | #endif |
137 | } |
138 | |
139 | ssize_t iov_send_recv(int sockfd, const struct iovec *_iov, unsigned iov_cnt, |
140 | size_t offset, size_t bytes, |
141 | bool do_send) |
142 | { |
143 | ssize_t total = 0; |
144 | ssize_t ret; |
145 | size_t orig_len, tail; |
146 | unsigned niov; |
147 | struct iovec *local_iov, *iov; |
148 | |
149 | if (bytes <= 0) { |
150 | return 0; |
151 | } |
152 | |
153 | local_iov = g_new0(struct iovec, iov_cnt); |
154 | iov_copy(local_iov, iov_cnt, _iov, iov_cnt, offset, bytes); |
155 | offset = 0; |
156 | iov = local_iov; |
157 | |
158 | while (bytes > 0) { |
159 | /* Find the start position, skipping `offset' bytes: |
160 | * first, skip all full-sized vector elements, */ |
161 | for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) { |
162 | offset -= iov[niov].iov_len; |
163 | } |
164 | |
165 | /* niov == iov_cnt would only be valid if bytes == 0, which |
166 | * we already ruled out in the loop condition. */ |
167 | assert(niov < iov_cnt); |
168 | iov += niov; |
169 | iov_cnt -= niov; |
170 | |
171 | if (offset) { |
172 | /* second, skip `offset' bytes from the (now) first element, |
173 | * undo it on exit */ |
174 | iov[0].iov_base += offset; |
175 | iov[0].iov_len -= offset; |
176 | } |
177 | /* Find the end position skipping `bytes' bytes: */ |
178 | /* first, skip all full-sized elements */ |
179 | tail = bytes; |
180 | for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) { |
181 | tail -= iov[niov].iov_len; |
182 | } |
183 | if (tail) { |
184 | /* second, fixup the last element, and remember the original |
185 | * length */ |
186 | assert(niov < iov_cnt); |
187 | assert(iov[niov].iov_len > tail); |
188 | orig_len = iov[niov].iov_len; |
189 | iov[niov++].iov_len = tail; |
190 | ret = do_send_recv(sockfd, iov, niov, do_send); |
191 | /* Undo the changes above before checking for errors */ |
192 | iov[niov-1].iov_len = orig_len; |
193 | } else { |
194 | ret = do_send_recv(sockfd, iov, niov, do_send); |
195 | } |
196 | if (offset) { |
197 | iov[0].iov_base -= offset; |
198 | iov[0].iov_len += offset; |
199 | } |
200 | |
201 | if (ret < 0) { |
202 | assert(errno != EINTR); |
203 | g_free(local_iov); |
204 | if (errno == EAGAIN && total > 0) { |
205 | return total; |
206 | } |
207 | return -1; |
208 | } |
209 | |
210 | if (ret == 0 && !do_send) { |
211 | /* recv returns 0 when the peer has performed an orderly |
212 | * shutdown. */ |
213 | break; |
214 | } |
215 | |
216 | /* Prepare for the next iteration */ |
217 | offset += ret; |
218 | total += ret; |
219 | bytes -= ret; |
220 | } |
221 | |
222 | g_free(local_iov); |
223 | return total; |
224 | } |
225 | |
226 | |
227 | void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, |
228 | FILE *fp, const char *prefix, size_t limit) |
229 | { |
230 | int v; |
231 | size_t size = 0; |
232 | char *buf; |
233 | |
234 | for (v = 0; v < iov_cnt; v++) { |
235 | size += iov[v].iov_len; |
236 | } |
237 | size = size > limit ? limit : size; |
238 | buf = g_malloc(size); |
239 | iov_to_buf(iov, iov_cnt, 0, buf, size); |
240 | qemu_hexdump(buf, fp, prefix, size); |
241 | g_free(buf); |
242 | } |
243 | |
244 | unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt, |
245 | const struct iovec *iov, unsigned int iov_cnt, |
246 | size_t offset, size_t bytes) |
247 | { |
248 | size_t len; |
249 | unsigned int i, j; |
250 | for (i = 0, j = 0; |
251 | i < iov_cnt && j < dst_iov_cnt && (offset || bytes); i++) { |
252 | if (offset >= iov[i].iov_len) { |
253 | offset -= iov[i].iov_len; |
254 | continue; |
255 | } |
256 | len = MIN(bytes, iov[i].iov_len - offset); |
257 | |
258 | dst_iov[j].iov_base = iov[i].iov_base + offset; |
259 | dst_iov[j].iov_len = len; |
260 | j++; |
261 | bytes -= len; |
262 | offset = 0; |
263 | } |
264 | assert(offset == 0); |
265 | return j; |
266 | } |
267 | |
268 | /* io vectors */ |
269 | |
270 | void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint) |
271 | { |
272 | qiov->iov = g_new(struct iovec, alloc_hint); |
273 | qiov->niov = 0; |
274 | qiov->nalloc = alloc_hint; |
275 | qiov->size = 0; |
276 | } |
277 | |
278 | void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov) |
279 | { |
280 | int i; |
281 | |
282 | qiov->iov = iov; |
283 | qiov->niov = niov; |
284 | qiov->nalloc = -1; |
285 | qiov->size = 0; |
286 | for (i = 0; i < niov; i++) |
287 | qiov->size += iov[i].iov_len; |
288 | } |
289 | |
290 | void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len) |
291 | { |
292 | assert(qiov->nalloc != -1); |
293 | |
294 | if (qiov->niov == qiov->nalloc) { |
295 | qiov->nalloc = 2 * qiov->nalloc + 1; |
296 | qiov->iov = g_renew(struct iovec, qiov->iov, qiov->nalloc); |
297 | } |
298 | qiov->iov[qiov->niov].iov_base = base; |
299 | qiov->iov[qiov->niov].iov_len = len; |
300 | qiov->size += len; |
301 | ++qiov->niov; |
302 | } |
303 | |
304 | /* |
305 | * Concatenates (partial) iovecs from src_iov to the end of dst. |
306 | * It starts copying after skipping `soffset' bytes at the |
307 | * beginning of src and adds individual vectors from src to |
308 | * dst copies up to `sbytes' bytes total, or up to the end |
309 | * of src_iov if it comes first. This way, it is okay to specify |
310 | * very large value for `sbytes' to indicate "up to the end |
311 | * of src". |
312 | * Only vector pointers are processed, not the actual data buffers. |
313 | */ |
314 | size_t qemu_iovec_concat_iov(QEMUIOVector *dst, |
315 | struct iovec *src_iov, unsigned int src_cnt, |
316 | size_t soffset, size_t sbytes) |
317 | { |
318 | int i; |
319 | size_t done; |
320 | |
321 | if (!sbytes) { |
322 | return 0; |
323 | } |
324 | assert(dst->nalloc != -1); |
325 | for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) { |
326 | if (soffset < src_iov[i].iov_len) { |
327 | size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done); |
328 | qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len); |
329 | done += len; |
330 | soffset = 0; |
331 | } else { |
332 | soffset -= src_iov[i].iov_len; |
333 | } |
334 | } |
335 | assert(soffset == 0); /* offset beyond end of src */ |
336 | |
337 | return done; |
338 | } |
339 | |
340 | /* |
341 | * Concatenates (partial) iovecs from src to the end of dst. |
342 | * It starts copying after skipping `soffset' bytes at the |
343 | * beginning of src and adds individual vectors from src to |
344 | * dst copies up to `sbytes' bytes total, or up to the end |
345 | * of src if it comes first. This way, it is okay to specify |
346 | * very large value for `sbytes' to indicate "up to the end |
347 | * of src". |
348 | * Only vector pointers are processed, not the actual data buffers. |
349 | */ |
350 | void qemu_iovec_concat(QEMUIOVector *dst, |
351 | QEMUIOVector *src, size_t soffset, size_t sbytes) |
352 | { |
353 | qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes); |
354 | } |
355 | |
356 | /* |
357 | * qiov_find_iov |
358 | * |
359 | * Return pointer to iovec structure, where byte at @offset in original vector |
360 | * @iov exactly is. |
361 | * Set @remaining_offset to be offset inside that iovec to the same byte. |
362 | */ |
363 | static struct iovec *iov_skip_offset(struct iovec *iov, size_t offset, |
364 | size_t *remaining_offset) |
365 | { |
366 | while (offset > 0 && offset >= iov->iov_len) { |
367 | offset -= iov->iov_len; |
368 | iov++; |
369 | } |
370 | *remaining_offset = offset; |
371 | |
372 | return iov; |
373 | } |
374 | |
375 | /* |
376 | * qiov_slice |
377 | * |
378 | * Find subarray of iovec's, containing requested range. @head would |
379 | * be offset in first iov (returned by the function), @tail would be |
380 | * count of extra bytes in last iovec (returned iov + @niov - 1). |
381 | */ |
382 | static struct iovec *qiov_slice(QEMUIOVector *qiov, |
383 | size_t offset, size_t len, |
384 | size_t *head, size_t *tail, int *niov) |
385 | { |
386 | struct iovec *iov, *end_iov; |
387 | |
388 | assert(offset + len <= qiov->size); |
389 | |
390 | iov = iov_skip_offset(qiov->iov, offset, head); |
391 | end_iov = iov_skip_offset(iov, *head + len, tail); |
392 | |
393 | if (*tail > 0) { |
394 | assert(*tail < end_iov->iov_len); |
395 | *tail = end_iov->iov_len - *tail; |
396 | end_iov++; |
397 | } |
398 | |
399 | *niov = end_iov - iov; |
400 | |
401 | return iov; |
402 | } |
403 | |
404 | int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len) |
405 | { |
406 | size_t head, tail; |
407 | int niov; |
408 | |
409 | qiov_slice(qiov, offset, len, &head, &tail, &niov); |
410 | |
411 | return niov; |
412 | } |
413 | |
414 | /* |
415 | * Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov, |
416 | * and @tail_buf buffer into new qiov. |
417 | */ |
418 | void qemu_iovec_init_extended( |
419 | QEMUIOVector *qiov, |
420 | void *head_buf, size_t head_len, |
421 | QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len, |
422 | void *tail_buf, size_t tail_len) |
423 | { |
424 | size_t mid_head, mid_tail; |
425 | int total_niov, mid_niov = 0; |
426 | struct iovec *p, *mid_iov; |
427 | |
428 | if (mid_len) { |
429 | mid_iov = qiov_slice(mid_qiov, mid_offset, mid_len, |
430 | &mid_head, &mid_tail, &mid_niov); |
431 | } |
432 | |
433 | total_niov = !!head_len + mid_niov + !!tail_len; |
434 | if (total_niov == 1) { |
435 | qemu_iovec_init_buf(qiov, NULL, 0); |
436 | p = &qiov->local_iov; |
437 | } else { |
438 | qiov->niov = qiov->nalloc = total_niov; |
439 | qiov->size = head_len + mid_len + tail_len; |
440 | p = qiov->iov = g_new(struct iovec, qiov->niov); |
441 | } |
442 | |
443 | if (head_len) { |
444 | p->iov_base = head_buf; |
445 | p->iov_len = head_len; |
446 | p++; |
447 | } |
448 | |
449 | if (mid_len) { |
450 | memcpy(p, mid_iov, mid_niov * sizeof(*p)); |
451 | p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head; |
452 | p[0].iov_len -= mid_head; |
453 | p[mid_niov - 1].iov_len -= mid_tail; |
454 | p += mid_niov; |
455 | } |
456 | |
457 | if (tail_len) { |
458 | p->iov_base = tail_buf; |
459 | p->iov_len = tail_len; |
460 | } |
461 | } |
462 | |
463 | /* |
464 | * Check if the contents of subrange of qiov data is all zeroes. |
465 | */ |
466 | bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t offset, size_t bytes) |
467 | { |
468 | struct iovec *iov; |
469 | size_t current_offset; |
470 | |
471 | assert(offset + bytes <= qiov->size); |
472 | |
473 | iov = iov_skip_offset(qiov->iov, offset, ¤t_offset); |
474 | |
475 | while (bytes) { |
476 | uint8_t *base = (uint8_t *)iov->iov_base + current_offset; |
477 | size_t len = MIN(iov->iov_len - current_offset, bytes); |
478 | |
479 | if (!buffer_is_zero(base, len)) { |
480 | return false; |
481 | } |
482 | |
483 | current_offset = 0; |
484 | bytes -= len; |
485 | iov++; |
486 | } |
487 | |
488 | return true; |
489 | } |
490 | |
491 | void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source, |
492 | size_t offset, size_t len) |
493 | { |
494 | qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0); |
495 | } |
496 | |
497 | void qemu_iovec_destroy(QEMUIOVector *qiov) |
498 | { |
499 | if (qiov->nalloc != -1) { |
500 | g_free(qiov->iov); |
501 | } |
502 | |
503 | memset(qiov, 0, sizeof(*qiov)); |
504 | } |
505 | |
506 | void qemu_iovec_reset(QEMUIOVector *qiov) |
507 | { |
508 | assert(qiov->nalloc != -1); |
509 | |
510 | qiov->niov = 0; |
511 | qiov->size = 0; |
512 | } |
513 | |
514 | size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset, |
515 | void *buf, size_t bytes) |
516 | { |
517 | return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes); |
518 | } |
519 | |
520 | size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset, |
521 | const void *buf, size_t bytes) |
522 | { |
523 | return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes); |
524 | } |
525 | |
526 | size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset, |
527 | int fillc, size_t bytes) |
528 | { |
529 | return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes); |
530 | } |
531 | |
532 | /** |
533 | * Check that I/O vector contents are identical |
534 | * |
535 | * The IO vectors must have the same structure (same length of all parts). |
536 | * A typical usage is to compare vectors created with qemu_iovec_clone(). |
537 | * |
538 | * @a: I/O vector |
539 | * @b: I/O vector |
540 | * @ret: Offset to first mismatching byte or -1 if match |
541 | */ |
542 | ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b) |
543 | { |
544 | int i; |
545 | ssize_t offset = 0; |
546 | |
547 | assert(a->niov == b->niov); |
548 | for (i = 0; i < a->niov; i++) { |
549 | size_t len = 0; |
550 | uint8_t *p = (uint8_t *)a->iov[i].iov_base; |
551 | uint8_t *q = (uint8_t *)b->iov[i].iov_base; |
552 | |
553 | assert(a->iov[i].iov_len == b->iov[i].iov_len); |
554 | while (len < a->iov[i].iov_len && *p++ == *q++) { |
555 | len++; |
556 | } |
557 | |
558 | offset += len; |
559 | |
560 | if (len != a->iov[i].iov_len) { |
561 | return offset; |
562 | } |
563 | } |
564 | return -1; |
565 | } |
566 | |
567 | typedef struct { |
568 | int src_index; |
569 | struct iovec *src_iov; |
570 | void *dest_base; |
571 | } IOVectorSortElem; |
572 | |
573 | static int sortelem_cmp_src_base(const void *a, const void *b) |
574 | { |
575 | const IOVectorSortElem *elem_a = a; |
576 | const IOVectorSortElem *elem_b = b; |
577 | |
578 | /* Don't overflow */ |
579 | if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) { |
580 | return -1; |
581 | } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) { |
582 | return 1; |
583 | } else { |
584 | return 0; |
585 | } |
586 | } |
587 | |
588 | static int sortelem_cmp_src_index(const void *a, const void *b) |
589 | { |
590 | const IOVectorSortElem *elem_a = a; |
591 | const IOVectorSortElem *elem_b = b; |
592 | |
593 | return elem_a->src_index - elem_b->src_index; |
594 | } |
595 | |
596 | /** |
597 | * Copy contents of I/O vector |
598 | * |
599 | * The relative relationships of overlapping iovecs are preserved. This is |
600 | * necessary to ensure identical semantics in the cloned I/O vector. |
601 | */ |
602 | void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf) |
603 | { |
604 | IOVectorSortElem sortelems[src->niov]; |
605 | void *last_end; |
606 | int i; |
607 | |
608 | /* Sort by source iovecs by base address */ |
609 | for (i = 0; i < src->niov; i++) { |
610 | sortelems[i].src_index = i; |
611 | sortelems[i].src_iov = &src->iov[i]; |
612 | } |
613 | qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base); |
614 | |
615 | /* Allocate buffer space taking into account overlapping iovecs */ |
616 | last_end = NULL; |
617 | for (i = 0; i < src->niov; i++) { |
618 | struct iovec *cur = sortelems[i].src_iov; |
619 | ptrdiff_t rewind = 0; |
620 | |
621 | /* Detect overlap */ |
622 | if (last_end && last_end > cur->iov_base) { |
623 | rewind = last_end - cur->iov_base; |
624 | } |
625 | |
626 | sortelems[i].dest_base = buf - rewind; |
627 | buf += cur->iov_len - MIN(rewind, cur->iov_len); |
628 | last_end = MAX(cur->iov_base + cur->iov_len, last_end); |
629 | } |
630 | |
631 | /* Sort by source iovec index and build destination iovec */ |
632 | qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index); |
633 | for (i = 0; i < src->niov; i++) { |
634 | qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len); |
635 | } |
636 | } |
637 | |
638 | size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt, |
639 | size_t bytes) |
640 | { |
641 | size_t total = 0; |
642 | struct iovec *cur; |
643 | |
644 | for (cur = *iov; *iov_cnt > 0; cur++) { |
645 | if (cur->iov_len > bytes) { |
646 | cur->iov_base += bytes; |
647 | cur->iov_len -= bytes; |
648 | total += bytes; |
649 | break; |
650 | } |
651 | |
652 | bytes -= cur->iov_len; |
653 | total += cur->iov_len; |
654 | *iov_cnt -= 1; |
655 | } |
656 | |
657 | *iov = cur; |
658 | return total; |
659 | } |
660 | |
661 | size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt, |
662 | size_t bytes) |
663 | { |
664 | size_t total = 0; |
665 | struct iovec *cur; |
666 | |
667 | if (*iov_cnt == 0) { |
668 | return 0; |
669 | } |
670 | |
671 | cur = iov + (*iov_cnt - 1); |
672 | |
673 | while (*iov_cnt > 0) { |
674 | if (cur->iov_len > bytes) { |
675 | cur->iov_len -= bytes; |
676 | total += bytes; |
677 | break; |
678 | } |
679 | |
680 | bytes -= cur->iov_len; |
681 | total += cur->iov_len; |
682 | cur--; |
683 | *iov_cnt -= 1; |
684 | } |
685 | |
686 | return total; |
687 | } |
688 | |
689 | void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes) |
690 | { |
691 | size_t total; |
692 | unsigned int niov = qiov->niov; |
693 | |
694 | assert(qiov->size >= bytes); |
695 | total = iov_discard_back(qiov->iov, &niov, bytes); |
696 | assert(total == bytes); |
697 | |
698 | qiov->niov = niov; |
699 | qiov->size -= bytes; |
700 | } |
701 | |