util/iov.c

   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
  24 size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
  25                          size_t offset, const void *buf, size_t bytes)
  26 {
  27     size_t done;
  28     unsigned int i;
  29     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  30         if (offset < iov[i].iov_len) {
  31             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  32             memcpy(iov[i].iov_base + offset, buf + done, len);
  33             done += len;
  34             offset = 0;
  35         } else {
  36             offset -= iov[i].iov_len;
  37         }
  38     }
  39     assert(offset == 0);
  40     return done;
  41 }
  42
  43 size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
  44                        size_t offset, void *buf, size_t bytes)
  45 {
  46     size_t done;
  47     unsigned int i;
  48     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  49         if (offset < iov[i].iov_len) {
  50             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  51             memcpy(buf + done, iov[i].iov_base + offset, len);
  52             done += len;
  53             offset = 0;
  54         } else {
  55             offset -= iov[i].iov_len;
  56         }
  57     }
  58     assert(offset == 0);
  59     return done;
  60 }
  61
  62 size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
  63                   size_t offset, int fillc, size_t bytes)
  64 {
  65     size_t done;
  66     unsigned int i;
  67     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  68         if (offset < iov[i].iov_len) {
  69             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  70             memset(iov[i].iov_base + offset, fillc, len);
  71             done += len;
  72             offset = 0;
  73         } else {
  74             offset -= iov[i].iov_len;
  75         }
  76     }
  77     assert(offset == 0);
  78     return done;
  79 }
  80
  81 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
  82 {
  83     size_t len;
  84     unsigned int i;
  85
  86     len = 0;
  87     for (i = 0; i < iov_cnt; i++) {
  88         len += iov[i].iov_len;
  89     }
  90     return len;
  91 }
  92
  93 /* helper function for iov_send_recv() */
  94 static ssize_t
  95 do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send)
  96 {
  97 #ifdef CONFIG_POSIX
  98     ssize_t ret;
  99     struct msghdr msg;
 100     memset(&msg, 0, sizeof(msg));
 101     msg.msg_iov = iov;
 102     msg.msg_iovlen = iov_cnt;
 103     do {
 104         ret = do_send
 105             ? sendmsg(sockfd, &msg, 0)
 106             : recvmsg(sockfd, &msg, 0);
 107     } while (ret < 0 && errno == EINTR);
 108     return ret;
 109 #else
 110     /* else send piece-by-piece */
 111     /*XXX Note: windows has WSASend() and WSARecv() */
 112     unsigned i = 0;
 113     ssize_t ret = 0;
 114     while (i < iov_cnt) {
 115         ssize_t r = do_send
 116             ? send(sockfd, iov[i].iov_base, iov[i].iov_len, 0)
 117             : recv(sockfd, iov[i].iov_base, iov[i].iov_len, 0);
 118         if (r > 0) {
 119             ret += r;
 120         } else if (!r) {
 121             break;
 122         } else if (errno == EINTR) {
 123             continue;
 124         } else {
 125             /* else it is some "other" error,
 126              * only return if there was no data processed. */
 127             if (ret == 0) {
 128                 ret = -1;
 129             }
 130             break;
 131         }
 132         i++;
 133     }
 134     return ret;
 135 #endif
 136 }
 137
 138 ssize_t iov_send_recv(int sockfd, const struct iovec *_iov, unsigned iov_cnt,
 139                       size_t offset, size_t bytes,
 140                       bool do_send)
 141 {
 142     ssize_t total = 0;
 143     ssize_t ret;
 144     size_t orig_len, tail;
 145     unsigned niov;
 146     struct iovec *local_iov, *iov;
 147
 148     if (bytes <= 0) {
 149         return 0;
 150     }
 151
 152     local_iov = g_new0(struct iovec, iov_cnt);
 153     iov_copy(local_iov, iov_cnt, _iov, iov_cnt, offset, bytes);
 154     offset = 0;
 155     iov = local_iov;
 156
 157     while (bytes > 0) {
 158         /* Find the start position, skipping `offset' bytes:
 159          * first, skip all full-sized vector elements, */
 160         for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
 161             offset -= iov[niov].iov_len;
 162         }
 163
 164         /* niov == iov_cnt would only be valid if bytes == 0, which
 165          * we already ruled out in the loop condition.  */
 166         assert(niov < iov_cnt);
 167         iov += niov;
 168         iov_cnt -= niov;
 169
 170         if (offset) {
 171             /* second, skip `offset' bytes from the (now) first element,
 172              * undo it on exit */
 173             iov[0].iov_base += offset;
 174             iov[0].iov_len -= offset;
 175         }
 176         /* Find the end position skipping `bytes' bytes: */
 177         /* first, skip all full-sized elements */
 178         tail = bytes;
 179         for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
 180             tail -= iov[niov].iov_len;
 181         }
 182         if (tail) {
 183             /* second, fixup the last element, and remember the original
 184              * length */
 185             assert(niov < iov_cnt);
 186             assert(iov[niov].iov_len > tail);
 187             orig_len = iov[niov].iov_len;
 188             iov[niov++].iov_len = tail;
 189             ret = do_send_recv(sockfd, iov, niov, do_send);
 190             /* Undo the changes above before checking for errors */
 191             iov[niov-1].iov_len = orig_len;
 192         } else {
 193             ret = do_send_recv(sockfd, iov, niov, do_send);
 194         }
 195         if (offset) {
 196             iov[0].iov_base -= offset;
 197             iov[0].iov_len += offset;
 198         }
 199
 200         if (ret < 0) {
 201             assert(errno != EINTR);
 202             g_free(local_iov);
 203             if (errno == EAGAIN && total > 0) {
 204                 return total;
 205             }
 206             return -1;
 207         }
 208
 209         if (ret == 0 && !do_send) {
 210             /* recv returns 0 when the peer has performed an orderly
 211              * shutdown. */
 212             break;
 213         }
 214
 215         /* Prepare for the next iteration */
 216         offset += ret;
 217         total += ret;
 218         bytes -= ret;
 219     }
 220
 221     g_free(local_iov);
 222     return total;
 223 }
 224
 225
 226 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
 227                  FILE *fp, const char *prefix, size_t limit)
 228 {
 229     int v;
 230     size_t size = 0;
 231     char *buf;
 232
 233     for (v = 0; v < iov_cnt; v++) {
 234         size += iov[v].iov_len;
 235     }
 236     size = size > limit ? limit : size;
 237     buf = g_malloc(size);
 238     iov_to_buf(iov, iov_cnt, 0, buf, size);
 239     qemu_hexdump(buf, fp, prefix, size);
 240     g_free(buf);
 241 }
 242
 243 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
 244                  const struct iovec *iov, unsigned int iov_cnt,
 245                  size_t offset, size_t bytes)
 246 {
 247     size_t len;
 248     unsigned int i, j;
 249     for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
 250         if (offset >= iov[i].iov_len) {
 251             offset -= iov[i].iov_len;
 252             continue;
 253         }
 254         len = MIN(bytes, iov[i].iov_len - offset);
 255
 256         dst_iov[j].iov_base = iov[i].iov_base + offset;
 257         dst_iov[j].iov_len = len;
 258         j++;
 259         bytes -= len;
 260         offset = 0;
 261     }
 262     assert(offset == 0);
 263     return j;
 264 }
 265
 266 /* io vectors */
 267
 268 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
 269 {
 270     qiov->iov = g_new(struct iovec, alloc_hint);
 271     qiov->niov = 0;
 272     qiov->nalloc = alloc_hint;
 273     qiov->size = 0;
 274 }
 275
 276 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
 277 {
 278     int i;
 279
 280     qiov->iov = iov;
 281     qiov->niov = niov;
 282     qiov->nalloc = -1;
 283     qiov->size = 0;
 284     for (i = 0; i < niov; i++)
 285         qiov->size += iov[i].iov_len;
 286 }
 287
 288 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 289 {
 290     assert(qiov->nalloc != -1);
 291
 292     if (qiov->niov == qiov->nalloc) {
 293         qiov->nalloc = 2 * qiov->nalloc + 1;
 294         qiov->iov = g_renew(struct iovec, qiov->iov, qiov->nalloc);
 295     }
 296     qiov->iov[qiov->niov].iov_base = base;
 297     qiov->iov[qiov->niov].iov_len = len;
 298     qiov->size += len;
 299     ++qiov->niov;
 300 }
 301
 302 /*
 303  * Concatenates (partial) iovecs from src_iov to the end of dst.
 304  * It starts copying after skipping `soffset' bytes at the
 305  * beginning of src and adds individual vectors from src to
 306  * dst copies up to `sbytes' bytes total, or up to the end
 307  * of src_iov if it comes first.  This way, it is okay to specify
 308  * very large value for `sbytes' to indicate "up to the end
 309  * of src".
 310  * Only vector pointers are processed, not the actual data buffers.
 311  */
 312 size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
 313                              struct iovec *src_iov, unsigned int src_cnt,
 314                              size_t soffset, size_t sbytes)
 315 {
 316     int i;
 317     size_t done;
 318
 319     if (!sbytes) {
 320         return 0;
 321     }
 322     assert(dst->nalloc != -1);
 323     for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
 324         if (soffset < src_iov[i].iov_len) {
 325             size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
 326             qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
 327             done += len;
 328             soffset = 0;
 329         } else {
 330             soffset -= src_iov[i].iov_len;
 331         }
 332     }
 333     assert(soffset == 0); /* offset beyond end of src */
 334
 335     return done;
 336 }
 337
 338 /*
 339  * Concatenates (partial) iovecs from src to the end of dst.
 340  * It starts copying after skipping `soffset' bytes at the
 341  * beginning of src and adds individual vectors from src to
 342  * dst copies up to `sbytes' bytes total, or up to the end
 343  * of src if it comes first.  This way, it is okay to specify
 344  * very large value for `sbytes' to indicate "up to the end
 345  * of src".
 346  * Only vector pointers are processed, not the actual data buffers.
 347  */
 348 void qemu_iovec_concat(QEMUIOVector *dst,
 349                        QEMUIOVector *src, size_t soffset, size_t sbytes)
 350 {
 351     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
 352 }
 353
 354 /*
 355  * Check if the contents of the iovecs are all zero
 356  */
 357 bool qemu_iovec_is_zero(QEMUIOVector *qiov)
 358 {
 359     int i;
 360     for (i = 0; i < qiov->niov; i++) {
 361         size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
 362         uint8_t *ptr = qiov->iov[i].iov_base;
 363         if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
 364             return false;
 365         }
 366         for (; offs < qiov->iov[i].iov_len; offs++) {
 367             if (ptr[offs]) {
 368                 return false;
 369             }
 370         }
 371     }
 372     return true;
 373 }
 374
 375 void qemu_iovec_destroy(QEMUIOVector *qiov)
 376 {
 377     assert(qiov->nalloc != -1);
 378
 379     qemu_iovec_reset(qiov);
 380     g_free(qiov->iov);
 381     qiov->nalloc = 0;
 382     qiov->iov = NULL;
 383 }
 384
 385 void qemu_iovec_reset(QEMUIOVector *qiov)
 386 {
 387     assert(qiov->nalloc != -1);
 388
 389     qiov->niov = 0;
 390     qiov->size = 0;
 391 }
 392
 393 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
 394                          void *buf, size_t bytes)
 395 {
 396     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 397 }
 398
 399 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
 400                            const void *buf, size_t bytes)
 401 {
 402     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 403 }
 404
 405 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
 406                          int fillc, size_t bytes)
 407 {
 408     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
 409 }
 410
 411 /**
 412  * Check that I/O vector contents are identical
 413  *
 414  * The IO vectors must have the same structure (same length of all parts).
 415  * A typical usage is to compare vectors created with qemu_iovec_clone().
 416  *
 417  * @a:          I/O vector
 418  * @b:          I/O vector
 419  * @ret:        Offset to first mismatching byte or -1 if match
 420  */
 421 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
 422 {
 423     int i;
 424     ssize_t offset = 0;
 425
 426     assert(a->niov == b->niov);
 427     for (i = 0; i < a->niov; i++) {
 428         size_t len = 0;
 429         uint8_t *p = (uint8_t *)a->iov[i].iov_base;
 430         uint8_t *q = (uint8_t *)b->iov[i].iov_base;
 431
 432         assert(a->iov[i].iov_len == b->iov[i].iov_len);
 433         while (len < a->iov[i].iov_len && *p++ == *q++) {
 434             len++;
 435         }
 436
 437         offset += len;
 438
 439         if (len != a->iov[i].iov_len) {
 440             return offset;
 441         }
 442     }
 443     return -1;
 444 }
 445
 446 typedef struct {
 447     int src_index;
 448     struct iovec *src_iov;
 449     void *dest_base;
 450 } IOVectorSortElem;
 451
 452 static int sortelem_cmp_src_base(const void *a, const void *b)
 453 {
 454     const IOVectorSortElem *elem_a = a;
 455     const IOVectorSortElem *elem_b = b;
 456
 457     /* Don't overflow */
 458     if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
 459         return -1;
 460     } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
 461         return 1;
 462     } else {
 463         return 0;
 464     }
 465 }
 466
 467 static int sortelem_cmp_src_index(const void *a, const void *b)
 468 {
 469     const IOVectorSortElem *elem_a = a;
 470     const IOVectorSortElem *elem_b = b;
 471
 472     return elem_a->src_index - elem_b->src_index;
 473 }
 474
 475 /**
 476  * Copy contents of I/O vector
 477  *
 478  * The relative relationships of overlapping iovecs are preserved.  This is
 479  * necessary to ensure identical semantics in the cloned I/O vector.
 480  */
 481 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
 482 {
 483     IOVectorSortElem sortelems[src->niov];
 484     void *last_end;
 485     int i;
 486
 487     /* Sort by source iovecs by base address */
 488     for (i = 0; i < src->niov; i++) {
 489         sortelems[i].src_index = i;
 490         sortelems[i].src_iov = &src->iov[i];
 491     }
 492     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
 493
 494     /* Allocate buffer space taking into account overlapping iovecs */
 495     last_end = NULL;
 496     for (i = 0; i < src->niov; i++) {
 497         struct iovec *cur = sortelems[i].src_iov;
 498         ptrdiff_t rewind = 0;
 499
 500         /* Detect overlap */
 501         if (last_end && last_end > cur->iov_base) {
 502             rewind = last_end - cur->iov_base;
 503         }
 504
 505         sortelems[i].dest_base = buf - rewind;
 506         buf += cur->iov_len - MIN(rewind, cur->iov_len);
 507         last_end = MAX(cur->iov_base + cur->iov_len, last_end);
 508     }
 509
 510     /* Sort by source iovec index and build destination iovec */
 511     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
 512     for (i = 0; i < src->niov; i++) {
 513         qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
 514     }
 515 }
 516
 517 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
 518                          size_t bytes)
 519 {
 520     size_t total = 0;
 521     struct iovec *cur;
 522
 523     for (cur = *iov; *iov_cnt > 0; cur++) {
 524         if (cur->iov_len > bytes) {
 525             cur->iov_base += bytes;
 526             cur->iov_len -= bytes;
 527             total += bytes;
 528             break;
 529         }
 530
 531         bytes -= cur->iov_len;
 532         total += cur->iov_len;
 533         *iov_cnt -= 1;
 534     }
 535
 536     *iov = cur;
 537     return total;
 538 }
 539
 540 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
 541                         size_t bytes)
 542 {
 543     size_t total = 0;
 544     struct iovec *cur;
 545
 546     if (*iov_cnt == 0) {
 547         return 0;
 548     }
 549
 550     cur = iov + (*iov_cnt - 1);
 551
 552     while (*iov_cnt > 0) {
 553         if (cur->iov_len > bytes) {
 554             cur->iov_len -= bytes;
 555             total += bytes;
 556             break;
 557         }
 558
 559         bytes -= cur->iov_len;
 560         total += cur->iov_len;
 561         cur--;
 562         *iov_cnt -= 1;
 563     }
 564
 565     return total;
 566 }
 567
 568 void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes)
 569 {
 570     size_t total;
 571     unsigned int niov = qiov->niov;
 572
 573     assert(qiov->size >= bytes);
 574     total = iov_discard_back(qiov->iov, &niov, bytes);
 575     assert(total == bytes);
 576
 577     qiov->niov = niov;
 578     qiov->size -= bytes;
 579 }