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/iov.h"
  20 #include "qemu/sockets.h"
  21
  22 size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
  23                     size_t offset, const void *buf, size_t bytes)
  24 {
  25     size_t done;
  26     unsigned int i;
  27     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  28         if (offset < iov[i].iov_len) {
  29             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  30             memcpy(iov[i].iov_base + offset, buf + done, len);
  31             done += len;
  32             offset = 0;
  33         } else {
  34             offset -= iov[i].iov_len;
  35         }
  36     }
  37     assert(offset == 0);
  38     return done;
  39 }
  40
  41 size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
  42                   size_t offset, void *buf, size_t bytes)
  43 {
  44     size_t done;
  45     unsigned int i;
  46     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  47         if (offset < iov[i].iov_len) {
  48             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  49             memcpy(buf + done, iov[i].iov_base + offset, len);
  50             done += len;
  51             offset = 0;
  52         } else {
  53             offset -= iov[i].iov_len;
  54         }
  55     }
  56     assert(offset == 0);
  57     return done;
  58 }
  59
  60 size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
  61                   size_t offset, int fillc, size_t bytes)
  62 {
  63     size_t done;
  64     unsigned int i;
  65     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  66         if (offset < iov[i].iov_len) {
  67             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  68             memset(iov[i].iov_base + offset, fillc, len);
  69             done += len;
  70             offset = 0;
  71         } else {
  72             offset -= iov[i].iov_len;
  73         }
  74     }
  75     assert(offset == 0);
  76     return done;
  77 }
  78
  79 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
  80 {
  81     size_t len;
  82     unsigned int i;
  83
  84     len = 0;
  85     for (i = 0; i < iov_cnt; i++) {
  86         len += iov[i].iov_len;
  87     }
  88     return len;
  89 }
  90
  91 /* helper function for iov_send_recv() */
  92 static ssize_t
  93 do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send)
  94 {
  95 #ifdef CONFIG_POSIX
  96     ssize_t ret;
  97     struct msghdr msg;
  98     memset(&msg, 0, sizeof(msg));
  99     msg.msg_iov = iov;
 100     msg.msg_iovlen = iov_cnt;
 101     do {
 102         ret = do_send
 103             ? sendmsg(sockfd, &msg, 0)
 104             : recvmsg(sockfd, &msg, 0);
 105     } while (ret < 0 && errno == EINTR);
 106     return ret;
 107 #else
 108     /* else send piece-by-piece */
 109     /*XXX Note: windows has WSASend() and WSARecv() */
 110     unsigned i = 0;
 111     ssize_t ret = 0;
 112     while (i < iov_cnt) {
 113         ssize_t r = do_send
 114             ? send(sockfd, iov[i].iov_base, iov[i].iov_len, 0)
 115             : recv(sockfd, iov[i].iov_base, iov[i].iov_len, 0);
 116         if (r > 0) {
 117             ret += r;
 118         } else if (!r) {
 119             break;
 120         } else if (errno == EINTR) {
 121             continue;
 122         } else {
 123             /* else it is some "other" error,
 124              * only return if there was no data processed. */
 125             if (ret == 0) {
 126                 ret = -1;
 127             }
 128             break;
 129         }
 130         i++;
 131     }
 132     return ret;
 133 #endif
 134 }
 135
 136 ssize_t iov_send_recv(int sockfd, const struct iovec *_iov, unsigned iov_cnt,
 137                       size_t offset, size_t bytes,
 138                       bool do_send)
 139 {
 140     ssize_t total = 0;
 141     ssize_t ret;
 142     size_t orig_len, tail;
 143     unsigned niov;
 144     struct iovec *local_iov, *iov;
 145
 146     if (bytes <= 0) {
 147         return 0;
 148     }
 149
 150     local_iov = g_new0(struct iovec, iov_cnt);
 151     iov_copy(local_iov, iov_cnt, _iov, iov_cnt, offset, bytes);
 152     offset = 0;
 153     iov = local_iov;
 154
 155     while (bytes > 0) {
 156         /* Find the start position, skipping `offset' bytes:
 157          * first, skip all full-sized vector elements, */
 158         for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
 159             offset -= iov[niov].iov_len;
 160         }
 161
 162         /* niov == iov_cnt would only be valid if bytes == 0, which
 163          * we already ruled out in the loop condition.  */
 164         assert(niov < iov_cnt);
 165         iov += niov;
 166         iov_cnt -= niov;
 167
 168         if (offset) {
 169             /* second, skip `offset' bytes from the (now) first element,
 170              * undo it on exit */
 171             iov[0].iov_base += offset;
 172             iov[0].iov_len -= offset;
 173         }
 174         /* Find the end position skipping `bytes' bytes: */
 175         /* first, skip all full-sized elements */
 176         tail = bytes;
 177         for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
 178             tail -= iov[niov].iov_len;
 179         }
 180         if (tail) {
 181             /* second, fixup the last element, and remember the original
 182              * length */
 183             assert(niov < iov_cnt);
 184             assert(iov[niov].iov_len > tail);
 185             orig_len = iov[niov].iov_len;
 186             iov[niov++].iov_len = tail;
 187             ret = do_send_recv(sockfd, iov, niov, do_send);
 188             /* Undo the changes above before checking for errors */
 189             iov[niov-1].iov_len = orig_len;
 190         } else {
 191             ret = do_send_recv(sockfd, iov, niov, do_send);
 192         }
 193         if (offset) {
 194             iov[0].iov_base -= offset;
 195             iov[0].iov_len += offset;
 196         }
 197
 198         if (ret < 0) {
 199             assert(errno != EINTR);
 200             g_free(local_iov);
 201             if (errno == EAGAIN && total > 0) {
 202                 return total;
 203             }
 204             return -1;
 205         }
 206
 207         if (ret == 0 && !do_send) {
 208             /* recv returns 0 when the peer has performed an orderly
 209              * shutdown. */
 210             break;
 211         }
 212
 213         /* Prepare for the next iteration */
 214         offset += ret;
 215         total += ret;
 216         bytes -= ret;
 217     }
 218
 219     g_free(local_iov);
 220     return total;
 221 }
 222
 223
 224 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
 225                  FILE *fp, const char *prefix, size_t limit)
 226 {
 227     int v;
 228     size_t size = 0;
 229     char *buf;
 230
 231     for (v = 0; v < iov_cnt; v++) {
 232         size += iov[v].iov_len;
 233     }
 234     size = size > limit ? limit : size;
 235     buf = g_malloc(size);
 236     iov_to_buf(iov, iov_cnt, 0, buf, size);
 237     qemu_hexdump(buf, fp, prefix, size);
 238     g_free(buf);
 239 }
 240
 241 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
 242                  const struct iovec *iov, unsigned int iov_cnt,
 243                  size_t offset, size_t bytes)
 244 {
 245     size_t len;
 246     unsigned int i, j;
 247     for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
 248         if (offset >= iov[i].iov_len) {
 249             offset -= iov[i].iov_len;
 250             continue;
 251         }
 252         len = MIN(bytes, iov[i].iov_len - offset);
 253
 254         dst_iov[j].iov_base = iov[i].iov_base + offset;
 255         dst_iov[j].iov_len = len;
 256         j++;
 257         bytes -= len;
 258         offset = 0;
 259     }
 260     assert(offset == 0);
 261     return j;
 262 }
 263
 264 /* io vectors */
 265
 266 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
 267 {
 268     qiov->iov = g_new(struct iovec, alloc_hint);
 269     qiov->niov = 0;
 270     qiov->nalloc = alloc_hint;
 271     qiov->size = 0;
 272 }
 273
 274 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
 275 {
 276     int i;
 277
 278     qiov->iov = iov;
 279     qiov->niov = niov;
 280     qiov->nalloc = -1;
 281     qiov->size = 0;
 282     for (i = 0; i < niov; i++)
 283         qiov->size += iov[i].iov_len;
 284 }
 285
 286 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 287 {
 288     assert(qiov->nalloc != -1);
 289
 290     if (qiov->niov == qiov->nalloc) {
 291         qiov->nalloc = 2 * qiov->nalloc + 1;
 292         qiov->iov = g_renew(struct iovec, qiov->iov, qiov->nalloc);
 293     }
 294     qiov->iov[qiov->niov].iov_base = base;
 295     qiov->iov[qiov->niov].iov_len = len;
 296     qiov->size += len;
 297     ++qiov->niov;
 298 }
 299
 300 /*
 301  * Concatenates (partial) iovecs from src_iov to the end of dst.
 302  * It starts copying after skipping `soffset' bytes at the
 303  * beginning of src and adds individual vectors from src to
 304  * dst copies up to `sbytes' bytes total, or up to the end
 305  * of src_iov if it comes first.  This way, it is okay to specify
 306  * very large value for `sbytes' to indicate "up to the end
 307  * of src".
 308  * Only vector pointers are processed, not the actual data buffers.
 309  */
 310 size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
 311                              struct iovec *src_iov, unsigned int src_cnt,
 312                              size_t soffset, size_t sbytes)
 313 {
 314     int i;
 315     size_t done;
 316
 317     if (!sbytes) {
 318         return 0;
 319     }
 320     assert(dst->nalloc != -1);
 321     for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
 322         if (soffset < src_iov[i].iov_len) {
 323             size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
 324             qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
 325             done += len;
 326             soffset = 0;
 327         } else {
 328             soffset -= src_iov[i].iov_len;
 329         }
 330     }
 331     assert(soffset == 0); /* offset beyond end of src */
 332
 333     return done;
 334 }
 335
 336 /*
 337  * Concatenates (partial) iovecs from src to the end of dst.
 338  * It starts copying after skipping `soffset' bytes at the
 339  * beginning of src and adds individual vectors from src to
 340  * dst copies up to `sbytes' bytes total, or up to the end
 341  * of src if it comes first.  This way, it is okay to specify
 342  * very large value for `sbytes' to indicate "up to the end
 343  * of src".
 344  * Only vector pointers are processed, not the actual data buffers.
 345  */
 346 void qemu_iovec_concat(QEMUIOVector *dst,
 347                        QEMUIOVector *src, size_t soffset, size_t sbytes)
 348 {
 349     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
 350 }
 351
 352 /*
 353  * Check if the contents of the iovecs are all zero
 354  */
 355 bool qemu_iovec_is_zero(QEMUIOVector *qiov)
 356 {
 357     int i;
 358     for (i = 0; i < qiov->niov; i++) {
 359         size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
 360         uint8_t *ptr = qiov->iov[i].iov_base;
 361         if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
 362             return false;
 363         }
 364         for (; offs < qiov->iov[i].iov_len; offs++) {
 365             if (ptr[offs]) {
 366                 return false;
 367             }
 368         }
 369     }
 370     return true;
 371 }
 372
 373 void qemu_iovec_destroy(QEMUIOVector *qiov)
 374 {
 375     assert(qiov->nalloc != -1);
 376
 377     qemu_iovec_reset(qiov);
 378     g_free(qiov->iov);
 379     qiov->nalloc = 0;
 380     qiov->iov = NULL;
 381 }
 382
 383 void qemu_iovec_reset(QEMUIOVector *qiov)
 384 {
 385     assert(qiov->nalloc != -1);
 386
 387     qiov->niov = 0;
 388     qiov->size = 0;
 389 }
 390
 391 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
 392                          void *buf, size_t bytes)
 393 {
 394     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 395 }
 396
 397 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
 398                            const void *buf, size_t bytes)
 399 {
 400     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 401 }
 402
 403 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
 404                          int fillc, size_t bytes)
 405 {
 406     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
 407 }
 408
 409 /**
 410  * Check that I/O vector contents are identical
 411  *
 412  * The IO vectors must have the same structure (same length of all parts).
 413  * A typical usage is to compare vectors created with qemu_iovec_clone().
 414  *
 415  * @a:          I/O vector
 416  * @b:          I/O vector
 417  * @ret:        Offset to first mismatching byte or -1 if match
 418  */
 419 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
 420 {
 421     int i;
 422     ssize_t offset = 0;
 423
 424     assert(a->niov == b->niov);
 425     for (i = 0; i < a->niov; i++) {
 426         size_t len = 0;
 427         uint8_t *p = (uint8_t *)a->iov[i].iov_base;
 428         uint8_t *q = (uint8_t *)b->iov[i].iov_base;
 429
 430         assert(a->iov[i].iov_len == b->iov[i].iov_len);
 431         while (len < a->iov[i].iov_len && *p++ == *q++) {
 432             len++;
 433         }
 434
 435         offset += len;
 436
 437         if (len != a->iov[i].iov_len) {
 438             return offset;
 439         }
 440     }
 441     return -1;
 442 }
 443
 444 typedef struct {
 445     int src_index;
 446     struct iovec *src_iov;
 447     void *dest_base;
 448 } IOVectorSortElem;
 449
 450 static int sortelem_cmp_src_base(const void *a, const void *b)
 451 {
 452     const IOVectorSortElem *elem_a = a;
 453     const IOVectorSortElem *elem_b = b;
 454
 455     /* Don't overflow */
 456     if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
 457         return -1;
 458     } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
 459         return 1;
 460     } else {
 461         return 0;
 462     }
 463 }
 464
 465 static int sortelem_cmp_src_index(const void *a, const void *b)
 466 {
 467     const IOVectorSortElem *elem_a = a;
 468     const IOVectorSortElem *elem_b = b;
 469
 470     return elem_a->src_index - elem_b->src_index;
 471 }
 472
 473 /**
 474  * Copy contents of I/O vector
 475  *
 476  * The relative relationships of overlapping iovecs are preserved.  This is
 477  * necessary to ensure identical semantics in the cloned I/O vector.
 478  */
 479 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
 480 {
 481     IOVectorSortElem sortelems[src->niov];
 482     void *last_end;
 483     int i;
 484
 485     /* Sort by source iovecs by base address */
 486     for (i = 0; i < src->niov; i++) {
 487         sortelems[i].src_index = i;
 488         sortelems[i].src_iov = &src->iov[i];
 489     }
 490     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
 491
 492     /* Allocate buffer space taking into account overlapping iovecs */
 493     last_end = NULL;
 494     for (i = 0; i < src->niov; i++) {
 495         struct iovec *cur = sortelems[i].src_iov;
 496         ptrdiff_t rewind = 0;
 497
 498         /* Detect overlap */
 499         if (last_end && last_end > cur->iov_base) {
 500             rewind = last_end - cur->iov_base;
 501         }
 502
 503         sortelems[i].dest_base = buf - rewind;
 504         buf += cur->iov_len - MIN(rewind, cur->iov_len);
 505         last_end = MAX(cur->iov_base + cur->iov_len, last_end);
 506     }
 507
 508     /* Sort by source iovec index and build destination iovec */
 509     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
 510     for (i = 0; i < src->niov; i++) {
 511         qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
 512     }
 513 }
 514
 515 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
 516                          size_t bytes)
 517 {
 518     size_t total = 0;
 519     struct iovec *cur;
 520
 521     for (cur = *iov; *iov_cnt > 0; cur++) {
 522         if (cur->iov_len > bytes) {
 523             cur->iov_base += bytes;
 524             cur->iov_len -= bytes;
 525             total += bytes;
 526             break;
 527         }
 528
 529         bytes -= cur->iov_len;
 530         total += cur->iov_len;
 531         *iov_cnt -= 1;
 532     }
 533
 534     *iov = cur;
 535     return total;
 536 }
 537
 538 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
 539                         size_t bytes)
 540 {
 541     size_t total = 0;
 542     struct iovec *cur;
 543
 544     if (*iov_cnt == 0) {
 545         return 0;
 546     }
 547
 548     cur = iov + (*iov_cnt - 1);
 549
 550     while (*iov_cnt > 0) {
 551         if (cur->iov_len > bytes) {
 552             cur->iov_len -= bytes;
 553             total += bytes;
 554             break;
 555         }
 556
 557         bytes -= cur->iov_len;
 558         total += cur->iov_len;
 559         cur--;
 560         *iov_cnt -= 1;
 561     }
 562
 563     return total;
 564 }
 565
 566 void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes)
 567 {
 568     size_t total;
 569     unsigned int niov = qiov->niov;
 570
 571     assert(qiov->size >= bytes);
 572     total = iov_discard_back(qiov->iov, &niov, bytes);
 573     assert(total == bytes);
 574
 575     qiov->niov = niov;
 576     qiov->size -= bytes;
 577 }