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 #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  * Check if the contents of the iovecs are all zero
 358  */
 359 bool qemu_iovec_is_zero(QEMUIOVector *qiov)
 360 {
 361     int i;
 362     for (i = 0; i < qiov->niov; i++) {
 363         size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
 364         uint8_t *ptr = qiov->iov[i].iov_base;
 365         if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
 366             return false;
 367         }
 368         for (; offs < qiov->iov[i].iov_len; offs++) {
 369             if (ptr[offs]) {
 370                 return false;
 371             }
 372         }
 373     }
 374     return true;
 375 }
 376
 377 void qemu_iovec_destroy(QEMUIOVector *qiov)
 378 {
 379     assert(qiov->nalloc != -1);
 380
 381     qemu_iovec_reset(qiov);
 382     g_free(qiov->iov);
 383     qiov->nalloc = 0;
 384     qiov->iov = NULL;
 385 }
 386
 387 void qemu_iovec_reset(QEMUIOVector *qiov)
 388 {
 389     assert(qiov->nalloc != -1);
 390
 391     qiov->niov = 0;
 392     qiov->size = 0;
 393 }
 394
 395 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
 396                          void *buf, size_t bytes)
 397 {
 398     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 399 }
 400
 401 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
 402                            const void *buf, size_t bytes)
 403 {
 404     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 405 }
 406
 407 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
 408                          int fillc, size_t bytes)
 409 {
 410     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
 411 }
 412
 413 /**
 414  * Check that I/O vector contents are identical
 415  *
 416  * The IO vectors must have the same structure (same length of all parts).
 417  * A typical usage is to compare vectors created with qemu_iovec_clone().
 418  *
 419  * @a:          I/O vector
 420  * @b:          I/O vector
 421  * @ret:        Offset to first mismatching byte or -1 if match
 422  */
 423 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
 424 {
 425     int i;
 426     ssize_t offset = 0;
 427
 428     assert(a->niov == b->niov);
 429     for (i = 0; i < a->niov; i++) {
 430         size_t len = 0;
 431         uint8_t *p = (uint8_t *)a->iov[i].iov_base;
 432         uint8_t *q = (uint8_t *)b->iov[i].iov_base;
 433
 434         assert(a->iov[i].iov_len == b->iov[i].iov_len);
 435         while (len < a->iov[i].iov_len && *p++ == *q++) {
 436             len++;
 437         }
 438
 439         offset += len;
 440
 441         if (len != a->iov[i].iov_len) {
 442             return offset;
 443         }
 444     }
 445     return -1;
 446 }
 447
 448 typedef struct {
 449     int src_index;
 450     struct iovec *src_iov;
 451     void *dest_base;
 452 } IOVectorSortElem;
 453
 454 static int sortelem_cmp_src_base(const void *a, const void *b)
 455 {
 456     const IOVectorSortElem *elem_a = a;
 457     const IOVectorSortElem *elem_b = b;
 458
 459     /* Don't overflow */
 460     if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
 461         return -1;
 462     } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
 463         return 1;
 464     } else {
 465         return 0;
 466     }
 467 }
 468
 469 static int sortelem_cmp_src_index(const void *a, const void *b)
 470 {
 471     const IOVectorSortElem *elem_a = a;
 472     const IOVectorSortElem *elem_b = b;
 473
 474     return elem_a->src_index - elem_b->src_index;
 475 }
 476
 477 /**
 478  * Copy contents of I/O vector
 479  *
 480  * The relative relationships of overlapping iovecs are preserved.  This is
 481  * necessary to ensure identical semantics in the cloned I/O vector.
 482  */
 483 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
 484 {
 485     IOVectorSortElem sortelems[src->niov];
 486     void *last_end;
 487     int i;
 488
 489     /* Sort by source iovecs by base address */
 490     for (i = 0; i < src->niov; i++) {
 491         sortelems[i].src_index = i;
 492         sortelems[i].src_iov = &src->iov[i];
 493     }
 494     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
 495
 496     /* Allocate buffer space taking into account overlapping iovecs */
 497     last_end = NULL;
 498     for (i = 0; i < src->niov; i++) {
 499         struct iovec *cur = sortelems[i].src_iov;
 500         ptrdiff_t rewind = 0;
 501
 502         /* Detect overlap */
 503         if (last_end && last_end > cur->iov_base) {
 504             rewind = last_end - cur->iov_base;
 505         }
 506
 507         sortelems[i].dest_base = buf - rewind;
 508         buf += cur->iov_len - MIN(rewind, cur->iov_len);
 509         last_end = MAX(cur->iov_base + cur->iov_len, last_end);
 510     }
 511
 512     /* Sort by source iovec index and build destination iovec */
 513     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
 514     for (i = 0; i < src->niov; i++) {
 515         qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
 516     }
 517 }
 518
 519 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
 520                          size_t bytes)
 521 {
 522     size_t total = 0;
 523     struct iovec *cur;
 524
 525     for (cur = *iov; *iov_cnt > 0; cur++) {
 526         if (cur->iov_len > bytes) {
 527             cur->iov_base += bytes;
 528             cur->iov_len -= bytes;
 529             total += bytes;
 530             break;
 531         }
 532
 533         bytes -= cur->iov_len;
 534         total += cur->iov_len;
 535         *iov_cnt -= 1;
 536     }
 537
 538     *iov = cur;
 539     return total;
 540 }
 541
 542 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
 543                         size_t bytes)
 544 {
 545     size_t total = 0;
 546     struct iovec *cur;
 547
 548     if (*iov_cnt == 0) {
 549         return 0;
 550     }
 551
 552     cur = iov + (*iov_cnt - 1);
 553
 554     while (*iov_cnt > 0) {
 555         if (cur->iov_len > bytes) {
 556             cur->iov_len -= bytes;
 557             total += bytes;
 558             break;
 559         }
 560
 561         bytes -= cur->iov_len;
 562         total += cur->iov_len;
 563         cur--;
 564         *iov_cnt -= 1;
 565     }
 566
 567     return total;
 568 }
 569
 570 void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes)
 571 {
 572     size_t total;
 573     unsigned int niov = qiov->niov;
 574
 575     assert(qiov->size >= bytes);
 576     total = iov_discard_back(qiov->iov, &niov, bytes);
 577     assert(total == bytes);
 578
 579     qiov->niov = niov;
 580     qiov->size -= bytes;
 581 }