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, 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
 145     while (bytes > 0) {
 146         /* Find the start position, skipping `offset' bytes:
 147          * first, skip all full-sized vector elements, */
 148         for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
 149             offset -= iov[niov].iov_len;
 150         }
 151
 152         /* niov == iov_cnt would only be valid if bytes == 0, which
 153          * we already ruled out in the loop condition.  */
 154         assert(niov < iov_cnt);
 155         iov += niov;
 156         iov_cnt -= niov;
 157
 158         if (offset) {
 159             /* second, skip `offset' bytes from the (now) first element,
 160              * undo it on exit */
 161             iov[0].iov_base += offset;
 162             iov[0].iov_len -= offset;
 163         }
 164         /* Find the end position skipping `bytes' bytes: */
 165         /* first, skip all full-sized elements */
 166         tail = bytes;
 167         for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
 168             tail -= iov[niov].iov_len;
 169         }
 170         if (tail) {
 171             /* second, fixup the last element, and remember the original
 172              * length */
 173             assert(niov < iov_cnt);
 174             assert(iov[niov].iov_len > tail);
 175             orig_len = iov[niov].iov_len;
 176             iov[niov++].iov_len = tail;
 177             ret = do_send_recv(sockfd, iov, niov, do_send);
 178             /* Undo the changes above before checking for errors */
 179             iov[niov-1].iov_len = orig_len;
 180         } else {
 181             ret = do_send_recv(sockfd, iov, niov, do_send);
 182         }
 183         if (offset) {
 184             iov[0].iov_base -= offset;
 185             iov[0].iov_len += offset;
 186         }
 187
 188         if (ret < 0) {
 189             assert(errno != EINTR);
 190             if (errno == EAGAIN && total > 0) {
 191                 return total;
 192             }
 193             return -1;
 194         }
 195
 196         if (ret == 0 && !do_send) {
 197             /* recv returns 0 when the peer has performed an orderly
 198              * shutdown. */
 199             break;
 200         }
 201
 202         /* Prepare for the next iteration */
 203         offset += ret;
 204         total += ret;
 205         bytes -= ret;
 206     }
 207
 208     return total;
 209 }
 210
 211
 212 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
 213                  FILE *fp, const char *prefix, size_t limit)
 214 {
 215     int v;
 216     size_t size = 0;
 217     char *buf;
 218
 219     for (v = 0; v < iov_cnt; v++) {
 220         size += iov[v].iov_len;
 221     }
 222     size = size > limit ? limit : size;
 223     buf = g_malloc(size);
 224     iov_to_buf(iov, iov_cnt, 0, buf, size);
 225     qemu_hexdump(buf, fp, prefix, size);
 226     g_free(buf);
 227 }
 228
 229 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
 230                  const struct iovec *iov, unsigned int iov_cnt,
 231                  size_t offset, size_t bytes)
 232 {
 233     size_t len;
 234     unsigned int i, j;
 235     for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
 236         if (offset >= iov[i].iov_len) {
 237             offset -= iov[i].iov_len;
 238             continue;
 239         }
 240         len = MIN(bytes, iov[i].iov_len - offset);
 241
 242         dst_iov[j].iov_base = iov[i].iov_base + offset;
 243         dst_iov[j].iov_len = len;
 244         j++;
 245         bytes -= len;
 246         offset = 0;
 247     }
 248     assert(offset == 0);
 249     return j;
 250 }
 251
 252 /* io vectors */
 253
 254 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
 255 {
 256     qiov->iov = g_malloc(alloc_hint * sizeof(struct iovec));
 257     qiov->niov = 0;
 258     qiov->nalloc = alloc_hint;
 259     qiov->size = 0;
 260 }
 261
 262 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
 263 {
 264     int i;
 265
 266     qiov->iov = iov;
 267     qiov->niov = niov;
 268     qiov->nalloc = -1;
 269     qiov->size = 0;
 270     for (i = 0; i < niov; i++)
 271         qiov->size += iov[i].iov_len;
 272 }
 273
 274 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 275 {
 276     assert(qiov->nalloc != -1);
 277
 278     if (qiov->niov == qiov->nalloc) {
 279         qiov->nalloc = 2 * qiov->nalloc + 1;
 280         qiov->iov = g_realloc(qiov->iov, qiov->nalloc * sizeof(struct iovec));
 281     }
 282     qiov->iov[qiov->niov].iov_base = base;
 283     qiov->iov[qiov->niov].iov_len = len;
 284     qiov->size += len;
 285     ++qiov->niov;
 286 }
 287
 288 /*
 289  * Concatenates (partial) iovecs from src_iov to the end of dst.
 290  * It starts copying after skipping `soffset' bytes at the
 291  * beginning of src and adds individual vectors from src to
 292  * dst copies up to `sbytes' bytes total, or up to the end
 293  * of src_iov if it comes first.  This way, it is okay to specify
 294  * very large value for `sbytes' to indicate "up to the end
 295  * of src".
 296  * Only vector pointers are processed, not the actual data buffers.
 297  */
 298 void qemu_iovec_concat_iov(QEMUIOVector *dst,
 299                            struct iovec *src_iov, unsigned int src_cnt,
 300                            size_t soffset, size_t sbytes)
 301 {
 302     int i;
 303     size_t done;
 304
 305     if (!sbytes) {
 306         return;
 307     }
 308     assert(dst->nalloc != -1);
 309     for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
 310         if (soffset < src_iov[i].iov_len) {
 311             size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
 312             qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
 313             done += len;
 314             soffset = 0;
 315         } else {
 316             soffset -= src_iov[i].iov_len;
 317         }
 318     }
 319     assert(soffset == 0); /* offset beyond end of src */
 320 }
 321
 322 /*
 323  * Concatenates (partial) iovecs from src to the end of dst.
 324  * It starts copying after skipping `soffset' bytes at the
 325  * beginning of src and adds individual vectors from src to
 326  * dst copies up to `sbytes' bytes total, or up to the end
 327  * of src if it comes first.  This way, it is okay to specify
 328  * very large value for `sbytes' to indicate "up to the end
 329  * of src".
 330  * Only vector pointers are processed, not the actual data buffers.
 331  */
 332 void qemu_iovec_concat(QEMUIOVector *dst,
 333                        QEMUIOVector *src, size_t soffset, size_t sbytes)
 334 {
 335     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
 336 }
 337
 338 /*
 339  * Check if the contents of the iovecs are all zero
 340  */
 341 bool qemu_iovec_is_zero(QEMUIOVector *qiov)
 342 {
 343     int i;
 344     for (i = 0; i < qiov->niov; i++) {
 345         size_t offs = QEMU_ALIGN_DOWN(qiov->iov[i].iov_len, 4 * sizeof(long));
 346         uint8_t *ptr = qiov->iov[i].iov_base;
 347         if (offs && !buffer_is_zero(qiov->iov[i].iov_base, offs)) {
 348             return false;
 349         }
 350         for (; offs < qiov->iov[i].iov_len; offs++) {
 351             if (ptr[offs]) {
 352                 return false;
 353             }
 354         }
 355     }
 356     return true;
 357 }
 358
 359 void qemu_iovec_destroy(QEMUIOVector *qiov)
 360 {
 361     assert(qiov->nalloc != -1);
 362
 363     qemu_iovec_reset(qiov);
 364     g_free(qiov->iov);
 365     qiov->nalloc = 0;
 366     qiov->iov = NULL;
 367 }
 368
 369 void qemu_iovec_reset(QEMUIOVector *qiov)
 370 {
 371     assert(qiov->nalloc != -1);
 372
 373     qiov->niov = 0;
 374     qiov->size = 0;
 375 }
 376
 377 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
 378                          void *buf, size_t bytes)
 379 {
 380     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 381 }
 382
 383 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
 384                            const void *buf, size_t bytes)
 385 {
 386     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 387 }
 388
 389 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
 390                          int fillc, size_t bytes)
 391 {
 392     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
 393 }
 394
 395 /**
 396  * Check that I/O vector contents are identical
 397  *
 398  * The IO vectors must have the same structure (same length of all parts).
 399  * A typical usage is to compare vectors created with qemu_iovec_clone().
 400  *
 401  * @a:          I/O vector
 402  * @b:          I/O vector
 403  * @ret:        Offset to first mismatching byte or -1 if match
 404  */
 405 ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b)
 406 {
 407     int i;
 408     ssize_t offset = 0;
 409
 410     assert(a->niov == b->niov);
 411     for (i = 0; i < a->niov; i++) {
 412         size_t len = 0;
 413         uint8_t *p = (uint8_t *)a->iov[i].iov_base;
 414         uint8_t *q = (uint8_t *)b->iov[i].iov_base;
 415
 416         assert(a->iov[i].iov_len == b->iov[i].iov_len);
 417         while (len < a->iov[i].iov_len && *p++ == *q++) {
 418             len++;
 419         }
 420
 421         offset += len;
 422
 423         if (len != a->iov[i].iov_len) {
 424             return offset;
 425         }
 426     }
 427     return -1;
 428 }
 429
 430 typedef struct {
 431     int src_index;
 432     struct iovec *src_iov;
 433     void *dest_base;
 434 } IOVectorSortElem;
 435
 436 static int sortelem_cmp_src_base(const void *a, const void *b)
 437 {
 438     const IOVectorSortElem *elem_a = a;
 439     const IOVectorSortElem *elem_b = b;
 440
 441     /* Don't overflow */
 442     if (elem_a->src_iov->iov_base < elem_b->src_iov->iov_base) {
 443         return -1;
 444     } else if (elem_a->src_iov->iov_base > elem_b->src_iov->iov_base) {
 445         return 1;
 446     } else {
 447         return 0;
 448     }
 449 }
 450
 451 static int sortelem_cmp_src_index(const void *a, const void *b)
 452 {
 453     const IOVectorSortElem *elem_a = a;
 454     const IOVectorSortElem *elem_b = b;
 455
 456     return elem_a->src_index - elem_b->src_index;
 457 }
 458
 459 /**
 460  * Copy contents of I/O vector
 461  *
 462  * The relative relationships of overlapping iovecs are preserved.  This is
 463  * necessary to ensure identical semantics in the cloned I/O vector.
 464  */
 465 void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf)
 466 {
 467     IOVectorSortElem sortelems[src->niov];
 468     void *last_end;
 469     int i;
 470
 471     /* Sort by source iovecs by base address */
 472     for (i = 0; i < src->niov; i++) {
 473         sortelems[i].src_index = i;
 474         sortelems[i].src_iov = &src->iov[i];
 475     }
 476     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_base);
 477
 478     /* Allocate buffer space taking into account overlapping iovecs */
 479     last_end = NULL;
 480     for (i = 0; i < src->niov; i++) {
 481         struct iovec *cur = sortelems[i].src_iov;
 482         ptrdiff_t rewind = 0;
 483
 484         /* Detect overlap */
 485         if (last_end && last_end > cur->iov_base) {
 486             rewind = last_end - cur->iov_base;
 487         }
 488
 489         sortelems[i].dest_base = buf - rewind;
 490         buf += cur->iov_len - MIN(rewind, cur->iov_len);
 491         last_end = MAX(cur->iov_base + cur->iov_len, last_end);
 492     }
 493
 494     /* Sort by source iovec index and build destination iovec */
 495     qsort(sortelems, src->niov, sizeof(sortelems[0]), sortelem_cmp_src_index);
 496     for (i = 0; i < src->niov; i++) {
 497         qemu_iovec_add(dest, sortelems[i].dest_base, src->iov[i].iov_len);
 498     }
 499 }
 500
 501 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
 502                          size_t bytes)
 503 {
 504     size_t total = 0;
 505     struct iovec *cur;
 506
 507     for (cur = *iov; *iov_cnt > 0; cur++) {
 508         if (cur->iov_len > bytes) {
 509             cur->iov_base += bytes;
 510             cur->iov_len -= bytes;
 511             total += bytes;
 512             break;
 513         }
 514
 515         bytes -= cur->iov_len;
 516         total += cur->iov_len;
 517         *iov_cnt -= 1;
 518     }
 519
 520     *iov = cur;
 521     return total;
 522 }
 523
 524 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
 525                         size_t bytes)
 526 {
 527     size_t total = 0;
 528     struct iovec *cur;
 529
 530     if (*iov_cnt == 0) {
 531         return 0;
 532     }
 533
 534     cur = iov + (*iov_cnt - 1);
 535
 536     while (*iov_cnt > 0) {
 537         if (cur->iov_len > bytes) {
 538             cur->iov_len -= bytes;
 539             total += bytes;
 540             break;
 541         }
 542
 543         bytes -= cur->iov_len;
 544         total += cur->iov_len;
 545         cur--;
 546         *iov_cnt -= 1;
 547     }
 548
 549     return total;
 550 }