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
  21 #ifdef _WIN32
  22 # include <windows.h>
  23 # include <winsock2.h>
  24 #else
  25 # include <sys/types.h>
  26 # include <sys/socket.h>
  27 #endif
  28
  29 size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
  30                     size_t offset, const void *buf, size_t bytes)
  31 {
  32     size_t done;
  33     unsigned int i;
  34     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  35         if (offset < iov[i].iov_len) {
  36             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  37             memcpy(iov[i].iov_base + offset, buf + done, len);
  38             done += len;
  39             offset = 0;
  40         } else {
  41             offset -= iov[i].iov_len;
  42         }
  43     }
  44     assert(offset == 0);
  45     return done;
  46 }
  47
  48 size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
  49                   size_t offset, void *buf, size_t bytes)
  50 {
  51     size_t done;
  52     unsigned int i;
  53     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  54         if (offset < iov[i].iov_len) {
  55             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  56             memcpy(buf + done, iov[i].iov_base + offset, len);
  57             done += len;
  58             offset = 0;
  59         } else {
  60             offset -= iov[i].iov_len;
  61         }
  62     }
  63     assert(offset == 0);
  64     return done;
  65 }
  66
  67 size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
  68                   size_t offset, int fillc, size_t bytes)
  69 {
  70     size_t done;
  71     unsigned int i;
  72     for (i = 0, done = 0; (offset || done < bytes) && i < iov_cnt; i++) {
  73         if (offset < iov[i].iov_len) {
  74             size_t len = MIN(iov[i].iov_len - offset, bytes - done);
  75             memset(iov[i].iov_base + offset, fillc, len);
  76             done += len;
  77             offset = 0;
  78         } else {
  79             offset -= iov[i].iov_len;
  80         }
  81     }
  82     assert(offset == 0);
  83     return done;
  84 }
  85
  86 size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt)
  87 {
  88     size_t len;
  89     unsigned int i;
  90
  91     len = 0;
  92     for (i = 0; i < iov_cnt; i++) {
  93         len += iov[i].iov_len;
  94     }
  95     return len;
  96 }
  97
  98 /* helper function for iov_send_recv() */
  99 static ssize_t
 100 do_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, bool do_send)
 101 {
 102 #ifdef CONFIG_POSIX
 103     ssize_t ret;
 104     struct msghdr msg;
 105     memset(&msg, 0, sizeof(msg));
 106     msg.msg_iov = iov;
 107     msg.msg_iovlen = iov_cnt;
 108     do {
 109         ret = do_send
 110             ? sendmsg(sockfd, &msg, 0)
 111             : recvmsg(sockfd, &msg, 0);
 112     } while (ret < 0 && errno == EINTR);
 113     return ret;
 114 #else
 115     /* else send piece-by-piece */
 116     /*XXX Note: windows has WSASend() and WSARecv() */
 117     unsigned i = 0;
 118     ssize_t ret = 0;
 119     while (i < iov_cnt) {
 120         ssize_t r = do_send
 121             ? send(sockfd, iov[i].iov_base, iov[i].iov_len, 0)
 122             : recv(sockfd, iov[i].iov_base, iov[i].iov_len, 0);
 123         if (r > 0) {
 124             ret += r;
 125         } else if (!r) {
 126             break;
 127         } else if (errno == EINTR) {
 128             continue;
 129         } else {
 130             /* else it is some "other" error,
 131              * only return if there was no data processed. */
 132             if (ret == 0) {
 133                 ret = -1;
 134             }
 135             break;
 136         }
 137         i++;
 138     }
 139     return ret;
 140 #endif
 141 }
 142
 143 ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt,
 144                       size_t offset, size_t bytes,
 145                       bool do_send)
 146 {
 147     ssize_t total = 0;
 148     ssize_t ret;
 149     size_t orig_len, tail;
 150     unsigned niov;
 151
 152     while (bytes > 0) {
 153         /* Find the start position, skipping `offset' bytes:
 154          * first, skip all full-sized vector elements, */
 155         for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
 156             offset -= iov[niov].iov_len;
 157         }
 158
 159         /* niov == iov_cnt would only be valid if bytes == 0, which
 160          * we already ruled out in the loop condition.  */
 161         assert(niov < iov_cnt);
 162         iov += niov;
 163         iov_cnt -= niov;
 164
 165         if (offset) {
 166             /* second, skip `offset' bytes from the (now) first element,
 167              * undo it on exit */
 168             iov[0].iov_base += offset;
 169             iov[0].iov_len -= offset;
 170         }
 171         /* Find the end position skipping `bytes' bytes: */
 172         /* first, skip all full-sized elements */
 173         tail = bytes;
 174         for (niov = 0; niov < iov_cnt && iov[niov].iov_len <= tail; ++niov) {
 175             tail -= iov[niov].iov_len;
 176         }
 177         if (tail) {
 178             /* second, fixup the last element, and remember the original
 179              * length */
 180             assert(niov < iov_cnt);
 181             assert(iov[niov].iov_len > tail);
 182             orig_len = iov[niov].iov_len;
 183             iov[niov++].iov_len = tail;
 184         }
 185
 186         ret = do_send_recv(sockfd, iov, niov, do_send);
 187
 188         /* Undo the changes above before checking for errors */
 189         if (tail) {
 190             iov[niov-1].iov_len = orig_len;
 191         }
 192         if (offset) {
 193             iov[0].iov_base -= offset;
 194             iov[0].iov_len += offset;
 195         }
 196
 197         if (ret < 0) {
 198             assert(errno != EINTR);
 199             if (errno == EAGAIN && total > 0) {
 200                 return total;
 201             }
 202             return -1;
 203         }
 204
 205         /* Prepare for the next iteration */
 206         offset += ret;
 207         total += ret;
 208         bytes -= ret;
 209     }
 210
 211     return total;
 212 }
 213
 214
 215 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
 216                  FILE *fp, const char *prefix, size_t limit)
 217 {
 218     int v;
 219     size_t size = 0;
 220     char *buf;
 221
 222     for (v = 0; v < iov_cnt; v++) {
 223         size += iov[v].iov_len;
 224     }
 225     size = size > limit ? limit : size;
 226     buf = g_malloc(size);
 227     iov_to_buf(iov, iov_cnt, 0, buf, size);
 228     hexdump(buf, fp, prefix, size);
 229     g_free(buf);
 230 }
 231
 232 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
 233                  const struct iovec *iov, unsigned int iov_cnt,
 234                  size_t offset, size_t bytes)
 235 {
 236     size_t len;
 237     unsigned int i, j;
 238     for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
 239         if (offset >= iov[i].iov_len) {
 240             offset -= iov[i].iov_len;
 241             continue;
 242         }
 243         len = MIN(bytes, iov[i].iov_len - offset);
 244
 245         dst_iov[j].iov_base = iov[i].iov_base + offset;
 246         dst_iov[j].iov_len = len;
 247         j++;
 248         bytes -= len;
 249         offset = 0;
 250     }
 251     assert(offset == 0);
 252     return j;
 253 }
 254
 255 /* io vectors */
 256
 257 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
 258 {
 259     qiov->iov = g_malloc(alloc_hint * sizeof(struct iovec));
 260     qiov->niov = 0;
 261     qiov->nalloc = alloc_hint;
 262     qiov->size = 0;
 263 }
 264
 265 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
 266 {
 267     int i;
 268
 269     qiov->iov = iov;
 270     qiov->niov = niov;
 271     qiov->nalloc = -1;
 272     qiov->size = 0;
 273     for (i = 0; i < niov; i++)
 274         qiov->size += iov[i].iov_len;
 275 }
 276
 277 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 278 {
 279     assert(qiov->nalloc != -1);
 280
 281     if (qiov->niov == qiov->nalloc) {
 282         qiov->nalloc = 2 * qiov->nalloc + 1;
 283         qiov->iov = g_realloc(qiov->iov, qiov->nalloc * sizeof(struct iovec));
 284     }
 285     qiov->iov[qiov->niov].iov_base = base;
 286     qiov->iov[qiov->niov].iov_len = len;
 287     qiov->size += len;
 288     ++qiov->niov;
 289 }
 290
 291 /*
 292  * Concatenates (partial) iovecs from src_iov to the end of dst.
 293  * It starts copying after skipping `soffset' bytes at the
 294  * beginning of src and adds individual vectors from src to
 295  * dst copies up to `sbytes' bytes total, or up to the end
 296  * of src_iov if it comes first.  This way, it is okay to specify
 297  * very large value for `sbytes' to indicate "up to the end
 298  * of src".
 299  * Only vector pointers are processed, not the actual data buffers.
 300  */
 301 void qemu_iovec_concat_iov(QEMUIOVector *dst,
 302                            struct iovec *src_iov, unsigned int src_cnt,
 303                            size_t soffset, size_t sbytes)
 304 {
 305     int i;
 306     size_t done;
 307
 308     if (!sbytes) {
 309         return;
 310     }
 311     assert(dst->nalloc != -1);
 312     for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
 313         if (soffset < src_iov[i].iov_len) {
 314             size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
 315             qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
 316             done += len;
 317             soffset = 0;
 318         } else {
 319             soffset -= src_iov[i].iov_len;
 320         }
 321     }
 322     assert(soffset == 0); /* offset beyond end of src */
 323 }
 324
 325 /*
 326  * Concatenates (partial) iovecs from src to the end of dst.
 327  * It starts copying after skipping `soffset' bytes at the
 328  * beginning of src and adds individual vectors from src to
 329  * dst copies up to `sbytes' bytes total, or up to the end
 330  * of src if it comes first.  This way, it is okay to specify
 331  * very large value for `sbytes' to indicate "up to the end
 332  * of src".
 333  * Only vector pointers are processed, not the actual data buffers.
 334  */
 335 void qemu_iovec_concat(QEMUIOVector *dst,
 336                        QEMUIOVector *src, size_t soffset, size_t sbytes)
 337 {
 338     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
 339 }
 340
 341 void qemu_iovec_destroy(QEMUIOVector *qiov)
 342 {
 343     assert(qiov->nalloc != -1);
 344
 345     qemu_iovec_reset(qiov);
 346     g_free(qiov->iov);
 347     qiov->nalloc = 0;
 348     qiov->iov = NULL;
 349 }
 350
 351 void qemu_iovec_reset(QEMUIOVector *qiov)
 352 {
 353     assert(qiov->nalloc != -1);
 354
 355     qiov->niov = 0;
 356     qiov->size = 0;
 357 }
 358
 359 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
 360                          void *buf, size_t bytes)
 361 {
 362     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 363 }
 364
 365 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
 366                            const void *buf, size_t bytes)
 367 {
 368     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 369 }
 370
 371 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
 372                          int fillc, size_t bytes)
 373 {
 374     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
 375 }
 376
 377 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
 378                          size_t bytes)
 379 {
 380     size_t total = 0;
 381     struct iovec *cur;
 382
 383     for (cur = *iov; *iov_cnt > 0; cur++) {
 384         if (cur->iov_len > bytes) {
 385             cur->iov_base += bytes;
 386             cur->iov_len -= bytes;
 387             total += bytes;
 388             break;
 389         }
 390
 391         bytes -= cur->iov_len;
 392         total += cur->iov_len;
 393         *iov_cnt -= 1;
 394     }
 395
 396     *iov = cur;
 397     return total;
 398 }
 399
 400 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
 401                         size_t bytes)
 402 {
 403     size_t total = 0;
 404     struct iovec *cur;
 405
 406     if (*iov_cnt == 0) {
 407         return 0;
 408     }
 409
 410     cur = iov + (*iov_cnt - 1);
 411
 412     while (*iov_cnt > 0) {
 413         if (cur->iov_len > bytes) {
 414             cur->iov_len -= bytes;
 415             total += bytes;
 416             break;
 417         }
 418
 419         bytes -= cur->iov_len;
 420         total += cur->iov_len;
 421         cur--;
 422         *iov_cnt -= 1;
 423     }
 424
 425     return total;
 426 }