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 #if defined CONFIG_IOVEC && defined 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 ret;
 148     unsigned si, ei;            /* start and end indexes */
 149     if (bytes == 0) {
 150         /* Catch the do-nothing case early, as otherwise we will pass an
 151          * empty iovec to sendmsg/recvmsg(), and not all implementations
 152          * accept this.
 153          */
 154         return 0;
 155     }
 156
 157     /* Find the start position, skipping `offset' bytes:
 158      * first, skip all full-sized vector elements, */
 159     for (si = 0; si < iov_cnt && offset >= iov[si].iov_len; ++si) {
 160         offset -= iov[si].iov_len;
 161     }
 162     if (offset) {
 163         assert(si < iov_cnt);
 164         /* second, skip `offset' bytes from the (now) first element,
 165          * undo it on exit */
 166         iov[si].iov_base += offset;
 167         iov[si].iov_len -= offset;
 168     }
 169     /* Find the end position skipping `bytes' bytes: */
 170     /* first, skip all full-sized elements */
 171     for (ei = si; ei < iov_cnt && iov[ei].iov_len <= bytes; ++ei) {
 172         bytes -= iov[ei].iov_len;
 173     }
 174     if (bytes) {
 175         /* second, fixup the last element, and remember
 176          * the length we've cut from the end of it in `bytes' */
 177         size_t tail;
 178         assert(ei < iov_cnt);
 179         assert(iov[ei].iov_len > bytes);
 180         tail = iov[ei].iov_len - bytes;
 181         iov[ei].iov_len = bytes;
 182         bytes = tail;  /* bytes is now equal to the tail size */
 183         ++ei;
 184     }
 185
 186     ret = do_send_recv(sockfd, iov + si, ei - si, do_send);
 187
 188     /* Undo the changes above */
 189     if (offset) {
 190         iov[si].iov_base -= offset;
 191         iov[si].iov_len += offset;
 192     }
 193     if (bytes) {
 194         iov[ei-1].iov_len += bytes;
 195     }
 196
 197     return ret;
 198 }
 199
 200
 201 void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
 202                  FILE *fp, const char *prefix, size_t limit)
 203 {
 204     int v;
 205     size_t size = 0;
 206     char *buf;
 207
 208     for (v = 0; v < iov_cnt; v++) {
 209         size += iov[v].iov_len;
 210     }
 211     size = size > limit ? limit : size;
 212     buf = g_malloc(size);
 213     iov_to_buf(iov, iov_cnt, 0, buf, size);
 214     hexdump(buf, fp, prefix, size);
 215     g_free(buf);
 216 }
 217
 218 unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
 219                  const struct iovec *iov, unsigned int iov_cnt,
 220                  size_t offset, size_t bytes)
 221 {
 222     size_t len;
 223     unsigned int i, j;
 224     for (i = 0, j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
 225         if (offset >= iov[i].iov_len) {
 226             offset -= iov[i].iov_len;
 227             continue;
 228         }
 229         len = MIN(bytes, iov[i].iov_len - offset);
 230
 231         dst_iov[j].iov_base = iov[i].iov_base + offset;
 232         dst_iov[j].iov_len = len;
 233         j++;
 234         bytes -= len;
 235         offset = 0;
 236     }
 237     assert(offset == 0);
 238     return j;
 239 }
 240
 241 /* io vectors */
 242
 243 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
 244 {
 245     qiov->iov = g_malloc(alloc_hint * sizeof(struct iovec));
 246     qiov->niov = 0;
 247     qiov->nalloc = alloc_hint;
 248     qiov->size = 0;
 249 }
 250
 251 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
 252 {
 253     int i;
 254
 255     qiov->iov = iov;
 256     qiov->niov = niov;
 257     qiov->nalloc = -1;
 258     qiov->size = 0;
 259     for (i = 0; i < niov; i++)
 260         qiov->size += iov[i].iov_len;
 261 }
 262
 263 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
 264 {
 265     assert(qiov->nalloc != -1);
 266
 267     if (qiov->niov == qiov->nalloc) {
 268         qiov->nalloc = 2 * qiov->nalloc + 1;
 269         qiov->iov = g_realloc(qiov->iov, qiov->nalloc * sizeof(struct iovec));
 270     }
 271     qiov->iov[qiov->niov].iov_base = base;
 272     qiov->iov[qiov->niov].iov_len = len;
 273     qiov->size += len;
 274     ++qiov->niov;
 275 }
 276
 277 /*
 278  * Concatenates (partial) iovecs from src_iov to the end of dst.
 279  * It starts copying after skipping `soffset' bytes at the
 280  * beginning of src and adds individual vectors from src to
 281  * dst copies up to `sbytes' bytes total, or up to the end
 282  * of src_iov if it comes first.  This way, it is okay to specify
 283  * very large value for `sbytes' to indicate "up to the end
 284  * of src".
 285  * Only vector pointers are processed, not the actual data buffers.
 286  */
 287 void qemu_iovec_concat_iov(QEMUIOVector *dst,
 288                            struct iovec *src_iov, unsigned int src_cnt,
 289                            size_t soffset, size_t sbytes)
 290 {
 291     int i;
 292     size_t done;
 293
 294     if (!sbytes) {
 295         return;
 296     }
 297     assert(dst->nalloc != -1);
 298     for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
 299         if (soffset < src_iov[i].iov_len) {
 300             size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
 301             qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
 302             done += len;
 303             soffset = 0;
 304         } else {
 305             soffset -= src_iov[i].iov_len;
 306         }
 307     }
 308     assert(soffset == 0); /* offset beyond end of src */
 309 }
 310
 311 /*
 312  * Concatenates (partial) iovecs from src to the end of dst.
 313  * It starts copying after skipping `soffset' bytes at the
 314  * beginning of src and adds individual vectors from src to
 315  * dst copies up to `sbytes' bytes total, or up to the end
 316  * of src if it comes first.  This way, it is okay to specify
 317  * very large value for `sbytes' to indicate "up to the end
 318  * of src".
 319  * Only vector pointers are processed, not the actual data buffers.
 320  */
 321 void qemu_iovec_concat(QEMUIOVector *dst,
 322                        QEMUIOVector *src, size_t soffset, size_t sbytes)
 323 {
 324     qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
 325 }
 326
 327 void qemu_iovec_destroy(QEMUIOVector *qiov)
 328 {
 329     assert(qiov->nalloc != -1);
 330
 331     qemu_iovec_reset(qiov);
 332     g_free(qiov->iov);
 333     qiov->nalloc = 0;
 334     qiov->iov = NULL;
 335 }
 336
 337 void qemu_iovec_reset(QEMUIOVector *qiov)
 338 {
 339     assert(qiov->nalloc != -1);
 340
 341     qiov->niov = 0;
 342     qiov->size = 0;
 343 }
 344
 345 size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
 346                          void *buf, size_t bytes)
 347 {
 348     return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 349 }
 350
 351 size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
 352                            const void *buf, size_t bytes)
 353 {
 354     return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
 355 }
 356
 357 size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
 358                          int fillc, size_t bytes)
 359 {
 360     return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
 361 }
 362
 363 size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
 364                          size_t bytes)
 365 {
 366     size_t total = 0;
 367     struct iovec *cur;
 368
 369     for (cur = *iov; *iov_cnt > 0; cur++) {
 370         if (cur->iov_len > bytes) {
 371             cur->iov_base += bytes;
 372             cur->iov_len -= bytes;
 373             total += bytes;
 374             break;
 375         }
 376
 377         bytes -= cur->iov_len;
 378         total += cur->iov_len;
 379         *iov_cnt -= 1;
 380     }
 381
 382     *iov = cur;
 383     return total;
 384 }
 385
 386 size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
 387                         size_t bytes)
 388 {
 389     size_t total = 0;
 390     struct iovec *cur;
 391
 392     if (*iov_cnt == 0) {
 393         return 0;
 394     }
 395
 396     cur = iov + (*iov_cnt - 1);
 397
 398     while (*iov_cnt > 0) {
 399         if (cur->iov_len > bytes) {
 400             cur->iov_len -= bytes;
 401             total += bytes;
 402             break;
 403         }
 404
 405         bytes -= cur->iov_len;
 406         total += cur->iov_len;
 407         cur--;
 408         *iov_cnt -= 1;
 409     }
 410
 411     return total;
 412 }