lib/util/iov_buf.c

   1 /*
   2  * Unix SMB/CIFS implementation.
   3  * Samba system utilities
   4  * Copyright (C) Volker Lendecke 2014
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "replace.h"
  21 #include "system/filesys.h"
  22 #include "iov_buf.h"
  23
  24 ssize_t iov_buflen(const struct iovec *iov, int iovcnt)
  25 {
  26         return iov_buf(iov, iovcnt, NULL, 0);
  27 }
  28
  29 ssize_t iov_buf(const struct iovec *iov, int iovcnt,
  30                 uint8_t *buf, size_t buflen)
  31 {
  32         size_t needed = 0;
  33         uint8_t *p = buf;
  34         int i;
  35
  36         for (i=0; i<iovcnt; i++) {
  37                 size_t thislen = iov[i].iov_len;
  38                 size_t tmp;
  39
  40                 tmp = needed + thislen;
  41
  42                 if (tmp < needed) {
  43                         /* wrap */
  44                         return -1;
  45                 }
  46                 needed = tmp;
  47
  48                 if (needed <= buflen) {
  49                         memcpy(p, iov[i].iov_base, thislen);
  50                         p += thislen;
  51                 }
  52         }
  53
  54         return needed;
  55 }
  56
  57 bool iov_advance(struct iovec **iov, int *iovcnt, size_t n)
  58 {
  59         struct iovec *v = *iov;
  60         int cnt = *iovcnt;
  61
  62         while (n > 0) {
  63                 if (cnt == 0) {
  64                         return false;
  65                 }
  66                 if (n < v->iov_len) {
  67                         v->iov_base = (char *)v->iov_base + n;
  68                         v->iov_len -= n;
  69                         break;
  70                 }
  71                 n -= v->iov_len;
  72                 v += 1;
  73                 cnt -= 1;
  74         }
  75
  76         /*
  77          * Skip 0-length iovec's
  78          *
  79          * There might be empty buffers at the end of iov. Next time we do a
  80          * readv/writev based on this iov would give 0 transferred bytes, also
  81          * known as EPIPE. So we need to be careful discarding them.
  82          */
  83
  84         while ((cnt > 0) && (v->iov_len == 0)) {
  85                 v += 1;
  86                 cnt -= 1;
  87         }
  88
  89         *iov = v;
  90         *iovcnt = cnt;
  91         return true;
  92 }