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 #include <talloc.h>
  24
  25 ssize_t iov_buflen(const struct iovec *iov, int iovcnt)
  26 {
  27         return iov_buf(iov, iovcnt, NULL, 0);
  28 }
  29
  30 ssize_t iov_buf(const struct iovec *iov, int iovcnt,
  31                 uint8_t *buf, size_t buflen)
  32 {
  33         size_t needed = 0;
  34         uint8_t *p = buf;
  35         int i;
  36
  37         for (i=0; i<iovcnt; i++) {
  38                 size_t thislen = iov[i].iov_len;
  39                 size_t tmp;
  40
  41                 tmp = needed + thislen;
  42
  43                 if (tmp < needed) {
  44                         /* wrap */
  45                         return -1;
  46                 }
  47                 needed = tmp;
  48
  49                 if ((p != NULL) && needed <= buflen && thislen > 0) {
  50                         memcpy(p, iov[i].iov_base, thislen);
  51                         p += thislen;
  52                 }
  53         }
  54
  55         return needed;
  56 }
  57
  58 bool iov_advance(struct iovec **iov, int *iovcnt, size_t n)
  59 {
  60         struct iovec *v = *iov;
  61         int cnt = *iovcnt;
  62
  63         while (n > 0) {
  64                 if (cnt == 0) {
  65                         return false;
  66                 }
  67                 if (n < v->iov_len) {
  68                         v->iov_base = (char *)v->iov_base + n;
  69                         v->iov_len -= n;
  70                         break;
  71                 }
  72                 n -= v->iov_len;
  73                 v += 1;
  74                 cnt -= 1;
  75         }
  76
  77         /*
  78          * Skip 0-length iovec's
  79          *
  80          * There might be empty buffers at the end of iov. Next time we do a
  81          * readv/writev based on this iov would give 0 transferred bytes, also
  82          * known as EPIPE. So we need to be careful discarding them.
  83          */
  84
  85         while ((cnt > 0) && (v->iov_len == 0)) {
  86                 v += 1;
  87                 cnt -= 1;
  88         }
  89
  90         *iov = v;
  91         *iovcnt = cnt;
  92         return true;
  93 }
  94
  95 uint8_t *iov_concat(TALLOC_CTX *mem_ctx, const struct iovec *iov, int count)
  96 {
  97         ssize_t buflen;
  98         uint8_t *buf;
  99
 100         buflen = iov_buflen(iov, count);
 101         if (buflen == -1) {
 102                 return NULL;
 103         }
 104
 105         buf = talloc_array(mem_ctx, uint8_t, buflen);
 106         if (buf == NULL) {
 107                 return NULL;
 108         }
 109
 110         iov_buf(iov, count, buf, buflen);
 111
 112         return buf;
 113 }