src/common/readwrite.c

   1 /*
   2  * Copyright (C) 2013 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   3  *
   4  * This library is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU Lesser General Public License, version 2.1 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This library is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  11  * for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this library; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18 #include <assert.h>
  19 #include <errno.h>
  20 #include <unistd.h>
  21
  22 #include "readwrite.h"
  23
  24 /*
  25  * lttng_read and lttng_write take care of EINTR and partial read/write.
  26  * Upon success, they return the "count" received as parameter.
  27  * They can return a negative value if an error occurs.
  28  * If a value lower than the requested "count" is returned, it means an
  29  * error occured.
  30  * The error can be checked by querying errno.
  31  */
  32 ssize_t lttng_read(int fd, void *buf, size_t count)
  33 {
  34         size_t i = 0;
  35         ssize_t ret;
  36
  37         assert(buf);
  38
  39         do {
  40                 ret = read(fd, buf + i, count - i);
  41                 if (ret < 0) {
  42                         if (errno == EINTR) {
  43                                 continue;       /* retry operation */
  44                         } else {
  45                                 goto error;
  46                         }
  47                 }
  48                 i += ret;
  49                 assert(i <= count);
  50         } while (count - i > 0 && ret > 0);
  51         return i;
  52
  53 error:
  54         if (i == 0) {
  55                 return -1;
  56         } else {
  57                 return i;
  58         }
  59 }
  60
  61 ssize_t lttng_write(int fd, const void *buf, size_t count)
  62 {
  63         size_t i = 0;
  64         ssize_t ret;
  65
  66         assert(buf);
  67
  68         do {
  69                 ret = write(fd, buf + i, count - i);
  70                 if (ret < 0) {
  71                         if (errno == EINTR) {
  72                                 continue;       /* retry operation */
  73                         } else {
  74                                 goto error;
  75                         }
  76                 }
  77                 i += ret;
  78                 assert(i <= count);
  79         } while (count - i > 0 && ret > 0);
  80         return i;
  81
  82 error:
  83         if (i == 0) {
  84                 return -1;
  85         } else {
  86                 return i;
  87         }
  88 }