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 #define _LGPL_SOURCE
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <limits.h>
  22 #include <unistd.h>
  23
  24 #include "readwrite.h"
  25
  26 /*
  27  * lttng_read and lttng_write take care of EINTR and partial read/write.
  28  * Upon success, they return the "count" received as parameter.
  29  * They can return a negative value if an error occurs.
  30  * If a value lower than the requested "count" is returned, it means an
  31  * error occurred.
  32  * The error can be checked by querying errno.
  33  */
  34 LTTNG_HIDDEN
  35 ssize_t lttng_read(int fd, void *buf, size_t count)
  36 {
  37         size_t i = 0;
  38         ssize_t ret;
  39
  40         assert(buf);
  41
  42         /*
  43          * Deny a read count that can be bigger then the returned value max size.
  44          * This makes the function to never return an overflow value.
  45          */
  46         if (count > SSIZE_MAX) {
  47                 return -EINVAL;
  48         }
  49
  50         do {
  51                 ret = read(fd, buf + i, count - i);
  52                 if (ret < 0) {
  53                         if (errno == EINTR) {
  54                                 continue;       /* retry operation */
  55                         } else {
  56                                 goto error;
  57                         }
  58                 }
  59                 i += ret;
  60                 assert(i <= count);
  61         } while (count - i > 0 && ret > 0);
  62         return i;
  63
  64 error:
  65         if (i == 0) {
  66                 return -1;
  67         } else {
  68                 return i;
  69         }
  70 }
  71
  72 LTTNG_HIDDEN
  73 ssize_t lttng_write(int fd, const void *buf, size_t count)
  74 {
  75         size_t i = 0;
  76         ssize_t ret;
  77
  78         assert(buf);
  79
  80         /*
  81          * Deny a write count that can be bigger then the returned value max size.
  82          * This makes the function to never return an overflow value.
  83          */
  84         if (count > SSIZE_MAX) {
  85                 return -EINVAL;
  86         }
  87
  88         do {
  89                 ret = write(fd, buf + i, count - i);
  90                 if (ret < 0) {
  91                         if (errno == EINTR) {
  92                                 continue;       /* retry operation */
  93                         } else {
  94                                 goto error;
  95                         }
  96                 }
  97                 i += ret;
  98                 assert(i <= count);
  99         } while (count - i > 0 && ret > 0);
 100         return i;
 101
 102 error:
 103         if (i == 0) {
 104                 return -1;
 105         } else {
 106                 return i;
 107         }
 108 }