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 _GNU_SOURCE
  19 #define _LGPL_SOURCE
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <limits.h>
  23 #include <unistd.h>
  24
  25 #include "readwrite.h"
  26
  27 /*
  28  * lttng_read and lttng_write take care of EINTR and partial read/write.
  29  * Upon success, they return the "count" received as parameter.
  30  * They can return a negative value if an error occurs.
  31  * If a value lower than the requested "count" is returned, it means an
  32  * error occured.
  33  * The error can be checked by querying errno.
  34  */
  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 ssize_t lttng_write(int fd, const void *buf, size_t count)
  73 {
  74         size_t i = 0;
  75         ssize_t ret;
  76
  77         assert(buf);
  78
  79         /*
  80          * Deny a write count that can be bigger then the returned value max size.
  81          * This makes the function to never return an overflow value.
  82          */
  83         if (count > SSIZE_MAX) {
  84                 return -EINVAL;
  85         }
  86
  87         do {
  88                 ret = write(fd, buf + i, count - i);
  89                 if (ret < 0) {
  90                         if (errno == EINTR) {
  91                                 continue;       /* retry operation */
  92                         } else {
  93                                 goto error;
  94                         }
  95                 }
  96                 i += ret;
  97                 assert(i <= count);
  98         } while (count - i > 0 && ret > 0);
  99         return i;
 100
 101 error:
 102         if (i == 0) {
 103                 return -1;
 104         } else {
 105                 return i;
 106         }
 107 }