src/base/atomicio.cc

   1 /*
   2  * Copyright (c) 2008 The Hewlett-Packard Development Company
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #include "base/atomicio.hh"
  30
  31 #include <cerrno>
  32 #include <cstdio>
  33
  34 ssize_t
  35 atomic_read(int fd, void *s, size_t n)
  36 {
  37     char *p = reinterpret_cast<char *>(s);
  38     size_t pos = 0;
  39
  40     // Keep reading until we've gotten all of the data.
  41     while (n > pos) {
  42         ssize_t result = read(fd, p + pos, n - pos);
  43
  44         // We didn't get any more data, so we should probably punt,
  45         // otherwise we'd just keep spinning
  46         if (result == 0)
  47             break;
  48
  49         // If there was an error, try again on EINTR/EAGAIN, pass the
  50         // error up otherwise.
  51         if (result == -1) {
  52             if (errno == EINTR || errno == EAGAIN)
  53                 continue;
  54             return result;
  55         }
  56
  57         pos += result;
  58     }
  59
  60     return pos;
  61 }
  62
  63 ssize_t
  64 atomic_write(int fd, const void *s, size_t n)
  65 {
  66     const char *p = reinterpret_cast<const char *>(s);
  67     size_t pos = 0;
  68
  69     // Keep writing until we've written all of the data
  70     while (n > pos) {
  71         ssize_t result = write(fd, p + pos, n - pos);
  72
  73         // We didn't manage to write anything this time, so we should
  74         // probably punt, otherwise we'd just keep spinning
  75         if (result == 0)
  76             break;
  77
  78         // If there was an error, try again on EINTR/EAGAIN, pass the
  79         // error up otherwise.
  80         if (result == -1) {
  81             if (errno == EINTR || errno == EAGAIN)
  82                 continue;
  83             return result;
  84         }
  85
  86         pos += result;
  87     }
  88
  89     return pos;
  90 }