sal/osl/unx/readwrite_helper.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #include <sal/config.h>
  11
  12 #include <algorithm>
  13 #include <cassert>
  14 #include <cstddef>
  15 #include <errno.h>
  16 #include <limits>
  17 #include <unistd.h>
  18
  19 #include "readwrite_helper.hxx"
  20
  21 namespace {
  22
  23 std::size_t cap_ssize_t(std::size_t value) {
  24     return std::min(value, std::size_t(std::numeric_limits<ssize_t>::max()));
  25 }
  26
  27 }
  28
  29 bool safeWrite(int fd, void* data, std::size_t dataSize)
  30 {
  31     auto nToWrite = dataSize;
  32     unsigned char* dataToWrite = static_cast<unsigned char *>(data);
  33
  34     while ( nToWrite ) {
  35         auto nWritten = write(fd, dataToWrite, cap_ssize_t(nToWrite));
  36         if ( nWritten < 0 ) {
  37             if ( errno == EINTR )
  38                 continue;
  39
  40             return false;
  41
  42         }
  43
  44         assert(nWritten > 0);
  45         nToWrite -= nWritten;
  46         dataToWrite += nWritten;
  47     }
  48
  49     return true;
  50 }
  51
  52 bool safeRead( int fd, void* buffer, std::size_t count )
  53 {
  54     auto nToRead = count;
  55     unsigned char* bufferForReading = static_cast<unsigned char *>(buffer);
  56
  57     while ( nToRead ) {
  58         auto nRead = read(fd, bufferForReading, cap_ssize_t(nToRead));
  59         if ( nRead < 0 ) {
  60             // We were interrupted before reading, retry.
  61             if (errno == EINTR)
  62                 continue;
  63
  64             return false;
  65         }
  66
  67         // If we reach the EOF, we consider this a partial transfer and thus
  68         // an error.
  69         if ( nRead == 0 )
  70             return false;
  71
  72         nToRead -= nRead;
  73         bufferForReading += nRead;
  74     }
  75
  76     return true;
  77 }
  78
  79 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */