src/base/atomicio.hh

   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 #ifndef __BASE_ATOMICIO_HH__
  30 #define __BASE_ATOMICIO_HH__
  31
  32 #include <unistd.h>
  33
  34 // These functions keep reading/writing, if possible, until all data
  35 // has been transferred.  Basically, try again when there's no error,
  36 // but there is data left also retry on EINTR.
  37 // This function blocks until it is done.
  38
  39 ssize_t atomic_read(int fd, void *s, size_t n);
  40 ssize_t atomic_write(int fd, const void *s, size_t n);
  41
  42 /**
  43  * Statically allocate a string and write it to a file descriptor.
  44  *
  45  * @warning The return value will from atomic_write will be ignored
  46  * which means that errors will be ignored. This is normally fine as
  47  * this macro is intended to be used in fatal signal handlers where
  48  * error handling might not be feasible.
  49  */
  50 #define STATIC_MSG(fd, m)                                       \
  51     do {                                                        \
  52         static const char msg[] = m;                            \
  53         atomic_write(fd, msg, sizeof(msg) - 1);                 \
  54     } while (0)
  55
  56 /**
  57  * Statically allocate a string and write it to STDERR.
  58  *
  59  * @warning The return value will from atomic_write will be ignored
  60  * which means that errors will be ignored. This is normally fine as
  61  * this macro is intended to be used in fatal signal handlers where
  62  * error handling might not be feasible.
  63  */
  64 #define STATIC_ERR(m) STATIC_MSG(STDERR_FILENO, m)
  65
  66 #endif // __BASE_ATOMICIO_HH__