libiberty/fopen_unlocked.c

   1 /* Implement fopen_unlocked and related functions.
   2    Copyright (C) 2005-2023 Free Software Foundation, Inc.
   3    Written by Kaveh R. Ghazi <ghazi@caip.rutgers.edu>.
   4
   5 This file is part of the libiberty library.
   6 Libiberty is free software; you can redistribute it and/or
   7 modify it under the terms of the GNU Library General Public
   8 License as published by the Free Software Foundation; either
   9 version 2 of the License, or (at your option) any later version.
  10
  11 Libiberty is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 Library General Public License for more details.
  15
  16 You should have received a copy of the GNU Library General Public
  17 License along with libiberty; see the file COPYING.LIB.  If
  18 not, write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
  19 Boston, MA 02110-1301, USA.  */
  20
  21 /*
  22
  23 @deftypefn Extension void unlock_stream (FILE * @var{stream})
  24
  25 If the OS supports it, ensure that the supplied stream is setup to
  26 avoid any multi-threaded locking.  Otherwise leave the @code{FILE}
  27 pointer unchanged.  If the @var{stream} is @code{NULL} do nothing.
  28
  29 @end deftypefn
  30
  31 @deftypefn Extension void unlock_std_streams (void)
  32
  33 If the OS supports it, ensure that the standard I/O streams,
  34 @code{stdin}, @code{stdout} and @code{stderr} are setup to avoid any
  35 multi-threaded locking.  Otherwise do nothing.
  36
  37 @end deftypefn
  38
  39 @deftypefn Extension {FILE *} fopen_unlocked (const char *@var{path}, @
  40   const char * @var{mode})
  41
  42 Opens and returns a @code{FILE} pointer via @code{fopen}.  If the
  43 operating system supports it, ensure that the stream is setup to avoid
  44 any multi-threaded locking.  Otherwise return the @code{FILE} pointer
  45 unchanged.
  46
  47 @end deftypefn
  48
  49 @deftypefn Extension {FILE *} fdopen_unlocked (int @var{fildes}, @
  50   const char * @var{mode})
  51
  52 Opens and returns a @code{FILE} pointer via @code{fdopen}.  If the
  53 operating system supports it, ensure that the stream is setup to avoid
  54 any multi-threaded locking.  Otherwise return the @code{FILE} pointer
  55 unchanged.
  56
  57 @end deftypefn
  58
  59 @deftypefn Extension {FILE *} freopen_unlocked (const char * @var{path}, @
  60   const char * @var{mode}, FILE * @var{stream})
  61
  62 Opens and returns a @code{FILE} pointer via @code{freopen}.  If the
  63 operating system supports it, ensure that the stream is setup to avoid
  64 any multi-threaded locking.  Otherwise return the @code{FILE} pointer
  65 unchanged.
  66
  67 @end deftypefn
  68
  69 */
  70
  71 #ifdef HAVE_CONFIG_H
  72 #include "config.h"
  73 #endif
  74 #include <stdio.h>
  75 #ifdef HAVE_STDIO_EXT_H
  76 #include <stdio_ext.h>
  77 #endif
  78
  79 #include "libiberty.h"
  80
  81 /* This is an inline helper function to consolidate attempts to unlock
  82    a stream.  */
  83
  84 static inline void
  85 unlock_1 (FILE *const fp ATTRIBUTE_UNUSED)
  86 {
  87 #if defined(HAVE___FSETLOCKING) && defined(FSETLOCKING_BYCALLER)
  88   if (fp)
  89     __fsetlocking (fp, FSETLOCKING_BYCALLER);
  90 #endif
  91 }
  92
  93 void
  94 unlock_stream (FILE *fp)
  95 {
  96   unlock_1 (fp);
  97 }
  98
  99 void
 100 unlock_std_streams (void)
 101 {
 102   unlock_1 (stdin);
 103   unlock_1 (stdout);
 104   unlock_1 (stderr);
 105 }
 106
 107 FILE *
 108 fopen_unlocked (const char *path, const char *mode)
 109 {
 110   FILE *const fp = fopen (path, mode);
 111   unlock_1 (fp);
 112   return fp;
 113 }
 114
 115 FILE *
 116 fdopen_unlocked (int fildes, const char *mode)
 117 {
 118   FILE *const fp = fdopen (fildes, mode);
 119   unlock_1 (fp);
 120   return fp;
 121 }
 122
 123 FILE *
 124 freopen_unlocked (const char *path, const char *mode, FILE *stream)
 125 {
 126   FILE *const fp = freopen (path, mode, stream);
 127   unlock_1 (fp);
 128   return fp;
 129 }