/* Creating and controlling threads.
   Copyright (C) 2005-2008 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2005.
   Based on GCC's gthr-posix.h, gthr-posix95.h, gthr-solaris.h,
   gthr-win32.h.  */

/* This file contains primitives for creating and controlling threads.

   Thread data type: gl_thread_t.

   Creating a thread:
       thread = gl_thread_create (func, arg);
   Or with control of error handling:
       err = glthread_create (&thread, func, arg);
       extern int glthread_create (gl_thread_t *result,
                                   void *(*func) (void *), void *arg);

   Querying and changing the signal mask of a thread (not supported on all
   platforms):
       gl_thread_sigmask (how, newmask, oldmask);
   Or with control of error handling:
       err = glthread_sigmask (how, newmask, oldmask);
       extern int glthread_sigmask (int how, const sigset_t *newmask, sigset_t *oldmask);

   Waiting for termination of another thread:
       gl_thread_join (thread, &return_value);
   Or with control of error handling:
       err = glthread_join (thread, &return_value);
       extern int glthread_join (gl_thread_t thread, void **return_value_ptr);

   Getting a reference to the current thread:
       current = gl_thread_self ();
       extern gl_thread_t gl_thread_self (void);

   Terminating the current thread:
       gl_thread_exit (return_value);
       extern void gl_thread_exit (void *return_value) __attribute__ ((noreturn));

   Requesting custom code to be executed at fork() time(not supported on all
   platforms):
       gl_thread_atfork (prepare_func, parent_func, child_func);
   Or with control of error handling:
       err = glthread_atfork (prepare_func, parent_func, child_func);
       extern int glthread_atfork (void (*prepare_func) (void),
                                   void (*parent_func) (void),
                                   void (*child_func) (void));
   Note that even on platforms where this is supported, use of fork() and
   threads together is problematic, see
     <http://lists.gnu.org/archive/html/bug-gnulib/2008-08/msg00062.html>
 */


#ifndef _GLTHREAD_THREAD_H
#define _GLTHREAD_THREAD_H

#include <errno.h>
#include <stdlib.h>

/* ========================================================================= */

#if USE_POSIX_THREADS

/* Use the POSIX threads library.  */

# include <pthread.h>

# ifdef __cplusplus
extern "C" {
# endif

# if PTHREAD_IN_USE_DETECTION_HARD

/* The pthread_in_use() detection needs to be done at runtime.  */
#  define pthread_in_use() \
     glthread_in_use ()
extern int glthread_in_use (void);

# endif

# if USE_POSIX_THREADS_WEAK

/* Use weak references to the POSIX threads library.  */

/* Weak references avoid dragging in external libraries if the other parts
   of the program don't use them.  Here we use them, because we don't want
   every program that uses libintl to depend on libpthread.  This assumes
   that libpthread would not be loaded after libintl; i.e. if libintl is
   loaded first, by an executable that does not depend on libpthread, and
   then a module is dynamically loaded that depends on libpthread, libintl
   will not be multithread-safe.  */

/* The way to test at runtime whether libpthread is present is to test
   whether a function pointer's value, such as &pthread_mutex_init, is
   non-NULL.  However, some versions of GCC have a bug through which, in
   PIC mode, &foo != NULL always evaluates to true if there is a direct
   call to foo(...) in the same function.  To avoid this, we test the
   address of a function in libpthread that we don't use.  */

#  pragma weak pthread_create
#  pragma weak pthread_sigmask
#  pragma weak pthread_join
#  ifndef pthread_self
#   pragma weak pthread_self
#  endif
#  pragma weak pthread_exit
#  if HAVE_PTHREAD_ATFORK
#   pragma weak pthread_atfork
#  endif

#  if !PTHREAD_IN_USE_DETECTION_HARD
#   pragma weak pthread_cancel
#   define pthread_in_use() (pthread_cancel != NULL)
#  endif

# else

#  if !PTHREAD_IN_USE_DETECTION_HARD
#   define pthread_in_use() 1
#  endif

# endif

/* -------------------------- gl_thread_t datatype -------------------------- */

typedef pthread_t gl_thread_t;
# define glthread_create(THREADP, FUNC, ARG) \
    (pthread_in_use () ? pthread_create (THREADP, NULL, FUNC, ARG) : ENOSYS)
# define glthread_sigmask(HOW, SET, OSET) \
    (pthread_in_use () ? pthread_sigmask (HOW, SET, OSET) : 0)
# define glthread_join(THREAD, RETVALP) \
    (pthread_in_use () ? pthread_join (THREAD, RETVALP) : 0)
# define gl_thread_self() \
    (pthread_in_use () ? (void *) pthread_self () : NULL)
# define gl_thread_exit(RETVAL) \
    (pthread_in_use () ? pthread_exit (RETVAL) : 0)

# if HAVE_PTHREAD_ATFORK
#  define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) \
     (pthread_in_use () ? pthread_atfork (PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) : 0)
# else
#  define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0
# endif

# ifdef __cplusplus
}
# endif

#endif

/* ========================================================================= */

#if USE_PTH_THREADS

/* Use the GNU Pth threads library.  */

# include <pth.h>

# ifdef __cplusplus
extern "C" {
# endif

# if USE_PTH_THREADS_WEAK

/* Use weak references to the GNU Pth threads library.  */

#  pragma weak pth_spawn
#  pragma weak pth_sigmask
#  pragma weak pth_join
#  pragma weak pth_self
#  pragma weak pth_exit

#  pragma weak pth_cancel
#  define pth_in_use() (pth_cancel != NULL)

# else

#  define pth_in_use() 1

# endif
/* -------------------------- gl_thread_t datatype -------------------------- */

typedef pth_t gl_thread_t;
# define glthread_create(THREADP, FUNC, ARG) \
    (pth_in_use () ? ((*(THREADP) = pth_spawn (NULL, FUNC, ARG)) ? 0 : errno) : 0)
# define glthread_sigmask(HOW, SET, OSET) \
    (pth_in_use () && !pth_sigmask (HOW, SET, OSET) ? errno : 0)
# define glthread_join(THREAD, RETVALP) \
    (pth_in_use () && !pth_join (THREAD, RETVALP) ? errno : 0)
# define gl_thread_self() \
    (pth_in_use () ? (void *) pth_self () : 0)
# define gl_thread_exit(RETVAL) \
    (pth_in_use () ? pth_exit (RETVAL) : 0)
# define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0

# ifdef __cplusplus
}
# endif

#endif

/* ========================================================================= */

#if USE_SOLARIS_THREADS

/* Use the old Solaris threads library.  */

# include <thread.h>
# include <synch.h>

# ifdef __cplusplus
extern "C" {
# endif

# if USE_SOLARIS_THREADS_WEAK

/* Use weak references to the old Solaris threads library.  */

#  pragma weak thr_create
#  pragma weak thr_join
#  pragma weak thr_self
#  pragma weak thr_exit

#  pragma weak thr_suspend
#  define thread_in_use() (thr_suspend != NULL)

# else

#  define thread_in_use() 1

# endif

/* -------------------------- gl_thread_t datatype -------------------------- */

typedef thread_t gl_thread_t;
# define glthread_create(THREADP, FUNC, ARG) \
    (thread_in_use () ? thr_create (NULL, 0, FUNC, ARG, 0, THREADP) : 0)
# define glthread_sigmask(HOW, SET, OSET) \
    (pthread_in_use () ? sigprocmask (HOW, SET, OSET) : 0)
# define glthread_join(THREAD, RETVALP) \
    (pthread_in_use () ? thr_join (THREAD, NULL, RETVALP) : 0)
# define gl_thread_self() \
    (pthread_in_use () ? (void *) thr_self () : 0)
# define gl_thread_exit(RETVAL) \
    (pthread_in_use () ? thr_exit (RETVAL) : 0)
# define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0

# ifdef __cplusplus
}
# endif

#endif

/* ========================================================================= */

#if !(USE_POSIX_THREADS || USE_PTH_THREADS || USE_SOLARIS_THREADS || USE_WIN32_THREADS)

/* Provide dummy implementation if threads are not supported.  */

typedef int gl_thread_t;
# define glthread_create(THREADP, FUNC, ARG) ENOSYS
# define glthread_sigmask(HOW, SET, OSET) 0
# define glthread_join(THREAD, RETVALP) 0
# define gl_thread_self() NULL
# define gl_thread_exit(RETVAL) 0
# define glthread_atfork(PREPARE_FUNC, PARENT_FUNC, CHILD_FUNC) 0

#endif

/* ========================================================================= */

/* Macros with built-in error handling.  */

#ifdef __cplusplus
extern "C" {
#endif

static inline gl_thread_t
gl_thread_create (void *(*func) (void *arg), void *arg)
{
  gl_thread_t thread;
  int ret;

  ret = glthread_create (&thread, func, arg);
  if (ret != 0)
    abort ();
  return thread;
}
#define gl_thread_sigmask(HOW, SET, OSET)     \
   do                                         \
     {                                        \
       if (glthread_sigmask (HOW, SET, OSET)) \
         abort ();                            \
     }                                        \
   while (0)
#define gl_thread_join(THREAD, RETVAL)     \
   do                                      \
     {                                     \
       if (glthread_join (THREAD, RETVAL)) \
         abort ();                         \
     }                                     \
   while (0)
#define gl_thread_atfork(PREPARE, PARENT, CHILD)     \
   do                                                \
     {                                               \
       if (glthread_atfork (PREPARE, PARENT, CHILD)) \
         abort ();                                   \
     }                                               \
   while (0)

#ifdef __cplusplus
}
#endif

#endif /* _GLTHREAD_THREAD_H */