gcc/gthr-win32.h

/* Threads compatibility routines for libgcc2 and libobjc.  */
/* Compile this one with gcc.  */
/* Copyright (C) 1999, 2000 Free Software Foundation, Inc.
   Contributed by Mumit Khan <khan@xraylith.wisc.edu>.

This file is part of GNU CC.

GNU CC 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.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* As a special exception, if you link this library with other files,
   some of which are compiled with GCC, to produce an executable,
   this library does not by itself cause the resulting executable
   to be covered by the GNU General Public License.
   This exception does not however invalidate any other reasons why
   the executable file might be covered by the GNU General Public License.  */

#ifndef __gthr_win32_h
#define __gthr_win32_h

/* Windows32 threads specific definitions. The windows32 threading model
   does not map well into pthread-inspired gcc's threading model, and so 
   there are caveats one needs to be aware of.

   1. The destructor supplied to __gthread_key_create is ignored for
      generic x86-win32 ports. This will certainly cause memory leaks 
      due to unreclaimed eh contexts (sizeof (eh_context) is at least 
      24 bytes for x86 currently).

      This memory leak may be significant for long-running applications
      that make heavy use of C++ EH.

      However, Mingw runtime (version 0.3 or newer) provides a mechanism
      to emulate pthreads key dtors; the runtime provides a special DLL,
      linked in if -mthreads option is specified, that runs the dtors in
      the reverse order of registration when each thread exits. If
      -mthreads option is not given, a stub is linked in instead of the
      DLL, which results in memory leak. Other x86-win32 ports can use 
      the same technique of course to avoid the leak.

   2. The error codes returned are non-POSIX like, and cast into ints.
      This may cause incorrect error return due to truncation values on 
      hw where sizeof (DWORD) > sizeof (int).
   
   3. We might consider using Critical Sections instead of Windows32 
      mutexes for better performance, but emulating __gthread_mutex_trylock 
      interface becomes more complicated (Win9x does not support
      TryEnterCriticalSectioni, while NT does).
  
   The basic framework should work well enough. In the long term, GCC
   needs to use Structured Exception Handling on Windows32.  */

#define __GTHREADS 1

#include <windows.h>
#include <errno.h>
#ifdef __MINGW32__
#include <_mingw.h>
#endif

#ifdef _LIBOBJC

/* Key structure for maintaining thread specific storage */
static DWORD	__gthread_objc_data_tls = (DWORD)-1;

/* Backend initialization functions */

/* Initialize the threads subsystem. */
int
__gthread_objc_init_thread_system(void)
{
  /* Initialize the thread storage key */
  if ((__gthread_objc_data_tls = TlsAlloc()) != (DWORD)-1)
    return 0;
  else
    return -1;
}

/* Close the threads subsystem. */
int
__gthread_objc_close_thread_system(void)
{
  if (__gthread_objc_data_tls != (DWORD)-1)
    TlsFree(__gthread_objc_data_tls);
  return 0;
}

/* Backend thread functions */

/* Create a new thread of execution. */
objc_thread_t
__gthread_objc_thread_detach(void (*func)(void *arg), void *arg)
{
  DWORD	thread_id = 0;
  HANDLE win32_handle;

  if (!(win32_handle = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)func,
                                   arg, 0, &thread_id)))
    thread_id = 0;
  
  return (objc_thread_t)thread_id;
}

/* Set the current thread's priority. */
int
__gthread_objc_thread_set_priority(int priority)
{
  int sys_priority = 0;

  switch (priority)
    {
    case OBJC_THREAD_INTERACTIVE_PRIORITY:
      sys_priority = THREAD_PRIORITY_NORMAL;
      break;
    default:
    case OBJC_THREAD_BACKGROUND_PRIORITY:
      sys_priority = THREAD_PRIORITY_BELOW_NORMAL;
      break;
    case OBJC_THREAD_LOW_PRIORITY:
      sys_priority = THREAD_PRIORITY_LOWEST;
      break;
    }

  /* Change priority */
  if (SetThreadPriority(GetCurrentThread(), sys_priority))
    return 0;
  else
    return -1;
}

/* Return the current thread's priority. */
int
__gthread_objc_thread_get_priority(void)
{
  int sys_priority;

  sys_priority = GetThreadPriority(GetCurrentThread());
  
  switch (sys_priority)
    {
    case THREAD_PRIORITY_HIGHEST:
    case THREAD_PRIORITY_TIME_CRITICAL:
    case THREAD_PRIORITY_ABOVE_NORMAL:
    case THREAD_PRIORITY_NORMAL:
      return OBJC_THREAD_INTERACTIVE_PRIORITY;

    default:
    case THREAD_PRIORITY_BELOW_NORMAL:
      return OBJC_THREAD_BACKGROUND_PRIORITY;
    
    case THREAD_PRIORITY_IDLE:
    case THREAD_PRIORITY_LOWEST:
      return OBJC_THREAD_LOW_PRIORITY;
    }

  /* Couldn't get priority. */
  return -1;
}

/* Yield our process time to another thread. */
void
__gthread_objc_thread_yield(void)
{
  Sleep(0);
}

/* Terminate the current thread. */
int
__gthread_objc_thread_exit(void)
{
  /* exit the thread */
  ExitThread(__gthread_objc_thread_exit_status);

  /* Failed if we reached here */
  return -1;
}

/* Returns an integer value which uniquely describes a thread. */
objc_thread_t
__gthread_objc_thread_id(void)
{
  return (objc_thread_t)GetCurrentThreadId();
}

/* Sets the thread's local storage pointer. */
int
__gthread_objc_thread_set_data(void *value)
{
  if (TlsSetValue(__gthread_objc_data_tls, value))
    return 0;
  else
    return -1;
}

/* Returns the thread's local storage pointer. */
void *
__gthread_objc_thread_get_data(void)
{
  DWORD lasterror;
  void *ptr;

  lasterror = GetLastError();

  ptr = TlsGetValue(__gthread_objc_data_tls);          /* Return thread data.      */

  SetLastError( lasterror );

  return ptr;
}

/* Backend mutex functions */

/* Allocate a mutex. */
int
__gthread_objc_mutex_allocate(objc_mutex_t mutex)
{
  if ((mutex->backend = (void *)CreateMutex(NULL, 0, NULL)) == NULL)
    return -1;
  else
    return 0;
}

/* Deallocate a mutex. */
int
__gthread_objc_mutex_deallocate(objc_mutex_t mutex)
{
  CloseHandle((HANDLE)(mutex->backend));
  return 0;
}

/* Grab a lock on a mutex. */
int
__gthread_objc_mutex_lock(objc_mutex_t mutex)
{
  int status;

  status = WaitForSingleObject((HANDLE)(mutex->backend), INFINITE);
  if (status != WAIT_OBJECT_0 && status != WAIT_ABANDONED)
    return -1;
  else
    return 0;
}

/* Try to grab a lock on a mutex. */
int
__gthread_objc_mutex_trylock(objc_mutex_t mutex)
{
  int status;

  status = WaitForSingleObject((HANDLE)(mutex->backend), 0);
  if (status != WAIT_OBJECT_0 && status != WAIT_ABANDONED)
    return -1;
  else
    return 0;
}

/* Unlock the mutex */
int
__gthread_objc_mutex_unlock(objc_mutex_t mutex)
{
  if (ReleaseMutex((HANDLE)(mutex->backend)) == 0)
    return -1;
  else
    return 0;
}

/* Backend condition mutex functions */

/* Allocate a condition. */
int
__gthread_objc_condition_allocate(objc_condition_t condition)
{
  /* Unimplemented. */
  return -1;
}

/* Deallocate a condition. */
int
__gthread_objc_condition_deallocate(objc_condition_t condition)
{
  /* Unimplemented. */
  return -1;
}

/* Wait on the condition */
int
__gthread_objc_condition_wait(objc_condition_t condition, objc_mutex_t mutex)
{
  /* Unimplemented. */
  return -1;
}

/* Wake up all threads waiting on this condition. */
int
__gthread_objc_condition_broadcast(objc_condition_t condition)
{
  /* Unimplemented. */
  return -1;
}

/* Wake up one thread waiting on this condition. */
int
__gthread_objc_condition_signal(objc_condition_t condition)
{
  /* Unimplemented. */
  return -1;
}

#else /* _LIBOBJC */

#ifdef __MINGW32__
#include <_mingw.h>
#endif

typedef DWORD __gthread_key_t;

typedef struct {
  int done;
  long started;
} __gthread_once_t;

typedef HANDLE __gthread_mutex_t;

#define __GTHREAD_ONCE_INIT {FALSE, -1}
#define __GTHREAD_MUTEX_INIT_FUNCTION __gthread_mutex_init_function

#if __MINGW32_MAJOR_VERSION >= 1 || \
  (__MINGW32_MAJOR_VERSION == 0 && __MINGW32_MINOR_VERSION > 2)
#define MINGW32_SUPPORTS_MT_EH 1
extern int __mingwthr_key_dtor PARAMS ((DWORD, void (*) (void *)));
/* Mingw runtime >= v0.3 provides a magic variable that is set to non-zero
   if -mthreads option was specified, or 0 otherwise. This is to get around 
   the lack of weak symbols in PE-COFF.  */
extern int _CRT_MT;
#endif

static inline int
__gthread_active_p (void)
{
#ifdef MINGW32_SUPPORTS_MT_EH
  return _CRT_MT;
#else
  return 1;
#endif
}

static inline int
__gthread_once (__gthread_once_t *once, void (*func) (void))
{
  if (! __gthread_active_p ())
    return -1;
  else if (once == NULL || func == NULL)
    return EINVAL;

  if (! once->done)
    {
      if (InterlockedIncrement (&(once->started)) == 0)
        {
	  (*func) ();
	  once->done = TRUE;
	}
      else
	{
	  /* Another thread is currently executing the code, so wait for it 
	     to finish; yield the CPU in the meantime.  If performance 
	     does become an issue, the solution is to use an Event that 
	     we wait on here (and set above), but that implies a place to 
	     create the event before this routine is called.  */ 
	  while (! once->done)
	    Sleep (0);
	}
    }
  
  return 0;
}

/* Windows32 thread local keys don't support destructors; this leads to
   leaks, especially in threaded applications making extensive use of 
   C++ EH. Mingw uses a thread-support DLL to work-around this problem.  */
static inline int
__gthread_key_create (__gthread_key_t *key, void (*dtor) (void *))
{
  int status = 0;
  DWORD tls_index = TlsAlloc ();
  if (tls_index != 0xFFFFFFFF)
    {
      *key = tls_index;
#ifdef MINGW32_SUPPORTS_MT_EH
      /* Mingw runtime will run the dtors in reverse order for each thread
         when the thread exits.  */
      status = __mingwthr_key_dtor (*key, dtor);
#endif
    }
  else
    status = (int) GetLastError ();
  return status;
}

/* Currently, this routine is called only for Mingw runtime, and if
   -mthreads option is chosen to link in the thread support DLL.  */ 
static inline int
__gthread_key_dtor (__gthread_key_t key, void *ptr)
{
  /* Nothing needed. */
  return 0;
}

static inline int
__gthread_key_delete (__gthread_key_t key)
{
  return (TlsFree (key) != 0) ? 0 : (int) GetLastError ();
}

static inline void *
__gthread_getspecific (__gthread_key_t key)
{
  DWORD lasterror;
  void *ptr;

  lasterror = GetLastError();

  ptr = TlsGetValue(key);

  SetLastError( lasterror );

  return ptr;
}

static inline int
__gthread_setspecific (__gthread_key_t key, const void *ptr)
{
  return (TlsSetValue (key, (void*) ptr) != 0) ? 0 : (int) GetLastError ();
}

static inline void
__gthread_mutex_init_function (__gthread_mutex_t *mutex)
{
  /* Create unnamed mutex with default security attr and no initial owner.  */ 
  *mutex = CreateMutex (NULL, 0, NULL);
}

static inline int
__gthread_mutex_lock (__gthread_mutex_t *mutex)
{
  int status = 0;

  if (__gthread_active_p ())
    {
      if (WaitForSingleObject (*mutex, INFINITE) == WAIT_OBJECT_0)
	status = 0;
      else
	status = 1;
    }
  return status;
}

static inline int
__gthread_mutex_trylock (__gthread_mutex_t *mutex)
{
  int status = 0;

  if (__gthread_active_p ())
    {
      if (WaitForSingleObject (*mutex, 0) == WAIT_OBJECT_0)
	status = 0;
      else
	status = 1;
    }
  return status;
}

static inline int
__gthread_mutex_unlock (__gthread_mutex_t *mutex)
{
  if (__gthread_active_p ())
    return (ReleaseMutex (*mutex) != 0) ? 0 : 1;
  else
    return 0;
}

#endif /* _LIBOBJC */

#endif /* not __gthr_win32_h */