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/* GNU Objective C Runtime Thread Interface

   Copyright (C) 1996, 1997 Free Software Foundation, Inc.

   Contributed by Galen C. Hunt (gchunt@cs.rochester.edu)

This file is part of GCC.

GCC 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.

GCC 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

GCC; see the file COPYING.  If not, write to the Free Software

Foundation, 51 Franklin Street, Fifth Floor,

Boston, MA 02110-1301, USA.  */

/* As a special exception, if you link this library with files compiled with

   GCC to produce an executable, this does not 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.  */

#include <stdlib.h>

#include "objc/runtime.h"

/* Global exit status. */

int __objc_thread_exit_status = 0;

/* Flag which lets us know if we ever became multi threaded */

int __objc_is_multi_threaded = 0;

/* The hook function called when the runtime becomes multi threaded */

objc_thread_callback _objc_became_multi_threaded = NULL;

/*

  Use this to set the hook function that will be called when the

  runtime initially becomes multi threaded.

  The hook function is only called once, meaning only when the

  2nd thread is spawned, not for each and every thread.

  It returns the previous hook function or NULL if there is none.

  A program outside of the runtime could set this to some function so

  it can be informed; for example, the GNUstep Base Library sets it

  so it can implement the NSBecomingMultiThreaded notification.

  */

objc_thread_callback objc_set_thread_callback (objc_thread_callback func)

{

  objc_thread_callback temp = _objc_became_multi_threaded;

  _objc_became_multi_threaded = func;

  return temp;

}

/*

  Private functions

  These functions are utilized by the frontend, but they are not

  considered part of the public interface.

  */

/*

  First function called in a thread, starts everything else.

  This function is passed to the backend by objc_thread_detach

  as the starting function for a new thread.

 */

struct __objc_thread_start_state

{

  SEL selector;

  id object;

  id argument;

};

static void __attribute__((noreturn))

__objc_thread_detach_function (struct __objc_thread_start_state *istate)

{

  /* Valid state? */

  if (istate) {

    id (*imp) (id, SEL, id);

    SEL selector = istate->selector;

    id object   = istate->object;

    id argument = istate->argument;

    /* Don't need anymore so free it */

    objc_free (istate);

    /* Clear out the thread local storage */

    objc_thread_set_data (NULL);

    /* Check to see if we just became multi threaded */

    if (! __objc_is_multi_threaded)

      {

        __objc_is_multi_threaded = 1;

        /* Call the hook function */

        if (_objc_became_multi_threaded != NULL)

          (*_objc_became_multi_threaded) ();

      }

    /* Call the method */

    if ((imp = (id (*) (id, SEL, id))objc_msg_lookup (object, selector)))

        (*imp) (object, selector, argument);

    else

      objc_error (object, OBJC_ERR_UNIMPLEMENTED,

                  "objc_thread_detach called with bad selector.\n");

  }

  else

    objc_error (nil, OBJC_ERR_BAD_STATE,

                "objc_thread_detach called with NULL state.\n");

  /* Exit the thread */

  objc_thread_exit ();

}

/*

  Frontend functions

  These functions constitute the public interface to the Objective-C thread

  and mutex functionality.

  */

/* Frontend thread functions */

/*

  Detach a new thread of execution and return its id.  Returns NULL if fails.

  Thread is started by sending message with selector to object.  Message

  takes a single argument.

  */

objc_thread_t

objc_thread_detach (SEL selector, id object, id argument)

{

  struct __objc_thread_start_state *istate;

  objc_thread_t        thread_id = NULL;

  /* Allocate the state structure */

  if (! (istate = (struct __objc_thread_start_state *)

         objc_malloc (sizeof (*istate))))

    return NULL;

  /* Initialize the state structure */

  istate->selector = selector;

  istate->object = object;

  istate->argument = argument;

  /* lock access */

  objc_mutex_lock (__objc_runtime_mutex);

  /* Call the backend to spawn the thread */

  if ((thread_id = __objc_thread_detach ((void *)__objc_thread_detach_function,

                                         istate)) == NULL)

    {

      /* failed! */

      objc_mutex_unlock (__objc_runtime_mutex);

      objc_free (istate);

      return NULL;

    }

  /* Increment our thread counter */

  __objc_runtime_threads_alive++;

  objc_mutex_unlock (__objc_runtime_mutex);

  return thread_id;

}

/* Set the current thread's priority. */

int

objc_thread_set_priority (int priority)

{

  /* Call the backend */

  return __objc_thread_set_priority (priority);

}

/* Return the current thread's priority. */

int

objc_thread_get_priority (void)

{

  /* Call the backend */

  return __objc_thread_get_priority ();

}

/*

  Yield our process time to another thread.  Any BUSY waiting that is done

  by a thread should use this function to make sure that other threads can

  make progress even on a lazy uniprocessor system.

  */

void

objc_thread_yield (void)

{

  /* Call the backend */

  __objc_thread_yield ();

}

/*

  Terminate the current tread.  Doesn't return.

  Actually, if it failed returns -1.

  */

int

objc_thread_exit (void)

{

  /* Decrement our counter of the number of threads alive */

  objc_mutex_lock (__objc_runtime_mutex);

  __objc_runtime_threads_alive--;

  objc_mutex_unlock (__objc_runtime_mutex);

  /* Call the backend to terminate the thread */

  return __objc_thread_exit ();

}

/*

  Returns an integer value which uniquely describes a thread.  Must not be

  NULL which is reserved as a marker for "no thread".

  */

objc_thread_t

objc_thread_id (void)

{

  /* Call the backend */

  return __objc_thread_id ();

}

/*

  Sets the thread's local storage pointer.

  Returns 0 if successful or -1 if failed.

  */

int

objc_thread_set_data (void *value)

{

  /* Call the backend */

  return __objc_thread_set_data (value);

}

/*

  Returns the thread's local storage pointer.  Returns NULL on failure.

  */

void *

objc_thread_get_data (void)

{

  /* Call the backend */

  return __objc_thread_get_data ();

}

/* Frontend mutex functions */

/*

  Allocate a mutex.  Return the mutex pointer if successful or NULL if the

  allocation failed for any reason.

  */

objc_mutex_t

objc_mutex_allocate (void)

{

  objc_mutex_t mutex;

  /* Allocate the mutex structure */

  if (! (mutex = (objc_mutex_t)objc_malloc (sizeof (struct objc_mutex))))

    return NULL;

  /* Call backend to create the mutex */

  if (__objc_mutex_allocate (mutex))

    {

      /* failed! */

      objc_free (mutex);

      return NULL;

    }

  /* Initialize mutex */

  mutex->owner = NULL;

  mutex->depth = 0;

  return mutex;

}

/*

  Deallocate a mutex.  Note that this includes an implicit mutex_lock to

  insure that no one else is using the lock.  It is legal to deallocate

  a lock if we have a lock on it, but illegal to deallocate a lock held

  by anyone else.

  Returns the number of locks on the thread.  (1 for deallocate).

  */

int

objc_mutex_deallocate (objc_mutex_t mutex)

{

  int depth;

  /* Valid mutex? */

  if (! mutex)

    return -1;

  /* Acquire lock on mutex */

  depth = objc_mutex_lock (mutex);

  /* Call backend to destroy mutex */

  if (__objc_mutex_deallocate (mutex))

    return -1;

  /* Free the mutex structure */

  objc_free (mutex);

  /* Return last depth */

  return depth;

}

/*

  Grab a lock on a mutex.  If this thread already has a lock on this mutex

  then we increment the lock count.  If another thread has a lock on the

  mutex we block and wait for the thread to release the lock.

  Returns the lock count on the mutex held by this thread.

  */

int

objc_mutex_lock (objc_mutex_t mutex)

{

  objc_thread_t thread_id;

  int status;

  /* Valid mutex? */

  if (! mutex)

    return -1;

  /* If we already own the lock then increment depth */

  thread_id = __objc_thread_id ();

  if (mutex->owner == thread_id)

    return ++mutex->depth;

  /* Call the backend to lock the mutex */

  status = __objc_mutex_lock (mutex);

  /* Failed? */

  if (status)

    return status;

  /* Successfully locked the thread */

  mutex->owner = thread_id;

  return mutex->depth = 1;

}

/*

  Try to grab a lock on a mutex.  If this thread already has a lock on

  this mutex then we increment the lock count and return it.  If another

  thread has a lock on the mutex returns -1.

  */

int

objc_mutex_trylock (objc_mutex_t mutex)

{

  objc_thread_t thread_id;

  int status;

  /* Valid mutex? */

  if (! mutex)

    return -1;

  /* If we already own the lock then increment depth */

  thread_id = __objc_thread_id ();

  if (mutex->owner == thread_id)

    return ++mutex->depth;

  /* Call the backend to try to lock the mutex */

  status = __objc_mutex_trylock (mutex);

  /* Failed? */

  if (status)

    return status;

  /* Successfully locked the thread */

  mutex->owner = thread_id;

  return mutex->depth = 1;

}

/*

  Unlocks the mutex by one level.

  Decrements the lock count on this mutex by one.

  If the lock count reaches zero, release the lock on the mutex.

  Returns the lock count on the mutex.

  It is an error to attempt to unlock a mutex which this thread

  doesn't hold in which case return -1 and the mutex is unaffected.

  */

int

objc_mutex_unlock (objc_mutex_t mutex)

{

  objc_thread_t thread_id;

  int status;

  /* Valid mutex? */

  if (! mutex)

    return -1;

  /* If another thread owns the lock then abort */

  thread_id = __objc_thread_id ();

  if (mutex->owner != thread_id)

    return -1;

  /* Decrement depth and return */

  if (mutex->depth > 1)

    return --mutex->depth;

  /* Depth down to zero so we are no longer the owner */

  mutex->depth = 0;

  mutex->owner = NULL;

  /* Have the backend unlock the mutex */

  status = __objc_mutex_unlock (mutex);

  /* Failed? */

  if (status)

    return status;

  return 0;

}

/* Frontend condition mutex functions */

/*

  Allocate a condition.  Return the condition pointer if successful or NULL

  if the allocation failed for any reason.

  */

objc_condition_t

objc_condition_allocate (void)

{

  objc_condition_t condition;

  /* Allocate the condition mutex structure */

  if (! (condition =

         (objc_condition_t) objc_malloc (sizeof (struct objc_condition))))

    return NULL;

  /* Call the backend to create the condition mutex */

  if (__objc_condition_allocate (condition))

    {

      /* failed! */

      objc_free (condition);

      return NULL;

    }

  /* Success! */

  return condition;

}

/*

  Deallocate a condition. Note that this includes an implicit

  condition_broadcast to insure that waiting threads have the opportunity

  to wake.  It is legal to dealloc a condition only if no other

  thread is/will be using it. Here we do NOT check for other threads

  waiting but just wake them up.

  */

int

objc_condition_deallocate (objc_condition_t condition)

{

  /* Broadcast the condition */

  if (objc_condition_broadcast (condition))

    return -1;

  /* Call the backend to destroy */

  if (__objc_condition_deallocate (condition))

    return -1;

  /* Free the condition mutex structure */

  objc_free (condition);

  return 0;

}

/*

  Wait on the condition unlocking the mutex until objc_condition_signal ()

  or objc_condition_broadcast () are called for the same condition. The

  given mutex *must* have the depth set to 1 so that it can be unlocked

  here, so that someone else can lock it and signal/broadcast the condition.

  The mutex is used to lock access to the shared data that make up the

  "condition" predicate.

  */

int

objc_condition_wait (objc_condition_t condition, objc_mutex_t mutex)

{

  objc_thread_t thread_id;

  /* Valid arguments? */

  if (! mutex || ! condition)

    return -1;

  /* Make sure we are owner of mutex */

  thread_id = __objc_thread_id ();

  if (mutex->owner != thread_id)

    return -1;

  /* Cannot be locked more than once */

  if (mutex->depth > 1)

    return -1;

  /* Virtually unlock the mutex */

  mutex->depth = 0;

  mutex->owner = (objc_thread_t)NULL;

  /* Call the backend to wait */

  __objc_condition_wait (condition, mutex);

  /* Make ourselves owner of the mutex */

  mutex->owner = thread_id;

  mutex->depth = 1;

  return 0;

}

/*

  Wake up all threads waiting on this condition. It is recommended that

  the called would lock the same mutex as the threads in objc_condition_wait

  before changing the "condition predicate" and make this call and unlock it

  right away after this call.

  */

int

objc_condition_broadcast (objc_condition_t condition)

{

  /* Valid condition mutex? */

  if (! condition)

    return -1;

  return __objc_condition_broadcast (condition);

}

/*

  Wake up one thread waiting on this condition. It is recommended that

  the called would lock the same mutex as the threads in objc_condition_wait

  before changing the "condition predicate" and make this call and unlock it

  right away after this call.

  */

int

objc_condition_signal (objc_condition_t condition)

{

  /* Valid condition mutex? */

  if (! condition)

    return -1;

  return __objc_condition_signal (condition);

}

/* Make the objc thread system aware that a thread which is managed

   (started, stopped) by external code could access objc facilities

   from now on.  This is used when you are interfacing with some

   external non-objc-based environment/system - you must call

   objc_thread_add () before an alien thread makes any calls to

   Objective-C.  Do not cause the _objc_became_multi_threaded hook to

   be executed. */

void

objc_thread_add (void)

{

  objc_mutex_lock (__objc_runtime_mutex);

  __objc_is_multi_threaded = 1;

  __objc_runtime_threads_alive++;

  objc_mutex_unlock (__objc_runtime_mutex);

}

/* Make the objc thread system aware that a thread managed (started,

   stopped) by some external code will no longer access objc and thus

   can be forgotten by the objc thread system.  Call

   objc_thread_remove () when your alien thread is done with making

   calls to Objective-C. */

void

objc_thread_remove (void)

{

  objc_mutex_lock (__objc_runtime_mutex);

  __objc_runtime_threads_alive--;

  objc_mutex_unlock (__objc_runtime_mutex);

}

/* End of File */