semaphore.c

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/*
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%        SS     E      MM MM  A   A  P   P  H   H  O   O  R   R  E            %
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%                        WizardCore Semaphore Methods                         %
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%                              Software Design                                %
%                             William Radcliffe                               %
%                                John Cristy                                  %
%                                 June 2000                                   %
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%  Copyright 1999-2010 ImageMagick Studio LLC, a non-profit organization      %
%  dedicated to making software imaging solutions freely available.           %
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%  You may not use this file except in compliance with the License.  You may  %
%  obtain a copy of the License at                                            %
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%    http://www.wizards-toolkit.org/script/license.php                        %
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%  Unless required by applicable law or agreed to in writing, software        %
%  distributed under the License is distributed on an "AS IS" BASIS,          %
%  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   %
%  See the License for the specific language governing permissions and        %
%  limitations under the License.                                             %
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*/

/*
  Include declarations.
*/
#include "wizard/studio.h"
#include "wizard/exception.h"
#include "wizard/exception-private.h"
#include "wizard/memory_.h"
#include "wizard/semaphore.h"
#include "wizard/semaphore-private.h"
#include "wizard/string_.h"
#include "wizard/thread_.h"
#include "wizard/thread-private.h"

/*
  Struct declaractions.
*/
struct SemaphoreInfo
{
  WizardMutexType
    mutex;

  WizardThreadType
    id;

  ssize_t
    reference_count;

  size_t
    signature;
};

/*
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%  AcquireSemaphoreInfo() acquires a semaphore.
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%  The format of the AcquireSemaphoreInfo method is:
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%      void AcquireSemaphoreInfo(SemaphoreInfo **semaphore_info)
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%  A description of each parameter follows:
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%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
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*/
WizardExport void AcquireSemaphoreInfo(SemaphoreInfo **semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo **) NULL);
  if (*semaphore_info == (SemaphoreInfo *) NULL)
    {
      LockWizardMutex();
      if (*semaphore_info == (SemaphoreInfo *) NULL)
        *semaphore_info=AllocateSemaphoreInfo();
      UnlockWizardMutex();
    }
}

/*
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%  AllocateSemaphoreInfo() initializes the SemaphoreInfo structure.
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%  The format of the AllocateSemaphoreInfo method is:
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%      SemaphoreInfo *AllocateSemaphoreInfo(void)
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*/
WizardExport SemaphoreInfo *AllocateSemaphoreInfo(void)
{
  SemaphoreInfo
    *semaphore_info;

  /*
    Allocate semaphore.
  */
  semaphore_info=(SemaphoreInfo *) AcquireAlignedMemory(1,
    sizeof(SemaphoreInfo));
  if (semaphore_info == (SemaphoreInfo *) NULL)
    ThrowFatalException(ResourceFatalError,"memory allocation failed `%s'");
  (void) ResetWizardMemory(semaphore_info,0,sizeof(SemaphoreInfo));
  /*
    Initialize the semaphore.
  */
#if defined(WIZARDSTOOLKIT_HAVE_PTHREAD)
  {
    int
      status;

    pthread_mutexattr_t
      mutex_info;

    status=pthread_mutexattr_init(&mutex_info);
    if (status != 0)
      {
        errno=status;
        ThrowFatalException(ResourceFatalError,
          "unable to instantiate semaphore `%s'");
      }
    status=pthread_mutex_init(&semaphore_info->mutex,&mutex_info);
    if (status != 0)
      {
        errno=status;
        ThrowFatalException(ResourceFatalError,
          "unable to instantiate semaphore `%s'");
      }
    status=pthread_mutexattr_destroy(&mutex_info);
    if (status != 0)
      {
        errno=status;
        ThrowFatalException(ResourceFatalError,
          "unable to instantiate semaphore `%s'");
      }
  }
#elif defined(WIZARDSTOOLKIT_HAVE_WINTHREADS)
  InitializeCriticalSection(&semaphore_info->mutex);
#endif
  semaphore_info->id=GetWizardThreadId();
  semaphore_info->reference_count=0;
  semaphore_info->signature=WizardSignature;
  return(semaphore_info);
}

/*
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%  DestroySemaphoreInfo() destroys a semaphore.
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%  The format of the DestroySemaphoreInfo method is:
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%      void DestroySemaphoreInfo(SemaphoreInfo **semaphore_info)
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%  A description of each parameter follows:
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%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
WizardExport void DestroySemaphoreInfo(SemaphoreInfo **semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo **) NULL);
  assert((*semaphore_info) != (SemaphoreInfo *) NULL);
  assert((*semaphore_info)->signature == WizardSignature);
  LockWizardMutex();
#if defined(WIZARDSTOOLKIT_HAVE_PTHREAD)
  {
    int
      status;

    status=pthread_mutex_destroy(&(*semaphore_info)->mutex);
    if (status != 0)
      {
        errno=status;
        ThrowFatalException(ResourceFatalError,
          "unable to destroy semaphore `%s'");
      }
  }
#elif defined(WIZARDSTOOLKIT_HAVE_WINTHREADS)
  DeleteCriticalSection(&(*semaphore_info)->mutex);
#endif
  (*semaphore_info)->signature=(~WizardSignature);
  *semaphore_info=(SemaphoreInfo *) RelinquishAlignedMemory(*semaphore_info);
  UnlockWizardMutex();
}

/*
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%   L o c k S e m a p h o r e I n f o                                         %
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%  LockSemaphoreInfo() locks a semaphore.
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%  The format of the LockSemaphoreInfo method is:
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%      void LockSemaphoreInfo(SemaphoreInfo *semaphore_info)
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%  A description of each parameter follows:
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%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
WizardExport void LockSemaphoreInfo(SemaphoreInfo *semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo *) NULL);
  assert(semaphore_info->signature == WizardSignature);
#if defined(WIZARDSTOOLKIT_HAVE_PTHREAD)
  {
    int
      status;

    status=pthread_mutex_lock(&semaphore_info->mutex);
    if (status != 0)
      {
        errno=status;
        ThrowFatalException(ResourceFatalError,
          "unable to lock semaphore `%s'");
      }
  }
#elif defined(WIZARDSTOOLKIT_HAVE_WINTHREADS)
  EnterCriticalSection(&semaphore_info->mutex);
#endif
#if defined(WIZARDSTOOLKIT_DEBUG)
  if ((semaphore_info->reference_count > 0) &&
      (IsWizardThreadEqual(semaphore_info->id) != WizardFalse))
    {
      (void) fprintf(stderr,"Warning: unexpected recursive lock!\n");
      (void) fflush(stderr);
    }
#endif
  semaphore_info->id=GetWizardThreadId();
  semaphore_info->reference_count++;
}

/*
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%  RelinquishSemaphoreInfo() relinquishes a semaphore.
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%  The format of the RelinquishSemaphoreInfo method is:
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%      RelinquishSemaphoreInfo(SemaphoreInfo *semaphore_info)
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%  A description of each parameter follows:
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%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
WizardExport void RelinquishSemaphoreInfo(SemaphoreInfo *semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo *) NULL);
  assert(semaphore_info->signature == WizardSignature);
  UnlockSemaphoreInfo(semaphore_info);
}

/*
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%  SemaphoreComponentGenesis() instantiates the semaphore component.
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%  The format of the SemaphoreComponentGenesis method is:
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%      WizardBooleanType SemaphoreComponentGenesis(void)
%
*/
WizardExport WizardBooleanType SemaphoreComponentGenesis(void)
{
  LockWizardMutex();
  UnlockWizardMutex();
  return(WizardTrue);
}

/*
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%   S e m a p h o r e C o m p o n e n t T e r m i n u s                       %
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%  SemaphoreComponentTerminus() destroys the semaphore environment.
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%  The format of the SemaphoreComponentTerminus method is:
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%      SemaphoreComponentTerminus(void)
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*/
WizardExport void SemaphoreComponentTerminus(void)
{
}

/*
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%  UnlockSemaphoreInfo() unlocks a semaphore.
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%  The format of the UnlockSemaphoreInfo method is:
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%      void UnlockSemaphoreInfo(SemaphoreInfo *semaphore_info)
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%  A description of each parameter follows:
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%    o semaphore_info: Specifies a pointer to an SemaphoreInfo structure.
%
*/
WizardExport void UnlockSemaphoreInfo(SemaphoreInfo *semaphore_info)
{
  assert(semaphore_info != (SemaphoreInfo *) NULL);
  assert(semaphore_info->signature == WizardSignature); 
#if defined(WIZARDSTOOLKIT_DEBUG)
  assert(IsWizardThreadEqual(semaphore_info->id) != WizardFalse);
  if (semaphore_info->reference_count == 0)
    {
      (void) fprintf(stderr,"Warning: semaphore lock already unlocked!\n");
      (void) fflush(stderr);
      return;
    }
  semaphore_info->reference_count--;
#endif
#if defined(WIZARDSTOOLKIT_HAVE_PTHREAD)
  {
    int
      status;

    status=pthread_mutex_unlock(&semaphore_info->mutex);
    if (status != 0)
      {
        errno=status;
        ThrowFatalException(ResourceFatalError,
          "unable to unlock semaphore `%s'");
      }
  }
#elif defined(WIZARDSTOOLKIT_HAVE_WINTHREADS)
  LeaveCriticalSection(&semaphore_info->mutex);
#endif
}