src/thread/os2/SDL_syssem.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "../../SDL_internal.h"

#if SDL_THREAD_OS2

/* An implementation of semaphores for OS/2 */

#include "SDL_thread.h"
#include "../../core/os2/SDL_os2.h"

#define INCL_DOSSEMAPHORES
#define INCL_DOSERRORS
#define INCL_DOSMISC
#include <os2.h>

struct SDL_semaphore {
  HEV        hEv;
  HMTX       hMtx;
  ULONG      cPost;
};


SDL_sem *
SDL_CreateSemaphore(Uint32 initial_value)
{
  ULONG      ulRC;
  SDL_sem    *pSDLSem = SDL_malloc( sizeof(SDL_sem) );

  if ( pSDLSem == NULL )
  {
    SDL_OutOfMemory();
    return NULL;
  }

  ulRC = DosCreateEventSem( NULL, &pSDLSem->hEv, DCE_AUTORESET, FALSE );
  if ( ulRC != NO_ERROR )
  {
    debug( "DosCreateEventSem(), rc = %u", ulRC );
    SDL_free( pSDLSem );
    return NULL;
  }

  ulRC = DosCreateMutexSem( NULL, &pSDLSem->hMtx, 0, FALSE );
  if ( ulRC != NO_ERROR )
  {
    debug( "DosCreateMutexSem(), rc = %u", ulRC );
    DosCloseEventSem( pSDLSem->hEv );
    SDL_free( pSDLSem );
    return NULL;
  }

  pSDLSem->cPost = initial_value;

  return pSDLSem;
}

void
SDL_DestroySemaphore(SDL_sem * sem)
{
  if ( sem == NULL )
    return;

  DosCloseMutexSem( sem->hMtx );
  DosCloseEventSem( sem->hEv );
  SDL_free( sem );
}

int
SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
{
  ULONG      ulRC;
  ULONG      ulStartTime, ulCurTime;
  ULONG      ulTimeout;
  ULONG      cPost;

  if ( sem == NULL )
    return SDL_SetError( "Passed a NULL sem" );

  if ( timeout != SEM_INDEFINITE_WAIT )
    DosQuerySysInfo( QSV_MS_COUNT, QSV_MS_COUNT, &ulStartTime, sizeof(ULONG) );

  while( TRUE )
  {
    ulRC = DosRequestMutexSem( sem->hMtx, SEM_INDEFINITE_WAIT );
    if ( ulRC != NO_ERROR )
      return SDL_SetError( "DosRequestMutexSem() failed, rc = %u", ulRC );
  
    cPost = sem->cPost;
    if ( sem->cPost != 0 )
      sem->cPost--;

    DosReleaseMutexSem( sem->hMtx );

    if ( cPost != 0 )
      break;

    if ( timeout == SEM_INDEFINITE_WAIT )
      ulTimeout = SEM_INDEFINITE_WAIT;
    else
    {
      DosQuerySysInfo( QSV_MS_COUNT, QSV_MS_COUNT, &ulCurTime, sizeof(ULONG) );
      ulTimeout = ulCurTime - ulStartTime;
      if ( timeout < ulTimeout )
        return SDL_MUTEX_TIMEDOUT;
      ulTimeout = timeout - ulTimeout;
    }

    ulRC = DosWaitEventSem( sem->hEv, ulTimeout );
    if ( ulRC == ERROR_TIMEOUT )
      return SDL_MUTEX_TIMEDOUT;

    if ( ulRC != NO_ERROR )
      return SDL_SetError( "DosWaitEventSem() failed, rc = %u", ulRC );
  }

  return 0;
}

int
SDL_SemTryWait(SDL_sem * sem)
{
  return SDL_SemWaitTimeout( sem, 0 );
}

int
SDL_SemWait(SDL_sem * sem)
{
  return SDL_SemWaitTimeout( sem, SDL_MUTEX_MAXWAIT );
}

Uint32
SDL_SemValue(SDL_sem * sem)
{
  ULONG      ulRC;

  if ( sem == NULL )
  {
    SDL_SetError( "Passed a NULL sem" );
    return 0;
  }

  ulRC = DosRequestMutexSem( sem->hMtx, SEM_INDEFINITE_WAIT );
  if ( ulRC != NO_ERROR )
    return SDL_SetError( "DosRequestMutexSem() failed, rc = %u", ulRC );

  ulRC = sem->cPost;
  DosReleaseMutexSem( sem->hMtx );

  return ulRC;
}

int
SDL_SemPost(SDL_sem * sem)
{
  ULONG      ulRC;

  if ( sem == NULL )
    return SDL_SetError( "Passed a NULL sem" );

  ulRC = DosRequestMutexSem( sem->hMtx, SEM_INDEFINITE_WAIT );
  if ( ulRC != NO_ERROR )
    return SDL_SetError( "DosRequestMutexSem() failed, rc = %u", ulRC );

  sem->cPost++;

  ulRC = DosPostEventSem( sem->hEv );
  if ( ( ulRC != NO_ERROR ) && ( ulRC != ERROR_ALREADY_POSTED ) )
    debug( "DosPostEventSem() failed, rc = %u", ulRC );

  DosReleaseMutexSem( sem->hMtx );

  return 0;
}

#endif /* SDL_THREAD_OS2 */

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