Mercurial > sdl-ios-xcode
view src/thread/win32/SDL_syssem.c @ 968:4675910b0b7b
Date: Mon, 11 Oct 2004 15:17:27 +0300 (EEST)
From: Hannu Savolainen
Subject: Re: SDL uses obsolete OSS features
I did some work on getting OSS to work better with SDL. There have been
some problems with select which should be fixed now.
I'm having some problems in understanding what is the purpose of the
DSP_WaitAudio() routine. I added a return to the very beginning of this
routine and commendted out the define for USE_BLOCKING_WRITES. At least
lbreakout2 seems to work as well as earlier. The latencies are the same.
An ordinary blocking write does exactly the same thing than DSP_WaitAudio
does. So I would recommend using the USE_BLOCKING_WRITES approach and
removing everything from the DSP_WaitAudio routine. Also enabling
USE_BLOCKING_WRITES makes it possible to simplify DSP_PlayAudio() because
you don't need to handle the partial writes (the do-while loop).
Attached is a patch against SDL-1.2.7. After these changes SDL will use
OSS as it's designed to be used (make it as simple as possible). This code
should work with all OSS implementations because it uses only the very
fundamental features that have been there since the jurassic times.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Fri, 12 Nov 2004 21:39:04 +0000 |
parents | b8d311d90021 |
children | c9b51268668f |
line wrap: on
line source
/* SDL - Simple DirectMedia Layer Copyright (C) 1997-2004 Sam Lantinga This library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This library 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 Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with this library; if not, write to the Free Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Sam Lantinga slouken@libsdl.org */ #ifdef SAVE_RCSID static char rcsid = "@(#) $Id$"; #endif /* Semaphore functions using the Win32 API */ #include <stdio.h> #include <stdlib.h> #include <windows.h> #include "SDL_error.h" #include "SDL_thread.h" #if defined(_WIN32_WCE) && (_WIN32_WCE < 300) #include "win_ce_semaphore.h" #endif struct SDL_semaphore { #if defined(_WIN32_WCE) && (_WIN32_WCE < 300) SYNCHHANDLE id; #else HANDLE id; #endif Uint32 volatile count; }; /* Create a semaphore */ SDL_sem *SDL_CreateSemaphore(Uint32 initial_value) { SDL_sem *sem; /* Allocate sem memory */ sem = (SDL_sem *)malloc(sizeof(*sem)); if ( sem ) { /* Create the semaphore, with max value 32K */ #if defined(_WIN32_WCE) && (_WIN32_WCE < 300) sem->id = CreateSemaphoreCE(NULL, initial_value, 32*1024, NULL); #else sem->id = CreateSemaphore(NULL, initial_value, 32*1024, NULL); #endif sem->count = initial_value; if ( ! sem->id ) { SDL_SetError("Couldn't create semaphore"); free(sem); sem = NULL; } } else { SDL_OutOfMemory(); } return(sem); } /* Free the semaphore */ void SDL_DestroySemaphore(SDL_sem *sem) { if ( sem ) { if ( sem->id ) { #if defined(_WIN32_WCE) && (_WIN32_WCE < 300) CloseSynchHandle(sem->id); #else CloseHandle(sem->id); #endif sem->id = 0; } free(sem); } } int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout) { int retval; DWORD dwMilliseconds; if ( ! sem ) { SDL_SetError("Passed a NULL sem"); return -1; } if ( timeout == SDL_MUTEX_MAXWAIT ) { dwMilliseconds = INFINITE; } else { dwMilliseconds = (DWORD)timeout; } #if defined(_WIN32_WCE) && (_WIN32_WCE < 300) switch (WaitForSemaphoreCE(sem->id, dwMilliseconds)) { #else switch (WaitForSingleObject(sem->id, dwMilliseconds)) { #endif case WAIT_OBJECT_0: --sem->count; retval = 0; break; case WAIT_TIMEOUT: retval = SDL_MUTEX_TIMEDOUT; break; default: SDL_SetError("WaitForSingleObject() failed"); retval = -1; break; } return retval; } int SDL_SemTryWait(SDL_sem *sem) { return SDL_SemWaitTimeout(sem, 0); } int SDL_SemWait(SDL_sem *sem) { return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT); } /* Returns the current count of the semaphore */ Uint32 SDL_SemValue(SDL_sem *sem) { if ( ! sem ) { SDL_SetError("Passed a NULL sem"); return 0; } return sem->count; } int SDL_SemPost(SDL_sem *sem) { if ( ! sem ) { SDL_SetError("Passed a NULL sem"); return -1; } /* Increase the counter in the first place, because * after a successful release the semaphore may * immediately get destroyed by another thread which * is waiting for this semaphore. */ ++sem->count; #if defined(_WIN32_WCE) && (_WIN32_WCE < 300) if ( ReleaseSemaphoreCE(sem->id, 1, NULL) == FALSE ) { #else if ( ReleaseSemaphore(sem->id, 1, NULL) == FALSE ) { #endif --sem->count; /* restore */ SDL_SetError("ReleaseSemaphore() failed"); return -1; } return 0; }