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Diffstat (limited to 'WinCE-PORT')
| -rw-r--r-- | WinCE-PORT | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/WinCE-PORT b/WinCE-PORT new file mode 100644 index 0000000..746eaaf --- /dev/null +++ b/WinCE-PORT @@ -0,0 +1,209 @@ +Some interesting news: + +I have been able to port pthread-win32 to Windows-CE, +which uses a subset of the WIN32 API. + +Since we intend to keep using pthread-win32 for our +Commercial WinCE developments, I would be very interested +if WinCE support could be added to the main source tree +of pthread-win32. Also, I would like to be credited +for this port :-) + +Now, here is the story... + +The port was performed and tested on a Casio "Cassiopeia" +PalmSize PC, which runs a MIP processor. The OS in the +Casio is WinCE version 2.11, but I used VC++ 6.0 with +the WinCE SDK for version 2.01. + +I used pthread-win32 to port a heavily multithreaded +commercial application (real-time MPEG video player) +from Linux to WinCE. I consider the changes that +I have done to be quite well tested. + +Overall the modifications that we had to do are minor. + +The WinCE port were based on pthread-win32-snap-1999-05-30, +but I am certain that they can be integrated very easiely +to more recent versions of the source. + +I have attached the modified source code: +pthread-win32-snap-1999-05-30-WinCE. + +All the changes do not affect the code compiled on non-WinCE +environment, provided that the macros used for WinCE compilation +are not used, of course! + +Overall description of the WinCE port: +------------------------------------- + +Most of the changes had to be made in areas where +pthread-win32 was relying on some standard-C librairies +(e.g. _ftime, calloc, errno), which are not available +on WinCE. We have changed the code to use native Win32 +API instead (or in some cases we made wrappers). + +The Win32 Semaphores are not available, +so we had to re-implement Semaphores using mutexes +and events. + +Limitations / known problems of the WinCE port: +---------------------------------------------- + +Not all the semaphore routines have been ported +(semaphores are defined by Posix but are not part +pf pthread). I have just done enough to make +pthread routines (that rely internally on semaphores) +work, like signal conditions. + +I noticed that the Win32 threads work slightly +differently on WinCE. This may have some impact +on some tricky parts of pthread-win32, but I have +not really investigated. For example, on WinCE, +the process is killed if the main thread falls off +the bottom (or calls pthread_exit), regardless +of the existence of any other detached thread. +Microsoft manual indicates that this behavior is +deffirent from that of Windows Threads for other +Win32 platforms. + + +Detailed descriptions of the changes and rationals: + +------------------------------------ +- use a new macro NEED_ERRNO. + +If defined, the code in errno.c that defines a reentrant errno +is compiled, regardless of _MT and _REENTRANT. + +Rational: On WinCE, there is no support for <stdio.h>, <errno.h> or +any other standard C library, i.e. even if _MT or _REENTRANT +is defined, errno is not provided by any library. NEED_ERRNO +must be set to compile for WinCE. + +------------------------------------ +- In implement.h, change #include <semaphore.h> to #include "semaphore.h". + +Rational: semaphore.h is provided in pthread-win32 and should not +be searched in the systems standard include. would not compile. +This change does not seem to create problems on "classic" win32 +(e.g. win95). + +------------------------------------ +- use a new macro NEED_CALLOC. + +If defined, some code in misc.c will provide a replacement +for calloc, which is not available on Win32. + + +------------------------------------ +- use a new macro _PTHREAD_CREATETHREAD. + +If defined, implement.h defined the macro _beginthreadex +and _endthreadex, regardless of the value of __CYGWIN32__ +and __CYGWIN__. + +Rational: On WinCE, the wrappers _beginthreadex and _endthreadex +do not exist. The native Win32 routines must be used. + +------------------------------------ +- in misc.c: + +#ifdef UNDER_CE + /* DuplicateHandle does not exist on WinCE */ + self->threadH = GetCurrentThread(); +#else + if( !DuplicateHandle( + GetCurrentProcess(), + GetCurrentThread(), + GetCurrentProcess(), + &self->threadH, + 0, + FALSE, + DUPLICATE_SAME_ACCESS ) ) + { + free( self ); + return (NULL); + } +#endif + +Rational: On WinCE, DuplicateHandle does not exist. I could not understand +why DuplicateHandle must be used. It seems to me that getting the current +thread handle with GetCurrentThread() is sufficient, and it seems to work +perfectly fine, so maybe DuplicateHandle was just plain useless to begin with ? + +------------------------------------ +- In private.c, added some code at the beginning of _pthread_processInitialize +to detect the case of multiple calls to _pthread_processInitialize. + +Rational: In order to debug pthread-win32, it is easier to compile +it as a regular library (it is not possible to debug DLL's on winCE). +In that case, the application must call _pthread_processInitialize() +explicitely, to initialize pthread-win32. It is safer in this circumstance +to handle the case where _pthread_processInitialize() is called on +an already initialized library: + +int +_pthread_processInitialize (void) +{ + if (_pthread_processInitialized) { + /* + * ignore if already initialized. this is useful for + * programs that uses a non-dll pthread + * library. such programs must call _pthread_processInitialize() explicitely, + * since this initialization routine is automatically called only when + * the dll is loaded. + */ + return TRUE; + } + _pthread_processInitialized = TRUE; + [...] +} + +------------------------------------ +- in private.c, if macro NEED_FTIME is defined, add routines to +convert timespec_to_filetime and filetime_to_timespec, and modified +code that was using _ftime() to use Win32 API instead. + +Rational: _ftime is not available on WinCE. It is necessary to use +the native Win32 time API instead. + +Note: the routine timespec_to_filetime is provided as a convenience and a mean +to test that filetime_to_timespec works, but it is not used by the library. + +------------------------------------ +- in semaphore.c, if macro NEED_SEM is defined, add code for the routines +_increase_semaphore and _decrease_semaphore, and modify significantly +the implementation of the semaphores so that it does not use CreateSemaphore. + +Rational: CreateSemaphore is not available on WinCE. I had to re-implement +semaphores using mutexes and Events. + +Note: Only the semaphore routines that are used by pthread are implemented +(i.e. signal conditions rely on a subset of the semaphores routines, and +this subset works). Some other semaphore routines (e.g. sem_trywait) are +not yet supported on my WinCE port (and since I don't need them, I am not +planning to do anything about them). + +------------------------------------ +- in tsd.c, changed the code that defines TLS_OUT_OF_INDEXES + +/* TLS_OUT_OF_INDEXES not defined on WinCE */ +#ifndef TLS_OUT_OF_INDEXES +#define TLS_OUT_OF_INDEXES 0xffffffff +#endif + +Rational: TLS_OUT_OF_INDEXES is not defined in any standard include file +on WinCE. + +------------------------------------ +- added file need_errno.h + +Rational: On WinCE, there is no errno.h file. need_errno.h is just a +copy of windows version of errno.h, with minor modifications due to the fact +that some of the error codes are defined by the WinCE socket library. +In pthread.h, if NEED_ERRNO is defined, the file need_errno.h is +included (instead of <errno.h>). + + +-- eof |