222 lines
7.6 KiB
Text
222 lines
7.6 KiB
Text
NOTE: The comments in this file relate to the original WinCE port
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done by Tristan Savatier. The semaphore routines have been
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completely rewritten since (2005-04-25), having been progressively
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broken more and more by changes to the library. All of the semaphore
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routines implemented for W9x/WNT/2000 and up should now also work for
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WinCE. Also, pthread_mutex_timedlock should now work.
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Additional WinCE updates have been applied since this as well. Check the
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ChangeLog file and search for WINCE for example. (2007-01-07)
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[RPJ]
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----
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Some interesting news:
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I have been able to port pthread-win32 to Windows-CE,
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which uses a subset of the WIN32 API.
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Since we intend to keep using pthread-win32 for our
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Commercial WinCE developments, I would be very interested
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if WinCE support could be added to the main source tree
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of pthread-win32. Also, I would like to be credited
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for this port :-)
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Now, here is the story...
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The port was performed and tested on a Casio "Cassiopeia"
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PalmSize PC, which runs a MIP processor. The OS in the
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Casio is WinCE version 2.11, but I used VC++ 6.0 with
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the WinCE SDK for version 2.01.
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I used pthread-win32 to port a heavily multithreaded
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commercial application (real-time MPEG video player)
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from Linux to WinCE. I consider the changes that
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I have done to be quite well tested.
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Overall the modifications that we had to do are minor.
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The WinCE port were based on pthread-win32-snap-1999-05-30,
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but I am certain that they can be integrated very easiely
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to more recent versions of the source.
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I have attached the modified source code:
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pthread-win32-snap-1999-05-30-WinCE.
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All the changes do not affect the code compiled on non-WinCE
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environment, provided that the macros used for WinCE compilation
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are not used, of course!
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Overall description of the WinCE port:
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-------------------------------------
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Most of the changes had to be made in areas where
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pthread-win32 was relying on some standard-C librairies
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(e.g. _ftime, calloc, errno), which are not available
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on WinCE. We have changed the code to use native Win32
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API instead (or in some cases we made wrappers).
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The Win32 Semaphores are not available,
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so we had to re-implement Semaphores using mutexes
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and events.
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Limitations / known problems of the WinCE port:
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----------------------------------------------
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Not all the semaphore routines have been ported
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(semaphores are defined by Posix but are not part
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pf pthread). I have just done enough to make
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pthread routines (that rely internally on semaphores)
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work, like signal conditions.
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I noticed that the Win32 threads work slightly
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differently on WinCE. This may have some impact
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on some tricky parts of pthread-win32, but I have
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not really investigated. For example, on WinCE,
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the process is killed if the main thread falls off
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the bottom (or calls pthread_exit), regardless
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of the existence of any other detached thread.
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Microsoft manual indicates that this behavior is
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deffirent from that of Windows Threads for other
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Win32 platforms.
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Detailed descriptions of the changes and rationals:
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------------------------------------
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- use a new macro NEED_ERRNO.
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If defined, the code in errno.c that defines a reentrant errno
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is compiled, regardless of _MT and _REENTRANT.
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Rational: On WinCE, there is no support for <stdio.h>, <errno.h> or
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any other standard C library, i.e. even if _MT or _REENTRANT
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is defined, errno is not provided by any library. NEED_ERRNO
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must be set to compile for WinCE.
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------------------------------------
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- In implement.h, change #include <semaphore.h> to #include "semaphore.h".
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Rational: semaphore.h is provided in pthread-win32 and should not
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be searched in the systems standard include. would not compile.
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This change does not seem to create problems on "classic" win32
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(e.g. win95).
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------------------------------------
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- use a new macro NEED_CALLOC.
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If defined, some code in misc.c will provide a replacement
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for calloc, which is not available on Win32.
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------------------------------------
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- use a new macro NEED_CREATETHREAD.
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If defined, implement.h defines the macro _beginthreadex
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and _endthreadex.
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Rational: On WinCE, the wrappers _beginthreadex and _endthreadex
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do not exist. The native Win32 routines must be used.
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------------------------------------
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- in misc.c:
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#ifdef NEED_DUPLICATEHANDLE
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/* DuplicateHandle does not exist on WinCE */
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self->threadH = GetCurrentThread();
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#else
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if( !DuplicateHandle(
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GetCurrentProcess(),
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GetCurrentThread(),
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GetCurrentProcess(),
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&self->threadH,
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0,
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FALSE,
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DUPLICATE_SAME_ACCESS ) )
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{
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free( self );
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return (NULL);
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}
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#endif
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Rational: On WinCE, DuplicateHandle does not exist. I could not understand
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why DuplicateHandle must be used. It seems to me that getting the current
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thread handle with GetCurrentThread() is sufficient, and it seems to work
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perfectly fine, so maybe DuplicateHandle was just plain useless to begin with ?
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------------------------------------
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- In private.c, added some code at the beginning of ptw32_processInitialize
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to detect the case of multiple calls to ptw32_processInitialize.
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Rational: In order to debug pthread-win32, it is easier to compile
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it as a regular library (it is not possible to debug DLL's on winCE).
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In that case, the application must call ptw32_rocessInitialize()
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explicitely, to initialize pthread-win32. It is safer in this circumstance
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to handle the case where ptw32_processInitialize() is called on
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an already initialized library:
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int
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ptw32_processInitialize (void)
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{
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if (ptw32_processInitialized) {
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/*
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* ignore if already initialized. this is useful for
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* programs that uses a non-dll pthread
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* library. such programs must call ptw32_processInitialize() explicitely,
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* since this initialization routine is automatically called only when
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* the dll is loaded.
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*/
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return TRUE;
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}
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ptw32_processInitialized = TRUE;
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[...]
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}
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------------------------------------
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- in private.c, if macro NEED_FTIME is defined, add routines to
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convert timespec_to_filetime and filetime_to_timespec, and modified
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code that was using _ftime() to use Win32 API instead.
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Rational: _ftime is not available on WinCE. It is necessary to use
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the native Win32 time API instead.
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Note: the routine timespec_to_filetime is provided as a convenience and a mean
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to test that filetime_to_timespec works, but it is not used by the library.
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------------------------------------
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- in semaphore.c, if macro NEED_SEM is defined, add code for the routines
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_increase_semaphore and _decrease_semaphore, and modify significantly
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the implementation of the semaphores so that it does not use CreateSemaphore.
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Rational: CreateSemaphore is not available on WinCE. I had to re-implement
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semaphores using mutexes and Events.
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Note: Only the semaphore routines that are used by pthread are implemented
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(i.e. signal conditions rely on a subset of the semaphores routines, and
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this subset works). Some other semaphore routines (e.g. sem_trywait) are
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not yet supported on my WinCE port (and since I don't need them, I am not
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planning to do anything about them).
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------------------------------------
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- in tsd.c, changed the code that defines TLS_OUT_OF_INDEXES
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/* TLS_OUT_OF_INDEXES not defined on WinCE */
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#ifndef TLS_OUT_OF_INDEXES
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#define TLS_OUT_OF_INDEXES 0xffffffff
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#endif
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Rational: TLS_OUT_OF_INDEXES is not defined in any standard include file
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on WinCE.
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------------------------------------
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- added file need_errno.h
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Rational: On WinCE, there is no errno.h file. need_errno.h is just a
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copy of windows version of errno.h, with minor modifications due to the fact
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that some of the error codes are defined by the WinCE socket library.
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In pthread.h, if NEED_ERRNO is defined, the file need_errno.h is
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included (instead of <errno.h>).
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-- eof
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