--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/thread/win32/win_ce_semaphore.c	Wed May 23 23:35:10 2001 +0000
@@ -0,0 +1,214 @@
+/* win_ce_semaphore.c
+
+   Copyright (c) 1998, Johnson M. Hart
+   (with corrections 2001 by Rainer Loritz)
+   Permission is granted for any and all use providing that this
+   copyright is properly acknowledged.
+   There are no assurances of suitability for any use whatsoever.
+
+   WINDOWS CE: There is a collection of Windows CE functions to simulate
+   semaphores using only a mutex and an event. As Windows CE events cannot
+   be named, these simulated semaphores cannot be named either.
+
+   Implementation notes:
+   1. All required internal data structures are allocated on the process's heap.
+   2. Where appropriate, a new error code is returned (see the header
+      file), or, if the error is a Win32 error, that code is unchanged.
+   3. Notice the new handle type "SYNCHHANDLE" that has handles, counters,
+      and other information. This structure will grow as new objects are added
+      to this set; some members are specific to only one or two of the objects.
+   4. Mutexes are used for critical sections. These could be replaced with
+      CRITICAL_SECTION objects but then this would give up the time out
+      capability.
+   5. The implementation shows several interesting aspects of synchronization, some
+      of which are specific to Win32 and some of which are general. These are pointed
+      out in the comments as appropriate.
+   6. The wait function emulates WaitForSingleObject only. An emulation of
+      WaitForMultipleObjects is much harder to implement outside the kernel,
+      and it is not clear how to handle a mixture of WCE semaphores and normal
+      events and mutexes. */
+
+#include <windows.h>
+#include "win_ce_semaphore.h"
+
+static SYNCHHANDLE CleanUp (SYNCHHANDLE hSynch, DWORD Flags);
+
+SYNCHHANDLE CreateSemaphoreCE (
+
+   LPSECURITY_ATTRIBUTES lpSemaphoreAttributes,  /* pointer to security attributes */
+      LONG lInitialCount,   /* initial count */
+      LONG lMaximumCount,   /* maximum count */
+      LPCTSTR lpName )
+
+/* Semaphore for use with Windows CE that does not support them directly.
+   Requires a counter, a mutex to protect the counter, and an
+   autoreset event.
+
+   Here are the rules that must always hold between the autoreset event
+   and the mutex (any violation of these rules by the CE semaphore functions
+   will, in all likelihood, result in a defect):
+    1. No thread can set, pulse, or reset the event,
+       nor can it access any part of the SYNCHHANDLE structure,
+       without first gaining ownership of the mutex.
+       BUT, a thread can wait on the event without owning the mutex
+       (this is clearly necessary or else the event could never be set).
+    2. The event is in a signaled state if and only if the current semaphore
+       count ("CurCount") is greater than zero.
+    3. The semaphore count is always >= 0 and <= the maximum count */
+
+{
+   SYNCHHANDLE hSynch = NULL, result = NULL;
+
+   __try
+	{
+      if (lInitialCount > lMaximumCount || lMaximumCount < 0 || lInitialCount < 0) 
+	  {
+              /* Bad parameters */
+         SetLastError (SYNCH_ERROR);
+         __leave;
+      }
+
+      hSynch = HeapAlloc (GetProcessHeap(), HEAP_ZERO_MEMORY, SYNCH_HANDLE_SIZE);
+      if (hSynch == NULL) __leave;
+
+      hSynch->MaxCount = lMaximumCount;
+      hSynch->CurCount = lInitialCount;
+      hSynch->lpName = lpName;
+
+      hSynch->hMutex = CreateMutex (lpSemaphoreAttributes, FALSE, NULL);
+
+      WaitForSingleObject (hSynch->hMutex, INFINITE);
+      /*  Create the event. It is initially signaled if and only if the
+          initial count is > 0 */
+      hSynch->hEvent = CreateEvent (lpSemaphoreAttributes, FALSE, 
+              lInitialCount > 0, NULL);
+      ReleaseMutex (hSynch->hMutex);
+      hSynch->hSemph = NULL;
+   }
+   __finally
+   {
+       /* Return with the handle, or, if there was any error, return
+        a null after closing any open handles and freeing any allocated memory. */
+      result=CleanUp(hSynch, 6 /* An event and a mutex, but no semaphore. */);
+   }
+
+   return result;
+}
+
+BOOL ReleaseSemaphoreCE (SYNCHHANDLE hSemCE, LONG cReleaseCount, LPLONG lpPreviousCount)
+/* Windows CE equivalent to ReleaseSemaphore. */
+{
+   BOOL Result = TRUE;
+
+   /* Gain access to the object to assure that the release count
+      would not cause the total count to exceed the maximum. */
+
+   __try 
+   {
+      WaitForSingleObject (hSemCE->hMutex, INFINITE);
+	  /* reply only if asked to */	
+	  if (lpPreviousCount!=NULL)
+		 *lpPreviousCount = hSemCE->CurCount;
+      if (hSemCE->CurCount + cReleaseCount > hSemCE->MaxCount || cReleaseCount <= 0)
+	  {
+         SetLastError (SYNCH_ERROR);
+         Result = FALSE;
+         __leave;
+      }
+      hSemCE->CurCount += cReleaseCount;
+
+      /*  Set the autoreset event, releasing exactly one waiting thread, now or
+          in the future.  */
+
+      SetEvent (hSemCE->hEvent);
+   }
+   __finally
+   {
+      ReleaseMutex (hSemCE->hMutex);
+   }
+
+   return Result;
+}
+
+DWORD WaitForSemaphoreCE (SYNCHHANDLE hSemCE, DWORD dwMilliseconds)
+   /* Windows CE semaphore equivalent of WaitForSingleObject. */
+{
+   DWORD WaitResult;
+
+   WaitResult = WaitForSingleObject (hSemCE->hMutex, dwMilliseconds);
+   if (WaitResult != WAIT_OBJECT_0 && WaitResult != WAIT_ABANDONED_0) return WaitResult;
+   while (hSemCE->CurCount <= 0) 
+   { 
+
+      /* The count is 0, and the thread must wait on the event (which, by
+         the rules, is currently reset) for semaphore resources to become
+         available. First, of course, the mutex must be released so that another
+         thread will be capable of setting the event. */
+
+      ReleaseMutex (hSemCE->hMutex);
+
+      /*  Wait for the event to be signaled, indicating a semaphore state change.
+          The event is autoreset and signaled with a SetEvent (not PulseEvent)
+          so exactly one waiting thread (whether or not there is currently
+          a waiting thread) is released as a result of the SetEvent. */
+
+      WaitResult = WaitForSingleObject (hSemCE->hEvent, dwMilliseconds);
+      if (WaitResult != WAIT_OBJECT_0) return WaitResult;
+
+      /*  This is where the properties of setting of an autoreset event is critical
+          to assure that, even if the semaphore state changes between the
+          preceding Wait and the next, and even if NO threads are waiting
+          on the event at the time of the SetEvent, at least one thread
+          will be released. 
+          Pulsing a manual reset event would appear to work, but it would have
+          a defect which could appear if the semaphore state changed between
+          the two waits. */
+
+      WaitResult = WaitForSingleObject (hSemCE->hMutex, dwMilliseconds);
+      if (WaitResult != WAIT_OBJECT_0 && WaitResult != WAIT_ABANDONED_0) return WaitResult;
+
+   }
+   /* The count is not zero and this thread owns the mutex.  */
+
+   hSemCE->CurCount--;
+   /* The event is now unsignaled, BUT, the semaphore count may not be
+      zero, in which case the event should be signaled again
+      before releasing the mutex. */
+
+   if (hSemCE->CurCount > 0) SetEvent (hSemCE->hEvent);
+   ReleaseMutex (hSemCE->hMutex);
+   return WaitResult;
+}
+
+BOOL CloseSynchHandle (SYNCHHANDLE hSynch)
+/* Close a synchronization handle. 
+   Improvement: Test for a valid handle before dereferencing the handle. */
+{
+   BOOL Result = TRUE;
+   if (hSynch->hEvent != NULL) Result = Result && CloseHandle (hSynch->hEvent);
+   if (hSynch->hMutex != NULL) Result = Result && CloseHandle (hSynch->hMutex);
+   if (hSynch->hSemph != NULL) Result = Result && CloseHandle (hSynch->hSemph);
+   HeapFree (GetProcessHeap (), 0, hSynch);
+   return (Result);
+}
+
+static SYNCHHANDLE CleanUp (SYNCHHANDLE hSynch, DWORD Flags)
+{ /* Prepare to return from a create of a synchronization handle.
+     If there was any failure, free any allocated resources.
+     "Flags" indicates which Win32 objects are required in the 
+     synchronization handle. */
+
+   BOOL ok = TRUE;
+
+   if (hSynch == NULL) return NULL;
+   if (Flags & 4 == 1 && hSynch->hEvent == NULL) ok = FALSE;
+   if (Flags & 2 == 1 && hSynch->hMutex == NULL) ok = FALSE;
+   if (Flags & 1 == 1 && hSynch->hEvent == NULL) ok = FALSE;
+   if (!ok) 
+   {
+      CloseSynchHandle (hSynch);
+      return NULL;
+   }
+   /* Everything worked */
+   return hSynch;
+}