summaryrefslogtreecommitdiff
path: root/src/thread/win32/win_ce_semaphore.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/thread/win32/win_ce_semaphore.c')
-rw-r--r--src/thread/win32/win_ce_semaphore.c216
1 files changed, 216 insertions, 0 deletions
diff --git a/src/thread/win32/win_ce_semaphore.c b/src/thread/win32/win_ce_semaphore.c
new file mode 100644
index 0000000..9db45c4
--- /dev/null
+++ b/src/thread/win32/win_ce_semaphore.c
@@ -0,0 +1,216 @@
+/* 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. */
+
+#define WIN32_LEAN_AND_MEAN
+#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;
+}