1 files changed, 188 insertions, 0 deletions
diff --git a/compat/win32/pthread.c b/compat/win32/pthread.c
new file mode 100644
index 0000000000..0f949fc425
--- /dev/null
+++ b/compat/win32/pthread.c
@@ -0,0 +1,188 @@
+/*
+ * Copyright (C) 2009 Andrzej K. Haczewski <ahaczewski@gmail.com>
+ *
+ * DISCLAIMER: The implementation is Git-specific, it is subset of original
+ * Pthreads API, without lots of other features that Git doesn't use.
+ * Git also makes sure that the passed arguments are valid, so there's
+ * no need for double-checking.
+ */
+
+#include "../../git-compat-util.h"
+#include "pthread.h"
+
+#include <errno.h>
+#include <limits.h>
+
+static unsigned __stdcall win32_start_routine(void *arg)
+{
+	pthread_t *thread = arg;
+	thread->arg = thread->start_routine(thread->arg);
+	return 0;
+}
+
+int pthread_create(pthread_t *thread, const void *unused,
+		   void *(*start_routine)(void*), void *arg)
+{
+	thread->arg = arg;
+	thread->start_routine = start_routine;
+	thread->handle = (HANDLE)
+		_beginthreadex(NULL, 0, win32_start_routine, thread, 0, NULL);
+
+	if (!thread->handle)
+		return errno;
+	else
+		return 0;
+}
+
+int win32_pthread_join(pthread_t *thread, void **value_ptr)
+{
+	DWORD result = WaitForSingleObject(thread->handle, INFINITE);
+	switch (result) {
+		case WAIT_OBJECT_0:
+			if (value_ptr)
+				*value_ptr = thread->arg;
+			return 0;
+		case WAIT_ABANDONED:
+			return EINVAL;
+		default:
+			return err_win_to_posix(GetLastError());
+	}
+}
+
+int pthread_cond_init(pthread_cond_t *cond, const void *unused)
+{
+	cond->waiters = 0;
+	cond->was_broadcast = 0;
+	InitializeCriticalSection(&cond->waiters_lock);
+
+	cond->sema = CreateSemaphore(NULL, 0, LONG_MAX, NULL);
+	if (!cond->sema)
+		die("CreateSemaphore() failed");
+
+	cond->continue_broadcast = CreateEvent(NULL,	/* security */
+				FALSE,			/* auto-reset */
+				FALSE,			/* not signaled */
+				NULL);			/* name */
+	if (!cond->continue_broadcast)
+		die("CreateEvent() failed");
+
+	return 0;
+}
+
+int pthread_cond_destroy(pthread_cond_t *cond)
+{
+	CloseHandle(cond->sema);
+	CloseHandle(cond->continue_broadcast);
+	DeleteCriticalSection(&cond->waiters_lock);
+	return 0;
+}
+
+int pthread_cond_wait(pthread_cond_t *cond, CRITICAL_SECTION *mutex)
+{
+	int last_waiter;
+
+	EnterCriticalSection(&cond->waiters_lock);
+	cond->waiters++;
+	LeaveCriticalSection(&cond->waiters_lock);
+
+	/*
+	 * Unlock external mutex and wait for signal.
+	 * NOTE: we've held mutex locked long enough to increment
+	 * waiters count above, so there's no problem with
+	 * leaving mutex unlocked before we wait on semaphore.
+	 */
+	LeaveCriticalSection(mutex);
+
+	/* let's wait - ignore return value */
+	WaitForSingleObject(cond->sema, INFINITE);
+
+	/*
+	 * Decrease waiters count. If we are the last waiter, then we must
+	 * notify the broadcasting thread that it can continue.
+	 * But if we continued due to cond_signal, we do not have to do that
+	 * because the signaling thread knows that only one waiter continued.
+	 */
+	EnterCriticalSection(&cond->waiters_lock);
+	cond->waiters--;
+	last_waiter = cond->was_broadcast && cond->waiters == 0;
+	LeaveCriticalSection(&cond->waiters_lock);
+
+	if (last_waiter) {
+		/*
+		 * cond_broadcast was issued while mutex was held. This means
+		 * that all other waiters have continued, but are contending
+		 * for the mutex at the end of this function because the
+		 * broadcasting thread did not leave cond_broadcast, yet.
+		 * (This is so that it can be sure that each waiter has
+		 * consumed exactly one slice of the semaphor.)
+		 * The last waiter must tell the broadcasting thread that it
+		 * can go on.
+		 */
+		SetEvent(cond->continue_broadcast);
+		/*
+		 * Now we go on to contend with all other waiters for
+		 * the mutex. Auf in den Kampf!
+		 */
+	}
+	/* lock external mutex again */
+	EnterCriticalSection(mutex);
+
+	return 0;
+}
+
+/*
+ * IMPORTANT: This implementation requires that pthread_cond_signal
+ * is called while the mutex is held that is used in the corresponding
+ * pthread_cond_wait calls!
+ */
+int pthread_cond_signal(pthread_cond_t *cond)
+{
+	int have_waiters;
+
+	EnterCriticalSection(&cond->waiters_lock);
+	have_waiters = cond->waiters > 0;
+	LeaveCriticalSection(&cond->waiters_lock);
+
+	/*
+	 * Signal only when there are waiters
+	 */
+	if (have_waiters)
+		return ReleaseSemaphore(cond->sema, 1, NULL) ?
+			0 : err_win_to_posix(GetLastError());
+	else
+		return 0;
+}
+
+/*
+ * DOUBLY IMPORTANT: This implementation requires that pthread_cond_broadcast
+ * is called while the mutex is held that is used in the corresponding
+ * pthread_cond_wait calls!
+ */
+int pthread_cond_broadcast(pthread_cond_t *cond)
+{
+	EnterCriticalSection(&cond->waiters_lock);
+
+	if ((cond->was_broadcast = cond->waiters > 0)) {
+		/* wake up all waiters */
+		ReleaseSemaphore(cond->sema, cond->waiters, NULL);
+		LeaveCriticalSection(&cond->waiters_lock);
+		/*
+		 * At this point all waiters continue. Each one takes its
+		 * slice of the semaphor. Now it's our turn to wait: Since
+		 * the external mutex is held, no thread can leave cond_wait,
+		 * yet. For this reason, we can be sure that no thread gets
+		 * a chance to eat *more* than one slice. OTOH, it means
+		 * that the last waiter must send us a wake-up.
+		 */
+		WaitForSingleObject(cond->continue_broadcast, INFINITE);
+		/*
+		 * Since the external mutex is held, no thread can enter
+		 * cond_wait, and, hence, it is safe to reset this flag
+		 * without cond->waiters_lock held.
+		 */
+		cond->was_broadcast = 0;
+	} else {
+		LeaveCriticalSection(&cond->waiters_lock);
+	}
+	return 0;
+}