Added SemaphorePool class.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@11930 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/add-ons/kernel/drivers/tty/Jamfile

@@ -8,4 +8,6 @@ KernelAddon <driver>tty : kernel drivers dev :
 	line_buffer.cpp
 	master.cpp
 	slave.cpp
+	SemaphorePool.cpp
 	;
+

src/add-ons/kernel/drivers/tty/SemaphorePool.cpp

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2005, Ingo Weinhold, bonefish@users.sf.net.
+ * Distributed under the terms of the MIT License.
+ */
+
+#include <new>
+
+#include <util/AutoLock.h>
+
+#include "SemaphorePool.h"
+
+
+status_t
+Semaphore::ZeroCount()
+{
+	int32 count;
+	status_t error = get_sem_count(fSemaphore, &count);
+	if (error != B_OK)
+		return error;
+
+	if (count > 0)
+		error = acquire_sem_etc(fSemaphore, count, B_RELATIVE_TIMEOUT, 0);
+	else if (count < 0)
+		error = release_sem_etc(fSemaphore, -count, 0);
+
+	return error;
+}
+
+
+// #pragma mark -
+
+SemaphorePool::SemaphorePool(int32 maxCached)
+	: fSemaphores(),
+	  fCount(0),
+	  fMaxCount(maxCached)
+{
+	if (fMaxCount < 0)
+		fMaxCount = 8;
+}
+
+
+SemaphorePool::~SemaphorePool()
+{
+	while (Semaphore *sem = fSemaphores.Head()) {
+		fSemaphores.Remove(sem);
+		delete sem;
+	}
+
+	mutex_destroy(&fLock);
+}
+
+
+status_t
+SemaphorePool::Init()
+{
+	return mutex_init(&fLock, "tty semaphore pool");
+}
+
+
+status_t
+SemaphorePool::Get(Semaphore *&semaphore)
+{
+	MutexLocker _(fLock);
+
+	// use a cached one, if available
+	if (fCount > 0) {
+		fCount--;
+		semaphore = fSemaphores.Head();
+		fSemaphores.Remove(semaphore);
+		return B_OK;
+	}
+
+	// create a new one
+	Semaphore *sem = new(nothrow) Semaphore(0, "pool semaphore");
+	if (!sem)
+		return B_NO_MEMORY;
+
+	status_t error = sem->ZeroCount();
+	if (error != B_OK) {
+		delete sem;
+		return error;
+	}
+
+	semaphore = sem;
+	return B_OK;
+}
+
+
+void
+SemaphorePool::Put(Semaphore *semaphore)
+{
+	if (!semaphore)
+		return;
+
+	MutexLocker _(fLock);
+
+	if (fCount >= fMaxCount || semaphore->InitCheck() != B_OK) {
+		delete semaphore;
+		return;
+	}
+
+	fSemaphores.Add(semaphore);
+	fCount++;
+}

src/add-ons/kernel/drivers/tty/SemaphorePool.h

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2005, Ingo Weinhold, bonefish@users.sf.net.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef TTY_SEMAPHORE_POOL_H
+#define TTY_SEMAPHORE_POOL_H
+
+#include <lock.h>
+#include <util/DoublyLinkedList.h>
+
+class Semaphore : public DoublyLinkedListLinkImpl<Semaphore> {
+public:
+	Semaphore(sem_id sem)
+		: fSemaphore(sem)
+	{
+	}
+
+	Semaphore(int32 count, const char *name)
+	{
+		fSemaphore = create_sem(count, name);
+	}
+
+	~Semaphore()
+	{
+		if (fSemaphore >= 0)
+			delete_sem(fSemaphore);
+	}
+
+	status_t InitCheck() const
+	{
+		return (fSemaphore >= 0 ? B_OK : fSemaphore);
+	}
+
+	sem_id ID() const
+	{
+		return fSemaphore;
+	}
+
+	status_t ZeroCount();
+
+private:
+	sem_id	fSemaphore;
+
+public:
+	Semaphore	*fNext;
+};
+
+class SemaphorePool {
+public:
+	SemaphorePool(int32 maxCached);
+	~SemaphorePool();
+
+	status_t Init();
+
+	status_t Get(Semaphore *&semaphore);
+	void Put(Semaphore *semaphore);
+
+private:
+	typedef DoublyLinkedList<Semaphore> SemaphoreList;
+
+	struct mutex	fLock;
+	SemaphoreList	fSemaphores;
+	int32			fCount;
+	int32			fMaxCount;
+};
+
+#endif	// TTY_SEMAPHORE_POOL_H