Pulled set_string() out of KPartition.cpp for it is useful also in other classes. Added a generic AutoLocker.

git-svn-id: file:///srv/svn/repos/haiku/trunk/current@3458 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/disk_device_manager/KDiskDeviceUtils.h

@@ -0,0 +1,167 @@
+// KDiskDeviceUtils.h
+
+#ifndef _K_DISK_DEVICE_UTILS_H
+#define _K_DISK_DEVICE_UTILS_H
+
+#include <string.h>
+
+#include <SupportDefs.h>
+
+namespace BPrivate {
+namespace DiskDevice {
+
+// helper functions
+
+// set_string
+static inline
+status_t
+set_string(char *&location, const char *newValue)
+{
+	// unset old value
+	if (location) {
+		free(location);
+		location = NULL;
+	}
+	// set new value
+	status_t error = B_OK;
+	if (newValue) {
+		location = strdup(newValue);
+		if (!location)
+			error = B_NO_MEMORY;
+	}
+	return error;
+}
+
+
+// locking
+
+// AutoLockerStandardLocking
+template<typename Lockable>
+class AutoLockerStandardLocking {
+public:
+	inline bool Lock(Lockable *lockable)
+	{
+		return lockable->Lock();
+	}
+
+	inline void Unlock(Lockable *lockable)
+	{
+		lockable->Unlock();
+	}
+};
+
+// AutoLockerReadLocking
+template<typename Lockable>
+class AutoLockerReadLocking {
+public:
+	inline bool Lock(Lockable *lockable)
+	{
+		return lockable->ReadLock();
+	}
+
+	inline void Unlock(Lockable *lockable)
+	{
+		lockable->ReadUnlock();
+	}
+};
+
+// AutoLockerWriteLocking
+template<typename Lockable>
+class AutoLockerWriteLocking {
+public:
+	inline bool Lock(Lockable *lockable)
+	{
+		return lockable->WriteLock();
+	}
+
+	inline void Unlock(Lockable *lockable)
+	{
+		lockable->WriteUnlock();
+	}
+};
+
+// AutoLocker
+template<typename Lockable,
+		 typename Locking = AutoLockerStandardLocking<Lockable> >
+class AutoLocker {
+private:
+	typedef AutoLocker<Lockable, Locking>	ThisClass;
+public:
+	inline AutoLocker(Lockable *lockable)
+		: fLockable(lockable),
+		  fLocked(false)
+	{
+		_Lock();
+	}
+
+	inline AutoLocker(Lockable &lockable)
+		: fLockable(&lockable),
+		  fLocked(false)
+	{
+		_Lock();
+	}
+
+	inline ~AutoLocker()
+	{
+		_Unlock();
+	}
+
+	inline AutoLocker<Lockable, Locking> &operator=(Lockable *lockable)
+	{
+		_Unlock();
+		fLockable = lockable;
+		_Lock();
+	}
+
+	inline AutoLocker<Lockable, Locking> &operator=(Lockable &lockable)
+	{
+		_Unlock();
+		fLockable = &lockable;
+		_Lock();
+	}
+
+	inline bool IsLocked() const	{ return fLocked; }
+
+	inline operator bool() const	{ return fLocked; }
+
+private:
+	inline void _Lock()
+	{
+		if (fLockable)
+			fLocked = fLocking.Lock(fLockable);
+	}
+
+	inline void _Unlock()
+	{
+		if (fLockable && fLocked) {
+			fLocking.Unlock(fLockable);
+			fLocked = false;
+		}
+	}
+
+private:
+	Lockable	*fLockable;
+	bool		fLocked;
+	Locking		fLocking;
+};
+
+// instantiations
+class KDiskDevice;
+class KDiskDeviceManager;
+
+typedef AutoLocker<KDiskDevice, AutoLockerReadLocking<KDiskDevice> >
+		DeviceReadLocker;
+typedef AutoLocker<KDiskDevice, AutoLockerWriteLocking<KDiskDevice> >
+		DeviceWriteLocker;
+typedef AutoLocker<KDiskDeviceManager > ManagerLocker;
+
+} // namespace DiskDevice
+} // namespace BPrivate
+
+using BPrivate::DiskDevice::set_string;
+using BPrivate::DiskDevice::AutoLocker;
+using BPrivate::DiskDevice::DeviceReadLocker;
+using BPrivate::DiskDevice::DeviceWriteLocker;
+using BPrivate::DiskDevice::ManagerLocker;
+
+#endif	// _K_DISK_DEVICE_H