1 files changed, 127 insertions, 0 deletions
diff --git a/plugins/Dbx_kv/src/hamsterdb/src/1base/spinlock.h b/plugins/Dbx_kv/src/hamsterdb/src/1base/spinlock.h
new file mode 100644
index 0000000000..e9d917212c
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+++ b/plugins/Dbx_kv/src/hamsterdb/src/1base/spinlock.h
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2005-2015 Christoph Rupp (chris@crupp.de).
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * A fast spinlock, taken from the boost documentation
+ * http://www.boost.org/doc/libs/1_57_0/doc/html/atomic/usage_examples.html
+ *
+ * @exception_safe: nothrow
+ * @thread_safe: yes
+ */
+
+#ifndef HAM_SPINLOCK_H
+#define HAM_SPINLOCK_H
+
+#include "0root/root.h"
+
+#include <stdio.h>
+#ifndef HAM_OS_WIN32
+#  include <sched.h>
+#  include <unistd.h>
+#endif
+#include <boost/atomic.hpp>
+
+// Always verify that a file of level N does not include headers > N!
+#include "1base/error.h"
+#include "1base/mutex.h"
+
+#ifndef HAM_ROOT_H
+#  error "root.h was not included"
+#endif
+
+namespace hamsterdb {
+
+#ifdef HAM_ENABLE_HELGRIND
+typedef Mutex Spinlock;
+#else
+
+class Spinlock {
+    typedef enum {
+      kLocked,
+      kUnlocked,
+      kSpinThreshold = 10
+    } LockState;
+
+  public:
+    Spinlock()
+      : m_state(kUnlocked) {
+    }
+
+    // Need user-defined copy constructor because boost::atomic<> is not
+    // copyable
+    Spinlock(const Spinlock &other)
+      : m_state(other.m_state.load()) {
+    }
+
+    void lock() {
+      int k = 0;
+      while (m_state.exchange(kLocked, boost::memory_order_acquire) == kLocked)
+        spin(++k);
+    }
+
+    void unlock() {
+      m_state.store(kUnlocked, boost::memory_order_release);
+    }
+
+    bool try_lock() {
+      return (m_state.exchange(kLocked, boost::memory_order_acquire)
+                      != kLocked);
+    }
+
+    static void spin(int loop) {
+      if (loop < kSpinThreshold) {
+#ifdef HAM_OS_WIN32
+        ::Sleep(0);
+#elif HAVE_SCHED_YIELD
+        ::sched_yield();
+#else
+        ham_assert(!"Please implement me");
+#endif 
+      }
+      else {
+#ifdef HAM_OS_WIN32
+        ::Sleep(25);
+#elif HAVE_USLEEP
+        ::usleep(25);
+#else
+        ham_assert(!"Please implement me");
+#endif 
+      }
+    }
+
+  private:
+    boost::atomic<LockState> m_state;
+};
+#endif // HAM_ENABLE_HELGRIND
+
+class ScopedSpinlock {
+  public:
+    ScopedSpinlock(Spinlock &lock)
+      : m_spinlock(lock) {
+      m_spinlock.lock();
+    }
+
+    ~ScopedSpinlock() {
+      m_spinlock.unlock();
+    }
+
+  private:
+    Spinlock &m_spinlock;
+};
+
+} // namespace hamsterdb
+
+#endif /* HAM_SPINLOCK_H */