1 files changed, 63 insertions, 0 deletions
diff --git a/xmrstak/cpputil/read_write_lock.h b/xmrstak/cpputil/read_write_lock.h
new file mode 100644
index 0000000..b2db609
--- /dev/null
+++ b/xmrstak/cpputil/read_write_lock.h
@@ -0,0 +1,63 @@
+#ifndef CPPUTIL_READ_WRITE_LOCK_H_
+#define CPPUTIL_READ_WRITE_LOCK_H_
+
+#include <mutex>
+#include <condition_variable>
+
+namespace cpputil {
+
+class RWLock {
+ public:
+  RWLock() : status_(0), waiting_readers_(0), waiting_writers_(0) {}
+  RWLock(const RWLock&) = delete;
+  RWLock(RWLock&&) = delete;
+  RWLock& operator = (const RWLock&) = delete;
+  RWLock& operator = (RWLock&&) = delete;
+
+  void ReadLock() {
+    std::unique_lock<std::mutex> lck(mtx_);
+    waiting_readers_ += 1;
+    read_cv_.wait(lck, [&]() { return waiting_writers_ == 0 && status_ >= 0; });
+    waiting_readers_ -= 1;
+    status_ += 1;
+  }
+
+  void WriteLock() {
+    std::unique_lock<std::mutex> lck(mtx_);
+    waiting_writers_ += 1;
+    write_cv_.wait(lck, [&]() { return status_ == 0; });
+    waiting_writers_ -= 1;
+    status_ = -1;
+  }
+
+  void UnLock() {
+    std::unique_lock<std::mutex> lck(mtx_);
+    if (status_ == -1) {
+      status_ = 0;
+    } else {
+      status_ -= 1;
+    }
+    if (waiting_writers_ > 0) {
+      if (status_ == 0) {
+        write_cv_.notify_one();
+      }
+    } else {
+      read_cv_.notify_all();
+    }
+  }
+
+ private:
+  // -1    : one writer
+  // 0     : no reader and no writer
+  // n > 0 : n reader
+  int32_t status_;
+  int32_t waiting_readers_;
+  int32_t waiting_writers_;
+  std::mutex mtx_;
+  std::condition_variable read_cv_;
+  std::condition_variable write_cv_;
+};
+
+}  // namespace cpputil
+
+#endif // CPPUTIL_READ_WRITE_LOCK_H_