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diff --git a/src/rwmutex.h b/src/rwmutex.h
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+// Copyright 2020 Google LLC
+//
+// 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
+//
+//     https://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.
+
+#ifndef dap_rwmutex_h
+#define dap_rwmutex_h
+
+#include <condition_variable>
+#include <mutex>
+
+namespace dap {
+
+////////////////////////////////////////////////////////////////////////////////
+// RWMutex
+////////////////////////////////////////////////////////////////////////////////
+
+// A RWMutex is a reader/writer mutual exclusion lock.
+// The lock can be held by an arbitrary number of readers or a single writer.
+// Also known as a shared mutex.
+class RWMutex {
+ public:
+  inline RWMutex() = default;
+
+  // lockReader() locks the mutex for reading.
+  // Multiple read locks can be held while there are no writer locks.
+  inline void lockReader();
+
+  // unlockReader() unlocks the mutex for reading.
+  inline void unlockReader();
+
+  // lockWriter() locks the mutex for writing.
+  // If the lock is already locked for reading or writing, lockWriter blocks
+  // until the lock is available.
+  inline void lockWriter();
+
+  // unlockWriter() unlocks the mutex for writing.
+  inline void unlockWriter();
+
+ private:
+  RWMutex(const RWMutex&) = delete;
+  RWMutex& operator=(const RWMutex&) = delete;
+
+  int readLocks = 0;
+  int pendingWriteLocks = 0;
+  std::mutex mutex;
+  std::condition_variable cv;
+};
+
+void RWMutex::lockReader() {
+  std::unique_lock<std::mutex> lock(mutex);
+  readLocks++;
+}
+
+void RWMutex::unlockReader() {
+  std::unique_lock<std::mutex> lock(mutex);
+  readLocks--;
+  if (readLocks == 0 && pendingWriteLocks > 0) {
+    cv.notify_one();
+  }
+}
+
+void RWMutex::lockWriter() {
+  std::unique_lock<std::mutex> lock(mutex);
+  if (readLocks > 0) {
+    pendingWriteLocks++;
+    cv.wait(lock, [&] { return readLocks == 0; });
+    pendingWriteLocks--;
+  }
+  lock.release();  // Keep lock held
+}
+
+void RWMutex::unlockWriter() {
+  if (pendingWriteLocks > 0) {
+    cv.notify_one();
+  }
+  mutex.unlock();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// RLock
+////////////////////////////////////////////////////////////////////////////////
+
+// RLock is a RAII read lock helper for a RWMutex.
+class RLock {
+ public:
+  inline RLock(RWMutex& mutex);
+  inline ~RLock();
+
+  inline RLock(RLock&&);
+  inline RLock& operator=(RLock&&);
+
+ private:
+  RLock(const RLock&) = delete;
+  RLock& operator=(const RLock&) = delete;
+
+  RWMutex* m;
+};
+
+RLock::RLock(RWMutex& mutex) : m(&mutex) {
+  m->lockReader();
+}
+
+RLock::~RLock() {
+  if (m != nullptr) {
+    m->unlockReader();
+  }
+}
+
+RLock::RLock(RLock&& other) {
+  m = other.m;
+  other.m = nullptr;
+}
+
+RLock& RLock::operator=(RLock&& other) {
+  m = other.m;
+  other.m = nullptr;
+  return *this;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// WLock
+////////////////////////////////////////////////////////////////////////////////
+
+// WLock is a RAII write lock helper for a RWMutex.
+class WLock {
+ public:
+  inline WLock(RWMutex& mutex);
+  inline ~WLock();
+
+  inline WLock(WLock&&);
+  inline WLock& operator=(WLock&&);
+
+ private:
+  WLock(const WLock&) = delete;
+  WLock& operator=(const WLock&) = delete;
+
+  RWMutex* m;
+};
+
+WLock::WLock(RWMutex& mutex) : m(&mutex) {
+  m->lockWriter();
+}
+
+WLock::~WLock() {
+  if (m != nullptr) {
+    m->unlockWriter();
+  }
+}
+
+WLock::WLock(WLock&& other) {
+  m = other.m;
+  other.m = nullptr;
+}
+
+WLock& WLock::operator=(WLock&& other) {
+  m = other.m;
+  other.m = nullptr;
+  return *this;
+}
+}  // namespace dap
+
+#endif