66 lines
1.8 KiB
C++
66 lines
1.8 KiB
C++
// Copyright 2019 Google LLC. All Rights Reserved. This file and proprietary
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// source code may only be used and distributed under the Widevine Master
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// License Agreement.
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#ifndef WVCDM_UTIL_RW_LOCK_H_
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#define WVCDM_UTIL_RW_LOCK_H_
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#include <stdint.h>
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#include <condition_variable>
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#include <mutex>
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#include "disallow_copy_and_assign.h"
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#include "util_common.h"
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namespace wvcdm {
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// A simple reader-writer mutex implementation that mimics the one from C++17
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class CORE_UTIL_EXPORT shared_mutex {
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public:
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shared_mutex() : reader_count_(0), has_writer_(false) {}
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~shared_mutex();
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// These methods take the mutex as a reader. They do not fulfill the
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// SharedMutex requirement from the C++14 STL, but they fulfill enough of it
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// to be used with |shared_lock| below.
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void lock_shared();
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void unlock_shared();
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// These methods take the mutex as a writer. They fulfill the Mutex
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// requirement from the C++11 STL so that this mutex can be used with
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// |std::unique_lock|.
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void lock() { lock_implementation(false); }
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bool try_lock() { return lock_implementation(true); }
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void unlock();
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private:
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bool lock_implementation(bool abort_if_unavailable);
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uint32_t reader_count_;
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bool has_writer_;
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std::mutex mutex_;
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std::condition_variable condition_variable_;
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CORE_DISALLOW_COPY_AND_ASSIGN(shared_mutex);
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};
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// A simple reader lock implementation that mimics the one from C++14
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template <typename Mutex>
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class shared_lock {
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public:
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explicit shared_lock(Mutex& lock) : lock_(&lock) { lock_->lock_shared(); }
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explicit shared_lock(Mutex* lock) : lock_(lock) { lock_->lock_shared(); }
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~shared_lock() { lock_->unlock_shared(); }
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private:
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Mutex* lock_;
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CORE_DISALLOW_COPY_AND_ASSIGN(shared_lock);
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};
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} // namespace wvcdm
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#endif // WVCDM_UTIL_RW_LOCK_H_
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