std::try_lock
來自 cppreference.com
| 定義於標頭檔案 <mutex> |
||
| template< class Lockable1, class Lockable2, class... LockableN > int try_lock( Lockable1& lock1, Lockable2& lock2, LockableN&... lockn ); |
(C++11 起) | |
嘗試透過按順序呼叫每個給定 Lockable 物件 lock1、lock2、...、lockn 的 try_lock 來鎖定它們，從第一個開始。
如果對 try_lock 的呼叫失敗，則不會執行對 try_lock 的後續呼叫，將對任何已鎖定的物件呼叫 unlock，並返回失敗鎖定物件的從 0 開始的索引。
如果對 try_lock 的呼叫導致異常，則在重新丟擲之前，會對任何已鎖定的物件呼叫 unlock。
目錄 |
[編輯] 引數
| lock1, lock2, ..., lockn | - | 要鎖定的 Lockable 物件 |
[編輯] 返回值
成功時返回 -1，或返回失敗鎖定物件的從 0 開始的索引值。
[編輯] 示例
以下示例使用 std::try_lock 定期對在單獨執行緒中執行的計數器進行統計和重置。
執行此程式碼
#include <chrono> #include <functional> #include <iostream> #include <mutex> #include <thread> #include <vector> int main() { int foo_count = 0; std::mutex foo_count_mutex; int bar_count = 0; std::mutex bar_count_mutex; int overall_count = 0; bool done = false; std::mutex done_mutex; auto increment = [](int& counter, std::mutex& m, const char* desc) { for (int i = 0; i < 10; ++i) { std::unique_lock<std::mutex> lock(m); ++counter; std::cout << desc << ": " << counter << '\n'; lock.unlock(); std::this_thread::sleep_for(std::chrono::seconds(1)); } }; std::thread increment_foo(increment, std::ref(foo_count), std::ref(foo_count_mutex), "foo"); std::thread increment_bar(increment, std::ref(bar_count), std::ref(bar_count_mutex), "bar"); std::thread update_overall([&]() { done_mutex.lock(); while (!done) { done_mutex.unlock(); int result = std::try_lock(foo_count_mutex, bar_count_mutex); if (result == -1) { overall_count += foo_count + bar_count; foo_count = 0; bar_count = 0; std::cout << "overall: " << overall_count << '\n'; foo_count_mutex.unlock(); bar_count_mutex.unlock(); } std::this_thread::sleep_for(std::chrono::seconds(2)); done_mutex.lock(); } done_mutex.unlock(); }); increment_foo.join(); increment_bar.join(); done_mutex.lock(); done = true; done_mutex.unlock(); update_overall.join(); std::cout << "Done processing\n" << "foo: " << foo_count << '\n' << "bar: " << bar_count << '\n' << "overall: " << overall_count << '\n'; }
可能的輸出
bar: 1 foo: 1 foo: 2 bar: 2 foo: 3 overall: 5 bar: 1 foo: 1 bar: 2 foo: 2 bar: 3 overall: 10 bar: 1 foo: 1 bar: 2 foo: 2 overall: 14 bar: 1 foo: 1 bar: 2 overall: 17 foo: 1 bar: 1 foo: 2 overall: 20 Done processing foo: 0 bar: 0 overall: 20
[編輯] 參閱
| (C++11) |
鎖定指定的互斥體，如果任何一個不可用則阻塞 (函式模板) |
