std::shared_lock<Mutex>::lock
來自 cppreference.com
< cpp | thread | shared_lock
| void lock(); |
(C++14 起) | |
以共享模式鎖定關聯的互斥體。實際上呼叫 mutex()->lock_shared()。
目錄 |
[編輯] 引數
(無)
[編輯] 返回值
(無)
[編輯] 異常
- 由 mutex()->lock_shared() 丟擲的任何異常。
- 如果沒有關聯的互斥體，則丟擲 std::system_error，錯誤程式碼為 std::errc::operation_not_permitted。
- 如果關聯的互斥體已經被此
shared_lock鎖定（即 owns_lock 返回 true），則丟擲 std::system_error，錯誤程式碼為 std::errc::resource_deadlock_would_occur。
[編輯] 示例
| 本節不完整 原因：展示 shared_lock::lock 的有意義用法 |
執行此程式碼
#include <iostream> #include <mutex> #include <shared_mutex> #include <string> #include <thread> std::string file = "Original content."; // Simulates a file std::mutex output_mutex; // mutex that protects output operations. std::shared_mutex file_mutex; // reader/writer mutex void read_content(int id) { std::string content; { std::shared_lock lock(file_mutex, std::defer_lock); // Do not lock it first. lock.lock(); // Lock it here. content = file; } std::lock_guard lock(output_mutex); std::cout << "Contents read by reader #" << id << ": " << content << '\n'; } void write_content() { { std::lock_guard file_lock(file_mutex); file = "New content"; } std::lock_guard output_lock(output_mutex); std::cout << "New content saved.\n"; } int main() { std::cout << "Two readers reading from file.\n" << "A writer competes with them.\n"; std::thread reader1{read_content, 1}; std::thread reader2{read_content, 2}; std::thread writer{write_content}; reader1.join(); reader2.join(); writer.join(); std::cout << "The first few operations to file are done.\n"; reader1 = std::thread{read_content, 3}; reader1.join(); }
可能的輸出
Two readers reading from file. A writer competes with them. Contents read by reader #1: Original content. Contents read by reader #2: Original content. New content saved. The first few operations to file are done. Contents read by reader #3: New content
[編輯] 參閱
| 嘗試鎖定關聯的互斥體 (公共成員函式) | |
| 解鎖關聯的互斥體 (公共成員函式) |
