R.1: Manage resources automatically using resource handles and RAII (Resource Acquisition Is Initialization)
R.1: 使用資源句柄自動管理資源並RAII(資源獲取即初始化)
Reason(原因)
To avoid leaks and the complexity of manual resource management. C++'s language-enforced constructor/destructor symmetry mirrors the symmetry inherent in resource acquire/release function pairs such as fopen/fclose, lock/unlock, and new/delete. Whenever you deal with a resource that needs paired acquire/release function calls, encapsulate that resource in an object that enforces pairing for you -- acquire the resource in its constructor, and release it in its destructor.
避免手動管理資源時發生泄露和複雜性。C++語言鼓勵構造函數/析構函數的對稱性映射資源確保/釋放函數對中包含的本質的對稱性。這些函數對包括fopen/fclose，lock/unlock，new/deletre等。無論什麼時候，你處理一個需要成對調用申請/釋放函數時，用一個強制進行成對操作的對象封裝資源--在它的構造函數中申請資源，在它的析構函數中釋放資源。
Example, bad(反面示例)
Consider(考慮如下代碼):
void send(X* x, cstring_span destination)
{
auto port = open_port(destination);
my_mutex.lock();
// ...
send(port, x);
// ...
my_mutex.unlock();
close_port(port);
delete x;
}
In this code, you have to remember to unlock, close_port, and delete on all paths, and do each exactly once. Further, if any of the code marked ... throws an exception, then x is leaked and my_mutex remains locked.
在這段代碼中，你必須記得在所有路徑上unlock，close_port和delete，而且確切地只做一次。另外，如果任何一處標有...的代碼拋出了異常，那麼x就會泄露，my_mutex會保持鎖定。
Example(示例)
Consider(考慮):
void send(unique_ptr<X> x, cstring_span destination) // x owns the X
{
Port port{destination}; // port owns the PortHandle
lock_guard<mutex> guard{my_mutex}; // guard owns the lock
// ...
send(port, x);
// ...
} // automatically unlocks my_mutex and deletes the pointer in x
Now all resource cleanup is automatic, performed once on all paths whether or not there is an exception. As a bonus, the function now advertises that it takes over ownership of the pointer.
現在所有的資源清除都是自動的，在每條路徑上執行一次。無論是否存在異常。作爲額外的獎勵，這個函數對外宣稱它負責資源的所有權。
What is Port? A handy wrapper that encapsulates the resource:
什麼是Port？一個封裝資源的便利的容器。
class Port {
PortHandle port;
public:
Port(cstring_span destination) : port{open_port(destination)} { }
~Port() { close_port(port); }
operator PortHandle() { return port; }
// port handles can't usually be cloned, so disable copying and assignment if necessary
Port(const Port&) = delete;
Port& operator=(const Port&) = delete;
};
Note(注意)
Where a resource is "ill-behaved" in that it isn't represented as a class with a destructor, wrap it in a class or use finally
當資源由於沒有表現爲一個帶有虛構函數的類而存在"病態行爲",用一個類封裝它或者使用finally。
See also: RAII
參照：RAII
參考：
Finally:
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Re-finally
RAII:
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rr-raii
原文鏈接：
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#r1-manage-resources-automatically-using-resource-handles-and-raii-resource-acquisition-is-initialization
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