CCriticalSection Class

Article
01/08/2013

Represents a "critical section" — a synchronization object that allows one thread at a time to access a resource or section of code.

class CCriticalSection : public CSyncObject

Members

Public Constructors

Name	Description
CCriticalSection::CCriticalSection	Constructs a CCriticalSection object.

Public Methods

Name	Description
CCriticalSection::Lock	Use to gain access to the CCriticalSection object.
CCriticalSection::Unlock	Releases the CCriticalSection object.

Public Operators

Name	Description
CCriticalSection::operator CRITICAL_SECTION*	Retrieves a pointer to the internal CRITICAL_SECTION object.

Public Data Members

Name	Description
CCriticalSection::m_sect	A CRITICAL_SECTION object.

Remarks

Critical sections are useful when only one thread at a time can be allowed to modify data or some other controlled resource. For example, adding nodes to a linked list is a process that should only be allowed by one thread at a time. By using a CCriticalSection object to control the linked list, only one thread at a time can gain access to the list.

Note

The functionality of the CCriticalSection class is provided by an actual Win32 CRITICAL_SECTION object.

Critical sections are used instead of mutexes (see CMutex) when speed is critical and the resource will not be used across process boundaries.

There are two methods for using a CCriticalSection object: stand-alone and embedded in a class.

Stand-alone method To use a stand-alone CCriticalSection object, construct the CCriticalSection object when it is needed. After a successful return from the constructor, explicitly lock the object with a call to Lock. Call Unlock when you are done accessing the critical section. This method, while clearer to someone reading your source code, is more prone to error as you must remember to lock and unlock the critical section before and after access.

A more preferable method is to use the CSingleLock class. It also has a Lock and Unlock method, but you don't have to worry about unlocking the resource if an exception occurs.
Embedded method You can also share a class with multiple threads by adding a CCriticalSection-type data member to the class and locking the data member when needed.

For more information on using CCriticalSection objects, see the article Multithreading: How to Use the Synchronization Classes.

Inheritance Hierarchy

CObject

CSyncObject

CCriticalSection

Requirements

Header: afxmt.h