| 1 | ///////////////////////////////////////////////////////////////////////////// |
| 2 | // Name: recguard.h |
| 3 | // Purpose: interface of wxRecursionGuardFlag |
| 4 | // Author: wxWidgets team |
| 5 | // RCS-ID: $Id$ |
| 6 | // Licence: wxWindows license |
| 7 | ///////////////////////////////////////////////////////////////////////////// |
| 8 | |
| 9 | /** |
| 10 | @class wxRecursionGuardFlag |
| 11 | |
| 12 | This is a completely opaque class which exists only to be used with |
| 13 | wxRecursionGuard, please see the example in that class' documentation. |
| 14 | |
| 15 | @remarks |
| 16 | |
| 17 | wxRecursionGuardFlag object must be declared @c static or the recursion |
| 18 | would never be detected. |
| 19 | |
| 20 | @library{wxbase} |
| 21 | @category{misc} |
| 22 | */ |
| 23 | class wxRecursionGuardFlag |
| 24 | { |
| 25 | public: |
| 26 | |
| 27 | }; |
| 28 | |
| 29 | |
| 30 | |
| 31 | /** |
| 32 | @class wxRecursionGuard |
| 33 | |
| 34 | wxRecursionGuard is a very simple class which can be used to prevent reentrancy |
| 35 | problems in a function. It is not thread-safe and so should be used only in |
| 36 | single-threaded programs or in combination with some thread synchronization |
| 37 | mechanisms. |
| 38 | |
| 39 | wxRecursionGuard is always used together with the |
| 40 | wxRecursionGuardFlag like in this example: |
| 41 | |
| 42 | @code |
| 43 | void Foo() |
| 44 | { |
| 45 | static wxRecursionGuardFlag s_flag; |
| 46 | wxRecursionGuard guard(s_flag); |
| 47 | if ( guard.IsInside() ) |
| 48 | { |
| 49 | // don't allow reentrancy |
| 50 | return; |
| 51 | } |
| 52 | |
| 53 | ... |
| 54 | } |
| 55 | @endcode |
| 56 | |
| 57 | As you can see, wxRecursionGuard simply tests the flag value and sets it to |
| 58 | @true if it hadn't been already set. |
| 59 | IsInside() allows testing the old flag |
| 60 | value. The advantage of using this class compared to directly manipulating the |
| 61 | flag is that the flag is always reset in the wxRecursionGuard destructor and so |
| 62 | you don't risk to forget to do it even if the function returns in an unexpected |
| 63 | way (for example because an exception has been thrown). |
| 64 | |
| 65 | @library{wxbase} |
| 66 | @category{misc} |
| 67 | */ |
| 68 | class wxRecursionGuard |
| 69 | { |
| 70 | public: |
| 71 | /** |
| 72 | A wxRecursionGuard object must always be initialized with a @c static |
| 73 | wxRecursionGuardFlag. The constructor saves the |
| 74 | value of the flag to be able to return the correct value from |
| 75 | IsInside(). |
| 76 | */ |
| 77 | wxRecursionGuard(wxRecursionGuardFlag& flag); |
| 78 | |
| 79 | /** |
| 80 | The destructor resets the flag value so that the function can be entered again |
| 81 | the next time. |
| 82 | |
| 83 | @note This is not virtual, so this class is not meant to be derived |
| 84 | from (besides, there is absolutely no reason to do it anyhow). |
| 85 | */ |
| 86 | ~wxRecursionGuard(); |
| 87 | |
| 88 | /** |
| 89 | Returns @true if we're already inside the code block "protected" by this |
| 90 | wxRecursionGuard (i.e. between this line and the end of current scope). |
| 91 | Usually the function using wxRecursionGuard takes some specific actions |
| 92 | in such case (may be simply returning) to prevent reentrant calls to itself. |
| 93 | |
| 94 | If this method returns @false, it is safe to continue. |
| 95 | */ |
| 96 | bool IsInside() const; |
| 97 | }; |
| 98 | |