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| <body> |
| <div class="document" id="boost-pointer-container-library"> |
| <h1 class="title"><img alt="Boost" src="boost.png" /> Pointer Container Library</h1> |
| <h2 class="subtitle" id="examples">Examples</h2> |
| <p>Some examples are given here and in the accompanying test files:</p> |
| <div class="contents local topic"> |
| <ul class="simple"> |
| <li><a class="reference" href="#null-pointers-cannot-be-stored-in-the-containers" id="id2" name="id2">1. Null pointers cannot be stored in the containers</a></li> |
| <li><a class="reference" href="#iterators-and-other-operations-return-indirected-values" id="id3" name="id3">2. Iterators and other operations return indirected values</a></li> |
| <li><a class="reference" href="#copy-semantics-of-pointer-containers" id="id4" name="id4">3. Copy-semantics of pointer containers</a></li> |
| <li><a class="reference" href="#making-a-non-copyable-type-cloneable" id="id5" name="id5">4. Making a non-copyable type Cloneable</a></li> |
| <li><a class="reference" href="#objects-are-cloned-before-insertion-inserted-pointers-are-owned-by-the-container" id="id6" name="id6">5. Objects are cloned before insertion, inserted pointers are owned by the container</a></li> |
| <li><a class="reference" href="#transferring-ownership-of-a-single-element" id="id7" name="id7">6. Transferring ownership of a single element</a></li> |
| <li><a class="reference" href="#transferring-ownership-of-pointers-between-different-pointer-containers" id="id8" name="id8">7. Transferring ownership of pointers between different pointer containers</a></li> |
| <li><a class="reference" href="#selected-test-files" id="id9" name="id9">8. Selected test files</a></li> |
| <li><a class="reference" href="#a-large-example" id="id10" name="id10">9. A large example</a></li> |
| </ul> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id2" id="null-pointers-cannot-be-stored-in-the-containers" name="null-pointers-cannot-be-stored-in-the-containers"><span id="example-1"></span>1. Null pointers cannot be stored in the containers</a></h1> |
| <pre class="literal-block"> |
| my_container.push_back( 0 ); // throws bad_ptr |
| my_container.replace( an_iterator, 0 ); // throws bad_ptr |
| my_container.insert( an_iterator, 0 ); // throws bad_ptr |
| std::auto_ptr<T> p( 0 ); |
| my_container.push_back( p ); // throws bad_ptr |
| </pre> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id3" id="iterators-and-other-operations-return-indirected-values" name="iterators-and-other-operations-return-indirected-values"><span id="example-2"></span>2. Iterators and other operations return indirected values</a></h1> |
| <pre class="literal-block"> |
| ptr_vector<X> pvec; |
| std::vector<X*> vec; |
| *vec.begin() = new X; // fine, memory leak |
| *pvec.begin() = new X; // compile time error |
| ( *vec.begin() )->foo(); // call X::foo(), a bit clumsy |
| pvec.begin()->foo(); // no indirection needed |
| *vec.front() = X(); // overwrite first element |
| pvec.front() = X(); // no indirection needed |
| </pre> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id4" id="copy-semantics-of-pointer-containers" name="copy-semantics-of-pointer-containers"><span id="example-3"></span>3. Copy-semantics of pointer containers</a></h1> |
| <pre class="literal-block"> |
| ptr_vector<T> vec1; |
| ... |
| ptr_vector<T> vec2( vec1.clone() ); // deep copy objects of 'vec1' and use them to construct 'vec2', could be very expensive |
| vec2 = vec1.release(); // give up ownership of pointers in 'vec1' and pass the ownership to 'vec2', rather cheap |
| vec2.release(); // give up ownership; the objects will be deallocated if not assigned to another container |
| vec1 = vec2; // deep copy objects of 'vec2' and assign them to 'vec1', could be very expensive |
| ptr_vector<T> vec3( vec1 ); // deep copy objects of 'vec1', could be very expensive |
| </pre> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id5" id="making-a-non-copyable-type-cloneable" name="making-a-non-copyable-type-cloneable"><span id="example-4"></span>4. Making a non-copyable type Cloneable</a></h1> |
| <pre class="literal-block"> |
| // a class that has no normal copy semantics |
| class X : boost::noncopyable { public: X* clone() const; ... }; |
| |
| // this will be found by the library by argument dependent lookup (ADL) |
| X* new_clone( const X& x ) |
| { return x.clone(); } |
| |
| // we can now use the interface that requires cloneability |
| ptr_vector<X> vec1, vec2; |
| ... |
| vec2 = vec1.clone(); // 'clone()' requires cloning <g> |
| vec2.insert( vec2.end(), vec1.begin(), vec1.end() ); // inserting always means inserting clones |
| </pre> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id6" id="objects-are-cloned-before-insertion-inserted-pointers-are-owned-by-the-container" name="objects-are-cloned-before-insertion-inserted-pointers-are-owned-by-the-container"><span id="example-5"></span>5. Objects are cloned before insertion, inserted pointers are owned by the container</a></h1> |
| <pre class="literal-block"> |
| class X { ... }; // assume 'X' is Cloneable |
| X x; // and 'X' can be stack-allocated |
| ptr_list<X> list; |
| list.push_back( new_clone( x ) ); // insert a clone |
| list.push_back( new X ); // always give the pointer directly to the container to avoid leaks |
| list.push_back( &x ); // don't do this!!! |
| std::auto_ptr<X> p( new X ); |
| list.push_back( p ); // give up ownership |
| BOOST_ASSERT( p.get() == 0 ); |
| </pre> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id7" id="transferring-ownership-of-a-single-element" name="transferring-ownership-of-a-single-element"><span id="example-6"></span>6. Transferring ownership of a single element</a></h1> |
| <pre class="literal-block"> |
| ptr_deque<T> deq; |
| typedef ptr_deque<T>::auto_type auto_type; |
| |
| // ... fill the container somehow |
| |
| auto_type ptr = deq.pop_back(); // remove back element from container and give up ownership |
| auto_type ptr2 = deq.release( deq.begin() + 2 ); // use an iterator to determine the element to release |
| ptr = deq.pop_front(); // supported for 'ptr_list' and 'ptr_deque' |
| |
| deq.push_back( ptr.release() ); // give ownership back to the container |
| </pre> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id8" id="transferring-ownership-of-pointers-between-different-pointer-containers" name="transferring-ownership-of-pointers-between-different-pointer-containers"><span id="example-7"></span>7. Transferring ownership of pointers between different pointer containers</a></h1> |
| <pre class="literal-block"> |
| ptr_list<X> list; ptr_vector<X> vec; |
| ... |
| // |
| // note: no cloning happens in these examples |
| // |
| list.transfer( list.begin(), vec.begin(), vec ); // make the first element of 'vec' the first element of 'list' |
| vec.transfer( vec.end(), list.begin(), list.end(), list ); // put all the lists element into the vector |
| </pre> |
| <p>We can also transfer objects from <tt class="docutils literal"><span class="pre">ptr_container<Derived></span></tt> to <tt class="docutils literal"><span class="pre">ptr_container<Base></span></tt> without any problems.</p> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id9" id="selected-test-files" name="selected-test-files"><span id="example-8"></span>8. Selected test files</a></h1> |
| <table class="docutils field-list" frame="void" rules="none"> |
| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <tr class="field"><th class="field-name" colspan="2"><a class="reference" href="../test/incomplete_type_test.cpp">incomplete_type_test.cpp</a>:</th></tr> |
| <tr><td> </td><td class="field-body">Shows how to implement the Composite pattern.</td> |
| </tr> |
| <tr class="field"><th class="field-name" colspan="2"><a class="reference" href="../test/simple_test.cpp">simple_test.cpp</a>:</th></tr> |
| <tr><td> </td><td class="field-body">Shows how the usage of pointer container compares with a |
| container of smart pointers</td> |
| </tr> |
| <tr class="field"><th class="field-name" colspan="2"><a class="reference" href="../test/view_example.cpp">view_example.cpp</a>:</th></tr> |
| <tr><td> </td><td class="field-body">Shows how to use a pointer container as a view into other container</td> |
| </tr> |
| <tr class="field"><th class="field-name"><a class="reference" href="../test/tree_test.cpp">tree_test.cpp</a>:</th><td class="field-body">Shows how to make a tree-structure</td> |
| </tr> |
| <tr class="field"><th class="field-name"><a class="reference" href="../test/ptr_array.cpp">array_test.cpp</a>:</th><td class="field-body">Shows how to make an n-ary tree</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section"> |
| <h1><a class="toc-backref" href="#id10" id="a-large-example" name="a-large-example">9. A large example</a></h1> |
| <p>This example shows many of the most common |
| features at work. The example provide lots of comments. |
| The source code can also be found <a class="reference" href="../test/tut1.cpp">here</a>.</p> |
| <html> |
| <head> |
| <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> |
| <title> </title> |
| <link rel="stylesheet" href="default.css" type="text/css"> |
| </head> |
| |
| <body> |
| <pre><span class=comment>// |
| // Boost.Pointer Container |
| // |
| // Copyright Thorsten Ottosen 2003-2005. Use, modification and |
| // distribution is subject to the Boost Software License, Version |
| // 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| // http://www.boost.org/LICENSE_1_0.txt) |
| // |
| // For more information, see http://www.boost.org/libs/ptr_container/ |
| // |
| |
| // |
| // This example is intended to get you started. |
| // Notice how the smart container |
| // |
| // 1. takes ownership of objects |
| // 2. transfers ownership |
| // 3. applies indirection to iterators |
| // 4. clones objects from other smart containers |
| // |
| |
| // |
| // First we select which container to use. |
| //</span> |
| <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>ptr_container</span><span class=special>/</span><span class=identifier>ptr_deque</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span> |
| |
| <span class=comment>// |
| // we need these later in the example |
| //</span> |
| <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>boost</span><span class=special>/</span><span class=identifier>assert</span><span class=special>.</span><span class=identifier>hpp</span><span class=special>></span> |
| <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>string</span><span class=special>></span> |
| <span class=preprocessor>#include</span> <span class=special><</span><span class=identifier>exception</span><span class=special>></span> |
| |
| |
| <span class=comment>// |
| // Then we define a small polymorphic class |
| // hierarchy. |
| //</span> |
| |
| <span class=keyword>class</span> <span class=identifier>animal</span> <span class=special>:</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>noncopyable</span> |
| <span class=special>{</span> |
| <span class=keyword>virtual</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>do_speak</span><span class=special>()</span> <span class=keyword>const</span> <span class=special>=</span> <span class=number>0</span><span class=special>;</span> |
| <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>name_</span><span class=special>;</span> |
| |
| <span class=keyword>protected</span><span class=special>:</span> |
| <span class=comment>// |
| // Animals cannot be copied... |
| //</span> |
| <span class=identifier>animal</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>animal</span><span class=special>&</span> <span class=identifier>r</span> <span class=special>)</span> <span class=special>:</span> <span class=identifier>name_</span><span class=special>(</span> <span class=identifier>r</span><span class=special>.</span><span class=identifier>name_</span> <span class=special>)</span> <span class=special>{</span> <span class=special>}</span> |
| <span class=keyword>void</span> <span class=keyword>operator</span><span class=special>=(</span> <span class=keyword>const</span> <span class=identifier>animal</span><span class=special>&</span> <span class=special>);</span> |
| |
| <span class=keyword>private</span><span class=special>:</span> |
| <span class=comment>// |
| // ...but due to advances in genetics, we can clone them! |
| //</span> |
| |
| <span class=keyword>virtual</span> <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>do_clone</span><span class=special>()</span> <span class=keyword>const</span> <span class=special>=</span> <span class=number>0</span><span class=special>;</span> |
| |
| <span class=keyword>public</span><span class=special>:</span> |
| <span class=identifier>animal</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>&</span> <span class=identifier>name</span> <span class=special>)</span> <span class=special>:</span> <span class=identifier>name_</span><span class=special>(</span><span class=identifier>name</span><span class=special>)</span> <span class=special>{</span> <span class=special>}</span> |
| <span class=keyword>virtual</span> <span class=special>~</span><span class=identifier>animal</span><span class=special>()</span> <span class=keyword>throw</span><span class=special>()</span> <span class=special>{</span> <span class=special>}</span> |
| |
| <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>speak</span><span class=special>()</span> <span class=keyword>const</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>do_speak</span><span class=special>();</span> |
| <span class=special>}</span> |
| |
| <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>name</span><span class=special>()</span> <span class=keyword>const</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>name_</span><span class=special>;</span> |
| <span class=special>}</span> |
| |
| <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>clone</span><span class=special>()</span> <span class=keyword>const</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>do_clone</span><span class=special>();</span> |
| <span class=special>}</span> |
| <span class=special>};</span> |
| |
| <span class=comment>// |
| // An animal is still not Clonable. We need this last hook. |
| // |
| // Notice that we pass the animal by const reference |
| // and return by pointer. |
| //</span> |
| |
| <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>new_clone</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>animal</span><span class=special>&</span> <span class=identifier>a</span> <span class=special>)</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>a</span><span class=special>.</span><span class=identifier>clone</span><span class=special>();</span> |
| <span class=special>}</span> |
| |
| <span class=comment>// |
| // We do not need to define 'delete_clone()' since |
| // since the default is to call the default 'operator delete()'. |
| //</span> |
| |
| <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>muuuh</span> <span class=special>=</span> <span class=string>"Muuuh!"</span><span class=special>;</span> |
| <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>oiink</span> <span class=special>=</span> <span class=string>"Oiiink"</span><span class=special>;</span> |
| |
| <span class=keyword>class</span> <span class=identifier>cow</span> <span class=special>:</span> <span class=keyword>public</span> <span class=identifier>animal</span> |
| <span class=special>{</span> |
| <span class=keyword>virtual</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>do_speak</span><span class=special>()</span> <span class=keyword>const</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>muuuh</span><span class=special>;</span> |
| <span class=special>}</span> |
| |
| <span class=keyword>virtual</span> <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>do_clone</span><span class=special>()</span> <span class=keyword>const</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=keyword>new</span> <span class=identifier>cow</span><span class=special>(</span> <span class=special>*</span><span class=keyword>this</span> <span class=special>);</span> |
| <span class=special>}</span> |
| |
| <span class=keyword>public</span><span class=special>:</span> |
| <span class=identifier>cow</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>&</span> <span class=identifier>name</span> <span class=special>)</span> <span class=special>:</span> <span class=identifier>animal</span><span class=special>(</span><span class=identifier>name</span><span class=special>)</span> <span class=special>{</span> <span class=special>}</span> |
| <span class=special>};</span> |
| |
| <span class=keyword>class</span> <span class=identifier>pig</span> <span class=special>:</span> <span class=keyword>public</span> <span class=identifier>animal</span> |
| <span class=special>{</span> |
| <span class=keyword>virtual</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span> <span class=identifier>do_speak</span><span class=special>()</span> <span class=keyword>const</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>oiink</span><span class=special>;</span> |
| <span class=special>}</span> |
| |
| <span class=keyword>virtual</span> <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>do_clone</span><span class=special>()</span> <span class=keyword>const</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=keyword>new</span> <span class=identifier>pig</span><span class=special>(</span> <span class=special>*</span><span class=keyword>this</span> <span class=special>);</span> |
| <span class=special>}</span> |
| |
| <span class=keyword>public</span><span class=special>:</span> |
| <span class=identifier>pig</span><span class=special>(</span> <span class=keyword>const</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>string</span><span class=special>&</span> <span class=identifier>name</span> <span class=special>)</span> <span class=special>:</span> <span class=identifier>animal</span><span class=special>(</span><span class=identifier>name</span><span class=special>)</span> <span class=special>{</span> <span class=special>}</span> |
| <span class=special>};</span> |
| |
| <span class=comment>// |
| // Then we, of course, need a place to put all |
| // those animals. |
| //</span> |
| |
| <span class=keyword>class</span> <span class=identifier>farm</span> |
| <span class=special>{</span> |
| <span class=comment>// |
| // This is where the smart containers are handy |
| //</span> |
| <span class=keyword>typedef</span> <span class=identifier>boost</span><span class=special>::</span><span class=identifier>ptr_deque</span><span class=special><</span><span class=identifier>animal</span><span class=special>></span> <span class=identifier>barn_type</span><span class=special>;</span> |
| <span class=identifier>barn_type</span> <span class=identifier>barn</span><span class=special>;</span> |
| |
| <span class=comment>// |
| // An error type |
| //</span> |
| <span class=keyword>struct</span> <span class=identifier>farm_trouble</span> <span class=special>:</span> <span class=keyword>public</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>exception</span> <span class=special>{</span> <span class=special>};</span> |
| |
| <span class=keyword>public</span><span class=special>:</span> |
| <span class=comment>// |
| // We would like to make it possible to |
| // iterate over the animals in the farm |
| //</span> |
| <span class=keyword>typedef</span> <span class=identifier>barn_type</span><span class=special>::</span><span class=identifier>iterator</span> <span class=identifier>animal_iterator</span><span class=special>;</span> |
| |
| <span class=comment>// |
| // We also need to count the farm's size... |
| //</span> |
| <span class=keyword>typedef</span> <span class=identifier>barn_type</span><span class=special>::</span><span class=identifier>size_type</span> <span class=identifier>size_type</span><span class=special>;</span> |
| |
| <span class=comment>// |
| // And we also want to transfer an animal |
| // safely around. The easiest way to think |
| // about '::auto_type' is to imagine a simplified |
| // 'std::auto_ptr<T>' ... this means you can expect |
| // |
| // T* operator->() |
| // T* release() |
| // deleting destructor |
| // |
| // but not more. |
| //</span> |
| <span class=keyword>typedef</span> <span class=identifier>barn_type</span><span class=special>::</span><span class=identifier>auto_type</span> <span class=identifier>animal_transport</span><span class=special>;</span> |
| |
| <span class=comment>// |
| // Create an empty farm. |
| //</span> |
| <span class=identifier>farm</span><span class=special>()</span> <span class=special>{</span> <span class=special>}</span> |
| |
| <span class=comment>// |
| // We need a constructor that can make a new |
| // farm by cloning a range of animals. |
| //</span> |
| <span class=identifier>farm</span><span class=special>(</span> <span class=identifier>animal_iterator</span> <span class=identifier>begin</span><span class=special>,</span> <span class=identifier>animal_iterator</span> <span class=identifier>end</span> <span class=special>)</span> |
| <span class=special>:</span> |
| <span class=comment>// |
| // Objects are always cloned before insertion |
| // unless we explicitly add a pointer or |
| // use 'release()'. Therefore we actually |
| // clone all animals in the range |
| //</span> |
| <span class=identifier>barn</span><span class=special>(</span> <span class=identifier>begin</span><span class=special>,</span> <span class=identifier>end</span> <span class=special>)</span> <span class=special>{</span> <span class=special>}</span> |
| |
| <span class=comment>// |
| // ... so we need some other function too |
| //</span> |
| |
| <span class=identifier>animal_iterator</span> <span class=identifier>begin</span><span class=special>()</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>begin</span><span class=special>();</span> |
| <span class=special>}</span> |
| |
| <span class=identifier>animal_iterator</span> <span class=identifier>end</span><span class=special>()</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>end</span><span class=special>();</span> |
| <span class=special>}</span> |
| |
| <span class=comment>// |
| // Here it is quite ok to have an 'animal*' argument. |
| // The smart container will handle all ownership |
| // issues. |
| //</span> |
| <span class=keyword>void</span> <span class=identifier>buy_animal</span><span class=special>(</span> <span class=identifier>animal</span><span class=special>*</span> <span class=identifier>a</span> <span class=special>)</span> |
| <span class=special>{</span> |
| <span class=identifier>barn</span><span class=special>.</span><span class=identifier>push_back</span><span class=special>(</span> <span class=identifier>a</span> <span class=special>);</span> |
| <span class=special>}</span> |
| |
| <span class=comment>// |
| // The farm can also be in economical trouble and |
| // therefore be in the need to sell animals. |
| //</span> |
| <span class=identifier>animal_transport</span> <span class=identifier>sell_animal</span><span class=special>(</span> <span class=identifier>animal_iterator</span> <span class=identifier>to_sell</span> <span class=special>)</span> |
| <span class=special>{</span> |
| <span class=keyword>if</span><span class=special>(</span> <span class=identifier>to_sell</span> <span class=special>==</span> <span class=identifier>end</span><span class=special>()</span> <span class=special>)</span> |
| <span class=keyword>throw</span> <span class=identifier>farm_trouble</span><span class=special>();</span> |
| |
| <span class=comment>// |
| // Here we remove the animal from the barn, |
| // but the animal is not deleted yet...it's |
| // up to the buyer to decide what |
| // to do with it. |
| //</span> |
| <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>release</span><span class=special>(</span> <span class=identifier>to_sell</span> <span class=special>);</span> |
| <span class=special>}</span> |
| |
| <span class=comment>// |
| // How big a farm do we have? |
| //</span> |
| <span class=identifier>size_type</span> <span class=identifier>size</span><span class=special>()</span> <span class=keyword>const</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>size</span><span class=special>();</span> |
| <span class=special>}</span> |
| |
| <span class=comment>// |
| // If things are bad, we might choose to sell all animals :-( |
| //</span> |
| <span class=identifier>std</span><span class=special>::</span><span class=identifier>auto_ptr</span><span class=special><</span><span class=identifier>barn_type</span><span class=special>></span> <span class=identifier>sell_farm</span><span class=special>()</span> |
| <span class=special>{</span> |
| <span class=keyword>return</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>release</span><span class=special>();</span> |
| <span class=special>}</span> |
| |
| <span class=comment>// |
| // However, if things are good, we might buy somebody |
| // else's farm :-) |
| //</span> |
| |
| <span class=keyword>void</span> <span class=identifier>buy_farm</span><span class=special>(</span> <span class=identifier>std</span><span class=special>::</span><span class=identifier>auto_ptr</span><span class=special><</span><span class=identifier>barn_type</span><span class=special>></span> <span class=identifier>other</span> <span class=special>)</span> |
| <span class=special>{</span> |
| <span class=comment>// |
| // This line inserts all the animals from 'other' |
| // and is guaranteed either to succeed or to have no |
| // effect |
| //</span> |
| <span class=identifier>barn</span><span class=special>.</span><span class=identifier>transfer</span><span class=special>(</span> <span class=identifier>barn</span><span class=special>.</span><span class=identifier>end</span><span class=special>(),</span> <span class=comment>// insert new animals at the end</span> |
| <span class=special>*</span><span class=identifier>other</span> <span class=special>);</span> <span class=comment>// we want to transfer all animals, |
| // so we use the whole container as argument |
| // |
| // You might think you would have to do |
| // |
| // other.release(); |
| // |
| // but '*other' is empty and can go out of scope as it wants |
| //</span> |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>other</span><span class=special>-></span><span class=identifier>empty</span><span class=special>()</span> <span class=special>);</span> |
| <span class=special>}</span> |
| |
| <span class=special>};</span> <span class=comment>// class 'farm'.</span> |
| |
| <span class=keyword>int</span> <span class=identifier>main</span><span class=special>()</span> |
| <span class=special>{</span> |
| <span class=comment>// |
| // First we make a farm |
| //</span> |
| <span class=identifier>farm</span> <span class=identifier>animal_farm</span><span class=special>;</span> |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>0u</span> <span class=special>);</span> |
| |
| <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>pig</span><span class=special>(</span><span class=string>"Betty"</span><span class=special>)</span> <span class=special>);</span> |
| <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>pig</span><span class=special>(</span><span class=string>"Benny"</span><span class=special>)</span> <span class=special>);</span> |
| <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>pig</span><span class=special>(</span><span class=string>"Jeltzin"</span><span class=special>)</span> <span class=special>);</span> |
| <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>cow</span><span class=special>(</span><span class=string>"Hanz"</span><span class=special>)</span> <span class=special>);</span> |
| <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>cow</span><span class=special>(</span><span class=string>"Mary"</span><span class=special>)</span> <span class=special>);</span> |
| <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=keyword>new</span> <span class=identifier>cow</span><span class=special>(</span><span class=string>"Frederik"</span><span class=special>)</span> <span class=special>);</span> |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>6u</span> <span class=special>);</span> |
| |
| <span class=comment>// |
| // Then we make another farm...it will actually contain |
| // a clone of the other farm. |
| //</span> |
| <span class=identifier>farm</span> <span class=identifier>new_farm</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(),</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>end</span><span class=special>()</span> <span class=special>);</span> |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>6u</span> <span class=special>);</span> |
| |
| <span class=comment>// |
| // Is it really clones in the new farm? |
| //</span> |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>begin</span><span class=special>()-></span><span class=identifier>name</span><span class=special>()</span> <span class=special>==</span> <span class=string>"Betty"</span> <span class=special>);</span> |
| |
| <span class=comment>// |
| // Then we search for an animal, Mary (the Crown Princess of Denmark), |
| // because we would like to buy her ... |
| //</span> |
| <span class=keyword>typedef</span> <span class=identifier>farm</span><span class=special>::</span><span class=identifier>animal_iterator</span> <span class=identifier>iterator</span><span class=special>;</span> |
| <span class=identifier>iterator</span> <span class=identifier>to_sell</span><span class=special>;</span> |
| <span class=keyword>for</span><span class=special>(</span> <span class=identifier>iterator</span> <span class=identifier>i</span> <span class=special>=</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(),</span> |
| <span class=identifier>end</span> <span class=special>=</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>end</span><span class=special>();</span> |
| <span class=identifier>i</span> <span class=special>!=</span> <span class=identifier>end</span><span class=special>;</span> <span class=special>++</span><span class=identifier>i</span> <span class=special>)</span> |
| <span class=special>{</span> |
| <span class=keyword>if</span><span class=special>(</span> <span class=identifier>i</span><span class=special>-></span><span class=identifier>name</span><span class=special>()</span> <span class=special>==</span> <span class=string>"Mary"</span> <span class=special>)</span> |
| <span class=special>{</span> |
| <span class=identifier>to_sell</span> <span class=special>=</span> <span class=identifier>i</span><span class=special>;</span> |
| <span class=keyword>break</span><span class=special>;</span> |
| <span class=special>}</span> |
| <span class=special>}</span> |
| |
| <span class=identifier>farm</span><span class=special>::</span><span class=identifier>animal_transport</span> <span class=identifier>mary</span> <span class=special>=</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>sell_animal</span><span class=special>(</span> <span class=identifier>to_sell</span> <span class=special>);</span> |
| |
| |
| <span class=keyword>if</span><span class=special>(</span> <span class=identifier>mary</span><span class=special>-></span><span class=identifier>speak</span><span class=special>()</span> <span class=special>==</span> <span class=identifier>muuuh</span> <span class=special>)</span> |
| <span class=comment>// |
| // Great, Mary is a cow, and she may live longer |
| //</span> |
| <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>buy_animal</span><span class=special>(</span> <span class=identifier>mary</span><span class=special>.</span><span class=identifier>release</span><span class=special>()</span> <span class=special>);</span> |
| <span class=keyword>else</span> |
| <span class=comment>// |
| // Then the animal would be destroyed (!) |
| // when we go out of scope. |
| //</span> |
| <span class=special>;</span> |
| |
| <span class=comment>// |
| // Now we can observe some changes to the two farms... |
| //</span> |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>5u</span> <span class=special>);</span> |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>7u</span> <span class=special>);</span> |
| |
| <span class=comment>// |
| // The new farm has however underestimated how much |
| // it cost to feed Mary and its owner is forced to sell the farm... |
| //</span> |
| <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>buy_farm</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>sell_farm</span><span class=special>()</span> <span class=special>);</span> |
| |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>new_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>0u</span> <span class=special>);</span> |
| <span class=identifier>BOOST_ASSERT</span><span class=special>(</span> <span class=identifier>animal_farm</span><span class=special>.</span><span class=identifier>size</span><span class=special>()</span> <span class=special>==</span> <span class=number>12u</span> <span class=special>);</span> |
| <span class=special>}</span> |
| </pre> |
| </body> |
| |
| </html> |
| <!-- 10. Changing the Clone Allocator |
| ++++++++++++++++++++++++++++++++ |
| |
| This example shows how we can change |
| the Clone Allocator to use the pointer containers |
| as view into other containers: |
| |
| .. raw:: html |
| :file: tut2.html --> |
| <hr><p><strong>Navigate:</strong></p> |
| <ul class="simple"> |
| <li><a class="reference" href="ptr_container.html">home</a></li> |
| <li><a class="reference" href="reference.html">reference</a></li> |
| </ul> |
| <hr><table class="docutils field-list" frame="void" rules="none"> |
| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <tr class="field"><th class="field-name">Copyright:</th><td class="field-body">Thorsten Ottosen 2004-2006. Use, modification and distribution is subject to the Boost Software License, Version 1.0 (see <a class="reference" href="http://www.boost.org/LICENSE_1_0.txt">LICENSE_1_0.txt</a>).</td> |
| </tr> |
| </tbody> |
| </table> |
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