5 C + + Boost smart pointer

Smart pointer class template [figure]scoped_ptr[figure]boost scoped_ptr correct construction boost shared_ptr[diagram]boost shared_ptr build. png[Diagram]boost shared_ PTR can reference pointers multiple times boost week ptr[figure]boost week_ptrboost intrusive intrusive pointer boost make_shared omit explicit newboost enable_shared_from_ Thisboost loop reference, object not destructor, memory leak boost weak_ptr break loop reference boost Pimpl interface private implementation Technology

Smart pointer class template [diagram]

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scoped_ptr[Map]

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The correct construction of boost scoped_ptr

[email protected]:~/boost $ cat main.cpp // *  operator Overloading// -> operator overloading # Include <iostream> #include  <boost/scoped_ptr.hpp>using namespace std;struct  a{a ()  { cout <<  "a:a ()" &NBSP;&LT;&LT;&NBSP;ENDL;} ~a ()  { cout <<  "A:~a ()" &NBSP;&LT;&LT;&NBSP;ENDL;} Void f ()  { cout <<  "a:f ()"  <<endl;}};/ /smart pointer correct construction mode Int main () {boost::scoped_ptr<int>sp (new int); cout << ++*sp  <<endl;//initialization is only one way, only for exclusive//BOOST::SCOPED_PTR&LT;INT&GT;SP2 (SP);//compile errorboost::scoped_ Ptr<a> ap (New a), ap->f ();cout <<  "-------------------"  <<  endl;//demonstrates the double free //a a;//stack area variable, leaving the scope to automatically refactor//boost::scoped_ptr<a> (&a);//Leave scope automatically destructors// compile error:note: previous declaration as  ' A a ' return 0;} [email protected]:~/boost $ g++  -wall main.cpp &&./a.out 129a:a () A:f ()--------------- ----A:~a () [email protected]:~/boost $

Boost Shared_ptr[Chart]

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Boost shared_ptr build. png[Map]

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boost shared_ptr can refer to the pointer multiple times

[email protected]:~/boost $ cat main.cpp  #include  <iostream> #include   <boost/shared_ptr.hpp>using namespace std;struct A{         a ()  { cout <<  "a:a ()" &NBSP;&LT;&LT;&NBSP;ENDL;}         ~a ()  { cout <<  "A:~a ()"  < < endl;}         void f ()  { cout <<  "a:f ()"  <<endl;}};/ /smart pointer correct construction mode Int main () {&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;BOOST::SHARED_PTR&LT;INT&GT;SP (new  int (+));        cout << ++*sp << ENDL;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;BOOST::SHARED_PTR&LT;INT&GT;SP2 (SP);//shared_ptr can be referenced multiple times         cout <<  "SP2 citations:"  << sp2.use _count ()  << endl;                 boost::shared_ptr<a> ap (new a);         ap- >f ();        cout <<  "-------------------"   << endl;        return 0;} [email protected]:~/boost $ g++  -wall main.cpp &&./a.out  129SP2 citations: 2a:a () a:f ()-------------------a:~a () [email protected]:~/boost $

Boost Week ptr[chart]

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Boost Week_ptr

[email protected]:~/boost $ cat main.cpp  #include  <iostream> #include   <boost/shared_ptr.hpp> #include  <boost/weak_ptr.hpp>using namespace std;int  Main () {&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;BOOST::SHARED_PTR&LT;INT&GT;SP (New int (128));         cout << ++*sp <<endl;   &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;BOOST::SHARED_PTR&LT;INT&GT;SP2 (SP);//shared_ptr can be quoted multiple times          cout <<  "SP2 citations:"  << sp2.use_count ()  < &LT;&NBSP;ENDL;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;BOOST::WEAK_PTR&LT;INT&GT;&NBSP;WP (SP2); cout  <<  "WP citations:"  <<wp.use_count ()  << endl;cout <<  " Wp.lock: " <<*wp.lock ()  << endl;//lock returns a compliant shared_ptr         //wp-&Gt;f ();//weak do not have operator overloading, compile error         cout <<  "------- ------------"&NBSP;&LT;&LT;&NBSP;ENDL;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;RETURN&NBSP;0;} [email protected]:~/boost $ g++  -wall main.cpp &&./a.out  129SP2 citations: 2wp citations: 2wp.lock:129-------------------[email protected]:~/boost $

Boost intrusive intrusive pointer

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[email protected]:~/boost $ cat main.cpp  #include  <iostream> #include   <boost/shared_ptr.hpp> #include  <boost/intrusive_ptr.hpp>using namespace std;class  referencecounter{public:referencecounter (): RefCount (0) {}virtual ~referencecounter () {}friend  Void intrusive_ptr_add_ref (referencecounter *p) {++p->refcount;} Friend void intrusive_ptr_release (referencecounter *p) {if (--p->refcount == 0) { Delete p;}} Int getrefcount ()  const{return refcount;} private:int refcount;}; Class d:public referencecounter{public:d () {cout <<  "D:D ()" &NBSP;&LT;&LT;&NBSP;ENDL;} ~d () {cout <<  "d:~d ()"  << endl;}}; Int main () {D*&NBSP;DP&NBSP;=&NBSP;NEW&NBSP;D;BOOST::INTRUSIVE_PTR&LT;D&GT;&NBSP;DP1 (DP); { Reference to local scope BOOST::INTRUSIVE_PTR&LT;D&GT;&NBSP;DP2 (DP);cout <<  "dp2 :" << dp2- >getrefcount ()  << endl;} cout <<  "dp1  Quote:" << dp1->getrefcount ()  << endl;         return 0;} [Email protected]:~/boost $ g++  -wall main.cpp &&./a.out d:d ( Reference to the dp2  reference:2dp1 : 1d:~d () [email protected]:~/boost $

Boost Make_shared omit the explicit new

#include  <iostream> #include  <boost/shared_ptr.hpp> #include  <boost/make_ Shared.hpp>struct d{d () { std::cout <<  "d:d ()" &NBSP;&LT;&LT;&NBSP;STD::ENDL;} D (int k,double d) {std::cout <<  "k=" <<k<< " d=" << d  << std::endl;} ~d () {std::cout <<  "d:~d ()"  << std::endl;}}; Struct e{e (std::string s)  {std::cout <<  "s=" &NBSP;&LT;&LT;S&LT;&LT;&NBSP;STD:: Endl;} ~e () {std::cout <<  "e:~e ()"  << std::endl;}}; Int main () {boost::shared_ptr<d> dp1 = boost::make_shared<d> (); boost::shared_ Ptr<d> dp2 = boost::make_shared<d> (12,3.14); boost::shared_ptr<e> ep1  = boost::make_shared<E> ("Boost");        return  0;} [email protected]:~/boost $ g++  -wall  Main.cpp &&./a.out d:d () k=12 d=3.14s=booste:~e () d:~d () d:~d () [email protected]:~/ boost $

boost enable_shared_from_this

 #include  <boost/shared_ptr.hpp> #include  <boost/enable_ shared_from_this.hpp>//using Shared_ptrclass a;void func (BOOST::SHARED_PTR<A>&NBSP;P) inside a class  {std::cout <<  "sizeof (P) =" <<sizeof (p)  <<std::endl;} Class a:public boost::enable_shared_from_this<a>{public:void f () {std::cout <<   "a f ()  \n"; Func (Shared_from_this ());} Void say_hi () {std::cout <<  "hello boost \n";}; Int main () {boost::shared_ptr <a> a (new a); A->f ();         return 0;} [Email protected]:~/boost $ g++  -wall main.cpp &&./a.out a  f ()  sizeof (p) =8[email protected]:~/boost $ 

boost Circular reference, object not destructor, memory leak

[email protected]:~/boost $ cat main.cpp  #include  <iostream> #include   <boost/shared_ptr.hpp> #include  <boost/enable_shared_from_this.hpp>struct b;struct a {A ()  {std::cout << "A ()" &NBSP;&LT;&LT;STD::ENDL;} ~a () {std::cout << "~a ()" &NBSP;&LT;&LT;STD::ENDL;} boost::shared_ptr<b> b;}; Struct b{b ()  {std::cout << "B ()" &NBSP;&LT;&LT;STD::ENDL;} ~b () {std::cout << "~b ()" &NBSP;&LT;&LT;STD::ENDL;} boost::shared_ptr<a> a;}; Int main () {boost::shared_ptr<a> ap (new a); boost::shared_ptr<b> bp (New B); ap->b = bp;bp->a = ap;std::cout <<  "------------\ n";         return 0;} [Email protected]:~/boost $ g++  -wall main.cpp &&./a.out a () B ()------------[email protected]:~/boost $

boost weak_ptr Break Circular reference

[email protected]:~/boost $ cat main.cpp  #include  <iostream> #include   <boost/shared_ptr.hpp> #include  <boost/enable_shared_from_this.hpp>struct b;struct a {A ()  {std::cout << "A ()" &NBSP;&LT;&LT;STD::ENDL;} ~a () {std::cout << "~a ()" &NBSP;&LT;&LT;STD::ENDL;} boost::shared_ptr<b> b;}; Struct b{b ()  {std::cout << "B ()" &NBSP;&LT;&LT;STD::ENDL;} ~b () {std::cout << "~b ()" &NBSP;&LT;&LT;STD::ENDL;} boost::shared_ptr<a> a;boost::weak_ptr<a> a;}; Int main () {boost::shared_ptr<a> ap (new a); boost::shared_ptr<b> bp (New B); ap->b = bp;bp->a = ap;std::cout <<  "------------\ n";         return 0;} [Email protected]:~/boost $ g++  -wall main.cpp &&./a.out a () B ()------------~a () ~b () [Email protected]:~/boost $ 

boost Pimpl Interface Private Implementation technology

[email protected]:~/boost $ cat example.h  #ifndef  example_h_#define example _h_#include <boost/shared_ptr.hpp>class example {public:example (); Void do_something ( );p rivate:class implementation;// hide implementation detailsboost::shared_ptr< implementation> _imp;}; #endif  /* example_h_ */[email protected]:~/boost $ cat example.cpp # include <iostream> #include   "Example.h" class example::implementation {public:~ Implementation ()  {std::cout <<  "destroying implementation\n";}; Example::example (): _imp (new implementation)  {}void example::d o_something ()  {std::cout  <<  "Use_count ()  is "  << _imp.use_count ()  <<  "\ n";} [email protected]:~/boost $ cat pimpl_test.cpp  #include   "Example.h" Int main ()  {  &Nbsp; example a;    a.do_something ();     example b (a);     b.do_something ();     example c;    c  = a;    c.do_something ();     return 0;} [email protected]:~/boost $ g++  -wall pimpl_test.cpp example.cpp   &&./a.out use_count ()  is 1use_count ()  is 2destroying  Implementationuse_count ()  is 3destroying implementation[email protected]:~/boost $

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5 C + + Boost smart pointer