research of list-new

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1、STLresearch–listSGI2.91Briefintroductionoflistmemoryallocate–allocatorTheinterfacesofallocatorTwotypesofallocatorsDatastructureoflist–BidirectionalcircularlinkedlistAlgorithmsandmembermethodsoflistBriefintroductionoflistlistisakindofsequencecontainer.Itisbidirectionalci

2、rcularlinkedlist,whichcanstoretheelementslocatedindiscontinuousstoragelocations.Advantages:Constanttimetoinsertordeleteanelementanywhereinthecontainer.Providingmoreefficientmemberfunctionthancommonalgorithmswithsamename,suchasremove()andunique().Theiteratorsoflistwillnot

3、beinvalidafterinsertionorremovalexcepttheonejustdeleted.Disadvantages:Lackdirectaccesstotheelementbyitsposition.memoryallocate-allocatorTheSTLcontainershavethefeatureofchangingtheirsizesduringtheruntime.Toachievethis,someformofdynamicmemoryallocationisrequired.Theimporta

4、ntinterfacesofalloctor:templateclassallocator{_Tp*allocate(size_type__n,constvoid*=0){return__n!=0?static_cast<_Tp*>(_Alloc::allocate(__n*sizeof(_Tp))):0;}voiddeallocate(pointer__p,size_type__n){_Alloc::deallocate(__p,__n*sizeof(_Tp));}voidconstruct(pointer__p,

5、const_Tp&__val){new(__p)_Tp(__val);}voiddestroy(pointer__p){__p->~_Tp();}}TwotypeofallocatorsTherearetwotypesofdefaultallocatorsusedbySTL:Firstlevelallocator:Handlethememoryrequestedthatismorethan128bytes.Secondlevelallocator:Handlethememoryrequestedwhichislessthan128byt

6、es.It’sdesignedtoavoidmemoryfragmentation.STLusesthesecondlevelallocatorindefaultunlessthememoryrequestedismorethan128bytes.Ifthemacroname“__USE_MALLOC”isdefined,itwillcallthefirstlevelallocator.memoryallocate–allocatorThefirstlevelallocatorThesecondlevelallocatorNexttem

7、plateclass__malloc_alloc_template{private://oom:outofmemorystaticvoid*_S_oom_malloc(size_t);staticvoid*_S_oom_realloc(void*,size_t);staticvoid(*__malloc_alloc_oom_handler)();public:staticvoid*allocate(size_t__n){void*__result=malloc(__n);if(0==__result)__resul

8、t=_S_oom_malloc(__n);return__result;}staticvoiddeallocate(void*__p,size_t/*__n*/){free(__p);}staticvoid