std::scoped_allocator_adaptor
Defined in header <scoped_allocator> | ? | ? |
|---|---|---|
template< class OuterAlloc, class... InnerAlloc > class scoped_allocator_adaptor : public OuterAlloc; | ? | (since C++11) |
大std::scoped_allocator_adaptor类模板是一个分配器，它可以与多级容器%28向量、映射元组列表的集合等一起使用。它是用一个外部分配器类型实例化的。OuterAlloc和零或多个内部分配器类型InnerAlloc....直接用scoped_allocator_adaptor使用OuterAlloc若要分配其元素，但如果元素本身是容器，则使用第一个内部分配器。该容器的元素，如果它们本身就是容器，使用第二个内部分配器，等等。如果容器的级别比内部分配器多，那么最后一个内部分配器将被重用到所有进一步嵌套的容器中。
为了...的目的scoped_allocator_adaptor，如果下一个内部分配器是A，任何阶级T对此std::uses_allocator<T,A>::value==true参与递归，就好像它是一个容器。此外，std::pair的特定重载处理为这样一个容器。scoped_allocator_adaptor::construct...
典型实现持有std::scoped_allocator_adaptor<InnerAllocs...>作为成员对象。
成员类型
Type | Definition |
|---|---|
outer_allocator_type | OuterAlloc |
inner_allocator_type | scoped_allocator_adaptor<InnerAllocs...> or, if sizeof...(InnerAllocs) == 0, scoped_allocator_adaptor<OuterAlloc> |
value_type | std::allocator_traits<OuterAlloc>::value_type |
size_type | std::allocator_traits<OuterAlloc>::size_type |
difference_type | std::allocator_traits<OuterAlloc>::difference_type |
pointer | std::allocator_traits<OuterAlloc>::pointer |
const_pointer | std::allocator_traits<OuterAlloc>::const_pointer |
void_pointer | std::allocator_traits<OuterAlloc>::void_pointer |
const_void_pointer | std::allocator_traits<OuterAlloc>::const_void_pointer |
传播[医]上[医]集装箱[医]复制[医]任务STD：：真[医]输入if std：：分配器[医]性状<A>*宣传[医]上[医]集装箱[医]复制[医]
传播[医]上[医]集装箱[医]移动[医]任务STD：：真[医]输入if std：：分配器[医]性状<A>*宣传[医]上[医]集装箱[医]移动[医]任务：在Outeralloc和Inneralloc之间至少有一个分配器A的值为真。
传播[医]上[医]集装箱[医]SWAP STD：：true[医]输入if std：：分配器[医]性状<A>*宣传[医]上[医]集装箱[医]交换：值是对至少一个分配器A在Outeralloc和Inneralloc之间。
是[医]总[医]等于%28C++17%29 std：：true[医]输入if std：：分配器[医]性状<A>*IS[医]总[医]===
重新绑定模板<class T>结构重新绑定{ty胡枝子f作用域分配器[医]适配器<std：：分配程序[医]性状<OuterAlloc>*模板重新绑定[医]异种<T>，InnerAllocs...>Other；}；
成员函数
(constructor) | creates a new scoped_allocator_adaptor instance (public member function) |
|---|---|
(destructor) | destructs a scoped_allocator_adaptor instance (public member function) |
operator= | assigns a scoped_allocator_adaptor (public member function) |
inner_allocator | obtains an inner_allocator reference (public member function) |
outer_allocator | obtains an outer_allocator reference (public member function) |
allocate | allocates uninitialized storage using the outer allocator (public member function) |
deallocate | deallocates storage using the outer allocator (public member function) |
max_size | returns the largest allocation size supported by the outer allocator (public member function) |
construct | constructs an object in allocated storage, passing the inner allocator to its constructor if appropriate (public member function) |
destroy | destructs an object in allocated storage (public member function) |
select_on_container_copy_construction | copies the state of scoped_allocator_adaptor and all its allocators (public member function) |
非会员职能
operator==operator!= | compares two scoped_allocator_adaptor instances (public member function) |
|---|
例
二次
#include <vector>
#include <scoped_allocator>
#include <boost/interprocess/managed_shared_memory.hpp>
#include <boost/interprocess/allocators/adaptive_pool.hpp>
namespace bi = boost::interprocess;
template<class T> using alloc = bi::adaptive_pool<T,
bi::managed_shared_memory::segment_manager>;
using ipc_row = std::vector<int, alloc<int>>;
using ipc_matrix = std::vector<ipc_row, std::scoped_allocator_adaptor<alloc<ipc_row>>>;
int main ()
{
bi::managed_shared_memory s(bi::create_only, "Demo", 65536);
alloc<int> a(s.get_segment_manager());
// create vector of vectors in shared memory
ipc_matrix v(a); // note: rebinds alloc<ipc_row> from this alloc<int>
// for all these additions, the inner vectors obtain their allocator arguments
// from the outer vector's scoped_allocator_adaptor
v.resize(1); v[0].push_back(1);
v.emplace_back(2);
std::vector<int> local_row = {1,2,3};
v.emplace_back(local_row.begin(), local_row.end());
bi::shared_memory_object::remove("Demo");
}二次
另见
allocator_traits (C++11) | provides information about allocator types (class template) |
|---|---|
uses_allocator (C++11) | checks if the specified type supports uses-allocator construction (class template) |
allocator | the default allocator (class template) |
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