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std::get_temporary_buffer(3) C++ Standard Libary std::get_temporary_buffer(3) NAME std::get_temporary_buffer - std::get_temporary_buffer Synopsis Defined in header <memory> template< class T > std::pair<T*, std::ptrdiff_t> (until C++11) get_temporary_buffer( std::ptrdiff_t count ); template< class T > (since C++11) std::pair<T*, std::ptrdiff_t> (depre- cated in C++17) (removed in C++20) get_temporary_buffer( std::ptrdiff_t count ) noexcept; If count is negative or zero, does nothing. Otherwise, requests to allocate uninitialized contiguous storage for count adjacent objects of type T. The request is non-binding, and the implementa- tion may instead allocate the storage for any other number of (including zero) adja- cent objects of type T. It is implementation-defined whether over-aligned types are sup- ported. (since C++11) Parameters count - the desired number of objects Return value A std::pair, the member first is a pointer to the beginning of the allocated storage and the member second is the number of objects that fit in the stor- age that was actually allocated. If count <= 0 or allocated storage is not enough to store a single element of type T, the member first of the result is a null pointer and the member second is zero. Notes This API was originally designed with the intent of providing a more efficient implementation than the general-purpose operator new, but no such implementation was created and the API was deprecated and removed. Example // Run this code #include <algorithm> #include <iostream> #include <iterator> #include <memory> #include <string> int main() { const std::string s[] = {"string", "1", "test", "..."}; const auto p = std::get_temporary_buffer<std::string>(4); // requires that p.first is passed to return_temporary_buffer // (beware of early exit points and exceptions), or better use: std::unique_ptr<std::string, void(*)(std::string*)> on_exit(p.first, [](std::string* p) { std::cout << "returning temporary buffer...\n"; std::return_temporary_buffer(p); }); std::copy(s, s + p.second, std::raw_storage_iterator<std::string*, std::string>(p.first)); // has same effect as: std::uninitialized_copy(s, s + p.second, p.first); // requires that each string in p is individually destroyed // (beware of early exit points and exceptions) std::copy(p.first, p.first + p.second, std::ostream_iterator<std::string>{std::cout, "\n"}); std::for_each(p.first, p.first + p.second, [](std::string& e) { e.~basic_string<char>(); }); // same as: std::destroy(p.first, p.first + p.second); // manually reclaim memory if unique_ptr-like technique is not used: // std::return_temporary_buffer(p.first); } Output: string 1 test ... returning temporary buffer... Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 425 C++98 the behavior when count <= 0 was unclear made clear LWG 2072 C++98 it was not allowed to allocate insufficient allowed memory See also return_temporary_buffer frees uninitialized storage (deprecated in C++17) (function template) (removed in C++20) allocates storage at least as large as the requested size allocate_at_least via an allocator [static] (C++23) (public static member function of std::allocator_traits<Alloc>) http://cppreference.com 2024.06.10 std::get_temporary_buffer(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Output: | See also
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