std::get_temporary_buffer - cppreference.com (original) (raw)

| Defined in header | | | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | ------------------------------------------------------ | | template< class T > std::pair<T*, std::ptrdiff_t> get_temporary_buffer( std::ptrdiff_t count ); | | (until C++11) | | template< class T > std::pair<T*, std::ptrdiff_t> get_temporary_buffer( std::ptrdiff_t count ) noexcept; | | (since C++11) (deprecated in C++17) (removed in C++20) |

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 implementation may instead allocate the storage for any other number of (including zero) adjacent objects of type T.

[edit] Parameters

[edit] 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 storage 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.

[edit] 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.

[edit] Example

#include #include #include #include #include   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, 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, & e) { e.~basic_string(); }); // 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...

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also