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Reference Guide
vo001_AdoptOrOwnMemory.C File Reference

Detailed Description

View in nbviewer Open in SWAN In this tutorial we learn how the RVec class can be used to adopt existing memory or allocate some.

// We use this class for didactic purposes: upon copy, a line is printed to the terminal.
class UponCopyPrinter {
UponCopyPrinter() = default;
UponCopyPrinter(UponCopyPrinter &&) = default;
UponCopyPrinter(const UponCopyPrinter &) { std::cout << "Invoking copy c'tor!" << std::endl; }
using namespace ROOT::VecOps;
// One of the essential features of RVec is its ability of adopting and owning memory.
// Internally this is handled by the ROOT::Detail::VecOps::RAdoptAllocator class.
// Let's create an RVec of UponCopyPrinter instances. We expect no printout:
// Let's adopt the memory from v into v2. We expect no printout:
RVec<UponCopyPrinter> v2(v.data(), v.size());
// OK, let's check the addresses of the memory associated to the two RVecs It is the same!
std::cout << v.data() << " and " << v2.data() << std::endl;
// Now, upon reallocation, the RVec stops adopting the memory and starts owning it. And yes,
// a copy is triggered. Indeed internally the storage of the RVec is an std::vector. Moreover,
// the interface of the RVec is very, very similar to the one of std::vector: you have already
// noticed it when the `data()` method was invoked, right?
// Of course, now the addresses are different.
std::cout << v.data() << " and " << v2.data() << std::endl;
A "std::vector"-like collection of values implementing handy operation to analyse them.
Definition: RVec.hxx:296
0x55a3dd70fd10 and 0x55a3dd70fd10
0x55a3dd70fd10 and 0x55a3dd5a76e0
May 2018
Danilo Piparo

Definition in file vo001_AdoptOrOwnMemory.C.