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   "source": [
    "# vo001_AdoptOrOwnMemory\n",
    "In this tutorial we learn how the RVec class can be used to\n",
    "adopt existing memory or allocate some.\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Author:** Danilo Piparo  \n",
    "<i><small>This notebook tutorial was automatically generated with <a href= \"https://github.com/root-project/root/blob/master/documentation/doxygen/converttonotebook.py\">ROOTBOOK-izer</a> from the macro found in the ROOT repository  on Tuesday, May 19, 2026 at 08:27 PM.</small></i>"
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   "source": [
    "%%cpp -d"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "530dfb3f",
   "metadata": {},
   "source": [
    "We use this class for didactic purposes: upon copy, a line is printed to the terminal."
   ]
  },
  {
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   "id": "ecf7c8f2",
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   "source": [
    "class UponCopyPrinter {\n",
    "public:\n",
    "   UponCopyPrinter() = default;\n",
    "   UponCopyPrinter(UponCopyPrinter &&) = default;\n",
    "   UponCopyPrinter(const UponCopyPrinter &) { std::cout << \"Invoking copy c'tor!\" << std::endl; }\n",
    "};"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "74d29221",
   "metadata": {},
   "source": [
    "One of the essential features of RVec is its ability of adopting and owning memory."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a1ed8216",
   "metadata": {},
   "source": [
    "Let's create an RVec of UponCopyPrinter instances. We expect no printout:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "e4ae60a0",
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    "execution": {
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    }
   },
   "outputs": [],
   "source": [
    "ROOT::RVec<UponCopyPrinter> v(3);"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "161abb26",
   "metadata": {},
   "source": [
    "Let's adopt the memory from v into v2. We expect no printout:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "b287664c",
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     "shell.execute_reply": "2026-05-19T20:27:57.041072Z"
    }
   },
   "outputs": [],
   "source": [
    "ROOT::RVec<UponCopyPrinter> v2(v.data(), v.size());"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c438f55e",
   "metadata": {},
   "source": [
    "OK, let's check the addresses of the memory associated to the two RVecs It is the same!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "8a9f795a",
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0x7f8713fb1010 and 0x7f8713fb1010\n"
     ]
    }
   ],
   "source": [
    "std::cout << v.data() << \" and \" << v2.data() << std::endl;"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "91b1dbee",
   "metadata": {},
   "source": [
    "Now, upon reallocation, the RVec stops adopting the memory and starts owning it. And yes,\n",
    "a copy is triggered. Indeed internally the storage of the RVec is an std::vector. Moreover,\n",
    "the interface of the RVec is very, very similar to the one of std::vector: you have already\n",
    "noticed it when the `data()` method was invoked, right?"
   ]
  },
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     "shell.execute_reply": "2026-05-19T20:27:57.459645Z"
    }
   },
   "outputs": [],
   "source": [
    "v2.push_back(UponCopyPrinter());"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "f8027ae6",
   "metadata": {},
   "source": [
    "Of course, now the addresses are different."
   ]
  },
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0x7f8713fb1010 and 0x7f86c5359800\n"
     ]
    }
   ],
   "source": [
    "std::cout << v.data() << \" and \" << v2.data() << std::endl;"
   ]
  }
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