#!/usr/bin/env python
# coding: utf-8

# # vo001_AdoptOrOwnMemory
# In this tutorial we learn how the RVec class can be used to
# adopt existing memory or allocate some.
# 
# 
# 
# 
# **Author:** Danilo Piparo  
# <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 Wednesday, April 17, 2024 at 11:24 AM.</small></i>

# In[1]:


import ROOT


# We use this class for didactic purposes: upon copy, a line is printed to the terminal.

# In[2]:


ROOT.gInterpreter.Declare('''
class UponCopyPrinter {
public:
   UponCopyPrinter() = default;
   UponCopyPrinter(UponCopyPrinter &&) = default;
   UponCopyPrinter(const UponCopyPrinter &) { std::cout << "Invoking copy c'tor!" << std::endl; }
};
''')

RVec_UponCopyPrinter = ROOT.ROOT.VecOps.RVec(ROOT.UponCopyPrinter)


# One of the essential features of RVec is its ability of adopting and owning memory.

# Let's create an RVec of UponCopyPrinter instances. We expect no printout:

# In[3]:


v = RVec_UponCopyPrinter(3)


# Let's adopt the memory from v into v2. We expect no printout:

# In[4]:


v2 = RVec_UponCopyPrinter(v.data(), v.size())


# OK, let's check the addresses of the memory associated to the two RVecs It is the same!

# In[5]:


print("%s and %s" %(v.data(), v2.data()))


# 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?

# In[6]:


v2.resize(4)


# Of course, now the addresses are different.

# In[7]:


print("%s and %s" %(v.data(), v2.data()))