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Moved shared_container_iterator.hpp in iterator directory, modernized code.

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shared_container_iterator now uses std::shared_ptr to store the reference
to the container. boost::shared_ptr is still supported and is wrapped
into std::shared_ptr on construction, so there is overhead due to allocation
of std::shared_ptr state. Going forward, std::shared_ptr is expected
to be the primary use case. As a bonus, this eliminates the dependency
on Boost.SmartPtr.

Moved shared_container_iterator.hpp into the iterator directory and left
a forwarding header for backward compatibility.
This commit is contained in:
Andrey Semashev
2025-02-07 02:07:12 +03:00
parent e446c6e05c
commit a7150173ed
9 changed files with 230 additions and 123 deletions
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2
doc/index.html
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@@ -140,7 +140,7 @@ sequence, rearranged according to some sequence of integer indices.</li>
bidirectional sequence in reverse. Corrects many of the
shortcomings of C++98's <tt class="docutils literal"><span class="pre">std::reverse_iterator</span></tt>.</li>
<li><a class="reference external" href="../../utility/shared_container_iterator.html"><tt class="docutils literal"><span class="pre">shared_container_iterator</span></tt></a>: an iterator over elements of a container whose
lifetime is maintained by a <a class="reference external" href="../../smart_ptr/shared_ptr.htm"><tt class="docutils literal"><span class="pre">shared_ptr</span></tt></a> stored in the iterator.</li>
lifetime is maintained by a <tt class="docutils literal"><span class="pre">shared_ptr</span></tt> stored in the iterator.</li>
<li><a class="reference external" href="transform_iterator.html"><tt class="docutils literal"><span class="pre">transform_iterator</span></tt></a> (<a class="reference external" href="transform_iterator.pdf">PDF</a>): an iterator over elements which are the result of
applying some functional transformation to the elements of an
underlying sequence. This component also replaces the old

122
doc/quickbook/shared_container_iterator.qbk
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@@ -1,6 +1,6 @@
[section:shared_container Shared Container Iterator]
Defined in header [@../../../boost/shared_container_iterator.hpp `boost/shared_container_iterator.hpp`].
Defined in header [@../../../boost/iterator/shared_container_iterator.hpp `boost/iterator/shared_container_iterator.hpp`].
The purpose of the shared container iterator is to attach the lifetime
of a container to the lifetime of its iterators. In other words, the
@@ -24,9 +24,22 @@ iterator.
[h2 Synopsis]
namespace boost {
namespace iterators {
template <typename Container>
class shared_container_iterator;
template <typename Container>
shared_container_iterator<Container>
make_shared_container_iterator(typename Container::iterator base,
std::shared_ptr<Container> const& container);
std::pair<
typename shared_container_iterator<Container>,
typename shared_container_iterator<Container>
>
make_shared_container_range(std::shared_ptr<Container> const& container);
// Backward compatibility with boost::shared_ptr
template <typename Container>
shared_container_iterator<Container>
make_shared_container_iterator(typename Container::iterator base,
@@ -38,6 +51,15 @@ iterator.
>
make_shared_container_range(boost::shared_ptr<Container> const& container);
}
}
[note `shared_container_iterator` and its factory functions support both
`std::shared_ptr` and `boost::shared_ptr` for a smart pointer that holds
a shared reference to the container. However, the support for `boost::shared_ptr`
comes at a cost of wrapping it in a `std::shared_ptr` internally. This means
that when constructing the iterator from a `boost::shared_ptr`, the construction
will have to allocate memory for `std::shared_ptr` shared state, which may
potentially fail. It is recommended to use `std::shared_ptr` directly.]
[section:shared_container_type The Shared Container Iterator Type]
@@ -57,18 +79,17 @@ the underlying vector and thereby extend the container's lifetime.
[example_link shared_iterator_example1.cpp..`shared_iterator_example1.cpp`]:
#include "shared_container_iterator.hpp"
#include "boost/shared_ptr.hpp"
#include <boost/iterator/shared_container_iterator.hpp>
#include <algorithm>
#include <iostream>
#include <vector>
#include <memory>
typedef boost::shared_container_iterator< std::vector<int> > iterator;
using iterator = boost::iterators::shared_container_iterator< std::vector<int> >;
void set_range(iterator& i, iterator& end) {
boost::shared_ptr< std::vector<int> > ints(new std::vector<int>());
void set_range(iterator& i, iterator& end) {
std::shared_ptr< std::vector<int> > ints(new std::vector<int>());
ints->push_back(0);
ints->push_back(1);
@@ -77,18 +98,17 @@ the underlying vector and thereby extend the container's lifetime.
ints->push_back(4);
ints->push_back(5);
i = iterator(ints->begin(),ints);
end = iterator(ints->end(),ints);
i = iterator(ints->begin(), ints);
end = iterator(ints->end(), ints);
}
int main() {
iterator i, end;
iterator i,end;
set_range(i, end);
set_range(i,end);
std::copy(i,end,std::ostream_iterator<int>(std::cout,","));
std::copy(i, end, std::ostream_iterator<int>(std::cout, ","));
std::cout.put('\n');
return 0;
@@ -116,8 +136,12 @@ The `shared_container_iterator` type implements the member functions
and operators required of the
[@http://www.sgi.com/tech/stl/RandomAccessIterator.html Random Access
Iterator] concept, though only operations defined for the base
iterator will be valid. In addition it has the following constructor:
iterator will be valid. In addition it has the following constructors:
shared_container_iterator(Container::iterator const& it,
std::shared_ptr<Container> const& container)
// Backward compatibility with boost::shared_ptr
shared_container_iterator(Container::iterator const& it,
boost::shared_ptr<Container> const& container)
@@ -125,6 +149,12 @@ iterator will be valid. In addition it has the following constructor:
[section:shared_container_object_generator The Shared Container Iterator Object Generator]
template <typename Container>
shared_container_iterator<Container>
make_shared_container_iterator(Container::iterator base,
std::shared_ptr<Container> const& container)
// Backward compatibility with boost::shared_ptr
template <typename Container>
shared_container_iterator<Container>
make_shared_container_iterator(Container::iterator base,
@@ -142,25 +172,23 @@ uses `make_shared_container_iterator()` to create the iterators.
[example_link shared_iterator_example2.cpp..`shared_iterator_example2.cpp`]:
#include "shared_container_iterator.hpp"
#include "boost/shared_ptr.hpp"
#include <boost/iterator/shared_container_iterator.hpp>
#include <algorithm>
#include <iterator>
#include <iostream>
#include <vector>
#include <memory>
template <typename Iterator>
void print_range_nl (Iterator begin, Iterator end) {
typedef typename std::iterator_traits<Iterator>::value_type val;
std::copy(begin,end,std::ostream_iterator<val>(std::cout,","));
void print_range_nl(Iterator begin, Iterator end) {
using val = typename std::iterator_traits<Iterator>::value_type;
std::copy(begin, end, std::ostream_iterator<val>(std::cout, ","));
std::cout.put('\n');
}
int main() {
typedef boost::shared_ptr< std::vector<int> > ints_t;
using ints_t = std::shared_ptr< std::vector<int> >;
{
ints_t ints(new std::vector<int>());
@@ -171,12 +199,10 @@ uses `make_shared_container_iterator()` to create the iterators.
ints->push_back(4);
ints->push_back(5);
print_range_nl(boost::make_shared_container_iterator(ints->begin(),ints),
boost::make_shared_container_iterator(ints->end(),ints));
print_range_nl(boost::iterators::make_shared_container_iterator(ints->begin(), ints),
boost::iterators::make_shared_container_iterator(ints->end(), ints));
}
return 0;
}
@@ -187,53 +213,61 @@ named. The output from this example is the same as the previous.
[section:shared_container_generator The Shared Container Iterator Range Generator]
template <typename Container>
std::pair<
shared_container_iterator<Container>,
shared_container_iterator<Container>
>
make_shared_container_range(std::shared_ptr<Container> const& container);
// Backward compatibility with boost::shared_ptr
template <typename Container>
std::pair<
shared_container_iterator<Container>,
shared_container_iterator<Container>
>
make_shared_container_range(boost::shared_ptr<Container> const& container);
Class shared_container_iterator is meant primarily to return, using iterators, a range of values that we can guarantee will be alive as long as the iterators are. This is a convenience function to do just that. It is equivalent to
std::make_pair(make_shared_container_iterator(container->begin(),container),
make_shared_container_iterator(container->end(),container));
Class `shared_container_iterator` is meant primarily to return, using iterators,
a range of values that we can guarantee will be alive as long as the iterators are.
This is a convenience function to do just that. It is functionally equivalent to this:
std::make_pair(make_shared_container_iterator(container->begin(), container),
make_shared_container_iterator(container->end(), container));
[h2 Example]
In the following example, a range of values is returned as a pair of shared_container_iterator objects.
In the following example, a range of values is returned as a pair of `shared_container_iterator` objects.
[example_link shared_iterator_example3.cpp..`shared_iterator_example3.cpp`]:
#include "shared_container_iterator.hpp"
#include "boost/shared_ptr.hpp"
#include "boost/tuple/tuple.hpp" // for boost::tie
#include <algorithm> // for std::copy
#include <boost/iterator/shared_container_iterator.hpp>
#include <algorithm> // for std::copy
#include <iostream>
#include <vector>
#include <memory>
#include <tuple> // for std::tie
typedef boost::shared_container_iterator< std::vector<int> > iterator;
using iterator = boost::iterators::shared_container_iterator< std::vector<int> >;
std::pair<iterator,iterator>
std::pair<iterator, iterator>
return_range() {
boost::shared_ptr< std::vector<int> > range(new std::vector<int>());
std::shared_ptr< std::vector<int> > range(new std::vector<int>());
range->push_back(0);
range->push_back(1);
range->push_back(2);
range->push_back(3);
range->push_back(4);
range->push_back(5);
return boost::make_shared_container_range(range);
return boost::iterators::make_shared_container_range(range);
}
int main() {
iterator i,end;
std::tie(i, end) = return_range();
boost::tie(i,end) = return_range();
std::copy(i,end,std::ostream_iterator<int>(std::cout,","));
std::copy(i, end, std::ostream_iterator<int>(std::cout, ","));
std::cout.put('\n');
return 0;