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Added Shared Container Iterator adaptor to iterator adaptor library.

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[SVN r15169]
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Ronald Garcia 2002-09-05 14:05:29 +00:00
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iterator_adaptors.htm
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<a href="generator_iterator.htm">Generator Iterator Adaptor</a>
<li>Header <tt><a href="../../boost/permutation_iterator.hpp">boost/permutation_iterator.hpp</a></tt><br>
<a href="permutation_iterator.htm">Permutation Iterator Adaptor</a>
<li>Header <tt><a href="../../boost/shared_container_iterator.hpp">boost/shared_container_iterator.hpp</a></tt><br>
<a href="shared_container_iterator.html">Shared_Container Iterator Adaptor</a>
</ul>
<p><b><a href="../../people/dave_abrahams.htm">Dave
@ -156,6 +158,9 @@
adaptor.<br>
Toon Knapen contributed the <a href="permutation_iterator.htm">permutation
iterator</a> adaptor.<br>
<b><a href="../../people/ronald_garcia.htm">Ronald Garcia</a></b>
contributed the <a href="shared_container_iterator.html">shared container iterator</a>
adaptor.<br>
<h2><a name="iterator_adaptor">Class template</a>
<tt>iterator_adaptor</tt></h2>

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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Shared Container Iterator Documentation</title>
</head>
<body bgcolor="#FFFFFF" text="#000000">
<img src="../../c++boost.gif" alt="c++boost.gif (8819 bytes)"
align="center" width="277" height="86">
<h1>Shared Container Iterator</h1>
Defined in header
<a href="../../boost/shared_container_iterator.hpp">boost/shared_container_iterator.hpp</a>
<p>
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 container will be deleted after the last iterator is destroyed.
The shared container iterator is typically used to implement functions
that return iterators over a
range of objects that will only be needed for the lifetime of
the iterators. By returning a pair of shared iterators from a
function, the callee can ensure that the underlying container's
lifetime will be properly managed.
<p>
The shared container iterator augments an iterator into a shared
container with a reference counted pointer to the container.
Assuming no other references exist to the container, it will be
destroyed when the last shared container iterator is destroyed.
In all other ways, the shared container iterator
behaves the same as its base iterator.
<h2>Synopsis</h2>
<pre>
namespace boost {
template &lt;typename <a href="http://www.sgi.com/tech/stl/Container.html">Container</a>&gt;
class shared_container_iterator_generator;
template &lt;typename <a href="http://www.sgi.com/tech/stl/Container.html">Container</a>&gt;
typename shared_container_iterator_generator&lt;Container&gt;::type
make_shared_container_iterator(typename Container::iterator base,
boost::shared_ptr&lt;Container&gt; const&amp; container);
std::pair&lt
typename shared_container_iterator_generator&lt;Container&gt;::type,
typename shared_container_iterator_generator&lt;Container&gt;::type
&gt;
make_shared_container_range(boost::shared_ptr&lt;Container&gt; const&amp; container);
}
</pre>
<hr>
<h2><a name="generator">The Shared Container Iterator Type Generator</a></h2>
The class <tt>shared_container_iterator_generator</tt> is a helper
class to construct a shared container iterator type. The template
parameter for this class is a type that models the
<a href="http://www.sgi.com/tech/stl/Container.html">Container</a>
concept.
<pre>
template &lt;typename Container&gt;
class shared_container_iterator_generator
{
public:
typedef <a href="./iterator_adaptors.htm#iterator_adaptor">iterator_adaptor</a>&lt;...&gt; type;
};
</pre>
<h3>Example</h3>
<p>
The following example illustrates how to use the
<tt>shared_counter_iterator_generator</tt> to create an iterator that
regulates the lifetime of a reference counted <tt>std::vector</tt>.
Though the original <tt>shared_ptr</tt> to the vector ceases to exist, the
<tt>shared_counter_iterator</tt>s extend the lifetime of the container.
<p>
<a href="./shared_iterator_example1.cpp">shared_iterator_example1.cpp</a>:
<PRE>
<font color="#008040">#include "shared_container_iterator.hpp"</font>
<font color="#008040">#include "boost/shared_ptr.hpp"</font>
<font color="#008040">#include &lt;algorithm&gt;</font>
<font color="#008040">#include &lt;iostream&gt;</font>
<font color="#008040">#include &lt;vector&gt;</font>
<B>typedef</B> boost::shared_container_iterator_generator&lt; std::vector&lt;<B>int</B>&gt; &gt;::type iterator;
<B>void</B> set_range(iterator& i, iterator& end) {
boost::shared_ptr&lt; std::vector&lt;<B>int</B>&gt; &gt; ints(<B>new</B> std::vector&lt;<B>int</B>&gt;());
ints-&gt;push_back(<font color="#0000A0">0</font>);
ints-&gt;push_back(<font color="#0000A0">1</font>);
ints-&gt;push_back(<font color="#0000A0">2</font>);
ints-&gt;push_back(<font color="#0000A0">3</font>);
ints-&gt;push_back(<font color="#0000A0">4</font>);
ints-&gt;push_back(<font color="#0000A0">5</font>);
i = iterator(ints-&gt;begin(),ints);
end = iterator(ints-&gt;end(),ints);
}
<B>int</B> main() {
iterator i,end;
set_range(i,end);
std::copy(i,end,std::ostream_iterator&lt;<B>int</B>&gt;(std::cout,<font color="#0000FF">","</font>));
std::cout.put(<font color="#0000FF">'\n'</font>);
<B>return</B> <font color="#0000A0">0</font>;
}
</PRE>
The output from this part is:
<pre>
0,1,2,3,4,5,
</pre>
<h3>Template Parameters</h3>
<Table border>
<TR>
<TH>Parameter</TH><TH>Description</TH>
</TR>
<TR>
<TD><a
href="http://www.sgi.com/tech/stl/Container.html"><tt>Container</tt></a></TD>
<TD>The type of the container that we wish to iterate over. It must be
a model of the
<a href="http://www.sgi.com/tech/stl/Container.html"><tt>Container</tt></a>
concept.
</TD>
</TR>
</Table>
<h3>Model of</h3>
The shared container iterator adaptor (the type
<tt>shared_container_iterator_generator<...>::type</tt>) models the
same iterator concept as the base iterator
(<tt>Container::iterator</tt>) up to
<a href="http://www.sgi.com/tech/stl/RandomAccessIterator.html">Random
Access Iterator</a>.
<h3>Members</h3>
The shared container iterator type implements the member functions and
operators required of the <a
href="http://www.sgi.com/tech/stl/RandomAccessIterator.html">Random Access Iterator</a>
concept, though only operations defined for the base iterator will be valid.
In addition it has the following constructor:
<pre>
shared_container_iterator_generator::type(Container::iterator const&amp; it,
boost::shared_ptr&lt;Container&gt; const&amp; container)
</pre>
<p>
<hr>
<p>
<h2><a name="make_iterator">The Shared Container Iterator Object Generator</a></h2>
<pre>
template &lt;typename Container&gt;
typename shared_container_iterator_generator&lt;AdaptableUnaryFunction,BaseIterator&gt;::type
make_shared_container_iterator(Container::iterator base,
boost::shared_ptr&lt;Container&gt; const&amp; container)
</pre>
This function provides an alternative to using the shared container
iterator type generator to create the iterator type before
construction. Using the object generator, a shared container iterator
can be created and passed to a function without explicitly specifying
its type.
<h3>Example</h3>
This example, similar to the previous, uses
<tt>make_shared_container_iterator()</tt> to create the iterators.
<p>
<a href="./shared_iterator_example2.cpp">shared_iterator_example2.cpp</a>:
<PRE>
<font color="#008040">#include "shared_container_iterator.hpp"</font>
<font color="#008040">#include "boost/shared_ptr.hpp"</font>
<font color="#008040">#include &lt;algorithm&gt;</font>
<font color="#008040">#include &lt;iterator&gt;</font>
<font color="#008040">#include &lt;iostream&gt;</font>
<font color="#008040">#include &lt;vector&gt;</font>
<B>template</B> &lt;<B>typename</B> Iterator&gt;
<B>void</B> print_range_nl (Iterator begin, Iterator end) {
<B>typedef</B> <B>typename</B> std::iterator_traits&lt;Iterator&gt;::value_type val;
std::copy(begin,end,std::ostream_iterator&lt;val&gt;(std::cout,<font color="#0000FF">","</font>));
std::cout.put(<font color="#0000FF">'\n'</font>);
}
<B>int</B> main() {
<B>typedef</B> boost::shared_ptr&lt; std::vector&lt;<B>int</B>&gt; &gt; ints_t;
{
ints_t ints(<B>new</B> std::vector&lt;<B>int</B>&gt;());
ints-&gt;push_back(<font color="#0000A0">0</font>);
ints-&gt;push_back(<font color="#0000A0">1</font>);
ints-&gt;push_back(<font color="#0000A0">2</font>);
ints-&gt;push_back(<font color="#0000A0">3</font>);
ints-&gt;push_back(<font color="#0000A0">4</font>);
ints-&gt;push_back(<font color="#0000A0">5</font>);
print_range_nl(boost::make_shared_container_iterator(ints-&gt;begin(),ints),
boost::make_shared_container_iterator(ints-&gt;end(),ints));
}
<B>return</B> <font color="#0000A0">0</font>;
}
</PRE>
Observe that the <tt>shared_container_iterator</tt> type is never
explicitly named. The output from this example is the same as the previous.
<h2><a name="make_range">The Shared Container Iterator Range Generator</a></h2>
<pre>
template &lt;typename Container&gt;
std::pair&lt
typename shared_container_iterator_generator&lt;Container&gt;::type,
typename shared_container_iterator_generator&lt;Container&gt;::type
&gt;
make_shared_container_range(boost::shared_ptr&lt;Container&gt; const&amp; container);
</pre>
Class <tt>shared_container_iterator</tt> is meant primarily to return
via 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. This function is equivalent to
<pre>
std::make_pair(make_shared_container_iterator(container-&gt;begin(),container),
make_shared_container_iterator(container-&gt;end(),container));
</pre>
<h3>Example</h3>
In the following example, a range of values is returned as a pair of
<tt>shared_container_iterator</tt>s.
<p>
<a href="./shared_iterator_example3.cpp">shared_iterator_example3.cpp</a>:
<PRE>
<font color="#008040">#include "shared_container_iterator.hpp"</font>
<font color="#008040">#include "boost/shared_ptr.hpp"</font>
<font color="#008040">#include "boost/tuple/tuple.hpp" // for boost::tie</font>
<font color="#008040">#include &lt;algorithm&gt; // for std::copy</font>
<font color="#008040">#include &lt;iostream&gt; </font>
<font color="#008040">#include &lt;vector&gt;</font>
<B>typedef</B> boost::shared_container_iterator_generator&lt; std::vector&lt;<B>int</B>&gt; &gt;::type
function_iterator;
std::pair&lt;function_iterator,function_iterator&gt;
return_range() {
boost::shared_ptr&lt; std::vector&lt;<B>int</B>&gt; &gt; range(<B>new</B> std::vector&lt;<B>int</B>&gt;());
range-&gt;push_back(<font color="#0000A0">0</font>);
range-&gt;push_back(<font color="#0000A0">1</font>);
range-&gt;push_back(<font color="#0000A0">2</font>);
range-&gt;push_back(<font color="#0000A0">3</font>);
range-&gt;push_back(<font color="#0000A0">4</font>);
range-&gt;push_back(<font color="#0000A0">5</font>);
<B>return</B> boost::make_shared_container_range(range);
}
<B>int</B> main() {
function_iterator i,end;
boost::tie(i,end) = return_range();
std::copy(i,end,std::ostream_iterator&lt;<B>int</B>&gt;(std::cout,<font color="#0000FF">","</font>));
std::cout.put(<font color="#0000FF">'\n'</font>);
<B>return</B> <font color="#0000A0">0</font>;
}
</PRE>
Though the <tt>range</tt> object only lives for the duration of the
<tt>return_range</tt> call, the reference counted
<tt>std::vector</tt> will live until <tt>i</tt> and <tt>end</tt>
are both destroyed. The output from this example is the same as
the previous two.
<hr>
<!-- hhmts start -->
Last modified: Wed Sep 4 15:52:17 EST 2002
<!-- hhmts end -->
<p>© Copyright Ronald Garcia 2002. Permission to copy, use,
modify, sell and distribute this document is granted provided this copyright
notice appears in all copies. This document is provided &quot;as is&quot;
without express or implied warranty, and with no claim as to its suitability for
any purpose.</p>
</body>
</html>

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// (C) Copyright Ronald Garcia 2002. Permission to copy, use, modify, sell and
// distribute this software is granted provided this copyright notice appears
// in all copies. This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
#include "boost/shared_container_iterator.hpp"
#include "boost/shared_ptr.hpp"
#include <algorithm>
#include <iostream>
#include <vector>
typedef boost::shared_container_iterator_generator< std::vector<int> >::type
iterator;
void set_range(iterator& i, iterator& end) {
boost::shared_ptr< std::vector<int> > ints(new std::vector<int>());
ints->push_back(0);
ints->push_back(1);
ints->push_back(2);
ints->push_back(3);
ints->push_back(4);
ints->push_back(5);
i = iterator(ints->begin(),ints);
end = iterator(ints->end(),ints);
}
int main() {
iterator i,end;
set_range(i,end);
std::copy(i,end,std::ostream_iterator<int>(std::cout,","));
std::cout.put('\n');
return 0;
}

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// (C) Copyright Ronald Garcia 2002. Permission to copy, use, modify, sell and
// distribute this software is granted provided this copyright notice appears
// in all copies. This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
#include "boost/shared_container_iterator.hpp"
#include "boost/shared_ptr.hpp"
#include <algorithm>
#include <iterator>
#include <iostream>
#include <vector>
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,","));
std::cout.put('\n');
}
int main() {
typedef boost::shared_ptr< std::vector<int> > ints_t;
{
ints_t ints(new std::vector<int>());
ints->push_back(0);
ints->push_back(1);
ints->push_back(2);
ints->push_back(3);
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));
}
return 0;
}

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// (C) Copyright Ronald Garcia 2002. Permission to copy, use, modify, sell and
// distribute this software is granted provided this copyright notice appears
// in all copies. This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
#include "boost/shared_container_iterator.hpp"
#include "boost/shared_ptr.hpp"
#include "boost/tuple/tuple.hpp" // for boost::tie
#include <algorithm> // for std::copy
#include <iostream>
#include <vector>
typedef boost::shared_container_iterator_generator< std::vector<int> >::type
function_iterator;
std::pair<function_iterator,function_iterator>
return_range() {
boost::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);
}
int main() {
function_iterator i,end;
boost::tie(i,end) = return_range();
std::copy(i,end,std::ostream_iterator<int>(std::cout,","));
std::cout.put('\n');
return 0;
}