forked from boostorg/smart_ptr
181 lines
9.6 KiB
HTML
181 lines
9.6 KiB
HTML
|
<html>
|
|||
|
|
|
|||
|
|
<head>
|
|||
|
|
<title>shared_array</title>
|
|||
|
|
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
|
|||
|
|
<meta name="ProgId" content="FrontPage.Editor.Document">
|
|||
|
|
</head>
|
|||
|
|
|
|||
|
|
<body bgcolor="#FFFFFF" text="#000000">
|
|||
|
|
|
|||
|
|
<h1><img src="../../c++boost.gif" alt="c++boost.gif (8819 bytes)" align="center" width="277" height="86">Class
|
|||
|
|
<a name="shared_array">shared_array</a></h1>
|
|||
|
|
<p>Class <strong>shared_array</strong> stores a pointer to a dynamically
|
|||
|
|
allocated array. (Dynamically allocated arrays are allocated with the C++ <tt>new[]</tt>
|
|||
|
|
expression.) The array pointed to is guaranteed to be deleted,
|
|||
|
|
either on destruction of the <strong>shared_array</strong>, on <strong>shared_array::operator=()</strong>,
|
|||
|
|
or via an explicit <strong>shared_array::reset()</strong>. See <a href="#shared_array_example">example</a>.</p>
|
|||
|
|
<p>Class<strong> shared_array</strong> meets the <strong>CopyConstuctible</strong>
|
|||
|
|
and <strong>Assignable</strong> requirements of the C++ Standard Library, and so
|
|||
|
|
can be used in C++ Standard Library containers. A specialization of std::
|
|||
|
|
less< > for boost::shared_ptr<Y> is supplied so that <strong>
|
|||
|
|
shared_array</strong> works by default for Standard Library's Associative
|
|||
|
|
Container Compare template parameter. For compilers not supporting partial
|
|||
|
|
specialization, the user must explicitly pass the less<> functor.</p>
|
|||
|
|
<p>Class<strong> shared_array</strong> cannot correctly hold a pointer to a
|
|||
|
|
single object. See <a href="shared_ptr.htm"><strong>shared_array</strong></a>
|
|||
|
|
for that usage.</p>
|
|||
|
|
<p>Class<strong> shared_array</strong> will not work correctly with cyclic data
|
|||
|
|
structures. For example, if main() holds a shared_array pointing to array A,
|
|||
|
|
which directly or indirectly holds a shared_array pointing back to array A, then
|
|||
|
|
array A's use_count() will be 2, and destruction of the main() shared_array will
|
|||
|
|
leave array A dangling with a use_count() of 1.</p>
|
|||
|
|
<p>A heavier duty alternative to a <strong>shared_array</strong> is a <strong>shared_ptr</strong>
|
|||
|
|
to a C++ Standard Library <strong>vector</strong>.</p>
|
|||
|
|
<p>The class is a template parameterized on <tt>T</tt>, the type of the object
|
|||
|
|
pointed to. <tt>T</tt> must meet the smart pointer <a href="smart_ptr.htm#Common requirements">Common
|
|||
|
|
requirements</a>.</p>
|
|||
|
|
<h2>Class shared_array Synopsis</h2>
|
|||
|
|
<pre>#include <boost/smart_ptr.hpp>
|
|||
|
|
namespace boost {
|
|||
|
|
|
|||
|
|
template<typename T> class shared_array {
|
|||
|
|
|
|||
|
|
public:
|
|||
|
|
typedef T <a href="#shared_array_element_type">element_type</a>;
|
|||
|
|
|
|||
|
|
explicit <a href="#shared_array_ctor">shared_array</a>( T* p=0 );
|
|||
|
|
<a href="#shared_array_ctor">shared_array</a>( const shared_array& ); // never throws
|
|||
|
|
<strong> </strong><a href="#shared_array_~shared_array">~shared_array</a>();
|
|||
|
|
|
|||
|
|
shared_array& <a href="#shared_array_operator=">operator=</a>( const shared_array& ); // never throws
|
|||
|
|
|
|||
|
|
void <a href="#shared_array_reset">reset</a>( T* p=0 );
|
|||
|
|
|
|||
|
|
T& <a href="#shared_array_operator[]">operator[]</a>(std::size_t i) const; // never throws
|
|||
|
|
T* <a href="#shared_array_get">get</a>() const; // never throws
|
|||
|
|
|
|||
|
|
long <a href="#shared_array_use_count">use_count</a>() const; // never throws
|
|||
|
|
bool <a href="#shared_array_unique">unique</a>() const; // never throws
|
|||
|
|
|
|||
|
|
void <a href="#shared_array_swap">swap</a>( shared_array<T>& other ) throw()
|
|||
|
|
};
|
|||
|
|
|
|||
|
|
template<typename T>
|
|||
|
|
inline bool operator==(const shared_array<T>& a, const shared_array<T>& b)
|
|||
|
|
{ return a.get() == b.get(); }
|
|||
|
|
|
|||
|
|
template<typename T>
|
|||
|
|
inline bool operator!=(const shared_array<T>& a, const shared_array<T>& b)
|
|||
|
|
{ return a.get() != b.get(); }
|
|||
|
|
}</pre>
|
|||
|
|
<pre>namespace std {
|
|||
|
|
|
|||
|
|
template<typename T>
|
|||
|
|
inline void swap(boost::shared_array<T>& a, boost::shared_array<T>& b)
|
|||
|
|
{ a.swap(b); }
|
|||
|
|
|
|||
|
|
template<typename T>
|
|||
|
|
struct less< boost::shared_array<T> >
|
|||
|
|
: binary_function<boost::shared_array<T>, boost::shared_array<T>, bool>
|
|||
|
|
{
|
|||
|
|
bool operator()(const boost::shared_array<T>& a,
|
|||
|
|
const boost::shared_array<T>& b) const
|
|||
|
|
{ return less<T*>()(a.get(),b.get()); }
|
|||
|
|
};
|
|||
|
|
|
|||
|
|
} // namespace std </pre>
|
|||
|
|
<p>Specialization of std::swap uses the fast, non-throwing swap that's provided
|
|||
|
|
as a member function instead of using the default algorithm which creates a
|
|||
|
|
temporary and uses assignment.<br>
|
|||
|
|
<br>
|
|||
|
|
Specialization of std::less allows use of shared arrays as keys in C++
|
|||
|
|
Standard Library associative collections.<br>
|
|||
|
|
<br>
|
|||
|
|
The std::less specializations use std::less<T*> to perform the
|
|||
|
|
comparison. This insures that pointers are handled correctly, since the
|
|||
|
|
standard mandates that relational operations on pointers are unspecified (5.9 [expr.rel]
|
|||
|
|
paragraph 2) but std::less<> on pointers is well-defined (20.3.3 [lib.comparisons]
|
|||
|
|
paragraph 8).<br>
|
|||
|
|
<br>
|
|||
|
|
It's still a controversial question whether supplying only std::less is better
|
|||
|
|
than supplying a full range of comparison operators (<, >, <=, >=).</p>
|
|||
|
|
<p>The current implementation does not supply the specializations if the macro
|
|||
|
|
name BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION is defined.</p>
|
|||
|
|
<h2>Class shared_array Members</h2>
|
|||
|
|
<h3>shared_array <a name="shared_array_element_type">element_type</a></h3>
|
|||
|
|
<pre>typedef T element_type;</pre>
|
|||
|
|
<p>Provides the type of the stored pointer.</p>
|
|||
|
|
<h3><a name="shared_array_ctor">shared_array constructors</a></h3>
|
|||
|
|
<pre>explicit shared_array( T* p=0 );</pre>
|
|||
|
|
<p>Constructs a <strong>shared_array</strong>, storing a copy of <tt>p</tt>,
|
|||
|
|
which must have been allocated via a C++ <tt>new</tt>[] expression or be 0.
|
|||
|
|
Afterwards, use_count() is 1 (even if p==0; see <a href="#shared_array_~shared_array">~shared_array</a>).</p>
|
|||
|
|
<p>The only exception which may be thrown is <tt>std::bad_alloc</tt>. If
|
|||
|
|
an exception is thrown, <tt>delete[] p</tt> is called.</p>
|
|||
|
|
<pre>shared_array( const shared_array& r); // never throws</pre>
|
|||
|
|
<p>Constructs a <strong>shared_array</strong>, as if by storing a copy of the
|
|||
|
|
pointer stored in <strong>r</strong>. Afterwards, <strong>use_count()</strong>
|
|||
|
|
for all copies is 1 more than the initial <strong>r.use_count()</strong>.</p>
|
|||
|
|
<h3><a name="shared_array_~shared_array">shared_array destructor</a></h3>
|
|||
|
|
<pre>~shared_array();</pre>
|
|||
|
|
<p>If <strong>use_count()</strong> == 1, deletes the array pointed to by the
|
|||
|
|
stored pointer. Otherwise, <strong>use_count()</strong> for any remaining
|
|||
|
|
copies is decremented by 1. Note that in C++ <tt>delete</tt>[] on a pointer with
|
|||
|
|
a value of 0 is harmless.</p>
|
|||
|
|
<p>Does not throw exceptions.</p>
|
|||
|
|
<h3>shared_array <a name="shared_array_operator=">operator=</a></h3>
|
|||
|
|
<pre>shared_array& operator=( const shared_array& r); // never throws</pre>
|
|||
|
|
<p>First, if <strong>use_count()</strong> == 1, deletes the array pointed to by
|
|||
|
|
the stored pointer. Otherwise, <strong>use_count()</strong> for any
|
|||
|
|
remaining copies is decremented by 1. Note that in C++ <tt>delete</tt>[] on a
|
|||
|
|
pointer with a value of 0 is harmless.</p>
|
|||
|
|
<p>Then replaces the contents of <strong>this</strong>, as if by storing a copy
|
|||
|
|
of the pointer stored in <strong>r</strong>. Afterwards, <strong>use_count()</strong>
|
|||
|
|
for all copies is 1 more than the initial <strong>r.use_count()</strong>. </p>
|
|||
|
|
<h3>shared_array <a name="shared_array_reset">reset</a></h3>
|
|||
|
|
<pre>void reset( T* p=0 );</pre>
|
|||
|
|
<p>First, if <strong>use_count()</strong> == 1, deletes the array pointed to by
|
|||
|
|
the stored pointer. Otherwise, <strong>use_count()</strong> for any
|
|||
|
|
remaining copies is decremented by 1. Note that in C++ <tt>delete</tt>[]
|
|||
|
|
on a pointer with a value of 0 is harmless.</p>
|
|||
|
|
<p>Then replaces the contents of <strong>this</strong>, as if by storing a copy
|
|||
|
|
of <strong>p</strong>, which must have been allocated via a C++ <tt>new</tt>[]
|
|||
|
|
expression or be 0. Afterwards, <strong>use_count()</strong> is 1 (even if p==0;
|
|||
|
|
see <a href="#shared_array_~shared_array">~shared_array</a>).</p>
|
|||
|
|
<p>The only exception which may be thrown is <tt>std::bad_alloc</tt>. If
|
|||
|
|
an exception is thrown, <tt>delete[] p</tt> is called.</p>
|
|||
|
|
<h3>shared_array <a name="shared_array_operator[]">operator[]</a></h3>
|
|||
|
|
<p><tt>T& operator[](std::size_t i) const; // never throws</tt></p>
|
|||
|
|
<p>Returns a reference to element <tt>i</tt> of the array pointed to by the
|
|||
|
|
stored pointer.</p>
|
|||
|
|
<p>Behavior is undefined (and almost certainly undesirable) if <tt>get()==0</tt>,
|
|||
|
|
or if <tt>i</tt> is less than 0 or is greater or equal to the number of elements
|
|||
|
|
in the array.</p>
|
|||
|
|
<h3>shared_array <a name="shared_array_get">get</a></h3>
|
|||
|
|
<pre>T* get() const; // never throws</pre>
|
|||
|
|
<p>Returns the stored pointer.</p>
|
|||
|
|
<h3>shared_array<a name="shared_array_use_count"> use_count</a></h3>
|
|||
|
|
<p><tt>long use_count() const; // never throws</tt></p>
|
|||
|
|
<p>Returns the number of <strong>shared_arrays</strong> sharing ownership of the
|
|||
|
|
stored pointer.</p>
|
|||
|
|
<h3>shared_array <a name="shared_array_unique">unique</a></h3>
|
|||
|
|
<p><tt>bool unique() const; // never throws</tt></p>
|
|||
|
|
<p>Returns <strong>use_count()</strong> == 1.</p>
|
|||
|
|
<h3><a name="shared_array_swap">shared_array swap</a></h3>
|
|||
|
|
<p><code>void swap( shared_array<T>& other ) throw()</code></p>
|
|||
|
|
<p>Swaps the two smart pointers, as if by std::swap.</p>
|
|||
|
|
<h2>Class <a name="shared_array_example">shared_array example</a></h2>
|
|||
|
|
<p>[To be supplied. In the meantime, see <a href="smart_ptr_test.cpp">smart_ptr_test.cpp</a>.]</p>
|
|||
|
|
<hr>
|
|||
|
|
<p>Revised December 8, 1999</p>
|
|||
|
|
<p><EFBFBD> Copyright Greg Colvin and Beman Dawes 1999. Permission to copy, use,
|
|||
|
|
modify, sell and distribute this document is granted provided this copyright
|
|||
|
|
notice appears in all copies. This document is provided "as is"
|
|||
|
|
without express or implied warranty, and with no claim as to its suitability for
|
|||
|
|
any purpose.</p>
|
|||
|
|
|
|||
|
|
</body>
|
|||
|
|
|
|||
|
|
</html>
|