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<h1><A href="../../index.htm"><img src="../../boost.png" alt="boost.png (6897 bytes)" align="middle" width="277" height="86"
border="0"></A>scoped_array class template</h1>
<p>The <b>scoped_array</b> class template stores a pointer to a dynamically
allocated array. (Dynamically allocated arrays are allocated with the C++ <b>new[]</b>
expression.) The array pointed to is guaranteed to be deleted, either on
destruction of the <b>scoped_array</b>, or via an explicit <b>reset</b>.</p>
<p>The <b>scoped_array</b> template is a simple solution for simple needs. It
supplies a basic "resource acquisition is initialization" facility, without
shared-ownership or transfer-of-ownership semantics. Both its name and
enforcement of semantics (by being <a href="../utility/utility.htm#Class_noncopyable">
noncopyable</a>) signal its intent to retain ownership solely within the
current scope. Because it is <a href="../utility/utility.htm#Class_noncopyable">noncopyable</a>,
it is safer than <b>shared_array</b> for pointers which should not be copied.</p>
<p>Because <b>scoped_array</b> is so simple, in its usual implementation every
operation is as fast as a built-in array pointer and it has no more space
overhead that a built-in array pointer.</p>
<p>It cannot be used in C++ standard library containers. See <a href="shared_array.htm">
<b>shared_array</b></a> if <b>scoped_array</b> does not meet your needs.</p>
<p>It cannot correctly hold a pointer to a single object. See <a href="scoped_ptr.htm"><b>scoped_ptr</b></a>
for that usage.</p>
<p>A <b>std::vector</b> is an alternative to a <b>scoped_array</b> that is a bit
heavier duty but far more flexible. A <b>boost::array</b> is an alternative
that does not use dynamic allocation.</p>
<p>The class template is parameterized on <b>T</b>, the type of the object pointed
to. <b>T</b> must meet the smart pointer <a href="smart_ptr.htm#common_requirements">
common requirements</a>.</p>
<h2>Synopsis</h2>
<pre>namespace boost {
template<class T> class scoped_array : <a href="../utility/utility.htm#Class_noncopyable">noncopyable</a> {
public:
typedef T <a href="#element_type">element_type</a>;
explicit <a href="#ctor">scoped_array</a>(T * p = 0); // never throws
<a href="#destructor">~scoped_array</a>(); // never throws
void <a href="#reset">reset</a>(T * p = 0); // never throws
T & <a href="#operator[]">operator[]</a>(std::ptrdiff_t i) const; // never throws
T * <a href="#get">get</a>() const; // never throws
operator <A href="#conversions" ><i>unspecified-bool-type</i></A>() const; // never throws
void <a href="#swap">swap</a>(scoped_array & b); // never throws
};
template<class T> void <a href="#free-swap">swap</a>(scoped_array<T> & a, scoped_array<T> & b); // never throws
}</pre>
<h2>Members</h2>
<h3>
<a name="element_type">element_type</a></h3>
<pre>typedef T element_type;</pre>
<p>Provides the type of the stored pointer.</p>
<h3><a name="ctor">constructors</a></h3>
<pre>explicit scoped_array(T * p = 0); // never throws</pre>
<p>Constructs a <b>scoped_array</b>, storing a copy of <b>p</b>, which must have
been allocated via a C++ <b>new</b>[] expression or be 0. <b>T</b> is not
required be a complete type. See the smart pointer <a href="smart_ptr.htm#common_requirements">
common requirements</a>.</p>
<h3><a name="destructor">destructor</a></h3>
<pre>~scoped_array(); // never throws</pre>
<p>Deletes the array pointed to by the stored pointer. Note that <b>delete[]</b> on
a pointer with a value of 0 is harmless. The guarantee that this does not throw
exceptions depends on the requirement that the deleted array's objects'
destructors do not throw exceptions. See the smart pointer <a href="smart_ptr.htm#common_requirements">
common requirements</a>.</p>
<h3><a name="reset">reset</a></h3>
<pre>void reset(T * p = 0); // never throws</pre>
<p>
Deletes the array pointed to by the stored pointer and then stores a copy of p,
which must have been allocated via a C++ <b>new[]</b> expression or be 0. The
guarantee that this does not throw exceptions depends on the requirement that
the deleted array's objects' destructors do not throw exceptions. See the smart
pointer <a href="smart_ptr.htm#common_requirements">common requirements</a>.</p>
<h3><a name="operator[]">subscripting</a></h3>
<pre>T & operator[](std::ptrdiff_t i) const; // never throws</pre>
<p>Returns a reference to element <b>i</b> of the array pointed to by the stored
pointer. Behavior is undefined and almost certainly undesirable if the stored
pointer is 0, or if <b>i</b> is less than 0 or is greater than or equal to the
number of elements in the array.</p>
<h3><a name="get">get</a></h3>
<pre>T * get() const; // never throws</pre>
<p>Returns the stored pointer. <b>T</b> need not be a complete type. See the smart
pointer <a href="smart_ptr.htm#common_requirements">common requirements</a>.</p>
<h3><a name="conversions">conversions</a></h3>
<pre>operator <i>unspecified-bool-type</i> () const; // never throws</pre>
<p>Returns an unspecified value that, when used in boolean contexts, is equivalent
to <code>get() != 0</code>.</p>
<h3><a name="swap">swap</a></h3>
<pre>void swap(scoped_array & b); // never throws</pre>
<p>Exchanges the contents of the two smart pointers. <b>T</b> need not be a
complete type. See the smart pointer <a href="smart_ptr.htm#common_requirements">common
requirements</a>.</p>
<h2><a name="functions">Free Functions</a></h2>
<h3><a name="free-swap">swap</a></h3>
<pre>template<class T> void swap(scoped_array<T> & a, scoped_array<T> & b); // never throws</pre>
<p>Equivalent to <b>a.swap(b)</b>. Matches the interface of <b>std::swap</b>.
Provided as an aid to generic programming.</p>
<hr>
<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B %Y" startspan-->
09 January 2003<!--webbot bot="Timestamp" endspan i-checksum="32310"--></p>
<p>Copyright 1999 Greg Colvin and Beman Dawes. Copyright 2002 Darin Adler.
Copyright 2002-2005 Peter Dimov. 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>
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