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scoped_array.htm
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>scoped_array</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body text="#000000" bgcolor="#ffffff" link="#0000ff" vlink="#0000ff">
<h1><img height="86" alt="boost.png (6897 bytes)" src="../../boost.png"
width="277" align="middle" border="0">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>$Date$</p>
<p><small>Copyright 1999 Greg Colvin and Beman Dawes. Copyright 2002 Darin Adler.
Copyright 2002-2005 Peter Dimov. Distributed under the Boost Software License, Version
1.0. See accompanying file <A href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</A> or
copy at <A href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>.</small></p>
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