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<title>scoped_array</title>
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<h1><img src="../../c++boost.gif" alt="c++boost.gif (8819 bytes)" align="middle" width="277" height="86"><a name="scoped_array">scoped_array</a>
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class template</h1>
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<p>The <b>scoped_array</b> class template stores a pointer to a dynamically
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allocated array. (Dynamically allocated arrays are allocated with the C++ <b>new[]</b>
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expression.) The array pointed to is guaranteed to be deleted, either on
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destruction of the <b>scoped_array</b>, or via an explicit <b>reset</b>.</p>
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<p>The <b>scoped_array</b> template is a simple solution for simple needs. It
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supplies a basic "resource acquisition is initialization" facility, without
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shared-ownership or transfer-of-ownership semantics. Both its name and
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enforcement of semantics (by being <a href="../utility/utility.htm#class noncopyable">
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noncopyable</a>) signal its intent to retain ownership solely within the
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current scope. Because it is <a href="../utility/utility.htm#class noncopyable">noncopyable</a>,
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it is safer than <b>shared_array</b> for pointers which should not be copied.</p>
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<p>Because <b>scoped_array</b> is so simple, in its usual implementation every
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operation is as fast as a built-in array pointer and it has no more space
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overhead that a built-in array pointer.</p>
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<p>It cannot be used in C++ standard library containers. See <a href="shared_array.htm">
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<b>shared_array</b></a> if <b>scoped_array</b> does not meet your needs.</p>
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<p>It cannot correctly hold a pointer to a single object. See <a href="scoped_ptr.htm"><b>scoped_ptr</b></a>
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for that usage.</p>
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<p>A <b>std::vector</b> is an alternative to a <b>scoped_array</b> that is a bit
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heavier duty but far more flexible. A <b>boost::array</b> is an alternative
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that does not use dynamic allocation.</p>
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<p>The class template is parameterized on <b>T</b>, the type of the object pointed
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to. <b>T</b> must meet the smart pointer <a href="smart_ptr.htm#Common requirements">
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common requirements</a>.</p>
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<h2>Synopsis</h2>
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<pre>namespace boost {
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template<typename T> class scoped_array : <a href="../utility/utility.htm#noncopyable">noncopyable</a> {
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public:
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typedef T <a href="#element_type">element_type</a>;
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explicit <a href="#ctor">scoped_array</a>(T * p = 0); // never throws
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<a href="#~scoped_array">~scoped_array</a>(); // never throws
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void <a href="#reset">reset</a>(T * p = 0); // never throws
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T & <a href="#operator[]">operator[]</a>(std::ptrdiff_t i) const; // never throws
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T * <a href="#get">get</a>() const; // never throws
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void <a href="#swap">swap</a>(scoped_array & b); // never throws
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};
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template<typename T> void <a href="#free-swap">swap</a>(scoped_array<T> & a, scoped_array<T> & b); // never throws
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}</pre>
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<h2>Members</h2>
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<h3>
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<a name="element_type">element_type</a></h3>
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<pre>typedef T element_type;</pre>
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<p>Provides the type of the stored pointer.</p>
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<h3><a name="ctor">constructors</a></h3>
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<pre>explicit scoped_array(T * p = 0); // never throws</pre>
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<p>Constructs a <b>scoped_array</b>, storing a copy of <b>p</b>, which must have
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been allocated via a C++ <b>new</b>[] expression or be 0. <b>T</b> is not
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required be a complete type. See the smart pointer <a href="smart_ptr.htm#Common requirements">
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common requirements</a>.</p>
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<h3><a name="~scoped_array">destructor</a></h3>
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<pre>~scoped_array(); // never throws</pre>
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<p>Deletes the array pointed to by the stored pointer. Note that <b>delete[]</b> on
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a pointer with a value of 0 is harmless. The guarantee that this does not throw
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exceptions depends on the requirement that the deleted array's objects'
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destructors do not throw exceptions. See the smart pointer <a href="smart_ptr.htm#Common requirements">
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common requirements</a>.</p>
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<h3><a name="reset">reset</a></h3>
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<pre>void reset(T * p = 0); // never throws</pre>
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<p>If p is not equal to the stored pointer, deletes the array pointed to by the
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stored pointer and then stores a copy of p, which must have been allocated via
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a C++ <b>new[]</b> expression or be 0. The guarantee that this does not throw
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exceptions depends on the requirement that the deleted array's objects'
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destructors do not throw exceptions. See the smart pointer <a href="smart_ptr.htm#Common requirements">
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common requirements</a>.</p>
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<h3><a name="operator[]">subscripting</a></h3>
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<pre>T & operator[](std::ptrdiff_t i) const; // never throws</pre>
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<p>Returns a reference to element <b>i</b> of the array pointed to by the stored
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pointer. Behavior is undefined and almost certainly undesirable if the stored
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pointer is 0, or if <b>i</b> is less than 0 or is greater than or equal to the
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number of elements in the array.</p>
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<h3><a name="get">get</a></h3>
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<pre>T * get() const; // never throws</pre>
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<p>Returns the stored pointer. <b>T</b> need not be a complete type. See the smart
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pointer <a href="smart_ptr.htm#Common requirements">common requirements</a>.</p>
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<h3><a name="swap">swap</a></h3>
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<pre>void swap(scoped_array & b); // never throws</pre>
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<p>Exchanges the contents of the two smart pointers. <b>T</b> need not be a
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complete type. See the smart pointer <a href="smart_ptr.htm#Common requirements">common
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requirements</a>.</p>
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<h2><a name="functions">Free Functions</a></h2>
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<h3><a name="free-swap">swap</a></h3>
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<pre>template<typename T> void swap(scoped_array<T> & a, scoped_array<T> & b); // never throws</pre>
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<p>Equivalent to <b>a.swap(b)</b>. Matches the interface of <b>std::swap</b>.
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Provided as an aid to generic programming.</p>
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<hr>
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<p>Revised <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B %Y" startspan-->
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1 February 2002<!--webbot bot="Timestamp" endspan i-checksum="13964"--></p>
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<p>Copyright 1999 Greg Colvin and Beman Dawes. Copyright 2002 Darin Adler.
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Permission to copy, use, modify, sell and distribute this document is granted
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provided this copyright notice appears in all copies. This document is provided
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"as is" without express or implied warranty, and with no claim as to its
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suitability for any purpose.</p>
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2000-07-27 14:27:00 +00:00
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