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<title>scoped_array</title>
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2005-09-25 21:49:08 +00:00
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<h1><A href="../../index.htm"><img src="../../boost.png" alt="boost.png (6897 bytes)" align="middle" width="277" height="86"
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border="0"></A>scoped_array 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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2003-01-09 13:11:10 +00:00
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template<class T> class scoped_array : <a href="../utility/utility.htm#Class_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="#destructor">~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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operator <A href="#conversions" ><i>unspecified-bool-type</i></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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2002-10-23 13:55:18 +00:00
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template<class 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="destructor">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>
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Deletes the array pointed to by the stored pointer and then stores a copy of p,
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which must have been allocated via a C++ <b>new[]</b> expression or be 0. The
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guarantee that this does not throw exceptions depends on the requirement that
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the deleted array's objects' destructors do not throw exceptions. 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="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="conversions">conversions</a></h3>
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<pre>operator <i>unspecified-bool-type</i> () const; // never throws</pre>
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<p>Returns an unspecified value that, when used in boolean contexts, is equivalent
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to <code>get() != 0</code>.</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<class 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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09 January 2003<!--webbot bot="Timestamp" endspan i-checksum="32310"--></p>
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2007-11-25 18:38:02 +00:00
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<p><small>Copyright 1999 Greg Colvin and Beman Dawes. Copyright 2002 Darin Adler.
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Copyright 2002-2005 Peter Dimov. Distributed under the Boost Software License, Version
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1.0. See accompanying file <A href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</A> or
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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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</body>
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</html>
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