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| <H2>3.3 Generic Streams and Stream Buffers</H2> |
| |
| <DL class="page-index"> |
| <DT><A href="#overview">Overview</A></DT> |
| <DT><A href="#headers">Headers</A></DT> |
| <DT><A href="#reference">Reference</A> |
| <DL> |
| <DT><A href="#stream_buffer">Class template <CODE>stream_buffer</CODE></A></DT> |
| <DT><A href="#stream">Class template <CODE>stream</CODE></A></DT> |
| </DL> |
| </DT> |
| <DT><A href="#examples">Examples</A></DT> |
| </DL> |
| |
| <HR STYLE="margin-top:1em"> |
| |
| <A NAME="overview"></A> |
| <H2>Overview</H2> |
| |
| <P> |
| The fundamental component provided by the Iostreams library is the class template <CODE>stream_buffer</CODE>, a derived class of <CODE>std::basic_streambuf</CODE> which performs i/o by delegating to a contained Device. Instances of the Device can be associated and disassociated with an instance of <CODE>stream_buffer</CODE> using member functions <CODE><A HREF="#stream_buffer_open">open</A></CODE> and <CODE><A HREF="#stream_buffer_close">close</A></CODE>. The interface is patterned after <CODE>std::basic_filebuf</CODE> and <CODE>std::basic_fstream</CODE>. |
| </P> |
| |
| <P> |
| The class template <CODE>stream</CODE> is a stream template which derives from one of <CODE>std::basic_istream</CODE>, <CODE>std::basic_ostream</CODE> and <CODE>std::basic_iostream</CODE> depending on the <A href="modes.html">mode</A> of the first template parameter. As with <CODE>stream_buffer</CODE>, instances of the Device can by associated and disassociated with an instance of <CODE>stream</CODE> using its member functions <CODE><A HREF="#stream_open">open</A></CODE> and <CODE><A HREF="#stream_close">close</A></CODE>. |
| </P> |
| |
| |
| <A NAME="headers"></A> |
| <H2>Headers</H2> |
| |
| <DL class="page-index"> |
| <DT><A CLASS="header" href="../../../../boost/iostreams/stream_buffer.hpp"><CODE><boost/iostreams/stream_buffer.hpp></CODE></A></DT> |
| <DT><A CLASS="header" href="../../../../boost/iostreams/stream.hpp"><CODE><boost/iostreams/stream.hpp></CODE></A></DT> |
| </DL> |
| |
| <A NAME="reference"></A> |
| <H2>Reference</H2> |
| |
| <A NAME="stream_buffer"></A> |
| <H3>Class template <CODE>stream_buffer</CODE></H3> |
| |
| <H4>Description</H4> |
| |
| <P> |
| Stream buffer template which performs i/o by delegating to a contained <A HREF="../concepts/device.html">Device</A>. The Device type is specified as the first template parameter to <CODE>stream_buffer</CODE>. Instances of the the Device type are attached and detached using the member functions <A HREF="#stream_buffer_open"><CODE>open</CODE></A> and <A HREF="#stream_buffer_close"><CODE>close</CODE></A>. |
| </P> |
| |
| <H4>Synopsis</H4> |
| |
| <PRE><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams { |
| |
| <SPAN CLASS="keyword">template</SPAN>< <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#stream_buffer_params">T</A>, |
| <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#stream_buffer_params">Tr</A> = std::char_traits<<SPAN CLASS="omitted">...</SPAN>>, |
| <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#stream_buffer_params">Alloc</A> = std::allocator<<SPAN CLASS="omitted">...</SPAN>>, |
| <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#stream_buffer_params">Mode</A> = <SPAN CLASS="omitted">...</SPAN> > |
| <SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#stream_buffer_params">stream_buffer</A> : <SPAN CLASS="keyword">public</SPAN> std::basic_streambuf<<SPAN CLASS="omitted">...</SPAN>> { |
| <SPAN CLASS="keyword">public</SPAN>: |
| <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">typename</SPAN> char_type_of<T>::type char_type; |
| <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">typename</SPAN> Tr traits_type; |
| |
| [<SPAN CLASS="omitted">Standard stream buffer typedefs: int_type, off_type, etc.</SPAN>] |
| |
| <A CLASS="documented" HREF="#stream_buffer_default_constructor">stream_buffer</A>(); |
| <A CLASS="documented" HREF="#stream_buffer_policy_constructor">stream_buffer</A>( <SPAN CLASS="keyword">const</SPAN> T& t, |
| std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN>, |
| std::streamsize pback_size = <SPAN CLASS="omitted">default_value</SPAN> ); |
| |
| <SPAN CLASS="comment">// Forwarding constructors</SPAN> |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U> |
| <A CLASS="documented" HREF="#stream_buffer_forwarding_constructors">stream_buffer</A>([<SPAN CLASS="keyword">const</SPAN>] U& u); |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="keyword">typename</SPAN> U2> |
| <A CLASS="documented" HREF="#stream_buffer_forwarding_constructors">stream_buffer</A>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2); |
| |
| <SPAN CLASS="omitted">...</SPAN> |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">typename</SPAN> UN> |
| <A CLASS="documented" HREF="#stream_buffer_forwarding_constructors">stream_buffer</A>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2 <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">const</SPAN> UN& uN); |
| |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_buffer_open">open</A>( <SPAN CLASS="keyword">const</SPAN> T& t, |
| std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN>, |
| std::streamsize pback_size = <SPAN CLASS="omitted">default_value</SPAN> ); |
| |
| <SPAN CLASS="comment">// Forwarding overloads of open()</SPAN> |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U> |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_buffer_forwarding_open">open</A>([<SPAN CLASS="keyword">const</SPAN>] U& u); |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="keyword">typename</SPAN> U2> |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_buffer_forwarding_open">open</A>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2); |
| |
| <SPAN CLASS="omitted">...</SPAN> |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">typename</SPAN> UN> |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_buffer_forwarding_open">open</A>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">const</SPAN> UN& uN); |
| |
| <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#stream_buffer_is_open">is_open</A>() <SPAN CLASS="keyword">const</SPAN>; |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_buffer_close">close</A>(); |
| |
| <SPAN CLASS="comment">// Device access</SPAN> |
| |
| T& <A CLASS='documented' HREF="#stream_buffer_operator_star"><SPAN CLASS="documented">operator</SPAN>*</A>(); |
| T* <A CLASS='documented' HREF="#stream_buffer_operator_arrow"><SPAN CLASS="documented">operator-></SPAN></A>(); |
| }; |
| |
| } } <SPAN CLASS="comment">// namespace boost::io</SPAN></PRE> |
| |
| <A NAME="stream_buffer_params"></A> |
| <H4>Template parameters</H4> |
| |
| <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> |
| <TR> |
| <TR> |
| <TD VALIGN="top"><I>T</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>A <A HREF="../../../../doc/html/CopyConstructible.html" TARGET="_top">CopyConstructible</A> model of one of the <A HREF="concepts.html#device_concepts">Device</A> concepts.</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>Tr</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>A C++ standard library charatcer traits type (<A CLASS="bib_ref" href="../bibliography.html#iso">[ISO]</A>, 21.1.1) with <CODE>char_type</CODE> equal to the <A HREF="traits.html#char_type">character type</A> <CODE>Ch</CODE> of T. Defaults to <CODE>std::char_traits<Ch></CODE>.</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>A C++ standard library allocator type (<A CLASS="bib_ref" href="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate any required character buffers. Defaults to <CODE>std::allocator<Ch></CODE>, where <CODE>Ch</CODE> is the <A HREF="traits.html#char_type">character type</A> of T.</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>Mode</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>A mode tag <I>convertible to the <A HREF="modes.html">mode</A> of T</I>. This parameter is principally for internal use. Specifying a <A HREF="modes.html#mode_tags">mode tag</A> properly refined by the mode of T can prevent an unneeded buffer from being allocated in some cases. Defaults to the mode of T.</TD> |
| </TR> |
| </TABLE> |
| |
| <H4><CODE>stream_buffer::stream_buffer</CODE></H4> |
| |
| <A NAME="stream_buffer_default_constructor"></A> |
| <PRE> <B>stream_buffer</B>();</PRE> |
| |
| <P> |
| Constructs a <CODE>stream_buffer</CODE> with no associated instance of the Device <CODE>T</CODE>. Before the instance can be used for i/o, one of its <CODE>open()</CODE> overloads must be invoked. |
| </P> |
| |
| <H4><CODE>stream_buffer::stream_buffer</CODE></H4> |
| |
| <A NAME="stream_buffer_policy_constructor"></A> |
| <PRE> <B>stream_buffer</B>( <SPAN CLASS="keyword">const</SPAN> T& t, |
| std::streamsize buffer_size, |
| std::streamsize pback_size );</PRE> |
| |
| <P> |
| Constructs a <CODE>stream_buffer</CODE> which is ready to perform i/o, where the parameters have the following interpretations: |
| |
| <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> |
| <TR> |
| <TR> |
| <TD VALIGN="top"><I>t</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>An instance of T</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>buffer_size</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>The size of any buffers that need to be allocated</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>pback_size</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>The size of the putback buffer, relevant only if <CODE>Mode</CODE> is a refinement of <A HREF="modes.html#input"><CODE>input</CODE></TD> |
| </TR> |
| </TABLE> |
| |
| <A NAME="stream_buffer_forwarding_constructors"></A> |
| <PRE> <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U> |
| <B>stream_buffer</B>([<SPAN CLASS="keyword">const</SPAN>] U& u); |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="keyword">typename</SPAN> U2> |
| <B>stream_buffer</B>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2); |
| |
| <SPAN CLASS="omitted">...</SPAN> |
| |
| template<<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">typename</SPAN> UN> |
| <B>stream_buffer</B>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">const</SPAN> UN& uN);</PRE> |
| |
| <P> |
| Each of these members constructs an instance of <CODE>stream_buffer</CODE> and associates it with an instance of the Device <CODE>T</CODE> constructed from the given lists of arguments. The <CODE>T</CODE> constructor must take all arguments other than the first by value or <CODE>const</CODE> reference. |
| </P> |
| <P> |
| It is not possible to specify a custom buffer size or putback buffer size using these constructors. |
| </P> |
| |
| <H4><CODE>stream_buffer::open</CODE></H4> |
| |
| <A NAME="stream_buffer_open"></A> |
| <PRE> void <B>open</B>( <SPAN CLASS="keyword">const</SPAN> T& t, |
| std::streamsize buffer_size, |
| std::streamsize pback_size );</PRE> |
| |
| <P> |
| Assocaites the given instance of <CODE>T</CODE> with <CODE>this</CODE> instance of <CODE>stream_buffer</CODE>, if there is no such instance currently associated; otherwise, throws <CODE>std::ios_base::failure</CODE>. The second parameter determines the size of any buffers that need to be allocated; a value of zero indicates that i/o should be unbuffered. The third parameter determines the size of the putback buffer; it is relevant only if <CODE>Mode</CODE> is a refinement of <A HREF="modes.html#input"><CODE>input</CODE></A>. |
| </P> |
| |
| <A NAME="stream_buffer_forwarding_open"></A> |
| <PRE> <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U> |
| <SPAN CLASS="keyword">void</SPAN> <B>open</B>(<SPAN CLASS="keyword">const</SPAN> U& u); |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="keyword">typename</SPAN> U2> |
| <SPAN CLASS="keyword">void</SPAN> <B>open</B>(<SPAN CLASS="keyword">const</SPAN> U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2); |
| |
| <SPAN CLASS="omitted">...</SPAN> |
| |
| template<<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">typename</SPAN> UN> |
| <SPAN CLASS="keyword">void</SPAN> <B>open</B>(<SPAN CLASS="keyword">const</SPAN> U1& u1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">const</SPAN> UN& uN);</PRE> |
| |
| <P> |
| Each of these members associates with <CODE>this</CODE> instance of <CODE>stream_buffer</CODE> a newly constructed instance of the Device <CODE>T</CODE> constructed from the given lists of arguments, if there is no such instance currently associated; otherwise, they throw <CODE>std::ios_base::failure</CODE>. The <CODE>T</CODE> constructor must take all arguments other than the first by value or <CODE>const</CODE> reference. |
| </P> |
| <P> |
| It is not possible to specify a custom buffer size or putback buffer size using these members. |
| </P> |
| |
| <A NAME="stream_buffer_is_open"></A> |
| <H4><CODE>stream_buffer::is_open</CODE></H4> |
| <PRE> <SPAN CLASS="keyword">bool</SPAN> <B>is_open</B>() <SPAN CLASS="keyword">const</SPAN>;</PRE> |
| |
| <P>Returns true if there is an instance of the Device <CODE>T</CODE> associated with <CODE>this</CODE> instance of <CODE>stream_buffer</CODE>.</P> |
| |
| <A NAME="stream_buffer_close"></A> |
| <H4><CODE>stream_buffer::close</CODE></H4> |
| <PRE> <SPAN CLASS="keyword">void</SPAN> <B>close</B>();</PRE> |
| |
| <P> |
| Disassociates from <CODE>this</CODE> instance of <CODE>stream_buffer</CODE> any instance of the Device <CODE>T</CODE> currently associated with it, calling cleanup functions as appropriate and destroying the associated instance of <CODE>T</CODE>. |
| </P> |
| |
| <A NAME="stream_buffer_operator_star"></A> |
| <H4><CODE>stream_buffer::operator*</CODE></H4> |
| <PRE> T& <B>operator*</B>();</PRE> |
| |
| <P> |
| Returns a reference to the instance of <CODE>T</CODE> associated with this <CODE>stream_buffer</CODE>, which must be <A HREF="#stream_buffer_is_open"><CODE>open</CODE></A>. |
| </P> |
| |
| <A NAME="stream_buffer_operator_arrow"></A> |
| <H4><CODE>stream_buffer::operator-></CODE></H4> |
| <PRE> T* <B>operator-></B>();</PRE> |
| |
| <P> |
| Returns a pointer to the instance of <CODE>T</CODE> associated with this <CODE>stream_buffer</CODE>, which must be <A HREF="#stream_buffer_is_open"><CODE>open</CODE></A>. |
| </P> |
| |
| <A NAME="stream"></A> |
| <H3>Class template <CODE>stream</CODE></H3> |
| |
| <H4>Description</H4> |
| |
| <P> |
| Stream template which performs i/o by delegating to a contained <A HREF="../concepts/device.html">Device</A>. The Device type is specified as the first template parameter to <CODE>stream</CODE>. Instances of the the Device type are attached and detached using the member functions <A HREF="#stream_open"><CODE>open</CODE></A> and <A HREF="#stream_close"><CODE>close</CODE></A>. |
| </P> |
| |
| <P> |
| The template <CODE>stream</CODE> derives from a specialization of <CODE>std::basic_istream</CODE>, <CODE>std::basic_ostream</CODE> or <CODE>std::basic_iostream</CODE>, depending on whether the underlying <A HREF="../concepts/device.html">Device</A> models <A HREF="../concepts/source.html">Source</A>, <A HREF="../concepts/sink.html">Sink</A> or both.. |
| </P> |
| |
| |
| <H4>Synopsis</H4> |
| |
| <PRE><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams { |
| |
| <SPAN CLASS="keyword">template</SPAN>< <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#stream_params">T</A>, |
| <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#stream_params">Tr</A> = std::char_traits<<SPAN CLASS="omitted">...</SPAN>>, |
| <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#stream_params">Alloc</A> = std::allocator<<SPAN CLASS="omitted">...</SPAN>>, |
| <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#stream_params">Mode</A> = <SPAN CLASS="omitted">...</SPAN> > |
| <SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#stream_params">stream</A> : <SPAN CLASS="keyword">public</SPAN> [<SPAN CLASS='omitted'>see Description</SPAN>] { |
| <SPAN CLASS="keyword">public</SPAN>: |
| <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">typename</SPAN> char_type_of<T>::type char_type; |
| <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">typename</SPAN> Tr traits_type; |
| |
| [<SPAN CLASS="omitted">Standard stream buffer typedefs: int_type, off_type, etc.</SPAN>] |
| |
| <A CLASS="documented" HREF="#stream_default_constructor">stream</A>(); |
| <A CLASS="documented" HREF="#stream_policy_constructor">stream</A>( <SPAN CLASS="keyword">const</SPAN> T& t, |
| std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN>, |
| std::streamsize pback_size = <SPAN CLASS="omitted">default_value</SPAN> ); |
| |
| <SPAN CLASS="comment">// Forwarding constructors</SPAN> |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U> |
| <A CLASS="documented" HREF="#stream_forwarding_constructors">stream</A>([<SPAN CLASS="keyword">const</SPAN>] U& u); |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="keyword">typename</SPAN> U2> |
| <A CLASS="documented" HREF="#stream_forwarding_constructors">stream</A>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2); |
| |
| <SPAN CLASS="omitted">...</SPAN> |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">typename</SPAN> UN> |
| <A CLASS="documented" HREF="#stream_forwarding_constructors">stream</A>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">const</SPAN> UN& uN); |
| |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_open">open</A>( <SPAN CLASS="keyword">const</SPAN> T& t, |
| std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN>, |
| std::streamsize pback_size = <SPAN CLASS="omitted">default_value</SPAN> ); |
| |
| <SPAN CLASS="comment">// Forwarding overloads of open()</SPAN> |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U> |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_forwarding_open">open</A>([<SPAN CLASS="keyword">const</SPAN>] U& u); |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="keyword">typename</SPAN> U2> |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_forwarding_open">open</A>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2); |
| |
| <SPAN CLASS="omitted">...</SPAN> |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">typename</SPAN> UN> |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_forwarding_open">open</A>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">const</SPAN> UN& uN); |
| |
| <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#stream_is_open">is_open</A>() <SPAN CLASS="keyword">const</SPAN>; |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#stream_close">close</A>(); |
| |
| <SPAN CLASS="comment">// Device access</SPAN> |
| |
| T& <A CLASS='documented' HREF="#stream_operator_star"><SPAN CLASS="documented">operator</SPAN>*</A>(); |
| T* <A CLASS='documented' HREF="#stream_operator_arrow"><SPAN CLASS="documented">operator-></SPAN></A>(); |
| }; |
| |
| } } <SPAN CLASS="comment">// namespace boost::io</SPAN></PRE> |
| |
| <A NAME="stream_params"></A> |
| <H4>Template parameters</H4> |
| |
| <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> |
| <TR> |
| <TR> |
| <TD VALIGN="top"><I>T</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>A <A HREF="../../../../doc/html/CopyConstructible.html" TARGET="_top">CopyConstructible</A> model of one of the <A HREF="concepts.html#device_concepts">Device</A> concepts.</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>Tr</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>A C++ standard library charatcer traits type (<A CLASS="bib_ref" href="../bibliography.html#iso">[ISO]</A>, 21.1.1) with <CODE>char_type</CODE> equal to the <A HREF="traits.html#char_type">character type</A> <CODE>Ch</CODE> of T. Defaults to <CODE>std::char_traits<Ch></CODE>.</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>A C++ standard library allocator type (<A CLASS="bib_ref" href="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate any required character buffers. Defaults to <CODE>std::allocator<Ch></CODE>, where <CODE>Ch</CODE> is the <A HREF="traits.html#char_type">character type</A> of T.</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>Mode</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>A mode tag <I>convertible to the <A HREF="modes.html">mode</A> of T</I>. This parameter is principally for internal use. Specifying a <A HREF="modes.html#mode_tags">mode tag</A> properly refined by the mode of T can prevent an unneeded buffer from being allocated in some cases. Defaults to the mode of T.</TD> |
| </TR> |
| </TABLE> |
| |
| <H4><CODE>stream::stream</CODE></H4> |
| |
| <A NAME="stream_default_constructor"></A> |
| <PRE> <B>stream</B>();</PRE> |
| |
| <P> |
| Constructs a <CODE>stream</CODE> with no associated instance of the Device <CODE>T</CODE>. Before the instance can be used for i/o, one of its <CODE>open()</CODE> overloads must be invoked. |
| </P> |
| |
| <H4><CODE>stream::stream</CODE></H4> |
| |
| <A NAME="stream_policy_constructor"></A> |
| <PRE> <B>stream</B>( <SPAN CLASS="keyword">const</SPAN> T& t, |
| std::streamsize buffer_size, |
| std::streamsize pback_size );</PRE> |
| |
| <P> |
| Constructs a <CODE>stream</CODE> which is ready to perform i/o, where the parameters have the following interpretations: |
| |
| <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> |
| <TR> |
| <TR> |
| <TD VALIGN="top"><I>t</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>An instance of T</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>buffer_size</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>The size of any buffers that need to be allocated</TD> |
| </TR> |
| <TR> |
| <TD VALIGN="top"><I>pback_size</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <TD>The size of the putback buffer, relevant only if <CODE>Mode</CODE> is a refinement of <A HREF="modes.html#input"><CODE>input</CODE></TD> |
| </TR> |
| </TABLE> |
| |
| <A NAME="stream_forwarding_constructors"></A> |
| <PRE> <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U> |
| <B>stream</B>([<SPAN CLASS="keyword">const</SPAN>] U& u); |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="keyword">typename</SPAN> U2> |
| <B>stream</B>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2); |
| |
| <SPAN CLASS="omitted">...</SPAN> |
| |
| template<<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">typename</SPAN> UN> |
| <B>stream</B>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">const</SPAN> UN& uN);</PRE> |
| |
| <P> |
| Each of these members constructs an instance of <CODE>stream</CODE> and associates it with an instance of the Device <CODE>T</CODE> constructed from the given lists of arguments. The <CODE>T</CODE> constructors involved must take all arguments by value or <CODE>const</CODE> reference. |
| </P> |
| <P> |
| It is not possible to specify a custom buffer size or putback buffer size using these constructors. |
| </P> |
| |
| <H4><CODE>stream::open</CODE></H4> |
| |
| <A NAME="stream_open"></A> |
| <PRE> void <B>open</B>( <SPAN CLASS="keyword">const</SPAN> T& t, |
| std::streamsize buffer_size, |
| std::streamsize pback_size );</PRE> |
| |
| <P> |
| Assocaites the given instance of <CODE>T</CODE> with <CODE>this</CODE> instance of <CODE>stream</CODE>, if there is no such instance currently associated; otherwise, throws <CODE>std::ios_base::failure</CODE>. The second parameter determines the size of any buffers that need to be allocated; a value of zero indicates that i/o should be unbuffered. The third parameter determines the size of the putback buffer; it is relevant only if <CODE>Mode</CODE> is a refinement of <A HREF="modes.html#input"><CODE>input</CODE></A>. |
| </P> |
| |
| <A NAME="stream_forwarding_open"></A> |
| <PRE> <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U> |
| <SPAN CLASS="keyword">void</SPAN> <B>open</B>([<SPAN CLASS="keyword">const</SPAN>] U& u); |
| |
| <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="keyword">typename</SPAN> U2> |
| <SPAN CLASS="keyword">void</SPAN> <B>open</B>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2); |
| |
| <SPAN CLASS="omitted">...</SPAN> |
| |
| template<<SPAN CLASS="keyword">typename</SPAN> U1, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">typename</SPAN> UN> |
| <SPAN CLASS="keyword">void</SPAN> <B>open</B>([<SPAN CLASS="keyword">const</SPAN>] U1& u1, <SPAN CLASS="keyword">const</SPAN> U2& u2, <SPAN CLASS="omitted">...</SPAN>, <SPAN CLASS="keyword">const</SPAN> UN& uN);</PRE> |
| |
| <P> |
| Each of these members associates with <CODE>this</CODE> instance of <CODE>stream</CODE> a newly constructed instance of the Device <CODE>T</CODE> constructed from the given lists of arguments, if there is no such instance currently associated; otherwise, they throw <CODE>std::ios_base::failure</CODE>. The <CODE>T</CODE> constructors involved must take all arguments by value or <CODE>const</CODE> reference. |
| </P> |
| <P> |
| It is not possible to specify a custom buffer size or putback buffer size using these members. |
| </P> |
| |
| <A NAME="stream_is_open"></A> |
| <H4><CODE>stream::is_open</CODE></H4> |
| <PRE> <SPAN CLASS="keyword">bool</SPAN> <B>is_open</B>() <SPAN CLASS="keyword">const</SPAN>;</PRE> |
| |
| <P>Returns true if there is an instance of the Device <CODE>T</CODE> associated with <CODE>this</CODE> instance of <CODE>stream</CODE>.</P> |
| |
| <A NAME="stream_close"></A> |
| <H4><CODE>stream::close</CODE></H4> |
| <PRE> <SPAN CLASS="keyword">void</SPAN> <B>close</B>();</PRE> |
| |
| <P> |
| Disassociates from <CODE>this</CODE> instance of <CODE>stream</CODE> any instance of the Device <CODE>T</CODE> currently associated with it, calling cleanup functions as appropriate and destroying the associated instance of <CODE>T</CODE>. |
| </P> |
| |
| <A NAME="stream_operator_star"></A> |
| <H4><CODE>stream::operator*</CODE></H4> |
| <PRE> T& <B>operator*</B>();</PRE> |
| |
| <P> |
| Returns a reference to the instance of <CODE>T</CODE> associated with this <CODE>stream</CODE>, which must be <A HREF="#stream_is_open"><CODE>open</CODE></A>. |
| </P> |
| |
| <A NAME="stream_operator_arrow"></A> |
| <H4><CODE>stream::operator-></CODE></H4> |
| <PRE> T* <B>operator-></B>();</PRE> |
| |
| <P> |
| Returns a pointer to the instance of <CODE>T</CODE> associated with this <CODE>stream</CODE>, which must be <A HREF="#stream_is_open"><CODE>open</CODE></A>. |
| </P> |
| |
| <A NAME="examples"></A> |
| <H2>Examples</H2> |
| |
| <H4>Defining a simple <CODE>ofstream</CODE></H4> |
| |
| <P>The following example uses a <A HREF="../classes/file.html#file_sink"><CODE>file_sink</CODE></A> to define a class similar to a <CODE>std::ofstream</CODE>. |
| |
| <PRE> <SPAN CLASS="preprocessor">#include</SPAN> <A STYLE="text-decoration:none" href="../../../../boost/iostreams/device/file.hpp"><SPAN CLASS="literal"><boost/iostreams/device/file.hpp></SPAN></A> |
| <SPAN CLASS="preprocessor">#include</SPAN> <A STYLE="text-decoration:none" href="../../../../boost/iostreams/stream.hpp"><SPAN CLASS="literal"><boost/iostreams/stream.hpp></SPAN></A> |
| |
| <SPAN CLASS="keyword">typedef</SPAN> stream<file_sink> ofstream; |
| |
| ofstream out(<SPAN CLASS="literal">"HeavyArtillery.txt"</SPAN>); <SPAN CLASS="comment">// Wilfred Owen</SPAN> |
| out << <SPAN CLASS="literal">"Reach at that Arrogance which needs thy harm,\n"</SPAN> |
| <SPAN CLASS="literal">"And beat it down before its sins grow worse.\n"</SPAN>; |
| out.close();</PRE> |
| |
| <H4>Reading from an array</H4> |
| |
| <P>The following example uses an <A href="../classes/array.html#array_source"><CODE>array_source</CODE></A> to construct an input stream from a C-style string. |
| |
| <PRE> <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><cstring></SPAN> |
| <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><iostream></SPAN> |
| <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><string></SPAN> |
| <SPAN CLASS="preprocessor">#include</SPAN> <A STYLE="text-decoration:none" href="../../../../boost/iostreams/device/array.hpp"><SPAN CLASS="literal"><boost/iostreams/device/array.hpp></SPAN></A> |
| <SPAN CLASS="preprocessor">#include</SPAN> <A STYLE="text-decoration:none" href="../../../../boost/iostreams/stream.hpp"><SPAN CLASS="literal"><boost/iostreams/stream.hpp></SPAN></A> |
| |
| const char* h = <SPAN CLASS="literal">"Hello World!"</SPAN>; |
| stream<array_source> in(h, std::strlen(h)); |
| std::string hello; |
| std::getline(in, hello); |
| std::cout << hello << "\n"; // <SPAN CLASS="comment">Prints "Hello World!"</SPAN></PRE> |
| |
| <!-- Begin Footer --> |
| |
| <HR> |
| <P CLASS="copyright">Revised 02 Feb 2008</P> |
| |
| <P CLASS="copyright">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>© Copyright 2004-2007 <a href="http://www.coderage.com/turkanis/" target="_top">Jonathan Turkanis</a></P> |
| <P CLASS="copyright"> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>) |
| </P> |
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