istream.html

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<CODE><A HREF="#basic_istream::gcount">gcount</A>()</CODE>.</P>

<H3><A NAME="basic_istream::seekg"><CODE>basic_istream::seekg</CODE></A></H3>

<PRE>basic_istream&amp; <B>seekg</B>(pos_type pos);
basic_istream&amp; <B>seekg</B>(off_type off,
    ios_base::seek_dir way);</PRE>

<P>If <CODE><A HREF="ios.html#basic_ios::fail">fail</A>()</CODE> is false,
the first member function calls
<CODE>newpos = <A HREF="ios.html#basic_ios::rdbuf">rdbuf</A>()-&gt;
<A HREF="streambu.html#basic_streambuf::pubseekpos">pubseekpos</A>(pos,
<A HREF="ios.html#ios_base::in">in</A>)</CODE>,
for some <CODE>pos_type</CODE> temporary object <CODE>newpos</CODE>.
If <CODE>fail()</CODE> is false, the second function calls
<CODE>newpos = rdbuf()-&gt;
<A HREF="streambu.html#basic_streambuf::pubseekoff">pubseekoff</A>(off, way,
<A HREF="ios.html#ios_base::in">in</A>)</CODE>.
In either case, if <CODE>(off_type)newpos == (off_type)(-1)</CODE>
(the positioning operation fails) the function calls
<CODE>istr.<A HREF="ios.html#basic_ios::setstate">setstate</A>(failbit)</CODE>.
Both functions return <CODE>*this</CODE>.</P>

<H3><A NAME="basic_istream::sentry"><CODE>basic_istream::sentry</CODE></A></H3>

<PRE>class <B>sentry</B> {
public:
    explicit <B>sentry</B>(basic_istream&amp; istr,
        bool noskip = false);
    <B>operator bool</B>() const;
    };</PRE>

<P>The nested class describes an object whose declaration structures the
<A HREF="#formatted input functions">formatted input functions</A> and the
<A HREF="#unformatted input functions">unformatted input functions</A>.
If <CODE>istr.<A HREF="ios.html#basic_ios::good">good</A>()</CODE>
is true, the constructor:</P>

<UL>
<LI>calls <CODE>istr.<A HREF="ios.html#basic_ios::tie">tie</A>-&gt;
<A HREF="ostream.html#basic_ostream::flush">flush</A>()</CODE>
if <CODE>istr.tie()</CODE> is not a null pointer</LI>

<LI>effectively calls <CODE><A HREF="#ws">ws</A>(istr)</CODE> if
<CODE>istr.<A HREF="ios.html#ios_base::flags">flags</A>() &amp;
<A HREF="ios.html#ios_base::skipws">skipws</A></CODE> is nonzero</LI>
</UL>

<P>If, after any such preparation,
<CODE>istr.good()</CODE> is false, the constructor calls
<CODE>istr.<A HREF="ios.html#basic_ios::setstate">setstate</A>(failbit)</CODE>.
In any case, the constructor stores the value returned by <CODE>istr.good()</CODE>
in <B>status</B>.
A later call to <CODE>operator bool()</CODE> delivers this stored value.</P>

<H3><A NAME="basic_istream::sync"><CODE>basic_istream::sync</CODE></A></H3>

<PRE>int <B>sync</B>();</PRE>

<P>If <CODE><A HREF="ios.html#basic_ios::rdbuf">rdbuf</A>()</CODE> is
a null pointer, the function returns -1. Otherwise, it calls
<CODE>rdbuf()-&gt;<A HREF="streambu.html#basic_streambuf::pubsync">pubsync</A>()</CODE>.
If that returns -1, the function calls
<CODE><A HREF="ios.html#basic_ios::setstate">setstate</A>(badbit)</CODE>
and returns -1. Otherwise, the function returns zero.</P>

<H3><A NAME="basic_istream::tellg"><CODE>basic_istream::tellg</CODE></A></H3>

<PRE>pos_type <B>tellg</B>();</PRE>

<P>If <CODE><A HREF="ios.html#basic_ios::fail">fail</A>()</CODE> is false,
the member function returns
<CODE><A HREF="ios.html#basic_ios::rdbuf">rdbuf</A>()-&gt;
<A HREF="streambu.html#basic_streambuf::pubseekoff">pubseekoff</A>(0,
<A HREF="ios.html#ios_base::cur">cur</A>,
<A HREF="ios.html#ios_base::in">in</A>)</CODE>.
Otherwise, it returns <CODE>pos_type(-1)</CODE>.</P>

<H3><A NAME="basic_istream::unget"><CODE>basic_istream::unget</CODE></A></H3>

<PRE>basic_istream&amp; <B>unget</B>();</PRE>

<P>The <A HREF="#unformatted input functions">unformatted input function</A>
puts back the previous element in the stream, if possible, as if by calling
<CODE>rdbuf()-&gt;<A HREF="streambu.html#basic_streambuf::sungetc">sungetc</A>()</CODE>.
If <CODE><A HREF="ios.html#basic_ios::rdbuf">rdbuf</A>()</CODE>
is a null pointer, or if the call to <CODE>sungetc</CODE> returns
<CODE>traits_type::<A HREF="string2.html#char_traits::eof">eof</A>()</CODE>,
the function calls
<CODE><A HREF="ios.html#basic_ios::setstate">setstate</A>(badbit)</CODE>.
In any case, it returns <CODE>*this</CODE>.</P>

<H2><A NAME="iostream"><CODE>iostream</CODE></A></H2>

<PRE>typedef basic_iostream&lt;char, char_traits&lt;char&gt; &gt; <B>iostream</B>;</PRE>

<P>The type is a synonym for template class
<A HREF="#basic_iostream"><CODE>basic_iostream</CODE></A>, specialized
for elements of type <I>char</I> with default
<A HREF="string2.html#character traits">character traits</A>.</P>

<H2><A NAME="istream"><CODE>istream</CODE></A></H2>

<PRE>typedef basic_istream&lt;char, char_traits&lt;char&gt; &gt; <B>istream</B>;</PRE>

<P>The type is a synonym for template class
<A HREF="#basic_istream"><CODE>basic_istream</CODE></A>, specialized
for elements of type <I>char</I> with default
<A HREF="string2.html#character traits">character traits</A>.</P>

<H2><A NAME="operator&gt;&gt;"><CODE>operator&gt;&gt;</CODE></A></H2>

<PRE>template&lt;class Elem, class Tr&gt;
    basic_istream&lt;Elem, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;Elem, Tr&gt;&amp; istr, Elem *str);
template&lt;class Elem, class Tr&gt;
    basic_istream&lt;Elem, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;Elem, Tr&gt;&amp; istr, Elem&amp; ch);
template&lt;class Tr&gt;
    basic_istream&lt;char, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;char, Tr&gt;&amp; istr,
            signed char *str);
template&lt;class Tr&gt;
    basic_istream&lt;char, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;char, Tr&gt;&amp; istr,
            signed char&amp; ch);
template&lt;class Tr&gt;
    basic_istream&lt;char, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;char, Tr&gt;&amp; istr,
            unsigned char *str);
template&lt;class Tr&gt;
    basic_istream&lt;char, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;char, Tr&gt;&amp; istr,
            unsigned char&amp; ch);</PRE>

<P>The template function:</P>

<PRE>template&lt;class Elem, class Tr&gt;
    basic_istream&lt;Elem, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;Elem, Tr&gt;&amp; istr, Elem *str);</PRE>

<P>extracts up to <CODE>N - 1</CODE> elements
and stores them in the array beginning at <CODE>str</CODE>.
If <CODE>istr.<A HREF="ios.html#ios_base::width">width</A>()</CODE> is greater
than zero, <CODE>N</CODE> is <CODE>istr.width()</CODE>; otherwise it is
the size of
the largest array of <CODE>Elem</CODE> that can be declared.
The function always stores
<CODE>Elem()</CODE> after
any extracted elements it stores. Extraction stops early on end-of-file,
on a character with value <CODE>Elem(0)</CODE> (which is not extracted),
or on any element (which is not extracted) that would be discarded by
<CODE><A HREF="#ws">ws</A></CODE>.
If the function extracts no elements, it calls
<CODE>istr.<A HREF="ios.html#basic_ios::setstate">setstate</A>(failbit)</CODE>.
In any case, it calls <CODE>istr.width(0)</CODE> and
returns <CODE>istr</CODE>.</P>

<P>The template function:</P>

<PRE>template&lt;class Elem, class Tr&gt;
    basic_istream&lt;Elem, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;Elem, Tr&gt;&amp; istr, char&amp; ch);</PRE>

<P>extracts an element, if possible, and stores it in <CODE>ch</CODE>.
Otherwise, it calls
<CODE>is.<A HREF="ios.html#basic_ios::setstate">setstate</A>(failbit)</CODE>.
In any case, it returns <CODE>istr</CODE>.</P>

<P>The template function:</P>

<PRE>template&lt;class Tr&gt;
    basic_istream&lt;char, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;char, Tr&gt;&amp; istr,
            signed char *str);</PRE>

<P>returns <CODE>istr &gt;&gt; (char *)str</CODE>.</P>

<P>The template function:</P>

<PRE>template&lt;class Tr&gt;
    basic_istream&lt;char, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;char, Tr&gt;&amp; istr,
            signed char&amp; ch);</PRE>

<P>returns <CODE>istr &gt;&gt; (char&amp;)ch</CODE>.</P>

<P>The template function:</P>

<PRE>template&lt;class Tr&gt;
    basic_istream&lt;char, Tr&gt;&amp;
       <B>operator&gt;&gt;</B>(basic_istream&lt;char, Tr&gt;&amp; istr,
           unsigned char *str);</PRE>

<P>returns <CODE>istr &gt;&gt; (char *)str</CODE>.</P>

<P>The template function:</P>

<PRE>template&lt;class Tr&gt;
    basic_istream&lt;char, Tr&gt;&amp;
        <B>operator&gt;&gt;</B>(basic_istream&lt;char, Tr&gt;&amp; istr,
            unsigned char&amp; ch);</PRE>

<P>returns <CODE>istr &gt;&gt; (char&amp;)ch</CODE>.</P>

<H2><A NAME="wiostream"><CODE>wiostream</CODE></A></H2>

<PRE>typedef basic_iostream&lt;wchar_t, char_traits&lt;wchar_t&gt; &gt;
    <B>wiostream</B>;</PRE>

<P>The type is a synonym for template class
<A HREF="#basic_iostream"><CODE>basic_iostream</CODE></A>, specialized
for elements of type <CODE>wchar_t</CODE> with default
<A HREF="string2.html#character traits">character traits</A>.</P>

<H2><A NAME="wistream"><CODE>wistream</CODE></A></H2>

<PRE>typedef basic_istream&lt;wchar_t, char_traits&lt;wchar_t&gt; &gt;
    <B>wistream</B>;</PRE>

<P>The type is a synonym for template class
<A HREF="#basic_istream"><CODE>basic_istream</CODE></A>, specialized
for elements of type <CODE>wchar_t</CODE> with default
<A HREF="string2.html#character traits">character traits</A>.</P>

<H2><A NAME="ws"><CODE>ws</CODE></A></H2>

<PRE>template class&lt;Elem, Tr&gt;
    basic_istream&lt;Elem, Tr&gt;&amp; <B>ws</B>(basic_istream&lt;Elem, Tr&gt;&amp; istr);</PRE>

<P>The manipulator extracts and discards any elements
<CODE>ch</CODE> for which
<CODE><A HREF="locale2.html#use_facet">use_facet</A>&lt;
<A HREF="locale2.html#ctype">ctype</A>&lt;Elem&gt; &gt;(
<A HREF="ios.html#ios_base::getloc">getloc</A>()).
<A HREF="locale2.html#ctype::is">is</A>(
ctype&lt;Elem&gt;::<A HREF="locale2.html#ctype_base::space">space</A>, ch)</CODE>
is true.</P>

<P>The function calls
<CODE><A HREF="ios.html#basic_ios::setstate">setstate</A>(eofbit)</CODE>
if it encounters end-of-file while extracting elements.
It returns <CODE>istr</CODE>.</P>

<HR>
<P>See also the
<B><A HREF="index.html#Table of Contents">Table of Contents</A></B> and the
<B><A HREF="_index.html">Index</A></B>.</P>

<P><I>
<A HREF="crit_pjp.html">Copyright</A> &#169; 1992-2002
by P.J. Plauger. All rights reserved.</I></P>

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