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<p><a href="../index.html"><img src="title-21.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.1" border="0"></a>
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<p class="hpath"><a href="index.html">Top</a>: <a href="streams.html">Streams</a>:
instm </p>
<blockquote>
<pre class="lang">#include <pstreams.h>
class instm: iobase {
bool get_eof();
bool get_eol();
char preview();
char get();
void putback();
string token(const cset& chars [, int limit ] );
int token(const cset& chars, char* buf, int size);
string line();
string line( [ int limit ] );
int line(char* buf, int size);
void skipline();
void skiptoken(const cset& chars);
int skip(int numbytes);
int read(char* buf, int count);
}
</pre>
</blockquote>
<p>This class implements the basic functionality of input streams. <span class="lang">Instm</span>
is derived from <a href="streams.iobase.html">iobase</a> and inherits all its
public methods and properties. All methods of <span class="lang">instm</span>
except <span class="lang">read()</span> and <span class="lang">get_eof()</span>
require buffering.</p>
<p><span class="def">bool instm::get_eof()</span> returns <span class="lang">true</span>
if the end of file is reached.</p>
<p><span class="def">bool instm::get_eol()</span> returns <span class="lang">true</span>
if the file pointer is currently at the end of a line. Since operating systems
use different end-of-line codes or combinations of codes, it is recommended to
check the end-of-line status using this property and skip the end-of-line sequence
by calling <span class="lang">skipline()</span> method.</p>
<p> <span class="def">char instm::preview()</span> returns the next character
from the stream but does not advance the file pointer. If the pointer is at the
end of file, <span class="lang">preview()</span> returns <span class="lang">eofchar</span>
(null character).</p>
<p><span class="def">char instm::get()</span> returns the next character from
the stream. If an attempt is made to read beyond the file (i.e. if the property
<span class="lang">eof</span> is set), this method returns <span class="lang">eofchar</span>
(null character).</p>
<p><span class="def">void instm::putback()</span> puts the last retrieved character
back to the stream; a faster equivalent to <span class="lang">seek(-1, IO_CURRENT)</span>.
This function can be called only after a call to <span class="lang">get()</span>
if the latter did not return an <span class="lang">eof</span> character.</p>
<p><span class="def">string instm::token(const cset& chars [, int limit ] )</span>
reads the next token that only contains characters of the given set <span class="lang">chars</span>.
The optional parameter <span class="lang">limit</span> specifies the maximum number
of bytes to read. If the token exceeds the limit, an exception <span class="lang">(estream*)</span>
is thrown with error number ERANGE.</p>
<p><span class="def">int instm::token(const cset& chars, char* buf, int size)</span>
-- this version of <span class="lang">token()</span> reads the next token to the
given buffer <span class="lang">buf</span>. The number of characters is limited
to <span class="lang">size</span>. This method returns the actual number of characters
read from the stream which can not be greater than <span class="lang">size</span>.
Unlike the other version of <span class="lang">token()</span>, does not throw
exceptions if the token exceeds the limit, but rather truncates it to <span class="lang">size</span>.
Note: this function does not put a terminating null symbol in the buffer.</p>
<p><span class="def">string instm::line( [ int limit ] )</span> reads the current
line from the stream. The end-of-line code(s) are not included in the returning
value, however, <span class="lang">line()</span> skips them and sets the file
pointer at the beginning of the next line. The optional parameter <span class="lang">limit</span>
specifies the maximum number of bytes to read. If the token exceeds the limit,
an exception <span class="lang">(estream*)</span> is thrown with error number
ERANGE.</p>
<p><span class="def">int instm::line(char* buf, int size)</span> -- this version
of <span class="lang">line()</span> reads the next line from the stream to the
buffer <span class="lang">buf</span>. The number of characters is limited to <span class="lang">size</span>.
This method returns the actual number of characters read from the stream which
can not be greater than <span class="lang">size</span>. Unlike the other version
of <span class="lang">line()</span>, does not throw exceptions if the token exceeds
the limit, but rather truncates it to <span class="lang">size</span>. Note: this
function does not put a terminating null symbol in the buffer.</p>
<p><span class="def">void instm::skiptoken(const cset& chars)</span> works like
previous versions of <span class="lang">token()</span> except that the token string
is not returned. Can be safely used to skip very large tokens.</p>
<p><span class="def">void instm::skipline()</span> skips the current line and
sets the file pointer at the beginning of the next line.</p>
<p><span class="lang">int instm::skip(int numbytes)</span> skips the specified
number of bytes from the input stream.</p>
<p><span class="def">int instm::read(char* buf, int count)</span> reads <span class="lang">count</span>
bytes from the stream and stores them in the buffer <span class="lang">buf</span>.
Returns the number of bytes actually read. This method does
not require buffering.</p>
<p class="seealso">See also: <a href="streams.iobase.html">iobase</a>, <a href="streams.outstm.html">outstm</a>,
<a href="string.html">string</a>, <a href="cset.html">cset</a>, <a href="streams.errors.html">Error
handling</a></p>
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