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<html><!-- #BeginTemplate "/Templates/tmpl.dwt" --><head><!-- #BeginEditable "doctitle" --> <title>PTypes: streams: instm</title><!-- #EndEditable --> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link rel="stylesheet" href="styles.css"></head><body bgcolor="#FFFFFF" leftmargin="40" marginwidth="40"><p><a href="../index.html"><img src="title-1.7.gif" width="213" height="34" alt="C++ Portable Types Library (PTypes) Version 1.7" border="0"></a> <hr noshade><!-- #BeginEditable "body" --> <p class="hpath"><a href="index.html">Top</a>: <a href="streams.html">Streams</a>: instm </p><blockquote> <pre class="lang">#include <pstreams.h>bool instm::get_eof();bool instm::get_eol();char instm::preview();char instm::get();void instm::putback();string instm::token(const cset& chars [, int limit ] );int instm::token(const cset& chars, char* buf, int size);string instm::line();string instm::line( [ int limit ] );int instm::line(char* buf, int size);void instm::skipline();void instm::skiptoken(const cset& chars);int instm::skip(int numbytes);int instm::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 different 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>. 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><!-- #EndEditable --><hr size="1"><a href="../index.html" class="ns">PTypes home</a></body><!-- #EndTemplate --></html>⌨️ 快捷键说明
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