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diff --git a/gcc-4.8.1/libstdc++-v3/doc/html/manual/streambufs.html b/gcc-4.8.1/libstdc++-v3/doc/html/manual/streambufs.html deleted file mode 100644 index 22644ba0c..000000000 --- a/gcc-4.8.1/libstdc++-v3/doc/html/manual/streambufs.html +++ /dev/null @@ -1,136 +0,0 @@ -<?xml version="1.0" encoding="UTF-8" standalone="no"?> -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Stream Buffers</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.77.1" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="io.html" title="Chapter 13. Input and Output" /><link rel="prev" href="io.html" title="Chapter 13. Input and Output" /><link rel="next" href="stringstreams.html" title="Memory Based Streams" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Stream Buffers</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="io.html">Prev</a> </td><th width="60%" align="center">Chapter 13. - Input and Output - -</th><td width="20%" align="right"> <a accesskey="n" href="stringstreams.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.io.streambufs"></a>Stream Buffers</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="io.streambuf.derived"></a>Derived streambuf Classes</h3></div></div></div><p> - </p><p>Creating your own stream buffers for I/O can be remarkably easy. - If you are interested in doing so, we highly recommend two very - excellent books: - <a class="link" href="http://www.angelikalanger.com/iostreams.html" target="_top">Standard C++ - IOStreams and Locales</a> by Langer and Kreft, ISBN 0-201-18395-1, and - <a class="link" href="http://www.josuttis.com/libbook/" target="_top">The C++ Standard Library</a> - by Nicolai Josuttis, ISBN 0-201-37926-0. Both are published by - Addison-Wesley, who isn't paying us a cent for saying that, honest. - </p><p>Here is a simple example, io/outbuf1, from the Josuttis text. It - transforms everything sent through it to uppercase. This version - assumes many things about the nature of the character type being - used (for more information, read the books or the newsgroups): - </p><pre class="programlisting"> - #include <iostream> - #include <streambuf> - #include <locale> - #include <cstdio> - - class outbuf : public std::streambuf - { - protected: - /* central output function - * - print characters in uppercase mode - */ - virtual int_type overflow (int_type c) { - if (c != EOF) { - // convert lowercase to uppercase - c = std::toupper(static_cast<char>(c),getloc()); - - // and write the character to the standard output - if (putchar(c) == EOF) { - return EOF; - } - } - return c; - } - }; - - int main() - { - // create special output buffer - outbuf ob; - // initialize output stream with that output buffer - std::ostream out(&ob); - - out << "31 hexadecimal: " - << std::hex << 31 << std::endl; - return 0; - } - </pre><p>Try it yourself! More examples can be found in 3.1.x code, in - <code class="code">include/ext/*_filebuf.h</code>, and in this article by James Kanze: - <a class="link" href="http://kanze.james.neuf.fr/articles/fltrsbf1.html" target="_top">Filtering - Streambufs</a>. - </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="io.streambuf.buffering"></a>Buffering</h3></div></div></div><p>First, are you sure that you understand buffering? Particularly - the fact that C++ may not, in fact, have anything to do with it? - </p><p>The rules for buffering can be a little odd, but they aren't any - different from those of C. (Maybe that's why they can be a bit - odd.) Many people think that writing a newline to an output - stream automatically flushes the output buffer. This is true only - when the output stream is, in fact, a terminal and not a file - or some other device -- and <span class="emphasis"><em>that</em></span> may not even be true - since C++ says nothing about files nor terminals. All of that is - system-dependent. (The "newline-buffer-flushing only occurring - on terminals" thing is mostly true on Unix systems, though.) - </p><p>Some people also believe that sending <code class="code">endl</code> down an - output stream only writes a newline. This is incorrect; after a - newline is written, the buffer is also flushed. Perhaps this - is the effect you want when writing to a screen -- get the text - out as soon as possible, etc -- but the buffering is largely - wasted when doing this to a file: - </p><pre class="programlisting"> - output << "a line of text" << endl; - output << some_data_variable << endl; - output << "another line of text" << endl; </pre><p>The proper thing to do in this case to just write the data out - and let the libraries and the system worry about the buffering. - If you need a newline, just write a newline: - </p><pre class="programlisting"> - output << "a line of text\n" - << some_data_variable << '\n' - << "another line of text\n"; </pre><p>I have also joined the output statements into a single statement. - You could make the code prettier by moving the single newline to - the start of the quoted text on the last line, for example. - </p><p>If you do need to flush the buffer above, you can send an - <code class="code">endl</code> if you also need a newline, or just flush the buffer - yourself: - </p><pre class="programlisting"> - output << ...... << flush; // can use std::flush manipulator - output.flush(); // or call a member fn </pre><p>On the other hand, there are times when writing to a file should - be like writing to standard error; no buffering should be done - because the data needs to appear quickly (a prime example is a - log file for security-related information). The way to do this is - just to turn off the buffering <span class="emphasis"><em>before any I/O operations at - all</em></span> have been done (note that opening counts as an I/O operation): - </p><pre class="programlisting"> - std::ofstream os; - std::ifstream is; - int i; - - os.rdbuf()->pubsetbuf(0,0); - is.rdbuf()->pubsetbuf(0,0); - - os.open("/foo/bar/baz"); - is.open("/qux/quux/quuux"); - ... - os << "this data is written immediately\n"; - is >> i; // and this will probably cause a disk read </pre><p>Since all aspects of buffering are handled by a streambuf-derived - member, it is necessary to get at that member with <code class="code">rdbuf()</code>. - Then the public version of <code class="code">setbuf</code> can be called. The - arguments are the same as those for the Standard C I/O Library - function (a buffer area followed by its size). - </p><p>A great deal of this is implementation-dependent. For example, - <code class="code">streambuf</code> does not specify any actions for its own - <code class="code">setbuf()</code>-ish functions; the classes derived from - <code class="code">streambuf</code> each define behavior that "makes - sense" for that class: an argument of (0,0) turns off buffering - for <code class="code">filebuf</code> but does nothing at all for its siblings - <code class="code">stringbuf</code> and <code class="code">strstreambuf</code>, and specifying - anything other than (0,0) has varying effects. - User-defined classes derived from <code class="code">streambuf</code> can - do whatever they want. (For <code class="code">filebuf</code> and arguments for - <code class="code">(p,s)</code> other than zeros, libstdc++ does what you'd expect: - the first <code class="code">s</code> bytes of <code class="code">p</code> are used as a buffer, - which you must allocate and deallocate.) - </p><p>A last reminder: there are usually more buffers involved than - just those at the language/library level. Kernel buffers, disk - buffers, and the like will also have an effect. Inspecting and - changing those are system-dependent. - </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="io.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="io.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="stringstreams.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 13. - Input and Output - - </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Memory Based Streams</td></tr></table></div></body></html>
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