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| author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
|---|---|---|
| committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
| commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
| tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libstdc++-v3/doc/html/manual/io_and_c.html | |
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Diffstat (limited to 'libstdc++-v3/doc/html/manual/io_and_c.html')
| -rw-r--r-- | libstdc++-v3/doc/html/manual/io_and_c.html | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/libstdc++-v3/doc/html/manual/io_and_c.html b/libstdc++-v3/doc/html/manual/io_and_c.html new file mode 100644 index 000000000..6b4066154 --- /dev/null +++ b/libstdc++-v3/doc/html/manual/io_and_c.html @@ -0,0 +1,57 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Interacting with C</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="io.html" title="Chapter 13. Input and Output"/><link rel="prev" href="fstreams.html" title="File Based Streams"/><link rel="next" href="atomics.html" title="Chapter 14. Atomics"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Interacting with C</th></tr><tr><td align="left"><a accesskey="p" href="fstreams.html">Prev</a> </td><th width="60%" align="center">Chapter 13. + Input and Output + +</th><td align="right"> <a accesskey="n" href="atomics.html">Next</a></td></tr></table><hr/></div><div class="section" title="Interacting with C"><div class="titlepage"><div><div><h2 class="title"><a id="std.io.c"/>Interacting with C</h2></div></div></div><div class="section" title="Using FILE* and file descriptors"><div class="titlepage"><div><div><h3 class="title"><a id="std.io.c.FILE"/>Using FILE* and file descriptors</h3></div></div></div><p> + See the <a class="link" href="ext_io.html" title="Chapter 26. Input and Output">extensions</a> for using + <span class="type">FILE</span> and <span class="type">file descriptors</span> with + <code class="classname">ofstream</code> and + <code class="classname">ifstream</code>. + </p></div><div class="section" title="Performance"><div class="titlepage"><div><div><h3 class="title"><a id="std.io.c.sync"/>Performance</h3></div></div></div><p> + Pathetic Performance? Ditch C. + </p><p>It sounds like a flame on C, but it isn't. Really. Calm down. + I'm just saying it to get your attention. + </p><p>Because the C++ library includes the C library, both C-style and + C++-style I/O have to work at the same time. For example: + </p><pre class="programlisting"> + #include <iostream> + #include <cstdio> + + std::cout << "Hel"; + std::printf ("lo, worl"); + std::cout << "d!\n"; + </pre><p>This must do what you think it does. + </p><p>Alert members of the audience will immediately notice that buffering + is going to make a hash of the output unless special steps are taken. + </p><p>The special steps taken by libstdc++, at least for version 3.0, + involve doing very little buffering for the standard streams, leaving + most of the buffering to the underlying C library. (This kind of + thing is tricky to get right.) + The upside is that correctness is ensured. The downside is that + writing through <code class="code">cout</code> can quite easily lead to awful + performance when the C++ I/O library is layered on top of the C I/O + library (as it is for 3.0 by default). Some patches have been applied + which improve the situation for 3.1. + </p><p>However, the C and C++ standard streams only need to be kept in sync + when both libraries' facilities are in use. If your program only uses + C++ I/O, then there's no need to sync with the C streams. The right + thing to do in this case is to call + </p><pre class="programlisting"> + #include <span class="emphasis"><em>any of the I/O headers such as ios, iostream, etc</em></span> + + std::ios::sync_with_stdio(false); + </pre><p>You must do this before performing any I/O via the C++ stream objects. + Once you call this, the C++ streams will operate independently of the + (unused) C streams. For GCC 3.x, this means that <code class="code">cout</code> and + company will become fully buffered on their own. + </p><p>Note, by the way, that the synchronization requirement only applies to + the standard streams (<code class="code">cin</code>, <code class="code">cout</code>, + <code class="code">cerr</code>, + <code class="code">clog</code>, and their wide-character counterchapters). File stream + objects that you declare yourself have no such requirement and are fully + buffered. + </p></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="fstreams.html">Prev</a> </td><td align="center"><a accesskey="u" href="io.html">Up</a></td><td align="right"> <a accesskey="n" href="atomics.html">Next</a></td></tr><tr><td align="left" valign="top">File Based Streams </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Chapter 14. + Atomics + +</td></tr></table></div></body></html> |