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Rename libs/integer to libs/endian

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git-svn-id: http://svn.boost.org/svn/boost/sandbox/endian@72096 b8fc166d-592f-0410-95f2-cb63ce0dd405
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bemandawes committed 2011-05-22 19:57:42 +00:00
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<html>
<head>
<meta http-equiv="Content-Language" content="en-us">
<meta name="GENERATOR" content="Microsoft FrontPage 5.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Binary Stream I/O</title>
<link rel="stylesheet" type="text/css" href="../../../doc/html/minimal.css">
</head>
<body>
<h1>Proposal for Binary Stream I/O</h1>
<h2>Introduction</h2>
<p>The C++ standard library's stream I/O facilities are type-safe and very
convenient for performing formatted (i.e. human readable) I/O. But they offer only
rudimentary and not very type-safe operations for performing unformatted binary I/O.&nbsp;
Although formatted I/O is often preferable, some applications need the speed and
storage efficiency of unformatted binary I/O or need to interoperate with third-party
applications that require unformatted binary file or network data formats.</p>
<p>Standard library streams can be opened with filemode <code>
std::ios_base::binary</code>, so binary I/O is possible. But the only
unformatted I/O functions available are <code>get()</code>, <code>put()</code>,
<code>read()</code>, and <code>write()</code>. These operate only on <code>char</code>
or array of <code>char</code> (with length explicitly specified), so require the
user to write casts, are hard to use, and are error prone.</p>
<p>There have been many requests on Boost and various C++ newsgroups for
unformatted binary I/O. For example, in 2003 Neal Becker wrote:</p>
<blockquote>
<p>I wonder if anyone has code for implementing unformatted I/O?&nbsp; What I
have in mind is for the simple case where the application that reads data knows
the data types, so this is not as complicated as the general marshalling
situation.</p>
</blockquote>
<p>This proposal provides a simple solution that works with standard library
input and output streams. The one caveat is that the stream must be opened with filemode <code>std::ios_base::binary</code>
to avoid certain data values being treated as line endings.</p>
<h2>Synopsis</h2>
<div dir="ltr">
<pre>namespace boost
{
template &lt;class T&gt;
<i>unspecified-type-1&lt;T&gt;</i> bin(const T&amp; x);
template &lt;class T&gt;
<i>unspecified-type-2&lt;T&gt;</i> bin(T&amp; x);
template &lt;class T&gt;
std::ostream&amp; operator&lt;&lt;(std::ostream&amp; os, <i>unspecified-type-1&lt;T&gt;</i> x);
template &lt;class T&gt;
std::ostream&amp; operator&lt;&lt;(std::ostream&amp; os, <i>unspecified-type-2&lt;T&gt;</i> x);
template &lt;class T&gt;
std::istream&amp; operator&gt;&gt;(std::istream&amp; is, <i>unspecified-type-2&lt;T&gt;</i> x);
}</pre>
</div>
<p><i><code>unspecified-type-1</code></i> and <i><code>unspecified-type-2</code></i>
are implementation supplied types.</p>
<h2>Example</h2>
<blockquote>
<pre>int main()
{
fstream f(&quot;binary_stream_example.dat&quot;,
std::ios_base::trunc | std::ios_base::in | std::ios_base::out | std::ios_base::binary);
int32_t x = 0x01020304;
int32_t y = 0;
f &lt;&lt; bin(x);
f.seekg(0);
f &gt;&gt; bin(y);
BOOST_ASSERT(x == y);
return 0;
}</pre>
</blockquote>
<p>The file produced with be four bytes in length. On a big-endian machine, the
contents in hexadecimal are:</p>
<blockquote>
<pre>01020304</pre>
</blockquote>
<p>On a little-endian machine, the contents in hexadecimal are:</p>
<blockquote>
<pre>04030201</pre>
</blockquote>
<hr>
<p>Last revised:
<!--webbot bot="Timestamp" s-type="EDITED" s-format="%d %B, %Y" startspan -->24 April, 2011<!--webbot bot="Timestamp" endspan i-checksum="29830" --></p>
<p>© Copyright Beman Dawes, 2009, 2011</p>
<p>Distributed under the Boost Software License, Version 1.0. See
<a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/ LICENSE_1_0.txt</a></p>
<p>&nbsp;</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
</body>
</html>