75 lines
3.0 KiB
HTML
75 lines
3.0 KiB
HTML
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
|
||
|
|
<HTML>
|
||
|
|
<HEAD>
|
||
|
|
<META NAME="AUTHOR" CONTENT="pme@sources.redhat.com (Phil Edwards)">
|
||
|
|
<META NAME="KEYWORDS" CONTENT="libstdc++, libstdc++-v3, GCC, g++">
|
||
|
|
<META NAME="DESCRIPTION" CONTENT="Explanatory notes about libstdc++-v3.">
|
||
|
|
<META NAME="GENERATOR" CONTENT="vi and eight fingers">
|
||
|
|
<TITLE>Explanatory notes about libstdc++-v3 design</TITLE>
|
||
|
|
<LINK REL=StyleSheet HREF="lib3styles.css">
|
||
|
|
<!-- $Id: configopts.html,v 1.10 2001/04/20 08:59:25 bkoz Exp $ -->
|
||
|
|
</HEAD>
|
||
|
|
<BODY>
|
||
|
|
|
||
|
|
<H1 CLASS="centered"><A NAME="top">Explanatory notes about libstdc++-v3
|
||
|
|
design</A></H1>
|
||
|
|
|
||
|
|
<P>The latest version of this document is always available at
|
||
|
|
<A HREF="http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html">
|
||
|
|
http://gcc.gnu.org/onlinedocs/libstdc++/explanations.html</A>.
|
||
|
|
</P>
|
||
|
|
|
||
|
|
<P>To the <A HREF="http://gcc.gnu.org/libstdc++/">libstdc++-v3 homepage</A>.
|
||
|
|
|
||
|
|
|
||
|
|
<!-- ####################################################### -->
|
||
|
|
<HR>
|
||
|
|
<A NAME="cstdio"><H3>"I/O packages", <TT>--enable-cstdio</TT></H3></A>
|
||
|
|
<P>In addition to all the nifty things which C++ can do for I/O, its library
|
||
|
|
also includes all of the I/O capabilites of C. Making them work together
|
||
|
|
can be a challenge, not only
|
||
|
|
<A HREF="27_io/howto.html#8">for the programmer</A> but for the
|
||
|
|
implementors as well.
|
||
|
|
</P>
|
||
|
|
<P>There are two ways to do a C++ library: the cool way, and the easy way.
|
||
|
|
More specifically, the cool-but-easy-to-get-wrong way, and the
|
||
|
|
easy-to-guarantee-correct-behavior way. For 3.0, the easy way is used.
|
||
|
|
</P>
|
||
|
|
<P>Choosing 'stdio' is the easy way. It builds a C++ library which forwards
|
||
|
|
all operations to the C library. Many of the C++ I/O functions are
|
||
|
|
specified in the standard 'as if' they called a certain C function; the
|
||
|
|
easiest way to get it correct is to actually call that function. The
|
||
|
|
disadvantage is that the C++ code will run slower (fortunately, the layer
|
||
|
|
is thin).
|
||
|
|
</P>
|
||
|
|
<P>Choosing 'libio' is the cool way; it allows C++ and C to share some
|
||
|
|
buffers. It's disabled because of tricky synchronization issues. Other
|
||
|
|
cool ways (various methods of sharing resources between C and C++
|
||
|
|
facilities, instead of layering) are possible. This approach can speed
|
||
|
|
up I/O significantly.
|
||
|
|
</P>
|
||
|
|
<P>Other packages are possible. For a new package, a header must be
|
||
|
|
written to provide types like streamsize (usually just a typedef), as
|
||
|
|
well as some internal types like<TT> __c_file_type </TT> and
|
||
|
|
<TT> __c_lock </TT> (for the stdio case, these are FILE (as in
|
||
|
|
"FILE*") and a simple POSIX mutex, respectively). An
|
||
|
|
interface class called <TT> __basic_file </TT> must also be filled in;
|
||
|
|
as an example, for the stdio case, these member functions are all
|
||
|
|
inline calles to fread, fwrite, etc.
|
||
|
|
</P>
|
||
|
|
<P>Return <A HREF="#top">to the top of the page</A> or
|
||
|
|
<A HREF="http://gcc.gnu.org/libstdc++/">to the homepage</A>.
|
||
|
|
</P>
|
||
|
|
|
||
|
|
|
||
|
|
<!-- ####################################################### -->
|
||
|
|
|
||
|
|
<HR>
|
||
|
|
<P CLASS="fineprint"><EM>
|
||
|
|
$Id$
|
||
|
|
</EM></P>
|
||
|
|
|
||
|
|
|
||
|
|
</BODY>
|
||
|
|
</HTML>
|