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<TITLE>GNU autosprintf</TITLE>
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<BODY>
<H1>GNU autosprintf, version 1.0</H1>
<H2>Formatted Output to Strings in C++</H2>
<ADDRESS>Bruno Haible</ADDRESS>
<P>
<P><HR><P>
<H1>Table of Contents</H1>
<UL>
<LI><A NAME="TOC1" HREF="autosprintf.html#SEC1">1 Introduction</A>
<LI><A NAME="TOC2" HREF="autosprintf.html#SEC2">2 The <CODE>autosprintf</CODE> class</A>
<LI><A NAME="TOC3" HREF="autosprintf.html#SEC3">3 Using <CODE>autosprintf</CODE> in own programs</A>
</UL>
<P><HR><P>
<H1><A NAME="SEC1" HREF="autosprintf.html#TOC1">1 Introduction</A></H1>
<P>
This package makes the C formatted output routines (<CODE>fprintf</CODE> et al.)
usable in C++ programs, for use with the <CODE><string></CODE> strings and the
<CODE><iostream></CODE> streams.
</P>
<P>
It allows to write code like
</P>
<PRE>
cerr << autosprintf ("syntax error in %s:%d: %s", filename, line, errstring);
</PRE>
<P>
instead of
</P>
<PRE>
cerr << "syntax error in " << filename << ":" << line << ": " << errstring;
</PRE>
<P>
The benefits of the autosprintf syntax are:
</P>
<UL>
<LI>
It reuses the standard POSIX printf facility. Easy migration from C to C++.
<LI>
English sentences are kept together.
<LI>
It makes internationalization possible. Internationalization requires format
strings, because in some cases the translator needs to change the order of a
sentence, and more generally it is easier for the translator to work with a
single string for a sentence than with multiple string pieces.
<LI>
It reduces the risk of programming errors due to forgotten state in the
output stream (e.g. <CODE>cout << hex;</CODE> not followed by <CODE>cout << dec;</CODE>).
</UL>
<H1><A NAME="SEC2" HREF="autosprintf.html#TOC2">2 The <CODE>autosprintf</CODE> class</A></H1>
<P>
An instance of class <CODE>autosprintf</CODE> just contains a string with the
formatted output result. Such an instance is usually allocated as an
automatic storage variable, i.e. on the stack, not with <CODE>new</CODE> on the
heap.
</P>
<P>
The constructor <CODE>autosprintf (const char *format, ...)</CODE> takes a format
string and additional arguments, like the C function <CODE>printf</CODE>.
</P>
<P>
Conversions to <CODE>char *</CODE> and <CODE>std::string</CODE> are defined that return
the encapsulated string.
</P>
<P>
The destructor <CODE>~autosprintf ()</CODE> destroys the encapsulated string.
</P>
<P>
An <CODE>operator <<</CODE> is provided that outputs the encapsulated string to the
given <CODE>ostream</CODE>.
</P>
<H1><A NAME="SEC3" HREF="autosprintf.html#TOC3">3 Using <CODE>autosprintf</CODE> in own programs</A></H1>
<P>
To use the <CODE>autosprintf</CODE> class in your programs, you need to add
</P>
<PRE>
#include "autosprintf.h"
using gnu::autosprintf;
</PRE>
<P>
to your source code.
The include file defines the class <CODE>autosprintf</CODE>, in a namespace called
<CODE>gnu</CODE>. The <SAMP>‘using’</SAMP> statement makes it possible to use the class
without the (otherwise natural) <CODE>gnu::</CODE> prefix.
</P>
<P>
When linking your program, you need to link with <CODE>libasprintf</CODE>, because
that's where the class is defined. In projects using GNU <CODE>autoconf</CODE>,
this means adding <SAMP>‘AC_LIB_LINKFLAGS([asprintf])’</SAMP> to <CODE>configure.in</CODE>
or <CODE>configure.ac</CODE>, and using the @LIBASPRINTF@ Makefile variable that
it provides.
</P>
<P><HR><P>
This document was generated on 22 August 2006 using the
<A HREF="http://wwwinfo.cern.ch/dis/texi2html/">texi2html</A>
translator version 1.52b.</P>
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