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<TITLE>GNU autosprintf</TITLE>
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<H1>GNU autosprintf, version 1.0</H1>
<H2>Formatted Output to Strings in C++</H2>
<ADDRESS>Bruno Haible</ADDRESS>
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<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>
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<H1><A NAME="SEC1" HREF="autosprintf.html#TOC1">1  Introduction</A></H1>

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This package makes the C formatted output routines (<CODE>fprintf</CODE> et al.)
usable in C++ programs, for use with the <CODE>&#60;string&#62;</CODE> strings and the
<CODE>&#60;iostream&#62;</CODE> streams.

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It allows to write code like

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<PRE>
cerr &#60;&#60; autosprintf ("syntax error in %s:%d: %s", filename, line, errstring);
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instead of

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<PRE>
cerr &#60;&#60; "syntax error in " &#60;&#60; filename &#60;&#60; ":" &#60;&#60; line &#60;&#60; ": " &#60;&#60; errstring;
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The benefits of the autosprintf syntax are:

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It reuses the standard POSIX printf facility. Easy migration from C to C++.

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English sentences are kept together.

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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.

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It reduces the risk of programming errors due to forgotten state in the
output stream (e.g. <CODE>cout &#60;&#60; hex;</CODE> not followed by <CODE>cout &#60;&#60; dec;</CODE>).
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<H1><A NAME="SEC2" HREF="autosprintf.html#TOC2">2  The <CODE>autosprintf</CODE> class</A></H1>

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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.

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The constructor <CODE>autosprintf (const char *format, ...)</CODE> takes a format
string and additional arguments, like the C function <CODE>printf</CODE>.

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Conversions to <CODE>char *</CODE> and <CODE>std::string</CODE> are defined that return
the encapsulated string.

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The destructor <CODE>~autosprintf ()</CODE> destroys the encapsulated string.

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An <CODE>operator &#60;&#60;</CODE> is provided that outputs the encapsulated string to the
given <CODE>ostream</CODE>.

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<H1><A NAME="SEC3" HREF="autosprintf.html#TOC3">3  Using <CODE>autosprintf</CODE> in own programs</A></H1>

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To use the <CODE>autosprintf</CODE> class in your programs, you need to add

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<PRE>
#include "autosprintf.h"
using gnu::autosprintf;
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to your source code.
The include file defines the class <CODE>autosprintf</CODE>, in a namespace called
<CODE>gnu</CODE>. The <SAMP>&lsquo;using&rsquo;</SAMP> statement makes it possible to use the class
without the (otherwise natural) <CODE>gnu::</CODE> prefix.

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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>&lsquo;AC_LIB_LINKFLAGS([asprintf])&rsquo;</SAMP> to <CODE>configure.in</CODE>
or <CODE>configure.ac</CODE>, and using the @LIBASPRINTF@ Makefile variable that
it provides.

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