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GNU autosprintf

This manual documents the GNU autosprintf class, version 1.0.

* Menu:

* Introduction::                Introduction
* Class autosprintf::           The 'autosprintf' class
* Using autosprintf::           Using 'autosprintf' in own programs

File:,  Node: Introduction,  Next: Class autosprintf,  Prev: Top,  Up: Top

1 Introduction

This package makes the C formatted output routines ('fprintf' et al.)
usable in C++ programs, for use with the '<string>' strings and the
'<iostream>' streams.

   It allows to write code like

     cerr << autosprintf ("syntax error in %s:%d: %s", filename, line, errstring);

instead of

     cerr << "syntax error in " << filename << ":" << line << ": " << errstring;

   The benefits of the autosprintf syntax are:

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

   * English sentences are kept together.

   * 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.

   * It reduces the risk of programming errors due to forgotten state in
     the output stream (e.g. 'cout << hex;' not followed by 'cout <<

File:,  Node: Class autosprintf,  Next: Using autosprintf,  Prev: Introduction,  Up: Top

2 The 'autosprintf' class

An instance of class 'autosprintf' 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 'new' on the

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

   Conversions to 'char *' and 'std::string' are defined that return the
encapsulated string.  The conversion to 'char *' returns a freshly
allocated copy of the encapsulated string; it needs to be freed using
'delete[]'.  The conversion to 'std::string' returns a copy of the
encapsulated string, with automatic memory management.

   The destructor '~autosprintf ()' destroys the encapsulated string.

   An 'operator <<' is provided that outputs the encapsulated string to
the given 'ostream'.

File:,  Node: Using autosprintf,  Prev: Class autosprintf,  Up: Top

3 Using 'autosprintf' in own programs

To use the 'autosprintf' class in your programs, you need to add

     #include "autosprintf.h"
     using gnu::autosprintf;

to your source code.  The include file defines the class 'autosprintf',
in a namespace called 'gnu'.  The 'using' statement makes it possible to
use the class without the (otherwise natural) 'gnu::' prefix.

   When linking your program, you need to link with 'libasprintf',
because that's where the class is defined.  In projects using GNU
'autoconf', this means adding 'AC_LIB_LINKFLAGS([asprintf])' to
'' or '', and using the @LIBASPRINTF@ Makefile
variable that it provides.

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