genode/repos/base/include/base/snprintf.h
Norman Feske eba9c15746 Follow practices suggested by "Effective C++"
The patch adjust the code of the base, base-<kernel>, and os repository.
To adapt existing components to fix violations of the best practices
suggested by "Effective C++" as reported by the -Weffc++ compiler
argument. The changes follow the patterns outlined below:

* A class with virtual functions can no longer publicly inherit base
  classed without a vtable. The inherited object may either be moved
  to a member variable, or inherited privately. The latter would be
  used for classes that inherit 'List::Element' or 'Avl_node'. In order
  to enable the 'List' and 'Avl_tree' to access the meta data, the
  'List' must become a friend.

* Instead of adding a virtual destructor to abstract base classes,
  we inherit the new 'Interface' class, which contains a virtual
  destructor. This way, single-line abstract base classes can stay
  as compact as they are now. The 'Interface' utility resides in
  base/include/util/interface.h.

* With the new warnings enabled, all member variables must be explicitly
  initialized. Basic types may be initialized with '='. All other types
  are initialized with braces '{ ... }' or as class initializers. If
  basic types and non-basic types appear in a row, it is nice to only
  use the brace syntax (also for basic types) and align the braces.

* If a class contains pointers as members, it must now also provide a
  copy constructor and assignment operator. In the most cases, one
  would make them private, effectively disallowing the objects to be
  copied. Unfortunately, this warning cannot be fixed be inheriting
  our existing 'Noncopyable' class (the compiler fails to detect that
  the inheriting class cannot be copied and still gives the error).
  For now, we have to manually add declarations for both the copy
  constructor and assignment operator as private class members. Those
  declarations should be prepended with a comment like this:

        /*
         * Noncopyable
         */
        Thread(Thread const &);
        Thread &operator = (Thread const &);

  In the future, we should revisit these places and try to replace
  the pointers with references. In the presence of at least one
  reference member, the compiler would no longer implicitly generate
  a copy constructor. So we could remove the manual declaration.

Issue #465
2018-01-17 12:14:35 +01:00

99 lines
2.0 KiB
C++

/*
* \brief Facility to write format string into character buffer
* \author Norman Feske
* \date 2006-07-17
*/
/*
* Copyright (C) 2006-2017 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__BASE__SNPRINTF_H_
#define _INCLUDE__BASE__SNPRINTF_H_
#include <base/console.h>
#include <base/stdint.h>
namespace Genode {
class String_console;
/**
* Print format string into character buffer
*
* \param dst destination buffer
* \param dst_len size of 'dst' in bytes
* \param format format string followed by the list of arguments
*
* \return number of characters written to destination buffer
*/
inline int snprintf(char *dst, size_t dst_size, const char *format, ...)
__attribute__((format(printf, 3, 4)));
}
class Genode::String_console : public Console
{
private:
char *_dst;
size_t _dst_len;
size_t _w_offset { 0 };
/*
* Noncopyable
*/
String_console &operator = (String_console const &);
String_console(String_console const &);
public:
/**
* Constructor
*
* \param dst destination character buffer
* \param dst_len size of 'dst'
*/
String_console(char *dst, size_t dst_len)
: _dst(dst), _dst_len(dst_len)
{ _dst[0] = 0; }
/**
* Return number of characters in destination buffer
*/
size_t len() { return _w_offset; }
/***********************
** Console interface **
***********************/
void _out_char(char c) override
{
/* ensure to leave space for null-termination */
if (_w_offset + 2 > _dst_len)
return;
_dst[_w_offset++] = c;
_dst[_w_offset] = 0;
}
};
inline int Genode::snprintf(char *dst, size_t dst_len, const char *format, ...)
{
va_list list;
va_start(list, format);
String_console sc(dst, dst_len);
sc.vprintf(format, list);
va_end(list);
return sc.len();
}
#endif /* _INCLUDE__BASE__SNPRINTF_H_ */