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os: add util/formatted_output.h utilities

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The utilities of the new util/formatted_output.h header complement the
existing base/output.h with the text-formatting support needed to
produce tabular output.

Fixes #4449
This commit is contained in:
Norman Feske 2022-03-14 12:00:23 +01:00 committed by Christian Helmuth
parent a5c9830706
commit 232a45bc14
1 changed files with 122 additions and 0 deletions
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repos/os/include/util/formatted_output.h Normal file
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/*
* \brief Utilities for formatted text output
* \author Norman Feske
* \date 2022-03-14
*/
/*
* Copyright (C) 2022 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__OS__UTIL__FORMATTED_OUTPUT_H_
#define _INCLUDE__OS__UTIL__FORMATTED_OUTPUT_H_
#include <base/output.h>
namespace Genode {
template <typename> struct Truncated;
template <typename> struct Repeated;
template <typename> struct Left_aligned;
template <typename> struct Right_aligned;
/**
* Return the number of characters needed when rendering 'args' as text
*/
template <typename... ARGS>
static unsigned printed_length(ARGS &&... args)
{
struct _Output : Output
{
unsigned count = 0;
void out_char(char) override { count++; }
} _output;
print(_output, args...);
return _output.count;
}
}
template <typename T>
struct Genode::Truncated
{
unsigned const _limit;
T const &_arg;
Truncated(unsigned limit, T const &arg) : _limit(limit), _arg(arg) { }
void print(Output &out) const
{
struct _Output : Output
{
Output &out;
unsigned const limit;
unsigned count = 0;
void out_char(char c) override
{
if (count++ < limit)
out.out_char(c);
}
_Output(Output &out, unsigned limit) : out(out), limit(limit) { }
} _output(out, _limit);
Genode::print(_output, _arg);
}
};
template <typename T>
struct Genode::Repeated
{
unsigned const _n;
T const &_arg;
Repeated(unsigned n, T const &arg) : _n(n), _arg(arg) { }
void print(Output &out) const
{
for (unsigned i = 0; i < _n; i++)
Genode::print(out, _arg);
}
};
template <typename T>
struct Genode::Left_aligned
{
unsigned const _n;
T const &_arg;
Left_aligned(unsigned n, T const &arg) : _n(n), _arg(arg) { }
void print(Output &out) const
{
unsigned const len = min(printed_length(_arg), _n);
Genode::print(out, Truncated(len, _arg), Repeated(_n - len, Char(' ')));
}
};
template <typename T>
struct Genode::Right_aligned
{
unsigned const _n;
T const &_arg;
Right_aligned(unsigned n, T const &arg) : _n(n), _arg(arg) { }
void print(Output &out) const
{
unsigned const len = min(printed_length(_arg), _n);
Genode::print(out, Repeated(_n - len, Char(' ')), Truncated(len, _arg));
}
};
#endif /* _INCLUDE__OS__UTIL__FORMATTED_OUTPUT_H_ */