83 lines
2.5 KiB
C++
83 lines
2.5 KiB
C++
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/*
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IOS-SAVEPOINT.hpp - capture and restore std::ostream format settings
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Copyright (C) Lumiera.org
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2022, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file ios-savepoint.hpp
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** Capture previous settings of an `std::ostream` and restore them when leaving scope.
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** The stream manipulators of the IOS-Framework from the C++ standard lib allow to adjust
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** various aspects of output formatting for following data fed to the output stream.
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** Unfortunately many of these settings are _sticky_ and thus may "taint" common
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** output streams like `std::cout`. By planting this RAII capsule into a local scope,
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** the internal settings of an output stream can be recorded and restored automatically,
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** once control flow leaves the scope.
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** @remark based on this [stackoverflow] by «[qbert220]», 2013
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**
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** @see IosSavepoint_test
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**
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** [qbert220]: https://stackoverflow.com/users/617617/qbert220
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** [stackoverflow]: https://stackoverflow.com/a/18822888 "Restore state of `std::cout` after manipulating it"
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**
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**
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*/
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#ifndef LIB_IOS_SAVEPOINT_H
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#define LIB_IOS_SAVEPOINT_H
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#include "lib/nocopy.hpp"
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#include <ostream>
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namespace util {
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/**
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* RAII helper to capture and restore
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* output stream format settings.
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*/
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class IosSavepoint
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: MoveOnly
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{
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std::ostream& theStream_;
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std::ios_base::fmtflags prevFlags_;
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char fillChar_;
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public:
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explicit
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IosSavepoint(std::ostream& stream_to_capture)
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: theStream_{stream_to_capture}
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, prevFlags_{theStream_.flags()}
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, fillChar_{theStream_.fill()}
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{ }
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~IosSavepoint()
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{
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theStream_.flags(prevFlags_);
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theStream_.fill(fillChar_);
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}
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};
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} // namespace util
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#endif /*LIB_IOS_SAVEPOINT_H*/
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