98 lines
2.6 KiB
C++
98 lines
2.6 KiB
C++
// Locked.hh
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// This file is part of libpbe; see http://anyterm.org/
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// (C) 2007 Philip Endecott
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// any later version.
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//
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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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//
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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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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// This provides a class template that augments a variable with a mutex, and
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// allows access only when the mutex is locked. Example:
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//
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// typedef Locked< vector<int> > x_t;
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// x_t x;
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//
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// // We can only modify x via an x_t::writer:
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// x_t::writer xw;
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// // Creating xw locks the mutex.
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// // xw behaves like a pointer to the underlying vector<int>:
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// xw->push_back(123);
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// xw->push_back(321);
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// // The lock is released when xw goes out of scope.
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//
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// To read, use an x_t::reader. It behaves like a const pointer to the
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// underlying data.
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//
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// The mutex and lock types can be specified with template parameters, but
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// they default to the boost versions.
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//
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// I had hoped to allow conversion-to-reference for the writer and reader, so
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// that you could write xw.push_back(123) rather than xw->push_back(123).
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// But this didn't work, presumably because I don't really understand how
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// implict type conversion is supposed to work. My attempt is still present,
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// commented out.
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#ifndef libpbe_Locked_hh
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#define libpbe_Locked_hh
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#include "Mutex.hh"
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namespace pbe {
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template <typename T,
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typename MUTEX_T = pbe::Mutex<>,
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typename LOCK_T = pbe::Lock<MUTEX_T> >
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class Locked {
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private:
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T data;
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MUTEX_T mutex;
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public:
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class writer {
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Locked& locked;
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LOCK_T l;
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public:
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writer(Locked& locked_):
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locked(locked_),
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l(locked.mutex)
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{}
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// operator T&() { return locked.data; }
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T& operator*() { return locked.data; }
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T* operator->() { return &locked.data; }
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};
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class reader {
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Locked& locked;
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LOCK_T l;
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public:
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reader(Locked& locked_):
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locked(locked_),
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l(locked.mutex)
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{}
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// operator const T&() const { return locked.data; }
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const T& operator*() const { return locked.data; }
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const T* operator->() const { return &locked.data; }
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};
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};
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};
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#endif
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