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eba9c15746
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
150 lines
2.8 KiB
C++
150 lines
2.8 KiB
C++
/*
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* \brief Ring buffer
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* \author Norman Feske
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* \date 2007-09-28
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*/
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/*
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* Copyright (C) 2007-2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__OS__RING_BUFFER_H_
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#define _INCLUDE__OS__RING_BUFFER_H_
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#include <base/semaphore.h>
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#include <base/exception.h>
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#include <util/string.h>
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namespace Genode {
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struct Ring_buffer_unsynchronized;
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struct Ring_buffer_synchronized;
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template <typename, int, typename SYNC_POLICY = Ring_buffer_synchronized>
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class Ring_buffer;
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}
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struct Genode::Ring_buffer_unsynchronized
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{
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struct Sem
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{
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void down() { }
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void up() { }
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};
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struct Lock
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{
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void lock() { }
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void unlock() { }
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};
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struct Lock_guard
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{
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Lock_guard(Lock &) { }
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};
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};
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struct Genode::Ring_buffer_synchronized
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{
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typedef Genode::Semaphore Sem;
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typedef Genode::Lock Lock;
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typedef Genode::Lock::Guard Lock_guard;
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};
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/**
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* Ring buffer template
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*
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* \param ET element type
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* \param QUEUE_SIZE number of element slots in the ring. the maximum number of
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* ring-buffer elements is QUEUE_SIZE - 1
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*
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* The ring buffer manages its elements as values.
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* When inserting an element, a copy of the element is
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* stored in the buffer. Hence, the ring buffer is suited
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* for simple plain-data element types.
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*/
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template <typename ET, int QUEUE_SIZE, typename SYNC_POLICY>
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class Genode::Ring_buffer
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{
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private:
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int _head = 0;
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int _tail = 0;
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typename SYNC_POLICY::Sem _sem { }; /* element counter */
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typename SYNC_POLICY::Lock _head_lock { }; /* synchronize add */
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ET _queue[QUEUE_SIZE] { };
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public:
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class Overflow : public Exception { };
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/**
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* Constructor
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*/
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Ring_buffer() { }
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/**
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* Place element into ring buffer
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*
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* \throw Overflow the ring buffer is full
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*/
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void add(ET ev)
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{
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typename SYNC_POLICY::Lock_guard lock_guard(_head_lock);
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if ((_head + 1)%QUEUE_SIZE != _tail) {
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_queue[_head] = ev;
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_head = (_head + 1)%QUEUE_SIZE;
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_sem.up();
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} else
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throw Overflow();
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}
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/**
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* Take element from ring buffer
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*
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* \return element
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*
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* If the ring buffer is empty, this method blocks until an element
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* gets available.
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*/
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ET get()
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{
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_sem.down();
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ET e = _queue[_tail];
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_tail = (_tail + 1)%QUEUE_SIZE;
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return e;
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}
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/**
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* Return true if ring buffer is empty
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*/
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bool empty() const { return _tail == _head; }
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/**
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* Return the remaining capacity
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*/
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int avail_capacity() const
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{
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if (_head >= _tail)
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return QUEUE_SIZE - _head + _tail - 1;
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else
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return _tail - _head - 1;
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}
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/**
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* Discard all ring-buffer elements
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*/
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void reset() { _head = _tail; }
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};
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#endif /* _INCLUDE__OS__RING_BUFFER_H_ */
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