libcruft-util/pool.ipp

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/*
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* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
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*
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* Copyright 2011-2016 Danny Robson <danny@nerdcruft.net>
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*/
#ifdef __UTIL_POOL_IPP
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#error
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#endif
#define __UTIL_POOL_IPP
namespace util {
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//-------------------------------------------------------------------------
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template <typename T>
pool<T>::pool (unsigned int _capacity):
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m_capacity (_capacity),
m_remain (_capacity)
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{
static_assert (sizeof (T) >= sizeof (uintptr_t),
"pool<T>'s chained block system requires that T be at least pointer sized");
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// allocate the memory and note the base address for deletion in destructor
m_next = m_head = new node[m_capacity]; // static_cast<node *> (operator new (sizeof (T) * m_capacity));
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// initialise the linked list of nodes
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for (unsigned int i = 0; i < m_capacity - 1; ++i)
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m_next[i]._node = m_next + i + 1;
m_next[m_capacity - 1]._node = nullptr;
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}
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//-------------------------------------------------------------------------
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template <typename T>
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pool<T>::~pool ()
{
// don't check if everything's been returned as pools are often used
// for PODs which don't need to be destructed via calling release.
delete [] m_head;
}
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//-------------------------------------------------------------------------
template <typename T>
size_t
pool<T>::capacity (void) const
{
return m_capacity;
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}
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//-------------------------------------------------------------------------
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template <typename T>
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size_t
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pool<T>::remain (void) const
{
return m_remain;
}
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//-------------------------------------------------------------------------
template <typename T>
bool
pool<T>::empty (void) const
{
return m_remain == 0;
}
//-------------------------------------------------------------------------
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template <typename T>
template <typename ...Args>
T*
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pool<T>::acquire (Args&... args)
{
// double check we have enough capacity left
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if (!m_next)
throw std::bad_alloc ();
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CHECK_GT (m_remain, 0);
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// save what will become the next node shortly. it could be overwritten
// in the constructor we're about to call.
node *newnext = m_next->_node;
T *data = reinterpret_cast<T*> (m_next->_data);
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// try to construct the returnable object.
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try {
new (data) T (args...);
} catch (...) {
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// the constructor may have overwritten the node linkages before
// throwing. fix this up before forwarding the exception.
m_next->_node = newnext;
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throw;
}
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// the object is valid. save the new linked list head and bump the
// stats for availability.
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m_next = newnext;
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m_remain--;
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return data;
}
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//-------------------------------------------------------------------------
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template <typename T>
void
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pool<T>::release (T *data)
{
CHECK_LT (m_remain, m_capacity);
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data->~T();
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node *newnode = reinterpret_cast<node *> (data);
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newnode->_node = m_next;
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m_next = newnode;
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m_remain++;
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}
}