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/***********************************************************************
cpool.cpp - Implements the ConnectionPool class.
Copyright (c) 2007 by Educational Technology Resources, Inc. and
(c) 2007 by Jonathan Wakely. Others may also hold copyrights on
code in this file. See the CREDITS.txt file in the top directory
of the distribution for details.
This file is part of MySQL++.
MySQL++ is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
MySQL++ is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public
License along with MySQL++; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
USA
***********************************************************************/
#include "cpool.h"
#include "connection.h"
#include <algorithm>
#include <functional>
namespace mysqlpp {
/// \brief Functor to test whether a given ConnectionInfo object is
/// "too old".
///
/// \internal This is a template only because ConnectionInfo is private.
/// Making it a template means the private type is only used at the point
/// of instantiation, where it is accessible.
template <typename ConnInfoT>
class TooOld : std::unary_function<ConnInfoT, bool>
{
public:
#if !defined(DOXYGEN_IGNORE)
TooOld(unsigned int tmax) :
min_age_(time(0) - tmax)
{
}
bool operator()(const ConnInfoT& conn_info) const
{
return !conn_info.in_use && conn_info.last_used <= min_age_;
}
#endif
private:
time_t min_age_;
};
//// clear /////////////////////////////////////////////////////////////
// Destroy connections in the pool, either all of them (completely
// draining the pool) or just those not currently in use. The public
// method shrink() is an alias for clear(false).
void
ConnectionPool::clear(bool all)
{
ScopedLock lock(mutex_); // ensure we're not interfered with
PoolIt it = pool_.begin(), doomed;
while (it != pool_.end()) {
if (all || !it->in_use) {
doomed = it++;
destroy(doomed->conn);
pool_.erase(doomed);
}
else {
++it;
}
}
}
//// find_mru //////////////////////////////////////////////////////////
// Find most recently used available connection. Uses operator< for
// ConnectionInfo to order pool with MRU connection last. Returns 0 if
// there are no connections not in use.
Connection*
ConnectionPool::find_mru()
{
PoolIt mru = std::max_element(pool_.begin(), pool_.end());
if (mru != pool_.end() && !mru->in_use) {
mru->in_use = true;
return mru->conn;
}
else {
return 0;
}
}
//// grab //////////////////////////////////////////////////////////////
Connection*
ConnectionPool::grab()
{
ScopedLock lock(mutex_); // ensure we're not interfered with
remove_old_connections();
if (Connection* mru = find_mru()) {
return mru;
}
else {
// No free connections, so create and return a new one.
pool_.push_back(ConnectionInfo(create()));
return pool_.back().conn;
}
}
//// release ///////////////////////////////////////////////////////////
void
ConnectionPool::release(const Connection* pc)
{
ScopedLock lock(mutex_); // ensure we're not interfered with
for (PoolIt it = pool_.begin(); it != pool_.end(); ++it) {
if (it->conn == pc) {
it->in_use = false;
it->last_used = time(0);
break;
}
}
}
//// remove_old_connections ////////////////////////////////////////////
// Remove connections that were last used too long ago.
void
ConnectionPool::remove_old_connections()
{
TooOld<ConnectionInfo> too_old(max_idle_time());
PoolIt it = pool_.begin();
while ((it = std::find_if(it, pool_.end(), too_old)) != pool_.end()) {
destroy(it->conn);
pool_.erase(it++);
}
}
} // end namespace mysqlpp
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