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/*
* Copyright (C) 2015 Canonical Ltd.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Authored by: James Henstridge <james.henstridge@canonical.com>
* Michi Henning <michi.henning@canonical.com>
*/
#include "ratelimiter.h"
#include <cassert>
using namespace std;
namespace lomiri
{
namespace thumbnailer
{
RateLimiter::RateLimiter(int concurrency)
: concurrency_(concurrency)
, running_(0)
{
assert(concurrency > 0);
}
RateLimiter::~RateLimiter()
{
// No assert here because this code is linked by the calling application.
// If the application terminates without waiting for outstanding requests
// to finish, we don't want to cause a core dump.
// assert(running_ == 0);
}
RateLimiter::CancelFunc RateLimiter::schedule(function<void()> job)
{
assert(job);
assert (running_ >= 0);
if (running_ < concurrency_)
{
return schedule_now(job);
}
list_.emplace_back(make_shared<function<void()>>(move(job)));
// Returned function clears the job when called, provided the job is still in the queue.
// done() removes any cleared jobs from the queue without calling them.
weak_ptr<function<void()>> weak_p(list_.back());
return [this, weak_p]() noexcept
{
auto job_p = weak_p.lock();
if (job_p)
{
*job_p = nullptr;
}
return job_p != nullptr;
};
}
RateLimiter::CancelFunc RateLimiter::schedule_now(function<void()> job)
{
assert(job);
++running_;
job();
return []{ return false; }; // Wasn't queued, so cancel does nothing.
}
void RateLimiter::done()
{
assert(running_ > 0);
--running_;
// Find the next job, discarding any cancelled jobs.
shared_ptr<function<void()>> job_p;
while (!list_.empty())
{
job_p = list_.back();
assert(job_p);
list_.pop_back();
if (*job_p != nullptr)
{
break;
}
}
// If we found an uncancelled job, call it.
if (job_p && *job_p)
{
schedule_now(*job_p);
}
}
} // namespace thumbnailer
} // namespace lomiri
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