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// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MOJO_CORE_PORTS_PORT_LOCKER_H_
#define MOJO_CORE_PORTS_PORT_LOCKER_H_
#include <stdint.h>
#include "base/logging.h"
#include "mojo/core/ports/port_ref.h"
namespace mojo {
namespace core {
namespace ports {
class Port;
class PortRef;
// A helper which must be used to acquire individual Port locks. Any given
// thread may have at most one of these alive at any time. This ensures that
// when multiple ports are locked, they're locked in globally consistent order.
//
// Port locks are acquired upon construction of this object and released upon
// destruction.
class PortLocker {
public:
// Constructs a PortLocker over a sequence of |num_ports| contiguous
// |PortRef*|s. The sequence may be reordered by this constructor, and upon
// return, all referenced ports' locks are held.
PortLocker(const PortRef** port_refs, size_t num_ports);
~PortLocker();
PortLocker(const PortLocker&) = delete;
void operator=(const PortLocker&) = delete;
// Provides safe access to a PortRef's Port. Note that in release builds this
// doesn't do anything other than pass through to the private accessor on
// |port_ref|, but it does force callers to go through a PortLocker to get to
// the state, thus minimizing the likelihood that they'll go and do something
// stupid.
Port* GetPort(const PortRef& port_ref) const {
#ifdef DEBUG
// Sanity check when DEBUG is on to ensure this is actually a port whose
// lock is held by this PortLocker.
bool is_port_locked = false;
for (size_t i = 0; i < num_ports_ && !is_port_locked; ++i) {
if (port_refs_[i]->port() == port_ref.port()) {
is_port_locked = true;
}
}
DCHECK(is_port_locked);
#endif
return port_ref.port();
}
// A helper which can be used to verify that no Port locks are held on the
// current thread. In non-DCHECK builds this is a no-op.
#ifdef DEBUG
static void AssertNoPortsLockedOnCurrentThread();
#else
static void AssertNoPortsLockedOnCurrentThread() {}
#endif
private:
const PortRef** const port_refs_;
const size_t num_ports_;
};
// Convenience wrapper for a PortLocker that locks a single port.
class SinglePortLocker {
public:
explicit SinglePortLocker(const PortRef* port_ref);
~SinglePortLocker();
SinglePortLocker(const SinglePortLocker&) = delete;
void operator=(const SinglePortLocker&) = delete;
Port* port() const { return locker_.GetPort(*port_ref_); }
private:
const PortRef* port_ref_;
PortLocker locker_;
};
} // namespace ports
} // namespace core
} // namespace mojo
#endif // MOJO_CORE_PORTS_PORT_LOCKER_H_
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