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// Copyright 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// This file supports network stack independent notification of progress
// towards resolving a hostname.
#include <windows.h>
#include <string>
#include "net/base/dns_resolution_observer.h"
#include "base/logging.h"
namespace net {
static DnsResolutionObserver* dns_resolution_observer;
void AddDnsResolutionObserver(DnsResolutionObserver* new_observer) {
if (new_observer == dns_resolution_observer)
return; // Facilitate unit tests that init/teardown repeatedly.
DCHECK(!dns_resolution_observer);
if (InterlockedCompareExchangePointer(
reinterpret_cast<PVOID*>(&dns_resolution_observer),
new_observer, NULL))
DCHECK(0) << "Second attempt to setup observer";
}
DnsResolutionObserver* RemoveDnsResolutionObserver() {
// We really need to check that the entire network subsystem is shutting down,
// and hence no additional calls can even *possibly* still be lingering in the
// notification path that includes our observer. Until we have a way to
// really assert that fact, we will outlaw the calling of this function.
// Darin suggested that the caller use a static initializer for the observer,
// so that it can safely be destroyed after process termination, and without
// inducing a memory leak.
// Bottom line: Don't call this function! You will crash for now.
CHECK(0);
DnsResolutionObserver* old_observer = dns_resolution_observer;
dns_resolution_observer = NULL;
return old_observer;
}
// Locking access to dns_resolution_observer is not really critical... but we
// should test the value of dns_resolution_observer that we use.
// Worst case, we'll get an "out of date" value... which is no big deal for the
// DNS prefetching system (the most common (only?) observer).
void DidStartDnsResolution(const std::string& name, void* context) {
DnsResolutionObserver* current_observer = dns_resolution_observer;
if (current_observer)
current_observer->OnStartResolution(name, context);
}
void DidFinishDnsResolutionWithStatus(bool was_resolved, void* context) {
DnsResolutionObserver* current_observer = dns_resolution_observer;
if (current_observer) {
current_observer->OnFinishResolutionWithStatus(was_resolved, context);
}
}
} // namspace net
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