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// Copyright (c) 2006-2008 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 NET_BASE_HOST_RESOLVER_H_
#define NET_BASE_HOST_RESOLVER_H_
#include <string>
#include "base/basictypes.h"
#include "base/ref_counted.h"
#include "net/base/completion_callback.h"
namespace net {
class AddressList;
// This class represents the task of resolving a hostname (or IP address
// literal) to an AddressList object. It can only resolve a single hostname at
// a time, so if you need to resolve multiple hostnames at the same time, you
// will need to allocate a HostResolver object for each hostname.
//
// No attempt is made at this level to cache or pin resolution results. For
// each request, this API talks directly to the underlying name resolver of
// the local system, which may or may not result in a DNS query. The exact
// behavior depends on the system configuration.
//
class HostResolver {
public:
HostResolver();
// If a completion callback is pending when the resolver is destroyed, the
// host resolution is cancelled, and the completion callback will not be
// called.
~HostResolver();
// Resolves the given hostname (or IP address literal), filling out the
// |addresses| object upon success. The |port| parameter will be set as the
// sin(6)_port field of the sockaddr_in{6} struct. Returns OK if successful
// or an error code upon failure.
//
// When callback is null, the operation completes synchronously.
//
// When callback is non-null, the operation will be performed asynchronously.
// ERR_IO_PENDING is returned if it has been scheduled successfully. Real
// result code will be passed to the completion callback.
int Resolve(const std::string& hostname, int port,
AddressList* addresses, CompletionCallback* callback);
private:
class Request;
friend class Request;
scoped_refptr<Request> request_;
DISALLOW_COPY_AND_ASSIGN(HostResolver);
};
// A helper class used in unit tests to alter hostname mappings. See
// SetHostMapper for details.
class HostMapper : public base::RefCountedThreadSafe<HostMapper> {
public:
virtual ~HostMapper() {}
virtual std::string Map(const std::string& host) = 0;
protected:
// Ask previous host mapper (if set) for mapping of given host.
std::string MapUsingPrevious(const std::string& host);
private:
friend class ScopedHostMapper;
// Set mapper to ask when this mapper doesn't want to modify the result.
void set_previous_mapper(HostMapper* mapper) {
previous_mapper_ = mapper;
}
scoped_refptr<HostMapper> previous_mapper_;
};
#ifdef UNIT_TEST
// This function is designed to allow unit tests to override the behavior of
// HostResolver. For example, a HostMapper instance can force all hostnames
// to map to a fixed IP address such as 127.0.0.1.
//
// The previously set HostMapper (or NULL if there was none) is returned.
//
// NOTE: This function is not thread-safe, so take care to only call this
// function while there are no outstanding HostResolver instances.
//
// NOTE: In most cases, you should use ScopedHostMapper instead, which is
// defined in host_resolver_unittest.h
//
HostMapper* SetHostMapper(HostMapper* host_mapper);
#endif
} // namespace net
#endif // NET_BASE_HOST_RESOLVER_H_
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