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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef NET_DNS_SINGLE_REQUEST_HOST_RESOLVER_H_
      6 #define NET_DNS_SINGLE_REQUEST_HOST_RESOLVER_H_
      7 
      8 #include "base/basictypes.h"
      9 
     10 #include "net/base/completion_callback.h"
     11 #include "net/base/net_export.h"
     12 #include "net/base/request_priority.h"
     13 #include "net/dns/host_resolver.h"
     14 
     15 namespace net {
     16 
     17 class AddressList;
     18 class BoundNetLog;
     19 
     20 // This class represents the task of resolving a hostname (or IP address
     21 // literal) to an AddressList object.  It wraps HostResolver to resolve only a
     22 // single hostname at a time and cancels this request when going out of scope.
     23 class NET_EXPORT SingleRequestHostResolver {
     24  public:
     25   // |resolver| must remain valid for the lifetime of |this|.
     26   explicit SingleRequestHostResolver(HostResolver* resolver);
     27 
     28   // If a completion callback is pending when the resolver is destroyed, the
     29   // host resolution is cancelled, and the completion callback will not be
     30   // called.
     31   ~SingleRequestHostResolver();
     32 
     33   // Resolves the given hostname (or IP address literal), filling out the
     34   // |addresses| object upon success. See HostResolver::Resolve() for details.
     35   int Resolve(const HostResolver::RequestInfo& info,
     36               RequestPriority priority,
     37               AddressList* addresses,
     38               const CompletionCallback& callback,
     39               const BoundNetLog& net_log);
     40 
     41   // Cancels the in-progress request, if any. This prevents the callback
     42   // from being invoked. Resolve() can be called again after cancelling.
     43   void Cancel();
     44 
     45  private:
     46   // Callback for when the request to |resolver_| completes, so we dispatch
     47   // to the user's callback.
     48   void OnResolveCompletion(int result);
     49 
     50   // The actual host resolver that will handle the request.
     51   HostResolver* const resolver_;
     52 
     53   // The current request (if any).
     54   HostResolver::RequestHandle cur_request_;
     55   CompletionCallback cur_request_callback_;
     56 
     57   // Completion callback for when request to |resolver_| completes.
     58   CompletionCallback callback_;
     59 
     60   DISALLOW_COPY_AND_ASSIGN(SingleRequestHostResolver);
     61 };
     62 
     63 }  // namespace net
     64 
     65 #endif  // NET_DNS_SINGLE_REQUEST_HOST_RESOLVER_H_
     66