extensions/browser/api/dns/host_resolver_wrapper.h

   1 // Copyright 2014 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 EXTENSIONS_BROWSER_API_DNS_HOST_RESOLVER_WRAPPER_H_
   6 #define EXTENSIONS_BROWSER_API_DNS_HOST_RESOLVER_WRAPPER_H_
   7
   8 #include "base/memory/singleton.h"
   9
  10 namespace content {
  11 class ResourceContext;
  12 }
  13
  14 namespace net {
  15 class HostResolver;
  16 }
  17
  18 namespace extensions {
  19
  20 // Used for testing. In production code, this class does nothing interesting.
  21 // This class is a singleton that holds a pointer to a mock HostResolver, or
  22 // else to NULL. API classes that need to resolve hostnames ask this class for
  23 // the correct HostResolver to use, passing in the one that they want to use,
  24 // thereby avoiding most lifetime issues, and it will reply with either that
  25 // same one, or else the test version to use instead.
  26 //
  27 // This is a pretty complicated way to replace a single pointer with another.
  28 // TODO(miket): make the previous statement obsolete.
  29 class HostResolverWrapper {
  30  public:
  31   static HostResolverWrapper* GetInstance();
  32
  33   // Given a pointer to a ResourceContext, returns its HostResolver if
  34   // SetHostResolverForTesting() hasn't been called, or else a
  35   // a substitute MockHostResolver to use instead.
  36   net::HostResolver* GetHostResolver(content::ResourceContext* context);
  37
  38   // Sets the MockHostResolver to return in GetHostResolver().
  39   void SetHostResolverForTesting(net::HostResolver* mock_resolver);
  40
  41  private:
  42   HostResolverWrapper();
  43   friend struct DefaultSingletonTraits<HostResolverWrapper>;
  44
  45   net::HostResolver* resolver_;
  46
  47   DISALLOW_COPY_AND_ASSIGN(HostResolverWrapper);
  48 };
  49
  50 }  // namespace extensions
  51
  52 #endif  // EXTENSIONS_BROWSER_API_DNS_HOST_RESOLVER_WRAPPER_H_