Refactorings surrounding HostResolver:

(1) Extract HostResolver to an interface.

The existing concrete implementation is now named HostResolverImpl. This makes it possible to create mocks with more complex behavior (i.e. choose via rules if response will be sync vs async).

(2) Transform HostMapper into HostResolverProc.

Conceptually HostResolverProc maps a hostname to a socket address, whereas HostMapper mapped a hostname to another hostname (so you were still at the mercy of the system's host resolver). With HostResolverProc you can specify the exact AddressList, making it possible to run tests requiring IPv6 socketaddrs on systems (like WinXP) that don't actually support it.

(3) Add a MockHostResolver implementation of HostResolver.

This replaces the [ScopedHostMapper + RuleBasedHostMapper + HostResolver] combo. It is less clunky and a bit more expressive.

BUG=http://crbug.com/16452
R=willchan
TEST=existing

Review URL: http://codereview.chromium.org/149511

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@20795 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 69 insertions, 0 deletions

diff --git a/net/base/host_resolver_proc.h b/net/base/host_resolver_proc.h
new file mode 100644
index 0000000..2690987
--- /dev/null
+++ b/net/base/host_resolver_proc.h
@@ -0,0 +1,69 @@
+// Copyright (c) 2009 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_PROC_H_
+#define NET_BASE_HOST_RESOLVER_PROC_H_
+
+#include <string>
+
+#include "base/ref_counted.h"
+
+namespace net {
+
+class AddressList;
+
+// Interface for a getaddrinfo()-like procedure. This is used by unit-tests
+// to control the underlying resolutions in HostResolverImpl. HostResolverProcs
+// can be chained together; they fallback to the next procedure in the chain
+// by calling ResolveUsingPrevious().
+//
+// Note that implementations of HostResolverProc *MUST BE THREADSAFE*, since
+// the HostResolver implementation using them can be multi-threaded.
+class HostResolverProc : public base::RefCountedThreadSafe<HostResolverProc> {
+ public:
+  explicit HostResolverProc(HostResolverProc* previous);
+  virtual ~HostResolverProc() {}
+
+  // Resolves |host| to an address list. If successful returns OK and fills
+  // |addrlist| with a list of socket addresses. Otherwise returns a
+  // network error code.
+  virtual int Resolve(const std::string& host, AddressList* addrlist) = 0;
+
+ protected:
+  // Asks the fallback procedure (if set) to do the resolve.
+  int ResolveUsingPrevious(const std::string& host, AddressList* addrlist);
+
+ private:
+  friend class HostResolverImpl;
+  friend class MockHostResolver;
+  friend class ScopedDefaultHostResolverProc;
+
+  // Sets the previous procedure in the chain.
+  void set_previous_proc(HostResolverProc* proc) {
+    previous_proc_ = proc;
+  }
+
+  // Sets the default host resolver procedure that is used by HostResolverImpl.
+  // This can be used through ScopedDefaultHostResolverProc to set a catch-all
+  // DNS block in unit-tests (individual tests should use MockHostResolver to
+  // prevent hitting the network).
+  static HostResolverProc* SetDefault(HostResolverProc* proc);
+  static HostResolverProc* GetDefault();
+
+ private:
+  scoped_refptr<HostResolverProc> previous_proc_;
+  static HostResolverProc* default_proc_;
+
+  DISALLOW_COPY_AND_ASSIGN(HostResolverProc);
+};
+
+// Resolves |host| to an address list, using the system's default host resolver.
+// (i.e. this calls out to getaddrinfo()). If successful returns OK and fills
+// |addrlist| with a list of socket addresses. Otherwise returns a
+// network error code.
+int SystemHostResolverProc(const std::string& host, AddressList* addrlist);
+
+}  // namespace net
+
+#endif  // NET_BASE_HOST_RESOLVER_PROC_H_