Do GetAdaptersAddresses on a worker thread.

net/proxy/dhcp_proxy_script_fetcher_win.cc

 // Copyright (c) 2011 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.
 
 #include "net/proxy/dhcp_proxy_script_fetcher_win.h"
 
 #include "base/metrics/histogram.h"
 #include "base/perftimer.h"
+#include "base/threading/worker_pool.h"
 #include "net/base/net_errors.h"
 #include "net/proxy/dhcp_proxy_script_adapter_fetcher_win.h"
 
 #include <winsock2.h>
 #include <iphlpapi.h>
 #pragma comment(lib, "iphlpapi.lib")
 
 namespace {
 
 // How long to wait at maximum after we get results (a PAC file or
@@ skipping 19 matching lines @@
       ALLOW_THIS_IN_INITIALIZER_LIST(fetcher_callback_(
           this, &DhcpProxyScriptFetcherWin::OnFetcherDone)),
       num_pending_fetchers_(0),
       url_request_context_(url_request_context) {
   DCHECK(url_request_context_);
 }
 
 DhcpProxyScriptFetcherWin::~DhcpProxyScriptFetcherWin() {
   // Count as user-initiated if we are not yet in STATE_DONE.
   Cancel();
+
+  // The WeakPtr we passed to the worker thread may be destroyed on the
+  // worker thread.  This detaches any outstanding WeakPtr state from
+  // the current thread.
+  base::SupportsWeakPtr<DhcpProxyScriptFetcherWin>::DetachFromThread();
 }
 
 int DhcpProxyScriptFetcherWin::Fetch(string16* utf16_text,
                                      CompletionCallback* callback) {
   DCHECK(CalledOnValidThread());
   if (state_ != STATE_START && state_ != STATE_DONE) {
     NOTREACHED();
     return ERR_UNEXPECTED;
   }
 
   fetch_start_time_ = base::TimeTicks::Now();
 
-  std::set<std::string> adapter_names;
-  if (!ImplGetCandidateAdapterNames(&adapter_names)) {
-    return ERR_UNEXPECTED;
-  }
-  if (adapter_names.empty()) {
-    return ERR_PAC_NOT_IN_DHCP;
-  }
-
   state_ = STATE_NO_RESULTS;
-
   client_callback_ = callback;
   destination_string_ = utf16_text;
 
-  for (std::set<std::string>::iterator it = adapter_names.begin();
-       it != adapter_names.end();
-       ++it) {
-    DhcpProxyScriptAdapterFetcher* fetcher(ImplCreateAdapterFetcher());
-    fetcher->Fetch(*it, &fetcher_callback_);
-    fetchers_.push_back(fetcher);
-  }
-  num_pending_fetchers_ = fetchers_.size();
+  worker_thread_ = ImplCreateWorkerThread(AsWeakPtr());
+  worker_thread_->Start();
 
   return ERR_IO_PENDING;
 }
 
 void DhcpProxyScriptFetcherWin::Cancel() {
   DCHECK(CalledOnValidThread());
 
   if (state_ != STATE_DONE) {
     // We only count this stat if the cancel was explicitly initiated by
     // our client, and if we weren't already in STATE_DONE.
@@ skipping 14 matching lines @@
     for (FetcherVector::iterator it = fetchers_.begin();
          it != fetchers_.end();
          ++it) {
       (*it)->Cancel();
     }
 
     fetchers_.reset();
   }
 }
 
+void DhcpProxyScriptFetcherWin::OnGetCandidateAdapterNamesDone(
+    const std::set<std::string>& adapter_names) {
+  if (adapter_names.empty()) {
+    TransitionToDone();
+    return;
+  }
+
+  for (std::set<std::string>::const_iterator it = adapter_names.begin();
+       it != adapter_names.end();
+       ++it) {
+    DhcpProxyScriptAdapterFetcher* fetcher(ImplCreateAdapterFetcher());
+    fetcher->Fetch(*it, &fetcher_callback_);
+    fetchers_.push_back(fetcher);
+  }
+  num_pending_fetchers_ = fetchers_.size();
+}
+
 std::string DhcpProxyScriptFetcherWin::GetFetcherName() const {
   DCHECK(CalledOnValidThread());
   return "win";
 }
 
 const GURL& DhcpProxyScriptFetcherWin::GetPacURL() const {
   DCHECK(CalledOnValidThread());
   DCHECK_EQ(state_, STATE_DONE);
 
   return pac_url_;
@@ skipping 42 matching lines @@
                            fetchers_.size());
   UMA_HISTOGRAM_COUNTS_100("Net.DhcpWpadNumPendingAdaptersAtWaitTimer",
                            num_pending_fetchers_);
 
   TransitionToDone();
 }
 
 void DhcpProxyScriptFetcherWin::TransitionToDone() {
   DCHECK(state_ == STATE_NO_RESULTS || state_ == STATE_SOME_RESULTS);
 
-  // Should have returned immediately at Fetch() if no adapters to check.
-  DCHECK(!fetchers_.empty());
-
-  // Scan twice for the result; once through the whole list for success,
-  // then if no success, return result for most preferred network adapter,
-  // preferring "real" network errors to the ERR_PAC_NOT_IN_DHCP error.
-  // Default to ERR_ABORTED if no fetcher completed.
-  int result = ERR_ABORTED;
-  for (FetcherVector::iterator it = fetchers_.begin();
-       it != fetchers_.end();
-       ++it) {
-    if ((*it)->DidFinish() && (*it)->GetResult() == OK) {
-      result = OK;
-      *destination_string_ = (*it)->GetPacScript();
-      pac_url_ = (*it)->GetPacURL();
-      break;
-    }
-  }
-  if (result != OK) {
-    destination_string_->clear();
+  int result = ERR_PAC_NOT_IN_DHCP;  // Default if no fetchers.
+  if (!fetchers_.empty()) {
+    // Scan twice for the result; once through the whole list for success,
+    // then if no success, return result for most preferred network adapter,
+    // preferring "real" network errors to the ERR_PAC_NOT_IN_DHCP error.
+    // Default to ERR_ABORTED if no fetcher completed.
+    result = ERR_ABORTED;
     for (FetcherVector::iterator it = fetchers_.begin();
          it != fetchers_.end();
          ++it) {
-      if ((*it)->DidFinish()) {
-        result = (*it)->GetResult();
-        if (result != ERR_PAC_NOT_IN_DHCP) {
-          break;
+      if ((*it)->DidFinish() && (*it)->GetResult() == OK) {
+        result = OK;
+        *destination_string_ = (*it)->GetPacScript();
+        pac_url_ = (*it)->GetPacURL();
+        break;
+      }
+    }
+    if (result != OK) {
+      destination_string_->clear();
+      for (FetcherVector::iterator it = fetchers_.begin();
+           it != fetchers_.end();
+           ++it) {
+        if ((*it)->DidFinish()) {
+          result = (*it)->GetResult();
+          if (result != ERR_PAC_NOT_IN_DHCP) {
+            break;
+          }
         }
       }
     }
   }
 
   CancelImpl();
   DCHECK_EQ(state_, STATE_DONE);
   DCHECK(fetchers_.empty());
 
   UMA_HISTOGRAM_TIMES("Net.DhcpWpadCompletionTime",
@@ skipping 13 matching lines @@
 
 URLRequestContext* DhcpProxyScriptFetcherWin::url_request_context() const {
   return url_request_context_;
 }
 
 DhcpProxyScriptAdapterFetcher*
     DhcpProxyScriptFetcherWin::ImplCreateAdapterFetcher() {
   return new DhcpProxyScriptAdapterFetcher(url_request_context_);
 }
 
-bool DhcpProxyScriptFetcherWin::ImplGetCandidateAdapterNames(
-    std::set<std::string>* adapter_names) {
-  return GetCandidateAdapterNames(adapter_names);
+DhcpProxyScriptFetcherWin::WorkerThread*
+    DhcpProxyScriptFetcherWin::ImplCreateWorkerThread(
+        const base::WeakPtr<DhcpProxyScriptFetcherWin>& owner) {
+  return new WorkerThread(owner);
 }
 
 int DhcpProxyScriptFetcherWin::ImplGetMaxWaitMs() {
   return kMaxWaitAfterFirstResultMs;
 }
 
 bool DhcpProxyScriptFetcherWin::GetCandidateAdapterNames(
     std::set<std::string>* adapter_names) {
   DCHECK(adapter_names);
   adapter_names->clear();
@@ skipping 52 matching lines @@
     if ((adapter->Flags & IP_ADAPTER_DHCP_ENABLED) == 0)
       continue;
 
     DCHECK(adapter->AdapterName);
     adapter_names->insert(adapter->AdapterName);
   }
 
   return true;
 }
 
+DhcpProxyScriptFetcherWin::WorkerThread::WorkerThread(
+    const base::WeakPtr<DhcpProxyScriptFetcherWin>& owner) {
+  Init(owner);
+}
+
+DhcpProxyScriptFetcherWin::WorkerThread::~WorkerThread() {
+}
+
+void DhcpProxyScriptFetcherWin::WorkerThread::Start() {
+  bool succeeded = base::WorkerPool::PostTask(
+      FROM_HERE,
+      NewRunnableMethod(
+          this,
+          &DhcpProxyScriptFetcherWin::WorkerThread::ThreadFunc),
+      true);
+  DCHECK(succeeded);
+}
+
+void DhcpProxyScriptFetcherWin::WorkerThread::ThreadFunc() {
+  ImplGetCandidateAdapterNames(&adapter_names_);
+
+  bool succeeded = origin_loop_->PostTask(
+      FROM_HERE,
+      NewRunnableMethod(
+          this,
+          &DhcpProxyScriptFetcherWin::WorkerThread::OnThreadDone));
+  DCHECK(succeeded);
+}
+
+void DhcpProxyScriptFetcherWin::WorkerThread::OnThreadDone() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (owner_)
+    owner_->OnGetCandidateAdapterNamesDone(adapter_names_);

[eroman, 2011/06/21 03:02:54]

How is cancellation handled?

I understand that if |owner_| is deleted, then the weakpointer will be marked as
such.

However what if |owner_| is still alive, but DhcpProxyScriptFetcherWin::Cancel()
was called on it.

In that case, I believe we will go ahead and start fetching for each adapter,
when really we should not do anything.

+}
+
+DhcpProxyScriptFetcherWin::WorkerThread::WorkerThread() {
+}
+
+void DhcpProxyScriptFetcherWin::WorkerThread::Init(
+    const base::WeakPtr<DhcpProxyScriptFetcherWin>& owner) {
+  owner_ = owner;
+  origin_loop_ = base::MessageLoopProxy::CreateForCurrentThread();
+}
+
+bool DhcpProxyScriptFetcherWin::WorkerThread::ImplGetCandidateAdapterNames(
+    std::set<std::string>* adapter_names) {
+  return DhcpProxyScriptFetcherWin::GetCandidateAdapterNames(adapter_names);
+}
+
 }  // namespace net