Refactorings surrounding HostResolver:...

net/base/host_resolver_proc.cc

Index: net/base/host_resolver_proc.cc
===================================================================
--- net/base/host_resolver_proc.cc	(revision 20435)
+++ net/base/host_resolver_proc.cc	(working copy)
@@ -2,8 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "net/base/host_resolver.h"
+#include "net/base/host_resolver_proc.h"
 
+#include "build/build_config.h"
+
 #if defined(OS_WIN)
 #include <ws2tcpip.h>
 #include <wspiapi.h>  // Needed for Win2k compat.
@@ -15,12 +17,8 @@
 #include <resolv.h>
 #endif
 
-#include "base/compiler_specific.h"
-#include "base/message_loop.h"
-#include "base/stl_util-inl.h"
-#include "base/string_util.h"
+#include "base/logging.h"
 #include "base/time.h"
-#include "base/worker_pool.h"
 #include "net/base/address_list.h"
 #include "net/base/net_errors.h"
 
@@ -29,25 +27,39 @@
 #include "base/thread_local_storage.h"
 #endif
 
-#if defined(OS_WIN)
-#include "net/base/winsock_init.h"
-#endif
-
 namespace net {
 
-//-----------------------------------------------------------------------------
+HostResolverProc* HostResolverProc::default_proc_ = NULL;
 
-static HostMapper* host_mapper;
+HostResolverProc::HostResolverProc(HostResolverProc* previous) {
+  set_previous_proc(previous);
 
-std::string HostMapper::MapUsingPrevious(const std::string& host) {
-  return previous_mapper_.get() ? previous_mapper_->Map(host) : host;
+  // Implicitly fall-back to the global default procedure.
+  if (!previous)
+    set_previous_proc(default_proc_);
 }
 
-HostMapper* SetHostMapper(HostMapper* value) {
-  std::swap(host_mapper, value);
-  return value;
+// static
+HostResolverProc* HostResolverProc::SetDefault(HostResolverProc* proc) {
+  HostResolverProc* old = default_proc_;
+  default_proc_ = proc;
+  return old;
 }
 
+// static
+HostResolverProc* HostResolverProc::GetDefault() {
+  return default_proc_;
+}
+
+int HostResolverProc::ResolveUsingPrevious(const std::string& host,
+                                           AddressList* addrlist) {
+  if (previous_proc_)
+    return previous_proc_->Resolve(host, addrlist);
+
+  // Final fallback is the system resolver.
+  return SystemHostResolverProc(host, addrlist);
+}
+
 #if defined(OS_LINUX)
 // On Linux changes to /etc/resolv.conf can go unnoticed thus resulting in
 // DNS queries failing either because nameservers are unknown on startup
@@ -112,7 +124,8 @@
 
 #endif  // defined(OS_LINUX)
 
-static int HostResolverProc(const std::string& host, struct addrinfo** out) {
+int SystemHostResolverProc(const std::string& host, AddressList* addrlist) {
+  struct addrinfo* ai = NULL;
   struct addrinfo hints = {0};
   hints.ai_family = AF_UNSPEC;
 
@@ -145,7 +158,7 @@
   // Restrict result set to only this socket type to avoid duplicates.
   hints.ai_socktype = SOCK_STREAM;
 
-  int err = getaddrinfo(host.c_str(), NULL, &hints, out);
+  int err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
 #if defined(OS_LINUX)
   net::DnsReloadTimer* dns_timer = Singleton<net::DnsReloadTimer>::get();
   // If we fail, re-initialise the resolver just in case there have been any
@@ -153,515 +166,15 @@
   if (err && dns_timer->Expired()) {
     res_nclose(&_res);
     if (!res_ninit(&_res))
-      err = getaddrinfo(host.c_str(), NULL, &hints, out);
+      err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
   }
 #endif
 
-  return err ? ERR_NAME_NOT_RESOLVED : OK;
-}
+  if (err)
+    return ERR_NAME_NOT_RESOLVED;
 
-static int ResolveAddrInfo(HostMapper* mapper, const std::string& host,
-                           struct addrinfo** out) {
-  if (mapper) {
-    std::string mapped_host = mapper->Map(host);
-
-    if (mapped_host.empty())
-      return ERR_NAME_NOT_RESOLVED;
-
-    return HostResolverProc(mapped_host, out);
-  } else {
-    return HostResolverProc(host, out);
-  }
+  addrlist->Adopt(ai);
+  return OK;
 }
 
-//-----------------------------------------------------------------------------
-
-class HostResolver::Request {
- public:
-  Request(int id, const RequestInfo& info, CompletionCallback* callback,
-          AddressList* addresses)
-      : id_(id), info_(info), job_(NULL), callback_(callback),
-        addresses_(addresses) {}
-
-  // Mark the request as cancelled.
-  void MarkAsCancelled() {
-    job_ = NULL;
-    callback_ = NULL;
-    addresses_ = NULL;
-  }
-
-  bool was_cancelled() const {
-    return callback_ == NULL;
-  }
-
-  void set_job(Job* job) {
-    DCHECK(job != NULL);
-    // Identify which job the request is waiting on.
-    job_ = job;
-  }
-
-  void OnComplete(int error, const AddressList& addrlist) {
-    if (error == OK)
-      addresses_->SetFrom(addrlist, port());
-    callback_->Run(error);
-  }
-
-  int port() const {
-    return info_.port();
-  }
-
-  Job* job() const {
-    return job_;
-  }
-
-  int id() const {
-    return id_;
-  }
-
-  const RequestInfo& info() const {
-    return info_;
-  }
-
- private:
-  // Unique ID for this request. Used by observers to identify requests.
-  int id_;
-
-  // The request info that started the request.
-  RequestInfo info_;
-
-  // The resolve job (running in worker pool) that this request is dependent on.
-  Job* job_;
-
-  // The user's callback to invoke when the request completes.
-  CompletionCallback* callback_;
-
-  // The address list to save result into.
-  AddressList* addresses_;
-
-  DISALLOW_COPY_AND_ASSIGN(Request);
-};
-
-//-----------------------------------------------------------------------------
-
-// This class represents a request to the worker pool for a "getaddrinfo()"
-// call.
-class HostResolver::Job : public base::RefCountedThreadSafe<HostResolver::Job> {
- public:
-  Job(HostResolver* resolver, const std::string& host)
-      : host_(host),
-        resolver_(resolver),
-        origin_loop_(MessageLoop::current()),
-        host_mapper_(host_mapper),
-        error_(OK),
-        results_(NULL) {
-  }
-
-  ~Job() {
-    if (results_)
-      freeaddrinfo(results_);
-
-    // Free the requests attached to this job.
-    STLDeleteElements(&requests_);
-  }
-
-  // Attaches a request to this job. The job takes ownership of |req| and will
-  // take care to delete it.
-  void AddRequest(HostResolver::Request* req) {
-    req->set_job(this);
-    requests_.push_back(req);
-  }
-
-  // Called from origin loop.
-  void Start() {
-    // Dispatch the job to a worker thread.
-    if (!WorkerPool::PostTask(FROM_HERE,
-            NewRunnableMethod(this, &Job::DoLookup), true)) {
-      NOTREACHED();
-
-      // Since we could be running within Resolve() right now, we can't just
-      // call OnLookupComplete().  Instead we must wait until Resolve() has
-      // returned (IO_PENDING).
-      error_ = ERR_UNEXPECTED;
-      MessageLoop::current()->PostTask(
-          FROM_HERE, NewRunnableMethod(this, &Job::OnLookupComplete));
-    }
-  }
-
-  // Cancels the current job. Callable from origin thread.
-  void Cancel() {
-    HostResolver* resolver = resolver_;
-    resolver_ = NULL;
-
-    // Mark the job as cancelled, so when worker thread completes it will
-    // not try to post completion to origin loop.
-    {
-      AutoLock locked(origin_loop_lock_);
-      origin_loop_ = NULL;
-    }
-
-    // We don't have to do anything further to actually cancel the requests
-    // that were attached to this job (since they are unreachable now).
-    // But we will call HostResolver::CancelRequest(Request*) on each one
-    // in order to notify any observers.
-    for (RequestsList::const_iterator it = requests_.begin();
-         it != requests_.end(); ++it) {
-      HostResolver::Request* req = *it;
-      if (!req->was_cancelled())
-        resolver->CancelRequest(req);
-    }
-  }
-
-  // Called from origin thread.
-  bool was_cancelled() const {
-    return resolver_ == NULL;
-  }
-
-  // Called from origin thread.
-  const std::string& host() const {
-    return host_;
-  }
-
-  // Called from origin thread.
-  const RequestsList& requests() const {
-    return requests_;
-  }
-
- private:
-  void DoLookup() {
-    // Running on the worker thread
-    error_ = ResolveAddrInfo(host_mapper_, host_, &results_);
-
-    Task* reply = NewRunnableMethod(this, &Job::OnLookupComplete);
-
-    // The origin loop could go away while we are trying to post to it, so we
-    // need to call its PostTask method inside a lock.  See ~HostResolver.
-    {
-      AutoLock locked(origin_loop_lock_);
-      if (origin_loop_) {
-        origin_loop_->PostTask(FROM_HERE, reply);
-        reply = NULL;
-      }
-    }
-
-    // Does nothing if it got posted.
-    delete reply;
-  }
-
-  // Callback for when DoLookup() completes (runs on origin thread).
-  void OnLookupComplete() {
-    // Should be running on origin loop.
-    // TODO(eroman): this is being hit by URLRequestTest.CancelTest*,
-    // because MessageLoop::current() == NULL.
-    //DCHECK_EQ(origin_loop_, MessageLoop::current());
-    DCHECK(error_ || results_);
-
-    if (was_cancelled())
-      return;
-
-    DCHECK(!requests_.empty());
-
-     // Adopt the address list using the port number of the first request.
-    AddressList addrlist;
-    if (error_ == OK) {
-      addrlist.Adopt(results_);
-      addrlist.SetPort(requests_[0]->port());
-      results_ = NULL;
-    }
-
-    resolver_->OnJobComplete(this, error_, addrlist);
-  }
-
-  // Set on the origin thread, read on the worker thread.
-  std::string host_;
-
-  // Only used on the origin thread (where Resolve was called).
-  HostResolver* resolver_;
-  RequestsList requests_;  // The requests waiting on this job.
-
-  // Used to post ourselves onto the origin thread.
-  Lock origin_loop_lock_;
-  MessageLoop* origin_loop_;
-
-  // Hold an owning reference to the host mapper that we are going to use.
-  // This may not be the current host mapper by the time we call
-  // ResolveAddrInfo, but that's OK... we'll use it anyways, and the owning
-  // reference ensures that it remains valid until we are done.
-  scoped_refptr<HostMapper> host_mapper_;
-
-  // Assigned on the worker thread, read on the origin thread.
-  int error_;
-  struct addrinfo* results_;
-
-  DISALLOW_COPY_AND_ASSIGN(Job);
-};
-
-//-----------------------------------------------------------------------------
-
-HostResolver::HostResolver(int max_cache_entries, int cache_duration_ms)
-    : cache_(max_cache_entries, cache_duration_ms), next_request_id_(0),
-      shutdown_(false) {
-#if defined(OS_WIN)
-  EnsureWinsockInit();
-#endif
-}
-
-HostResolver::~HostResolver() {
-  // Cancel the outstanding jobs. Those jobs may contain several attached
-  // requests, which will also be cancelled.
-  for (JobMap::iterator it = jobs_.begin(); it != jobs_.end(); ++it)
-    it->second->Cancel();
-
-  // In case we are being deleted during the processing of a callback.
-  if (cur_completing_job_)
-    cur_completing_job_->Cancel();
-}
-
-// TODO(eroman): Don't create cache entries for hostnames which are simply IP
-// address literals.
-int HostResolver::Resolve(const RequestInfo& info,
-                          AddressList* addresses,
-                          CompletionCallback* callback,
-                          Request** out_req) {
-  if (shutdown_)
-    return ERR_UNEXPECTED;
-
-  // Choose a unique ID number for observers to see.
-  int request_id = next_request_id_++;
-
-  // Notify registered observers.
-  NotifyObserversStartRequest(request_id, info);
-
-  // If we have an unexpired cache entry, use it.
-  if (info.allow_cached_response()) {
-    const HostCache::Entry* cache_entry = cache_.Lookup(
-        info.hostname(), base::TimeTicks::Now());
-    if (cache_entry) {
-      addresses->SetFrom(cache_entry->addrlist, info.port());
-      int error = OK;
-
-      // Notify registered observers.
-      NotifyObserversFinishRequest(request_id, info, error);
-
-      return error;
-    }
-  }
-
-  // If no callback was specified, do a synchronous resolution.
-  if (!callback) {
-    struct addrinfo* results;
-    int error = ResolveAddrInfo(host_mapper, info.hostname(), &results);
-
-    // Adopt the address list.
-    AddressList addrlist;
-    if (error == OK) {
-      addrlist.Adopt(results);
-      addrlist.SetPort(info.port());
-      *addresses = addrlist;
-    }
-
-    // Write to cache.
-    cache_.Set(info.hostname(), error, addrlist, base::TimeTicks::Now());
-
-    // Notify registered observers.
-    NotifyObserversFinishRequest(request_id, info, error);
-
-    return error;
-  }
-
-  // Create a handle for this request, and pass it back to the user if they
-  // asked for it (out_req != NULL).
-  Request* req = new Request(request_id, info, callback, addresses);
-  if (out_req)
-    *out_req = req;
-
-  // Next we need to attach our request to a "job". This job is responsible for
-  // calling "getaddrinfo(hostname)" on a worker thread.
-  scoped_refptr<Job> job;
-
-  // If there is already an outstanding job to resolve |info.hostname()|, use
-  // it. This prevents starting concurrent resolves for the same hostname.
-  job = FindOutstandingJob(info.hostname());
-  if (job) {
-    job->AddRequest(req);
-  } else {
-    // Create a new job for this request.
-    job = new Job(this, info.hostname());
-    job->AddRequest(req);
-    AddOutstandingJob(job);
-    // TODO(eroman): Bound the total number of concurrent jobs.
-    // http://crbug.com/9598
-    job->Start();
-  }
-
-  // Completion happens during OnJobComplete(Job*).
-  return ERR_IO_PENDING;
-}
-
-// See OnJobComplete(Job*) for why it is important not to clean out
-// cancelled requests from Job::requests_.
-void HostResolver::CancelRequest(Request* req) {
-  DCHECK(req);
-  DCHECK(req->job());
-  // NULL out the fields of req, to mark it as cancelled.
-  req->MarkAsCancelled();
-  NotifyObserversCancelRequest(req->id(), req->info());
-}
-
-void HostResolver::AddObserver(Observer* observer) {
-  observers_.push_back(observer);
-}
-
-void HostResolver::RemoveObserver(Observer* observer) {
-  ObserversList::iterator it =
-      std::find(observers_.begin(), observers_.end(), observer);
-
-  // Observer must exist.
-  DCHECK(it != observers_.end());
-
-  observers_.erase(it);
-}
-
-void HostResolver::Shutdown() {
-  shutdown_ = true;
-
-  // Cancel the outstanding jobs.
-  for (JobMap::iterator it = jobs_.begin(); it != jobs_.end(); ++it)
-    it->second->Cancel();
-  jobs_.clear();
-}
-
-void HostResolver::AddOutstandingJob(Job* job) {
-  scoped_refptr<Job>& found_job = jobs_[job->host()];
-  DCHECK(!found_job);
-  found_job = job;
-}
-
-HostResolver::Job* HostResolver::FindOutstandingJob(
-    const std::string& hostname) {
-  JobMap::iterator it = jobs_.find(hostname);
-  if (it != jobs_.end())
-    return it->second;
-  return NULL;
-}
-
-void HostResolver::RemoveOutstandingJob(Job* job) {
-  JobMap::iterator it = jobs_.find(job->host());
-  DCHECK(it != jobs_.end());
-  DCHECK_EQ(it->second.get(), job);
-  jobs_.erase(it);
-}
-
-void HostResolver::OnJobComplete(Job* job,
-                                 int error,
-                                 const AddressList& addrlist) {
-  RemoveOutstandingJob(job);
-
-  // Write result to the cache.
-  cache_.Set(job->host(), error, addrlist, base::TimeTicks::Now());
-
-  // Make a note that we are executing within OnJobComplete() in case the
-  // HostResolver is deleted by a callback invocation.
-  DCHECK(!cur_completing_job_);
-  cur_completing_job_ = job;
-
-  // Complete all of the requests that were attached to the job.
-  for (RequestsList::const_iterator it = job->requests().begin();
-       it != job->requests().end(); ++it) {
-    Request* req = *it;
-    if (!req->was_cancelled()) {
-      DCHECK_EQ(job, req->job());
-
-      // Notify registered observers.
-      NotifyObserversFinishRequest(req->id(), req->info(), error);
-
-      req->OnComplete(error, addrlist);
-
-      // Check if the job was cancelled as a result of running the callback.
-      // (Meaning that |this| was deleted).
-      if (job->was_cancelled())
-        return;
-    }
-  }
-
-  cur_completing_job_ = NULL;
-}
-
-void HostResolver::NotifyObserversStartRequest(int request_id,
-                                               const RequestInfo& info) {
-  for (ObserversList::iterator it = observers_.begin();
-       it != observers_.end(); ++it) {
-    (*it)->OnStartResolution(request_id, info);
-  }
-}
-
-void HostResolver::NotifyObserversFinishRequest(int request_id,
-                                                const RequestInfo& info,
-                                                int error) {
-  bool was_resolved = error == OK;
-  for (ObserversList::iterator it = observers_.begin();
-       it != observers_.end(); ++it) {
-    (*it)->OnFinishResolutionWithStatus(request_id, was_resolved, info);
-  }
-}
-
-void HostResolver::NotifyObserversCancelRequest(int request_id,
-                                                const RequestInfo& info) {
-  for (ObserversList::iterator it = observers_.begin();
-       it != observers_.end(); ++it) {
-    (*it)->OnCancelResolution(request_id, info);
-  }
-}
-
-//-----------------------------------------------------------------------------
-
-SingleRequestHostResolver::SingleRequestHostResolver(HostResolver* resolver)
-    : resolver_(resolver),
-      cur_request_(NULL),
-      cur_request_callback_(NULL),
-      ALLOW_THIS_IN_INITIALIZER_LIST(
-          callback_(this, &SingleRequestHostResolver::OnResolveCompletion)) {
-  DCHECK(resolver_ != NULL);
-}
-
-SingleRequestHostResolver::~SingleRequestHostResolver() {
-  if (cur_request_) {
-    resolver_->CancelRequest(cur_request_);
-  }
-}
-
-int SingleRequestHostResolver::Resolve(const HostResolver::RequestInfo& info,
-                                       AddressList* addresses,
-                                       CompletionCallback* callback) {
-  DCHECK(!cur_request_ && !cur_request_callback_) << "resolver already in use";
-
-  HostResolver::Request* request = NULL;
-
-  // We need to be notified of completion before |callback| is called, so that
-  // we can clear out |cur_request_*|.
-  CompletionCallback* transient_callback = callback ? &callback_ : NULL;
-
-  int rv = resolver_->Resolve(info, addresses, transient_callback, &request);
-
-  if (rv == ERR_IO_PENDING) {
-    // Cleared in OnResolveCompletion().
-    cur_request_ = request;
-    cur_request_callback_ = callback;
-  }
-
-  return rv;
-}
-
-void SingleRequestHostResolver::OnResolveCompletion(int result) {
-  DCHECK(cur_request_ && cur_request_callback_);
-
-  CompletionCallback* callback = cur_request_callback_;
-
-  // Clear the outstanding request information.
-  cur_request_ = NULL;
-  cur_request_callback_ = NULL;
-
-  // Call the user's original callback.
-  callback->Run(result);
-}
-
 }  // namespace net