First pass at implementing the MessageLoop interface. This includes a simple

ppapi/proxy/ppb_message_loop_proxy.cc

Index: ppapi/proxy/ppb_message_loop_proxy.cc
diff --git a/ppapi/proxy/ppb_message_loop_proxy.cc b/ppapi/proxy/ppb_message_loop_proxy.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c0552458e6ae364bf6c57379385cc15ccd359739
--- /dev/null
+++ b/ppapi/proxy/ppb_message_loop_proxy.cc
@@ -0,0 +1,284 @@
+// Copyright (c) 2012 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 "ppapi/proxy/ppb_message_loop_proxy.h"
+
+#include <vector>
+
+#include "base/bind.h"
+#include "base/compiler_specific.h"
+#include "base/message_loop.h"
+#include "base/threading/thread_local_storage.h"
+#include "ppapi/c/dev/ppb_message_loop_dev.h"
+#include "ppapi/c/pp_errors.h"
+#include "ppapi/proxy/plugin_dispatcher.h"
+#include "ppapi/shared_impl/resource.h"
+#include "ppapi/thunk/enter.h"
+#include "ppapi/thunk/ppb_message_loop_api.h"
+
+using ppapi::thunk::PPB_MessageLoop_API;
+
+namespace ppapi {
+namespace proxy {
+
+namespace {
+
+typedef thunk::EnterResource<PPB_MessageLoop_API> EnterMessageLoop;
+
+static base::ThreadLocalStorage::Slot tls_slot(base::LINKER_INITIALIZED);
+
+class MessageLoopResource : public Resource, public PPB_MessageLoop_API {
+ public:
+  MessageLoopResource(PP_Instance instance);
+  virtual ~MessageLoopResource();
+
+  // Resource overrides.
+  virtual PPB_MessageLoop_API* AsPPB_MessageLoop_API() OVERRIDE;
+
+  // PPB_MessageLoop_API implementation.
+  virtual int32_t AttachToCurrentThread() OVERRIDE;
+  virtual int32_t Run() OVERRIDE;
+  virtual int32_t PostWork(PP_CompletionCallback callback,
+                           int64_t delay_ms);

[bbudge, 2012/01/23 18:15:12]

OVERRIDE?

+  virtual int32_t PostQuit(PP_Bool should_destroy) OVERRIDE;
+
+  void DetachFromThread();
+
+ private:
+  struct TaskInfo {
+    tracked_objects::Location from_here;
+    base::Closure closure;
+    int64 delay_ms;
+  };
+
+  // Returns true if the object is associated with the current thread.
+  bool IsCurrent() const;
+
+  // Handles posting to the message loop if there is one, or the pending queue
+  // if there isn't.
+  void PostClosure(const tracked_objects::Location& from_here,
+                   const base::Closure& closure,
+                   int64 delay_ms);
+
+  // TLS destructor function.
+  static void ReleaseMessageLoop(void* value);
+
+  // Created when we attach to the current thread, since MessageLoop assumes
+  // that it's created on the thread it will run on.
+  scoped_ptr<MessageLoop> loop_;
+
+  // Number of invocations of Run currently on the stack.
+  int nested_invocations_;
+
+  // Set to true when the message loop is destroyed to prevent forther
+  // posting of work.
+  bool destroyed_;
+
+  // Set to true if all message loop invocations should exit and that the
+  // loop should be destroyed once it reaches the outermost Run invocation.
+  bool should_destroy_;
+
+  // Since we allow tasks to be posted before the message loop is actually
+  // created (when it's associated with a thread), we keep tasks posted here
+  // until that happens. Once the loop_ is created, this is unused.
+  std::vector<TaskInfo> pending_tasks_;
+
+  DISALLOW_COPY_AND_ASSIGN(MessageLoopResource);
+};
+
+MessageLoopResource::MessageLoopResource(PP_Instance instance)
+    : Resource(HostResource::MakeInstanceOnly(instance)),
+      nested_invocations_(0),
+      destroyed_(false),
+      should_destroy_(false) {
+}
+
+MessageLoopResource::~MessageLoopResource() {
+}
+
+PPB_MessageLoop_API* MessageLoopResource::AsPPB_MessageLoop_API() {
+  return this;
+}
+
+int32_t MessageLoopResource::AttachToCurrentThread() {
+  if (tls_slot.initialized())
+    return PP_ERROR_INPROGRESS;
+  // TODO(brettw) check that the current thread can support a message loop.
+
+  // Take a ref to the MessageLoop on behalf of the TLS. Note that this is an
+  // internal ref and not a plugin ref so the plugin can't accidentally
+  // release it. This is released by ReleaseMessageLoop().
+  AddRef();
+  tls_slot.Initialize(&ReleaseMessageLoop);
+  tls_slot.Set(this);
+
+  loop_.reset(new MessageLoop(MessageLoop::TYPE_DEFAULT));
+
+  // Post all pending work to the message loop.
+  for (size_t i = 0; i < pending_tasks_.size(); i++) {
+    const TaskInfo& info = pending_tasks_[i];
+    PostClosure(info.from_here, info.closure, info.delay_ms);
+  }
+  pending_tasks_.clear();
+
+  return PP_OK;
+}
+
+int32_t MessageLoopResource::Run() {
+  if (!IsCurrent())
+    return PP_ERROR_WRONG_THREAD;
+  // TODO(brettw) prevent this from happening on the main thread & return
+  // PP_ERROR_BLOCKS_MAIN_THREAD.  Maybe have a special constructor for that
+  // one?
+
+  // TODO(brettw) figure out how to release the lock. Can't run the message
+  // loop while holding the lock.
+  nested_invocations_++;
+  loop_->Run();
+  nested_invocations_--;
+
+  if (should_destroy_ && nested_invocations_ == 0) {
+    loop_.reset();
+    destroyed_ = true;
+  }
+  return PP_OK;
+}
+
+int32_t MessageLoopResource::PostWork(PP_CompletionCallback callback,
+                                      int64_t delay_ms) {
+  if (!callback.func)
+    return PP_ERROR_BADARGUMENT;

[bbudge, 2012/01/23 18:15:12]

Need to check destroyed_ here.

+  PostClosure(FROM_HERE,
+              base::Bind(callback.func, callback.user_data,
+                         static_cast<int32_t>(PP_OK)),
+              delay_ms);
+  return PP_OK;
+}
+
+int32_t MessageLoopResource::PostQuit(PP_Bool should_destroy) {
+  if (PP_ToBool(should_destroy))
+    should_destroy_ = true;
+
+  if (IsCurrent())
+    loop_->Quit();
+  else
+    PostClosure(FROM_HERE, MessageLoop::QuitClosure(), 0);
+  return PP_OK;
+}
+
+void MessageLoopResource::DetachFromThread() {
+  // Note that the message loop must be destroyed on the thread is was created.
+  loop_.reset();
+
+  // Cancel out the AddRef in AttachToCurrentThread().
+  Release();
+  // DANGER: may delete this.
+}
+
+bool MessageLoopResource::IsCurrent() const {
+  if (!tls_slot.initialized())
+    return false;  // Can't be current if there's nothing in the slot.
+  return static_cast<const void*>(tls_slot.Get()) ==
+         static_cast<const void*>(this);
+}
+
+void MessageLoopResource::PostClosure(
+    const tracked_objects::Location& from_here,
+    const base::Closure& closure,
+    int64 delay_ms) {
+  if (loop_.get()) {
+    loop_->PostDelayedTask(from_here, closure, delay_ms);
+  } else {
+    TaskInfo info;
+    info.from_here = FROM_HERE;
+    info.closure = closure;
+    info.delay_ms = delay_ms;
+    pending_tasks_.push_back(info);
+  }
+}
+
+// static
+void MessageLoopResource::ReleaseMessageLoop(void* value) {
+  static_cast<MessageLoopResource*>(value)->DetachFromThread();
+}
+
+// -----------------------------------------------------------------------------
+
+PP_Resource Create(PP_Instance instance) {
+  // Validate the instance.
+  PluginDispatcher* dispatcher = PluginDispatcher::GetForInstance(instance);
+  if (!dispatcher)
+    return 0;
+  return (new MessageLoopResource(instance))->GetReference();
+}
+
+PP_Resource GetForMainThread() {
+  // TODO(brettw).
+  return 0;
+}
+
+PP_Resource GetCurrent() {
+  if (!tls_slot.initialized())
+    return 0;
+  MessageLoopResource* loop = reinterpret_cast<MessageLoopResource*>(
+      tls_slot.Get());
+  return loop->GetReference();
+}
+
+int32_t AttachToCurrentThread(PP_Resource message_loop) {
+  EnterMessageLoop enter(message_loop, true);
+  if (enter.succeeded())
+    return enter.object()->AttachToCurrentThread();
+  return PP_ERROR_BADRESOURCE;
+}
+
+int32_t Run(PP_Resource message_loop) {
+  EnterMessageLoop enter(message_loop, true);
+  if (enter.succeeded())
+    return enter.object()->Run();
+  return PP_ERROR_BADRESOURCE;
+}
+
+int32_t PostWork(PP_Resource message_loop,
+                 PP_CompletionCallback callback,
+                 int64_t delay_ms) {
+  EnterMessageLoop enter(message_loop, true);
+  if (enter.succeeded())
+    return enter.object()->PostWork(callback, delay_ms);
+  return PP_ERROR_BADRESOURCE;
+}
+
+int32_t PostQuit(PP_Resource message_loop, PP_Bool should_destroy) {
+  EnterMessageLoop enter(message_loop, true);
+  if (enter.succeeded())
+    return enter.object()->PostQuit(should_destroy);
+  return PP_ERROR_BADRESOURCE;
+}
+
+const PPB_MessageLoop_Dev_0_1 ppb_message_loop_interface = {
+  &Create,
+  &GetForMainThread,
+  &GetCurrent,
+  &AttachToCurrentThread,
+  &Run,
+  &PostWork,
+  &PostQuit
+};
+
+}  // namespace
+
+PPB_MessageLoop_Proxy::PPB_MessageLoop_Proxy(Dispatcher* dispatcher)
+    : InterfaceProxy(dispatcher) {
+}
+
+PPB_MessageLoop_Proxy::~PPB_MessageLoop_Proxy() {
+}
+
+// static
+const PPB_MessageLoop_Dev_0_1* PPB_MessageLoop_Proxy::GetInterface() {
+  return &ppb_message_loop_interface;
+}
+
+}  // namespace proxy
+}  // namespace ppapi