media: Add static MojoCdmService::GetCdm().

media/mojo/services/mojo_cdm_service.cc

Index: media/mojo/services/mojo_cdm_service.cc
diff --git a/media/mojo/services/mojo_cdm_service.cc b/media/mojo/services/mojo_cdm_service.cc
index 4a163872305d5572e6c6abd2a1fb8716976c321f..23c040dc4ed2a40cfb1ab91a2000621796352f6d 100644
--- a/media/mojo/services/mojo_cdm_service.cc
+++ b/media/mojo/services/mojo_cdm_service.cc
@@ -4,7 +4,11 @@
 
 #include "media/mojo/services/mojo_cdm_service.h"
 
+#include <map>
+
 #include "base/bind.h"
+#include "base/lazy_instance.h"
+#include "base/synchronization/lock.h"
 #include "media/base/cdm_config.h"
 #include "media/base/cdm_context.h"
 #include "media/base/cdm_factory.h"
@@ -18,12 +22,58 @@
 
 namespace media {
 
+namespace {
+
+// Manages all CDMs created by MojoCdmService. Can only have one instance per
+// process so use a LazyInstance to ensure this.
+class CdmManager {
+ public:
+  CdmManager() {}
+  ~CdmManager() {}
+
+  // Returns the CDM associated with |cdm_id|. Can be called on any thread.
+  scoped_refptr<MediaKeys> GetCdm(int cdm_id) {
+    base::AutoLock lock(cdm_map_lock_);
+    return cdm_map_.count(cdm_id) ? cdm_map_[cdm_id] : nullptr;

[DaleCurtis, 2015/11/18 01:00:21]

General question: Why count instead of find? For a map count is always 1, but
other containers must by necessity traverse the whole container instead of
stopping at the first occurrence.

[xhwang, 2015/11/18 18:45:39]

Done.

+  }
+
+  // Registers the |cdm| for |cdm_id|.
+  void RegisterCdm(int cdm_id, const scoped_refptr<MediaKeys>& cdm) {
+    base::AutoLock lock(cdm_map_lock_);
+    DCHECK(!cdm_map_.count(cdm_id));
+    cdm_map_[cdm_id] = cdm;
+  }
+
+  // Unregisters the CDM associated with |cdm_id|.
+  void UnregisterCdm(int cdm_id) {
+    base::AutoLock lock(cdm_map_lock_);
+    DCHECK(cdm_map_.count(cdm_id));
+    cdm_map_.erase(cdm_id);
+  }
+
+ private:
+  base::Lock cdm_map_lock_;

[Tima Vaisburd, 2015/11/18 01:24:20]

nit: I would rename |cdm_map_lock_| into |lock_| because I'd expect some
meaningful names for locks only if they protect portions of the data. But this
is totally up to you.

[xhwang, 2015/11/18 18:45:39]

Done.

+  std::map<int, scoped_refptr<MediaKeys>> cdm_map_;

[DaleCurtis, 2015/11/18 01:00:21]

Map is fine, but if you only ever expect 1 or 2 of these a vector will be
better.

[xhwang, 2015/11/18 18:45:39]

I don't really see performance difference here and since we have the key (cdm
ID) and value (cdm) maps seems more natural.

+
+  DISALLOW_COPY_AND_ASSIGN(CdmManager);
+};
+
+base::LazyInstance<CdmManager>::Leaky g_cdm_manager = LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
 using SimpleMojoCdmPromise = MojoCdmPromise<>;
 using CdmIdMojoCdmPromise = MojoCdmPromise<int>;
 using NewSessionMojoCdmPromise = MojoCdmPromise<std::string>;
 
 int MojoCdmService::next_cdm_id_ = CdmContext::kInvalidCdmId + 1;
 
+// static
+scoped_refptr<MediaKeys> MojoCdmService::GetCdm(int cdm_id) {
+  DVLOG(1) << __FUNCTION__ << ": " << cdm_id;
+  return g_cdm_manager.Get().GetCdm(cdm_id);
+}
+
 MojoCdmService::MojoCdmService(
     base::WeakPtr<MojoCdmServiceContext> context,
     mojo::ServiceProvider* service_provider,
@@ -40,6 +90,8 @@ MojoCdmService::MojoCdmService(
 }
 
 MojoCdmService::~MojoCdmService() {
+  g_cdm_manager.Get().UnregisterCdm(cdm_id_);
+
   if (cdm_id_ != CdmContext::kInvalidCdmId && context_)
     context_->UnregisterCdm(cdm_id_);
 }
@@ -151,7 +203,11 @@ void MojoCdmService::OnCdmCreated(scoped_ptr<CdmIdMojoCdmPromise> promise,
 
   cdm_ = cdm;
   cdm_id_ = next_cdm_id_++;
+
   context_->RegisterCdm(cdm_id_, this);
+  g_cdm_manager.Get().RegisterCdm(cdm_id_, cdm);
+
+  DVLOG(1) << __FUNCTION__ << ": CDM successfully created with ID " << cdm_id_;
   promise->resolve(cdm_id_);
 }