Bug 1212027 - part 5 - add LoneManagedOrNull for simplifying a lot of upcoming code; r=jld

A lot of existing code has variations on:

  if (ManagedPFooChild().Length()) {
    ...(ManagedPFooChild()[0])...
  }
  // Do something with nullptr, or some other action.

It's pretty reasonable to repeat this code when the managed protocols
are stored in an array; the code gets much less nice when managed
protocols are stored in a hashtable.  Let's write a small utility
function to handle those details for us.  Then when we change the
underlying storage, we only need to update this function, rather than a
bunch of callsites.

ProtocolUtils.h is included by all the generated IPDL headers, so
LoneManagedOrNull should be available everywhere the above pattern would
be encountered.

dom/ipc/ContentBridgeChild.cpp

@@ -98,8 +98,8 @@ ContentBridgeChild::SendPBrowserConstructor(PBrowserChild* aActor,
 jsipc::CPOWManager*
 ContentBridgeChild::GetCPOWManager()
 {
-  if (ManagedPJavaScriptChild().Length()) {
-    return CPOWManagerFor(ManagedPJavaScriptChild()[0]);
+  if (PJavaScriptChild* c = LoneManagedOrNull(ManagedPJavaScriptChild())) {
+    return CPOWManagerFor(c);
   }
   return CPOWManagerFor(SendPJavaScriptConstructor());
 }

dom/ipc/ContentBridgeParent.cpp

@@ -180,8 +180,8 @@ ContentBridgeParent::NotifyTabDestroyed()
 jsipc::CPOWManager*
 ContentBridgeParent::GetCPOWManager()
 {
-  if (ManagedPJavaScriptParent().Length()) {
-    return CPOWManagerFor(ManagedPJavaScriptParent()[0]);
+  if (PJavaScriptParent* p = LoneManagedOrNull(ManagedPJavaScriptParent())) {
+    return CPOWManagerFor(p);
   }
   return nullptr;
 }

dom/ipc/ContentChild.cpp

@@ -1549,8 +1549,8 @@ ContentChild::DeallocPTestShellChild(PTestShellChild* shell)
 jsipc::CPOWManager*
 ContentChild::GetCPOWManager()
 {
-    if (ManagedPJavaScriptChild().Length()) {
-        return CPOWManagerFor(ManagedPJavaScriptChild()[0]);
+    if (PJavaScriptChild* c = LoneManagedOrNull(ManagedPJavaScriptChild())) {
+        return CPOWManagerFor(c);
     }
     return CPOWManagerFor(SendPJavaScriptConstructor());
 }
@@ -2038,11 +2038,11 @@ ContentChild::ProcessingError(Result aCode, const char* aReason)
     }
 
 #if defined(MOZ_CRASHREPORTER) && !defined(MOZ_B2G)
-    if (ManagedPCrashReporterChild().Length() > 0) {
+    if (PCrashReporterChild* c = LoneManagedOrNull(ManagedPCrashReporterChild())) {
         CrashReporterChild* crashReporter =
-            static_cast<CrashReporterChild*>(ManagedPCrashReporterChild()[0]);
-            nsDependentCString reason(aReason);
-            crashReporter->SendAnnotateCrashReport(
+            static_cast<CrashReporterChild*>(c);
+        nsDependentCString reason(aReason);
+        crashReporter->SendAnnotateCrashReport(
                 NS_LITERAL_CSTRING("ipc_channel_error"),
                 reason);
     }

dom/ipc/ContentParent.cpp

@@ -2081,9 +2081,9 @@ ContentParent::ActorDestroy(ActorDestroyReason why)
             // There's a window in which child processes can crash
             // after IPC is established, but before a crash reporter
             // is created.
-            if (ManagedPCrashReporterParent().Length() > 0) {
+            if (PCrashReporterParent* p = LoneManagedOrNull(ManagedPCrashReporterParent())) {
                 CrashReporterParent* crashReporter =
-                    static_cast<CrashReporterParent*>(ManagedPCrashReporterParent()[0]);
+                    static_cast<CrashReporterParent*>(p);
 
                 // If we're an app process, always stomp the latest URI
                 // loaded in the child process with our manifest URL.  We
@@ -2265,8 +2265,8 @@ ContentParent::NotifyTabDestroyed(const TabId& aTabId,
 jsipc::CPOWManager*
 ContentParent::GetCPOWManager()
 {
-    if (ManagedPJavaScriptParent().Length()) {
-        return CPOWManagerFor(ManagedPJavaScriptParent()[0]);
+    if (PJavaScriptParent* p = LoneManagedOrNull(ManagedPJavaScriptParent())) {
+        return CPOWManagerFor(p);
     }
     return nullptr;
 }
@@ -2286,9 +2286,8 @@ ContentParent::DestroyTestShell(TestShellParent* aTestShell)
 TestShellParent*
 ContentParent::GetTestShellSingleton()
 {
-    if (!ManagedPTestShellParent().Length())
-        return nullptr;
-    return static_cast<TestShellParent*>(ManagedPTestShellParent()[0]);
+    PTestShellParent* p = LoneManagedOrNull(ManagedPTestShellParent());
+    return static_cast<TestShellParent*>(p);
 }
 
 void
@@ -3545,9 +3544,9 @@ ContentParent::KillHard(const char* aReason)
     // We're about to kill the child process associated with this content.
     // Something has gone wrong to get us here, so we generate a minidump
     // of the parent and child for submission to the crash server.
-    if (ManagedPCrashReporterParent().Length() > 0) {
+    if (PCrashReporterParent* p = LoneManagedOrNull(ManagedPCrashReporterParent())) {
         CrashReporterParent* crashReporter =
-            static_cast<CrashReporterParent*>(ManagedPCrashReporterParent()[0]);
+            static_cast<CrashReporterParent*>(p);
         // GeneratePairedMinidump creates two minidumps for us - the main
         // one is for the content process we're about to kill, and the other
         // one is for the main browser process. That second one is the extra

dom/ipc/CrashReporterChild.cpp

@@ -32,10 +32,10 @@ CrashReporterChild::GetCrashReporter()
     default:
       break;
   }
-  if (reporters && reporters->Length() > 0) {
-    return reporters->ElementAt(0);
+  if (!reporters) {
+    return nullptr;
   }
-  return nullptr;
+  return LoneManagedOrNull(*reporters);
 }
 
 } // namespace dom

dom/ipc/TabParent.cpp

@@ -2579,10 +2579,8 @@ TabParent::GetTabIdFrom(nsIDocShell *docShell)
 RenderFrameParent*
 TabParent::GetRenderFrame()
 {
-  if (ManagedPRenderFrameParent().IsEmpty()) {
-    return nullptr;
-  }
-  return static_cast<RenderFrameParent*>(ManagedPRenderFrameParent()[0]);
+  PRenderFrameParent* p = LoneManagedOrNull(ManagedPRenderFrameParent());
+  return static_cast<RenderFrameParent*>(p);
 }
 
 bool

dom/media/gmp/GMPParent.cpp

@@ -583,10 +583,8 @@ GMPParent::WriteExtraDataForMinidump(CrashReporter::AnnotationTable& notes)
 void
 GMPParent::GetCrashID(nsString& aResult)
 {
-  CrashReporterParent* cr = nullptr;
-  if (ManagedPCrashReporterParent().Length() > 0) {
-    cr = static_cast<CrashReporterParent*>(ManagedPCrashReporterParent()[0]);
-  }
+  CrashReporterParent* cr =
+    static_cast<CrashReporterParent*>(LoneManagedOrNull(ManagedPCrashReporterParent()));
   if (NS_WARN_IF(!cr)) {
     return;
   }

dom/network/TCPServerSocketParent.cpp

@@ -65,27 +65,25 @@ TCPServerSocketParent::Init()
 uint32_t
 TCPServerSocketParent::GetAppId()
 {
-  uint32_t appId = nsIScriptSecurityManager::UNKNOWN_APP_ID;
   const PContentParent *content = Manager()->Manager();
-  const InfallibleTArray<PBrowserParent*>& browsers = content->ManagedPBrowserParent();
-  if (browsers.Length() > 0) {
-    TabParent *tab = TabParent::GetFrom(browsers[0]);
-    appId = tab->OwnAppId();
+  if (PBrowserParent* browser = LoneManagedOrNull(content->ManagedPBrowserParent())) {
+    TabParent *tab = TabParent::GetFrom(browser);
+    return tab->OwnAppId();
+  } else {
+    return nsIScriptSecurityManager::UNKNOWN_APP_ID;
   }
-  return appId;
 };
 
 bool
 TCPServerSocketParent::GetInBrowser()
 {
-  bool inBrowser = false;
   const PContentParent *content = Manager()->Manager();
-  const InfallibleTArray<PBrowserParent*>& browsers = content->ManagedPBrowserParent();
-  if (browsers.Length() > 0) {
-    TabParent *tab = TabParent::GetFrom(browsers[0]);
-    inBrowser = tab->IsBrowserElement();
+  if (PBrowserParent* browser = LoneManagedOrNull(content->ManagedPBrowserParent())) {
+    TabParent *tab = TabParent::GetFrom(browser);
+    return tab->IsBrowserElement();
+  } else {
+    return false;
   }
-  return inBrowser;
 }
 
 nsresult

dom/network/TCPSocketParent.cpp

@@ -67,27 +67,25 @@ TCPSocketParentBase::~TCPSocketParentBase()
 uint32_t
 TCPSocketParent::GetAppId()
 {
-  uint32_t appId = nsIScriptSecurityManager::UNKNOWN_APP_ID;
   const PContentParent *content = Manager()->Manager();
-  const InfallibleTArray<PBrowserParent*>& browsers = content->ManagedPBrowserParent();
-  if (browsers.Length() > 0) {
-    TabParent *tab = TabParent::GetFrom(browsers[0]);
-    appId = tab->OwnAppId();
+  if (PBrowserParent* browser = LoneManagedOrNull(content->ManagedPBrowserParent())) {
+    TabParent *tab = TabParent::GetFrom(browser);
+    return tab->OwnAppId();
+  } else {
+    return nsIScriptSecurityManager::UNKNOWN_APP_ID;
   }
-  return appId;
 };
 
 bool
 TCPSocketParent::GetInBrowser()
 {
-  bool inBrowser = false;
   const PContentParent *content = Manager()->Manager();
-  const InfallibleTArray<PBrowserParent*>& browsers = content->ManagedPBrowserParent();
-  if (browsers.Length() > 0) {
-    TabParent *tab = TabParent::GetFrom(browsers[0]);
-    inBrowser = tab->IsBrowserElement();
+  if (PBrowserParent* browser = LoneManagedOrNull(content->ManagedPBrowserParent())) {
+    TabParent *tab = TabParent::GetFrom(browser);
+    return tab->IsBrowserElement();
+  } else {
+    return false;
   }
-  return inBrowser;
 }
 
 nsresult
@@ -225,9 +223,8 @@ TCPSocketParent::RecvOpenBind(const nsCString& aRemoteHost,
   uint32_t appId = nsIScriptSecurityManager::NO_APP_ID;
   bool     inBrowser = false;
   const PContentParent *content = Manager()->Manager();
-  const InfallibleTArray<PBrowserParent*>& browsers = content->ManagedPBrowserParent();
-  if (browsers.Length() > 0) {
-    TabParent *tab = static_cast<TabParent*>(browsers[0]);
+  if (PBrowserParent* browser = LoneManagedOrNull(content->ManagedPBrowserParent())) {
+    TabParent *tab = TabParent::GetFrom(browser);
     appId = tab->OwnAppId();
     inBrowser = tab->IsBrowserElement();
   }

dom/plugins/ipc/PluginModuleParent.cpp

@@ -1484,7 +1484,7 @@ PluginModuleChromeParent::OnHangUIContinue()
 CrashReporterParent*
 PluginModuleChromeParent::CrashReporter()
 {
-    return static_cast<CrashReporterParent*>(ManagedPCrashReporterParent()[0]);
+    return static_cast<CrashReporterParent*>(LoneManagedOrNull(ManagedPCrashReporterParent()));
 }
 
 #ifdef MOZ_CRASHREPORTER_INJECTOR

ipc/glue/ProtocolUtils.h

@@ -327,6 +327,17 @@ DuplicateHandle(HANDLE aSourceHandle,
 #endif
 
 } // namespace ipc
+
+template<typename Protocol>
+Protocol*
+LoneManagedOrNull(const nsTArray<Protocol*>& aManagees)
+{
+    if (aManagees.Length() == 0) {
+        return nullptr;
+    }
+    return aManagees[0];
+}
+
 } // namespace mozilla