Bug 1231213 - Correctly choose nsBufferedStream's underlying nsIInputStream after initialization. r=asuth

Differential Revision: https://phabricator.services.mozilla.com/D26159

--HG--
extra : moz-landing-system : lando

netwerk/base/nsBufferedStreams.cpp

@@ -9,6 +9,7 @@
 #include "nsStreamUtils.h"
 #include "nsNetCID.h"
 #include "nsIClassInfoImpl.h"
+#include "mozilla/DebugOnly.h"
 #include "mozilla/ipc/InputStreamUtils.h"
 #include <algorithm>
 
@@ -38,6 +39,7 @@ static struct {
 #endif
 
 using namespace mozilla::ipc;
+using mozilla::DebugOnly;
 using mozilla::Maybe;
 using mozilla::MutexAutoLock;
 using mozilla::Nothing;
@@ -276,7 +278,16 @@ NS_IMPL_CLASSINFO(nsBufferedInputStream, nullptr, nsIClassInfo::THREADSAFE,
                   NS_BUFFEREDINPUTSTREAM_CID)
 
 NS_INTERFACE_MAP_BEGIN(nsBufferedInputStream)
-  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsIInputStream, nsIBufferedInputStream)
+  // Unfortunately there isn't a macro that combines ambiguous and conditional,
+  // and as far as I can tell, no other class would need such a macro.
+  if (mIsAsyncInputStream && aIID.Equals(NS_GET_IID(nsIInputStream))) {
+    foundInterface =
+        static_cast<nsIInputStream*>(static_cast<nsIAsyncInputStream*>(this));
+  } else if (!mIsAsyncInputStream && aIID.Equals(NS_GET_IID(nsIInputStream))) {
+    foundInterface = static_cast<nsIInputStream*>(
+        static_cast<nsIBufferedInputStream*>(this));
+  } else
+    NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIBufferedInputStream)
   NS_INTERFACE_MAP_ENTRY(nsIBufferedInputStream)
   NS_INTERFACE_MAP_ENTRY(nsIStreamBufferAccess)
   NS_INTERFACE_MAP_ENTRY_CONDITIONAL(nsIIPCSerializableInputStream,
@@ -348,6 +359,19 @@ nsBufferedInputStream::Init(nsIInputStream* stream, uint32_t bufferSize) {
   return NS_OK;
 }
 
+already_AddRefed<nsIInputStream> nsBufferedInputStream::GetInputStream() {
+  // A non-null mStream implies Init() has been called.
+  MOZ_ASSERT(mStream);
+
+  nsIInputStream* out = nullptr;
+  DebugOnly<nsresult> rv = QueryInterface(NS_GET_IID(nsIInputStream),
+                                          reinterpret_cast<void**>(&out));
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  MOZ_ASSERT(out);
+
+  return already_AddRefed<nsIInputStream>(out);
+}
+
 NS_IMETHODIMP
 nsBufferedInputStream::Close() {
   nsresult rv1 = NS_OK, rv2;
@@ -764,7 +788,9 @@ nsBufferedInputStream::Clone(nsIInputStream** aResult) {
   rv = bis->Init(clonedStream, mBufferSize);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  bis.forget(aResult);
+  *aResult =
+      static_cast<nsBufferedInputStream*>(bis.get())->GetInputStream().take();
+
   return NS_OK;
 }
 

netwerk/base/nsBufferedStreams.h

@@ -92,6 +92,22 @@ class nsBufferedInputStream final : public nsBufferedStream,
 
   nsIInputStream* Source() { return (nsIInputStream*)mStream.get(); }
 
+  /**
+   * If there's a reference/pointer to an nsBufferedInputStream BEFORE calling
+   * Init() AND the intent is to ultimately convert/assign that
+   * reference/pointer to an nsIInputStream, DO NOT use that initial
+   * reference/pointer. Instead, use the value of QueryInterface-ing to an
+   * nsIInputStream (and, again, the QueryInterface must be performed after
+   * Init()). This is because nsBufferedInputStream has multiple underlying
+   * nsIInputStreams (one from nsIBufferedInputStream and one from
+   * nsIAsyncInputStream), and the correct base nsIInputStream to use will be
+   * unknown until the final value of mIsAsyncInputStream is set in Init().
+   *
+   * This method, however, does just that but also hides the QI details and
+   * will assert if called before Init().
+   */
+  already_AddRefed<nsIInputStream> GetInputStream();
+
  protected:
   virtual ~nsBufferedInputStream() = default;
 

netwerk/base/nsNetUtil.cpp

@@ -30,6 +30,7 @@
 #include "nsIAuthPrompt2.h"
 #include "nsIAuthPromptAdapterFactory.h"
 #include "nsIBufferedStreams.h"
+#include "nsBufferedStreams.h"
 #include "nsIChannelEventSink.h"
 #include "nsIContentSniffer.h"
 #include "mozilla/dom/Document.h"
@@ -1269,7 +1270,9 @@ MOZ_MUST_USE nsresult NS_NewBufferedInputStream(
   if (NS_SUCCEEDED(rv)) {
     rv = in->Init(inputStream, aBufferSize);
     if (NS_SUCCEEDED(rv)) {
-      in.forget(aResult);
+      *aResult = static_cast<nsBufferedInputStream*>(in.get())
+                     ->GetInputStream()
+                     .take();
     }
   }
   return rv;