Add a callback to FetchTask API.

PiperOrigin-RevId: 696947943

quiche/quic/moqt/moqt_failed_fetch.h

@@ -21,6 +21,8 @@ class MoqtFailedFetch : public MoqtFetchTask {
     return kError;
   }
   absl::Status GetStatus() override { return status_; }
+  void SetObjectAvailableCallback(
+      ObjectsAvailableCallback /*callback*/) override {}
 
  private:
   absl::Status status_;

quiche/quic/moqt/moqt_outgoing_queue.h

@@ -103,6 +103,12 @@ class MoqtOutgoingQueue : public MoqtTrackPublisher {
     GetNextObjectResult GetNextObject(PublishedObject&) override;
     absl::Status GetStatus() override { return status_; }
 
+    void SetObjectAvailableCallback(
+        ObjectsAvailableCallback /*callback*/) override {
+      // Not needed since all objects in a fetch against an in-memory queue are
+      // guaranteed to resolve immediately.
+    }
+
    private:
     GetNextObjectResult GetNextObjectInner(PublishedObject&);
 

quiche/quic/moqt/moqt_publisher.h

@@ -15,6 +15,7 @@
 #include "quiche/quic/moqt/moqt_messages.h"
 #include "quiche/quic/moqt/moqt_priority.h"
 #include "quiche/common/platform/api/quiche_mem_slice.h"
+#include "quiche/common/quiche_callbacks.h"
 
 namespace moqt {
 
@@ -47,6 +48,8 @@ class MoqtObjectListener {
 // cancelled by deleting the object.
 class MoqtFetchTask {
  public:
+  using ObjectsAvailableCallback = quiche::MultiUseCallback<void()>;
+
   virtual ~MoqtFetchTask() = default;
 
   // Potential results of a GetNextObject() call.
@@ -65,6 +68,12 @@ class MoqtFetchTask {
   // Returns the next object received via the fetch, if available.
   virtual GetNextObjectResult GetNextObject(PublishedObject& output) = 0;
 
+  // Sets the callback that is called when GetNextObject() has previously
+  // returned kPending, but now a new object (or potentially an error or an
+  // end-of-fetch) is available.
+  virtual void SetObjectAvailableCallback(
+      ObjectsAvailableCallback callback) = 0;
+
   // Returns the error if fetch has completely failed, and OK otherwise.
   virtual absl::Status GetStatus() = 0;