Re-land extract state management from WebMediaPlayerImpl.

media/blink/pipeline_state.cc

+// Copyright 2015 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 "media/blink/pipeline_state.h"
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "build/build_config.h"
+#include "media/filters/chunk_demuxer.h"
+
+namespace media {
+
+PipelineState::PipelineState(Pipeline* pipeline,
+                             const RendererFactoryCB& renderer_factory_cb,
+                             const SeekedCB& seeked_cb,
+                             const SuspendedCB& suspended_cb,
+                             const PipelineStatusCB& error_cb)
+    : pipeline_(pipeline),
+      renderer_factory_cb_(renderer_factory_cb),
+      seeked_cb_(seeked_cb),
+      suspended_cb_(suspended_cb),
+      error_cb_(error_cb) {
+  DCHECK(pipeline_);
+  DCHECK(!renderer_factory_cb_.is_null());
+  DCHECK(!seeked_cb_.is_null());
+  DCHECK(!suspended_cb_.is_null());
+  DCHECK(!error_cb_.is_null());
+}
+
+PipelineState::~PipelineState() {}
+
+// TODO(sandersd): Move ChunkDemuxer API to Demuxer so that Pipeline can
+// implement all of this.
+void PipelineState::Start(ChunkDemuxer* chunk_demuxer,
+                          Demuxer* demuxer,
+                          const base::Closure& ended_cb,
+                          const PipelineMetadataCB& metadata_cb,
+                          const BufferingStateCB& buffering_state_cb,
+                          const base::Closure& duration_change_cb,
+                          const AddTextTrackCB& add_text_track_cb,
+                          const base::Closure& waiting_for_decryption_key_cb) {
+  chunk_demuxer_ = chunk_demuxer;
+  pipeline_->Start(demuxer, renderer_factory_cb_.Run(), ended_cb, error_cb_,
+                   base::Bind(&PipelineState::OnPipelineStatus,
+                              base::Unretained(this), State::PLAYING),
+                   metadata_cb, buffering_state_cb, duration_change_cb,
+                   add_text_track_cb, waiting_for_decryption_key_cb);
+}
+
+void PipelineState::Seek(base::TimeDelta time, bool time_updated) {
+  // It would be slightly more clear to set this in Dispatch(), but we want to
+  // be sure it gets updated even if the seek is elided.
+  // TODO(sandersd): Is it even possible to have an elided seek during Start()?

[sandersd (OOO until July 31), 2016/02/01 23:19:26]

FYI: I removed this TODO, because it turns out that we want that ability for
Resume(), even if Start() isn't affected.

+  // During this time playback should be paused, and so WMPI would handle the
+  // elision itself.
+  if (time_updated)
+    pending_time_update_ = true;
+  pending_seeked_ = true;
+
+  // If we are already seeking to |time|, just clear any pending seek. This does
+  // not apply to MSE because the underlying buffer could have been changed

[wolenetz, 2016/01/29 21:42:30]

nit: as you mentioned yesterday, this could also apply to file-backed blob urls,
backed by a potentially changing file (impacting multibuffer work, too)

[sandersd (OOO until July 31), 2016/02/01 23:19:26]

I added a comment about that for now.

+  // between the seek calls.
+  if ((state_ == State::SEEKING || state_ == State::RESUMING) &&
+      seek_time_ == time && !chunk_demuxer_) {
+    pending_seek_ = false;
+    return;
+  }
+
+  pending_seek_time_ = time;
+  pending_seek_ = true;
+  Dispatch();
+}
+
+void PipelineState::Suspend() {
+  pending_resume_ = false;
+  if (state_ != State::SUSPENDING && state_ != State::SUSPENDED) {
+    pending_suspend_ = true;
+    Dispatch();
+  }
+}
+
+void PipelineState::Resume() {
+  pending_suspend_ = false;
+  if (state_ == State::SUSPENDING || state_ == State::SUSPENDED) {
+    pending_resume_ = true;
+    Dispatch();
+  }
+}
+
+bool PipelineState::IsPlaying() {
+  return (state_ == State::PLAYING);
+}
+
+bool PipelineState::IsSuspended() {
+  return (state_ == State::SUSPENDED || state_ == State::RESUMING);
+}
+
+void PipelineState::OnPipelineStatus(State state,
+                                     PipelineStatus pipeline_status) {
+  if (pipeline_status != PIPELINE_OK) {
+    error_cb_.Run(pipeline_status);
+    return;
+  }
+
+  state_ = state;
+
+  // Start(), Seek(), or Resume() completed; we can be sure that
+  // |chunk_demuxer_| got the seek it was waiting for.
+  if (state == State::PLAYING)
+    waiting_for_seek_ = false;
+
+  // Sadly we need to signal this state change via a possibly reentrant
+  // callback. Keep in mind that the state may change inside the callback!
+  // (In particular, it must be safe to call Dispatch() twice in a row here.)
+  if (state == State::SUSPENDED)
+    suspended_cb_.Run();
+
+  Dispatch();
+}
+
+// Note: Dispatch() may be called twice in a row. (See OnPipelineStatus().)

[wolenetz, 2016/01/29 21:42:30]

nit: Saying it must support re-entrancy by (at least) OnPipelineStatus() would
be more clear.

[sandersd (OOO until July 31), 2016/02/01 23:19:26]

Done.

+void PipelineState::Dispatch() {
+  // Suspend/resume transitions take priority because seeks before a suspend
+  // are wasted, an seeks after can be merged into the resume operation.
+  if (pending_suspend_ && state_ == State::PLAYING) {
+    pending_suspend_ = false;
+    state_ = State::SUSPENDING;
+    pipeline_->Suspend(base::Bind(&PipelineState::OnPipelineStatus,

[wolenetz, 2016/01/29 21:42:30]

In the case of an already-in-progress pipeline_->Seek(...), does
pipeline_->Suspend(...) do the right thing? For instance, do we need to do
anything do enforce immediate renderer suspend independently from canceling or
pending further on a potentially blocked-pending-buffers-at-target-seek
operation from completing?

[sandersd (OOO until July 31), 2016/02/01 23:19:26]

While I tested this manually, and it seemed to work, you're correct that there
seems to be a logical hole where the resume time would not account for the seek
that was cancelled. I've added new logic to handle that case by turning the
current seek back into a pending seek. PTAL.

+                                  base::Unretained(this), State::SUSPENDED));
+    return;
+  }
+
+  if (pending_resume_ && state_ == State::SUSPENDED) {
+    // If there is a pending seek, resume to that time instead.
+    if (pending_seek_) {
+      seek_time_ = pending_seek_time_;
+      pending_seek_ = false;
+    } else {
+      seek_time_ = pipeline_->GetMediaTime();
+    }
+
+    // Tell |chunk_demuxer_| to expect our resume.
+    if (chunk_demuxer_) {
+      DCHECK(!waiting_for_seek_);
+      chunk_demuxer_->StartWaitingForSeek(seek_time_);
+      waiting_for_seek_ = true;
+    }
+
+    pending_resume_ = false;
+    state_ = State::RESUMING;
+    pipeline_->Resume(renderer_factory_cb_.Run(), seek_time_,
+                      base::Bind(&PipelineState::OnPipelineStatus,
+                                 base::Unretained(this), State::PLAYING));
+    return;
+  }
+
+  // |chunk_demuxer_| supports aborting seeks. Make use of that when we have
+  // iother pending operations.
+  if ((pending_seek_ || pending_suspend_) && waiting_for_seek_) {
+    CHECK(chunk_demuxer_);
+    // CancelPendingSeek() may be reentrant, so update state first and return
+    // immediately.
+    waiting_for_seek_ = false;
+    chunk_demuxer_->CancelPendingSeek(pending_seek_time_);
+    return;
+  }
+
+  if (pending_seek_ && state_ == State::PLAYING) {
+    seek_time_ = pending_seek_time_;
+
+    // Tell |chunk_demuxer_| to expect our seek.
+    if (chunk_demuxer_) {
+      DCHECK(!waiting_for_seek_);
+      waiting_for_seek_ = true;
+      chunk_demuxer_->StartWaitingForSeek(seek_time_);
+    }
+
+    pending_seek_ = false;
+    state_ = State::SEEKING;
+    pipeline_->Seek(seek_time_,
+                    base::Bind(&PipelineState::OnPipelineStatus,
+                               base::Unretained(this), State::PLAYING));
+    return;
+  }
+
+  // If |state_| is PLAYING and we didn't trigger an operation above then we
+  // are in a stable state. If there is a seeked callback pending, emit it.
+  if (state_ == State::PLAYING) {
+    if (pending_seeked_) {
+      // |seeked_cb_| may be reentrant, so update state first and return
+      // immediately.
+      pending_seeked_ = false;
+      bool was_pending_time_update = pending_time_update_;
+      pending_time_update_ = false;
+      seeked_cb_.Run(was_pending_time_update);
+      return;
+    }
+  }
+}
+
+}  // namespace media