ART: Add event callback support

Add basic event callback support infrastructure. Actual users will
follow.

Bug: 31684920
Test: m test-art-host
Change-Id: Ic496933ef3a94f9d27a2779b7f4fdc5b096eab22
diff --git a/runtime/openjdkjvmti/events.h b/runtime/openjdkjvmti/events.h
new file mode 100644
index 0000000..5716d03
--- /dev/null
+++ b/runtime/openjdkjvmti/events.h
@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_OPENJDKJVMTI_EVENTS_H_
+#define ART_RUNTIME_OPENJDKJVMTI_EVENTS_H_
+
+#include <bitset>
+#include <vector>
+
+#include "base/logging.h"
+#include "jvmti.h"
+#include "thread.h"
+
+namespace openjdkjvmti {
+
+struct ArtJvmTiEnv;
+
+struct EventMask {
+  static constexpr size_t kEventsSize = JVMTI_MAX_EVENT_TYPE_VAL - JVMTI_MIN_EVENT_TYPE_VAL + 1;
+  std::bitset<kEventsSize> bit_set;
+
+  static bool EventIsInRange(jvmtiEvent event) {
+    return event >= JVMTI_MIN_EVENT_TYPE_VAL && event <= JVMTI_MAX_EVENT_TYPE_VAL;
+  }
+
+  void Set(jvmtiEvent event, bool value = true) {
+    DCHECK(EventIsInRange(event));
+    bit_set.set(event - JVMTI_MIN_EVENT_TYPE_VAL, value);
+  }
+
+  bool Test(jvmtiEvent event) const {
+    DCHECK(EventIsInRange(event));
+    return bit_set.test(event - JVMTI_MIN_EVENT_TYPE_VAL);
+  }
+};
+
+struct EventMasks {
+  // The globally enabled events.
+  EventMask global_event_mask;
+
+  // The per-thread enabled events.
+
+  // It is not enough to store a Thread pointer, as these may be reused. Use the pointer and the
+  // thread id.
+  // Note: We could just use the tid like tracing does.
+  using UniqueThread = std::pair<art::Thread*, uint32_t>;
+  // TODO: Native thread objects are immovable, so we can use them as keys in an (unordered) map,
+  //       if necessary.
+  std::vector<std::pair<UniqueThread, EventMask>> thread_event_masks;
+
+  // A union of the per-thread events, for fast-pathing.
+  EventMask unioned_thread_event_mask;
+
+  EventMask& GetEventMask(art::Thread* thread);
+  EventMask* GetEventMaskOrNull(art::Thread* thread);
+  void EnableEvent(art::Thread* thread, jvmtiEvent event);
+  void DisableEvent(art::Thread* thread, jvmtiEvent event);
+};
+
+// Helper class for event handling.
+struct EventHandler {
+  // List of all JvmTiEnv objects that have been created, in their creation order.
+  std::vector<ArtJvmTiEnv*> envs;
+
+  // A union of all enabled events, anywhere.
+  EventMask global_mask;
+
+  // Register an env. It is assumed that this happens on env creation, that is, no events are
+  // enabled, yet.
+  void RegisterArtJvmTiEnv(ArtJvmTiEnv* env);
+
+  bool IsEventEnabledAnywhere(jvmtiEvent event) {
+    if (!EventMask::EventIsInRange(event)) {
+      return false;
+    }
+    return global_mask.Test(event);
+  }
+
+  jvmtiError SetEvent(ArtJvmTiEnv* env, art::Thread* thread, jvmtiEvent event, jvmtiEventMode mode);
+
+  template <typename ...Args>
+  ALWAYS_INLINE inline void DispatchEvent(art::Thread* thread, jvmtiEvent event, Args... args);
+};
+
+}  // namespace openjdkjvmti
+
+#endif  // ART_RUNTIME_OPENJDKJVMTI_EVENTS_H_