Add Service ID zones to service protocol

runtime/vm/object_id_ring.cc

Index: runtime/vm/object_id_ring.cc
diff --git a/runtime/vm/object_id_ring.cc b/runtime/vm/object_id_ring.cc
index 0b396e83cae8c5a49953dbfd048cb46626e9087d..9ae8b92bf52c50e62c5f2586742eadbebff77c04 100644
--- a/runtime/vm/object_id_ring.cc
+++ b/runtime/vm/object_id_ring.cc
@@ -4,6 +4,7 @@
 
 #include "platform/assert.h"
 #include "vm/dart_api_state.h"
+#include "vm/json_stream.h"
 #include "vm/object_id_ring.h"
 
 namespace dart {
@@ -25,14 +26,33 @@ ObjectIdRing::~ObjectIdRing() {
 }
 
 
-int32_t ObjectIdRing::GetIdForObject(RawObject* object) {
+int32_t ObjectIdRing::GetIdForObject(RawObject* object, IdPolicy policy) {
   // We do not allow inserting null because null is how we detect as entry was
   // reclaimed by the GC.
   ASSERT(object != Object::null());
+  if (policy == kAllocateId) {
+    return AllocateNewId(object);
+  }
+  ASSERT(policy == kReuseId);
+  int32_t id = FindExistingIdForObject(object);
+  if (id != kInvalidId) {
+    // Return a previous id for |object|.
+    return id;
+  }
   return AllocateNewId(object);
 }
 
 
+int32_t ObjectIdRing::FindExistingIdForObject(RawObject* raw_obj) {
+  for (int32_t i = 0; i < capacity_; i++) {
+    if (table_[i] == raw_obj) {
+      return IdOfIndex(i);
+    }
+  }
+  return kInvalidId;
+}
+
+
 RawObject* ObjectIdRing::GetObjectForId(int32_t id, LookupResult* kind) {
   int32_t index = IndexOfId(id);
   if (index == kInvalidId) {
@@ -46,6 +66,7 @@ RawObject* ObjectIdRing::GetObjectForId(int32_t id, LookupResult* kind) {
     return Object::null();
   }
   *kind = kValid;
+  ASSERT(IdOfIndex(index) == id);
   return table_[index];
 }
 
@@ -56,6 +77,28 @@ void ObjectIdRing::VisitPointers(ObjectPointerVisitor* visitor) {
 }
 
 
+void ObjectIdRing::PrintJSON(JSONStream* js) {
+  Thread* thread = Thread::Current();
+  Zone* zone = thread->zone();
+  ASSERT(zone != NULL);
+  JSONObject jsobj(js);
+  jsobj.AddProperty("type", "_IdZone");
+  jsobj.AddProperty("name", "default");
+  {
+    JSONArray objects(&jsobj, "objects");
+    Object& obj = Object::Handle();
+    for (int32_t i = 0; i < capacity_; i++) {
+      obj = table_[i];
+      if (obj.IsNull()) {
+        // Collected object.
+        continue;
+      }
+      objects.AddValue(obj, false);
+    }
+  }
+}
+
+
 ObjectIdRing::ObjectIdRing(Isolate* isolate, int32_t capacity) {
   ASSERT(capacity > 0);
   isolate_ = isolate;
@@ -74,7 +117,7 @@ void ObjectIdRing::SetCapacityAndMaxSerial(int32_t capacity,
     free(table_);
   }
   table_ = reinterpret_cast<RawObject**>(calloc(capacity_, kWordSize));
-  for (int i = 0; i < capacity_; i++) {
+  for (int32_t i = 0; i < capacity_; i++) {
     table_[i] = Object::null();
   }
   // The maximum serial number is a multiple of the capacity, so that when
@@ -98,14 +141,9 @@ int32_t ObjectIdRing::AllocateNewId(RawObject* raw_obj) {
   ASSERT(raw_obj->IsHeapObject());
   int32_t id = NextSerial();
   ASSERT(id != kInvalidId);
-  int32_t cursor = IndexOfId(id);
-  ASSERT(cursor != kInvalidId);
-  if (table_[cursor] != Object::null()) {
-    // Free old handle.
-    table_[cursor] = Object::null();
-  }
-  ASSERT(table_[cursor] == Object::null());
-  table_[cursor] = raw_obj;
+  int32_t index = IndexOfId(id);
+  ASSERT(index != kInvalidId);
+  table_[index] = raw_obj;
   return id;
 }
 
@@ -119,6 +157,48 @@ int32_t ObjectIdRing::IndexOfId(int32_t id) {
 }
 
 
+int32_t ObjectIdRing::IdOfIndex(int32_t index) {
+  if (index < 0) {
+    return kInvalidId;
+  }
+  if (index >= capacity_) {
+    return kInvalidId;
+  }
+  int32_t id = kInvalidId;
+  if (wrapped_) {
+    // Serial numbers have wrapped around 0.
+    ASSERT(serial_num_ < capacity_);
+    if (index < serial_num_) {
+      // index < serial_num_ have been handed out and are sequential starting
+      // at 0.
+      id = index;
+    } else {
+      // the other end of the array has the high ids.
+      const int32_t bottom = max_serial_ - capacity_;
+      id = bottom + index;
+    }
+  } else if (index < serial_num_) {
+    // Index into the array where id range splits.
+    int32_t split_point = serial_num_ % capacity_;
+    if (index < split_point) {
+      // index < split_point has serial_numbers starting at
+      // serial_num_ - split_point.
+      int bottom = serial_num_ - split_point;
+      ASSERT(bottom >= 0);
+      id = bottom + index;
+    } else {
+      // index >= split_point has serial_numbers starting at
+      // serial_num_ - split_point - capacity_.
+      int bottom = serial_num_ - capacity_ - split_point;
+      ASSERT(bottom >= 0);
+      id = bottom + index;
+    }
+  }
+  ASSERT(!IsValidId(id) || (IndexOfId(id) == index));
+  return id;
+}
+
+
 bool ObjectIdRing::IsValidContiguous(int32_t id) {
   ASSERT(id != kInvalidId);
   ASSERT((id >= 0) && (id < max_serial_));