Add Service ID zones to service protocol

runtime/vm/object_id_ring.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/assert.h"
 #include "vm/dart_api_state.h"
+#include "vm/json_stream.h"
 #include "vm/object_id_ring.h"
 
 namespace dart {
 
 void ObjectIdRing::Init(Isolate* isolate, int32_t capacity) {
   ObjectIdRing* ring = new ObjectIdRing(isolate, capacity);
   isolate->set_object_id_ring(ring);
 }
 
 
 ObjectIdRing::~ObjectIdRing() {
   ASSERT(table_ != NULL);
   free(table_);
   table_ = NULL;
   if (isolate_ != NULL) {
     isolate_->set_object_id_ring(NULL);
     isolate_ = NULL;
   }
 }
 
 
-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) {
     *kind = kExpired;
     return Object::null();
   }
   ASSERT(index >= 0);
   ASSERT(index < capacity_);
   if (table_[index] == Object::null()) {
     *kind = kCollected;
     return Object::null();
   }
   *kind = kValid;
+  ASSERT(IdOfIndex(index) == id);
   return table_[index];
 }
 
 
 void ObjectIdRing::VisitPointers(ObjectPointerVisitor* visitor) {
   ASSERT(table_ != NULL);
   visitor->VisitPointers(table_, capacity_);
 }
 
 
+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", "ObjectIdRing");

[turnidge, 2015/05/12 20:08:01]

Should the name be "default"?

[Cutch, 2015/05/12 23:32:59]

Done.

+  {
+    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);
+    }

[turnidge, 2015/05/12 20:08:01]

How does the user figure out what the id's of the objects in the dump are?  I
would think that we need to emit the id along with each object...

[Cutch, 2015/05/12 23:32:58]

Each object printed to the objects array includes an "id" property. No need to
include it twice.

+  }
+}
+
+
 ObjectIdRing::ObjectIdRing(Isolate* isolate, int32_t capacity) {
   ASSERT(capacity > 0);
   isolate_ = isolate;
   serial_num_ = 0;
   wrapped_ = false;
   table_ = NULL;
   SetCapacityAndMaxSerial(capacity, kMaxId);
 }
 
 
 void ObjectIdRing::SetCapacityAndMaxSerial(int32_t capacity,
                                            int32_t max_serial) {
   ASSERT(max_serial <= kMaxId);
   capacity_ = capacity;
   if (table_ != NULL) {
     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
   // the serial number wraps, the index into table_ wraps with it.
   max_serial_ = max_serial - (max_serial % capacity_);
 }
 
 
 int32_t ObjectIdRing::NextSerial() {
   int32_t r = serial_num_;
   serial_num_++;
   if (serial_num_ >= max_serial_) {
     serial_num_ = 0;
     wrapped_ = true;
   }
   return r;
 }
 
 
 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;
 }
 
 
 int32_t ObjectIdRing::IndexOfId(int32_t id) {
   if (!IsValidId(id)) {
     return kInvalidId;
   }
   ASSERT((id >= 0) && (id < max_serial_));
   return id % capacity_;
 }
 
 
+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_));
   if (id >= serial_num_) {
     // Too large.
     return false;
   }
   int32_t bottom = 0;
   if (serial_num_ >= capacity_) {
     bottom = serial_num_ - capacity_;
@@ skipping 35 matching lines @@
       const int32_t max_serial_num = max_serial_;
       const int32_t bottom = max_serial_num - (capacity_ - serial_num_);
       return id >= bottom && bottom < max_serial_num;
     }
   }
   ASSERT(wrapped_ == false);
   return IsValidContiguous(id);
 }
 
 }  // namespace dart