Simple BlinkGC heap compaction.

third_party/WebKit/Source/platform/heap/BlinkGC.h

 // 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.
 
 #ifndef BlinkGC_h
 #define BlinkGC_h
 
 // BlinkGC.h is a file that defines common things used by Blink GC.
 
 #include "platform/PlatformExport.h"
 #include "wtf/Allocator.h"
 
 namespace blink {
 
 class Visitor;
 
 #define PRINT_HEAP_STATS 0  // Enable this macro to print heap stats to stderr.
 
 using Address = uint8_t*;
 
 using FinalizationCallback = void (*)(void*);
 using VisitorCallback = void (*)(Visitor*, void* self);
 using TraceCallback = VisitorCallback;
 using WeakCallback = VisitorCallback;
 using EphemeronCallback = VisitorCallback;
 using PreFinalizerCallback = bool (*)(void*);
 
+// Simple alias to avoid heap compaction type signatures turning into
+// a sea of generic |void*|s.
+using MovableReference = void*;
+
+// Heap compaction supports registering callbacks that are to be invoked
+// when an object is moved during compaction. This is to support internal
+// location fixups that need to happen as a result.
+//
+// i.e., when the object residing at |from| is moved to |to| by the compaction
+// pass, invoke the callback to adjust any internal references that now need
+// to be |to|-relative.
+using MovingObjectCallback = void (*)(void* callbackData,
+                                      MovableReference from,
+                                      MovableReference to,
+                                      size_t);
+
 // List of typed arenas. The list is used to generate the implementation
 // of typed arena related methods.
 //
 // To create a new typed arena add a H(<ClassName>) to the
 // FOR_EACH_TYPED_ARENA macro below.
 #define FOR_EACH_TYPED_ARENA(H) \
   H(Node)                       \
   H(CSSValue)
 
 #define TypedArenaEnumName(Type) Type##ArenaIndex,
@@ skipping 63 matching lines @@
 
   enum ThreadHeapMode {
     MainThreadHeapMode,
     PerThreadHeapMode,
   };
 };
 
 }  // namespace blink
 
 #endif