Add a hash map for a raw object to id mapping, this table will be used during snapshot writing in o…

runtime/vm/weak_table.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 "vm/weak_table.h"
 
 #include "platform/assert.h"
 #include "vm/raw_object.h"
 
 namespace dart {
@@ skipping 57 matching lines @@
   set_used(used() + 1);
   set_count(count() + 1);
 
   // Rehash if needed to ensure that there are empty slots available.
   if (used_ >= limit()) {
     Rehash();
   }
 }
 
 
+void WeakTable::Reset() {
+  intptr_t* old_data = data_;
+  used_ = 0;
+  count_ = 0;
+  size_ = kMinSize;
+  data_ = reinterpret_cast<intptr_t*>(calloc(size_, kEntrySize * kWordSize));
+  free(old_data);
+}
+
+
 void WeakTable::Rehash() {
   intptr_t old_size = size();
   intptr_t* old_data = data_;
 
   intptr_t new_size = SizeFor(count(), size());
   ASSERT(Utils::IsPowerOfTwo(new_size));
   intptr_t* new_data = reinterpret_cast<intptr_t*>(
       calloc(new_size, kEntrySize * kWordSize));
 
   intptr_t mask = new_size - 1;
@@ skipping 18 matching lines @@
   // We should only have used valid entries.
   ASSERT(used() == count());
 
   // Switch to using the newly allocated backing store.
   size_ = new_size;
   data_ = new_data;
   free(old_data);
 }
 
 }  // namespace dart