Reimplement Symbols using hash table template.

runtime/vm/hash_table_test.cc

 // Copyright (c) 2014, 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 <algorithm>
 #include <cstring>
 #include <map>
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 15 matching lines @@
   static uword Hash(const char* key) {
     return static_cast<uword>(strlen(key));
   }
   static bool IsMatch(const Object& a, const Object& b) {
     return a.IsString() && b.IsString() &&
         String::Cast(a).Equals(String::Cast(b));
   }
   static uword Hash(const Object& obj) {
     return String::Cast(obj).Length();
   }
+  static RawObject* NewKey(const char* key) {
+    return String::New(key);
+  }
 };
 
 
 template<typename Table>
 void Validate(const Table& table) {
   // Verify consistency of entry state tracking.
   intptr_t num_entries = table.NumEntries();
   intptr_t num_unused = table.NumUnused();
   intptr_t num_occupied = table.NumOccupied();
   intptr_t num_deleted = table.NumDeleted();
@@ skipping 75 matching lines @@
   Table table(Array::Handle(HashTables::New<Table>(5)));
   table.UpdateOrInsert(String::Handle(String::New("a")),
                        String::Handle(String::New("A")));
   EXPECT(table.ContainsKey("a"));
   table.UpdateValue("a", String::Handle(String::New("AAA")));
   String& a_value = String::Handle();
   a_value ^= table.GetOrNull("a");
   EXPECT(a_value.Equals("AAA"));
   Object& null_value = Object::Handle(table.GetOrNull("0"));
   EXPECT(null_value.IsNull());
+
+  // Test on-demand allocation of a new key object using NewKey in traits.
+  String& b_value = String::Handle();
+  b_value ^=
+      table.InsertNewOrGetValue("b", String::Handle(String::New("BBB")));
+  EXPECT(b_value.Equals("BBB"));
+  {
+    // When the key is already present, there should be no allocation.
+    NoGCScope no_gc;
+    b_value ^= table.InsertNewOrGetValue("b", a_value);
+    EXPECT(b_value.Equals("BBB"));
+  }
   table.Release();
 }
 
 
 std::string ToStdString(const String& str) {
   EXPECT(str.IsOneByteString());
   std::string result;
   for (intptr_t i = 0; i < str.Length(); ++i) {
     result += static_cast<char>(str.CharAt(i));
   }
@@ skipping 137 matching lines @@
 TEST_CASE(Maps) {
   for (intptr_t initial_capacity = 0;
        initial_capacity < 32;
        ++initial_capacity) {
     TestMap<UnorderedHashMap<TestTraits> >(initial_capacity, false);
     TestMap<EnumIndexHashMap<TestTraits> >(initial_capacity, true);
   }
 }
 
 }  // namespace dart