Create frequently used symbols in the vm isolate

vm/symbols.h

+// Copyright (c) 2012, 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.
+
+#ifndef VM_SYMBOLS_H_
+#define VM_SYMBOLS_H_
+
+#include "vm/object.h"
+
+namespace dart {
+
+// Forward declarations.
+class Isolate;
+class ObjectPointerVisitor;
+
+// Contains a list of frequently used strings in a canonicalized form. This
+// list is kept in the vm_isolate in order to share the copy across isolates
+// without having to maintain copies in each isolate.
+class Symbols : public AllStatic {
+ public:
+  // List of strings that are pre created in the vm isolate.
+  static const char* kDot;
+
+  // Access methods for symbols stored in the vm isolate.
+  static RawString* Dot() { return dot_; }
+
+  // Initialize frequently used symbols in the vm isolate.
+  static void InitOnce(Isolate* isolate);
+
+  // Initialize and setup a symbol table for the isolate.
+  static void SetupSymbolTable(Isolate* isolate);
+
+  // Helper functions to create a symbol given a string or set of characters.
+  static RawString* New(const char* str);
+  template<typename T>
+  static RawString* New(const T* characters, intptr_t len);
+  static RawString* New(const String& str);
+  static RawString* New(const String& str,
+                        intptr_t begin_index,
+                        intptr_t length);
+
+
+ private:
+  static const int kInitialSymbolTableSize = 16;
+
+  // Add the string into the VM isolate symbol table.
+  static void Add(const Array& symbol_table, const String& str);
+
+  // Insert symbol into symbol table, growing it if necessary.
+  static void InsertIntoSymbolTable(const Array& symbol_table,
+                                    const String& symbol,
+                                    intptr_t index);
+
+  // Grow the symbol table.
+  static void GrowSymbolTable(const Array& symbol_table);
+
+  // Return index in symbol table if the symbol already exists or
+  // return the index into which the new symbol can be added.
+  template<typename T>
+  static intptr_t FindIndex(const Array& symbol_table,
+                            const T* characters,
+                            intptr_t len,
+                            intptr_t hash);
+  static intptr_t FindIndex(const Array& symbol_table,
+                            const String& str,
+                            intptr_t begin_index,
+                            intptr_t len,
+                            intptr_t hash);
+
+  // List of symbols that are stored in the vm isolate for easy access.
+  static RawString* dot_;  // "." string.
+
+  friend class SnapshotReader;
+
+  DISALLOW_COPY_AND_ASSIGN(Symbols);
+};
+
+}  // namespace dart
+
+#endif  // VM_SYMBOLS_H_