Introducing MemoryMappedExternalResource for creating an external...

src/v8utils.h

Index: src/v8utils.h
===================================================================
--- src/v8utils.h	(revision 6353)
+++ src/v8utils.h	(working copy)
@@ -316,6 +316,39 @@
   }
 }
 
+
+// A resource for using mmapped files to back external strings that are read
+// from files.
+class MemoryMappedExternalResource: public
+    v8::String::ExternalAsciiStringResource {
+ public:
+  explicit MemoryMappedExternalResource(const char* filename);
+  MemoryMappedExternalResource(const char* filename,
+                               bool remove_file_on_cleanup);
+  virtual ~MemoryMappedExternalResource();
+
+  virtual const char* data() const { return data_; }
+  virtual size_t length() const { return length_; }
+
+  bool exists() const { return file_ != NULL; }
+  bool is_empty() const { return length_ == 0; }
+
+  bool EnsureIsAscii(bool abort_if_failed) const;
+  bool EnsureIsAscii() const { return EnsureIsAscii(true); }
+  bool IsAscii() const { return EnsureIsAscii(false); }
+
+ private:
+  void Init(const char* filename);
+
+  char* filename_;
+  OS::MemoryMappedFile* file_;
+
+  const char* data_;
+  size_t length_;
+  bool remove_file_on_cleanup_;
+};
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_V8UTILS_H_