Add central bridge for liveedit support

src/liveedit.h

+// Copyright 2010 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_LIVEEDIT_H_
+#define V8_LIVEEDIT_H_
+
+
+
+// Live Edit feature implementation.
+// User should be able to change script on already running VM. This feature
+// matches hot swap features in other frameworks.
+//
+// The basic use-case is when user spots some mistake in function body
+// from debugger and wishes to change the algorithm without restart.
+//
+// A single change always has a form of a simple replacement (in pseudo-code):
+//   script.source[positions, positions+length] = new_string;
+// Implementation first determines, which function's body includes this
+// change area. Then both old and new versions of script are fully compiled
+// in order to analyze, whether the function changed its outer scope
+// expectations (or number of parameters). If it didn't, function's code is
+// patched with a newly compiled code. If it did change, enclosing function
+// gets patched. All inner functions are left untouched, whatever happened
+// to them in a new script version. However, new version of code will
+// instantiate newly compiled functions.
+
+
+#include "compiler.h"
+
+namespace v8 {
+namespace internal {
+
+// This class collects some specific information on structure of functions
+// in a particular script. It gets called from compiler all the time, but
+// actually records any data only when liveedit operation is in process;
+// in any other time this class is very cheap.
+//
+// The primary interest of the Tracker is to record function scope structures
+// in order to analyze whether function code maybe safely patched (with new
+// code successfully reading existing data from function scopes). The Tracker
+// also collects compiled function codes.
+class LiveEditFunctionTracker {
+ public:
+  LiveEditFunctionTracker(FunctionLiteral* fun);
+  ~LiveEditFunctionTracker();
+  void RecordFunctionCode(Handle<Code> code);
+  void RecordFunctionScope(Scope* scope);
+
+  static bool IsActive();
+};
+
+} }  // namespace v8::internal
+
+#endif /* V*_LIVEEDIT_H_ */