LiveEdit: calculate a real script difference

src/handles.cc

 // Copyright 2009 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
@@ skipping 439 matching lines @@
   if (!script->line_ends()->IsUndefined()) return;
 
   if (!script->source()->IsString()) {
     ASSERT(script->source()->IsUndefined());
     script->set_line_ends(*(Factory::NewFixedArray(0)));
     ASSERT(script->line_ends()->IsFixedArray());
     return;
   }
 
   Handle<String> src(String::cast(script->source()));
+
+  Handle<FixedArray> array = CalculateLineEnds(src, true);
+
+  script->set_line_ends(*array);
+  ASSERT(script->line_ends()->IsFixedArray());
+}
+
+
+Handle<FixedArray> CalculateLineEnds(Handle<String> src,
+                                     bool with_imaginary_last_new_line) {
   const int src_len = src->length();
   Handle<String> new_line = Factory::NewStringFromAscii(CStrVector("\n"));
 
   // Pass 1: Identify line count.
   int line_count = 0;
   int position = 0;
   while (position != -1 && position < src_len) {
     position = Runtime::StringMatch(src, new_line, position);
     if (position != -1) {
       position++;
     }
-    // Even if the last line misses a line end, it is counted.
-    line_count++;
+    if (position != -1) {
+      line_count++;
+    } else if (with_imaginary_last_new_line) {
+      // Even if the last line misses a line end, it is counted.
+      line_count++;
+    }
   }
 
   // Pass 2: Fill in line ends positions
   Handle<FixedArray> array = Factory::NewFixedArray(line_count);
   int array_index = 0;
   position = 0;
   while (position != -1 && position < src_len) {
     position = Runtime::StringMatch(src, new_line, position);
-    // If the script does not end with a line ending add the final end
-    // position as just past the last line ending.
-    array->set(array_index++,
-               Smi::FromInt(position != -1 ? position++ : src_len));
+    if (position != -1) {
+      array->set(array_index++, Smi::FromInt(position++));
+    } else if (with_imaginary_last_new_line) {
+      // If the script does not end with a line ending add the final end
+      // position as just past the last line ending.
+      array->set(array_index++, Smi::FromInt(src_len));
+    }
   }
   ASSERT(array_index == line_count);
 
-  script->set_line_ends(*array);
-  ASSERT(script->line_ends()->IsFixedArray());
+  return array;
 }
 
 
 // Convert code position into line number.
 int GetScriptLineNumber(Handle<Script> script, int code_pos) {
   InitScriptLineEnds(script);
   AssertNoAllocation no_allocation;
   FixedArray* line_ends_array = FixedArray::cast(script->line_ends());
   const int line_ends_len = line_ends_array->length();
 
@@ skipping 280 matching lines @@
 
 OptimizedObjectForAddingMultipleProperties::
 ~OptimizedObjectForAddingMultipleProperties() {
   // Reoptimize the object to allow fast property access.
   if (has_been_transformed_) {
     TransformToFastProperties(object_, unused_property_fields_);
   }
 }
 
 } }  // namespace v8::internal