Refactor code for determining line position in a source file....

src/objects.cc

Index: src/objects.cc
===================================================================
--- src/objects.cc	(revision 1220)
+++ src/objects.cc	(working copy)
@@ -6781,45 +6781,53 @@
 
   Handle<String> src(String::cast(source()));
   const int src_len = src->length();
-  Handle<JSArray> array = Factory::NewJSArray(0);
-  int array_index = 0;
   Handle<String> new_line = Factory::NewStringFromAscii(CStrVector("\n"));
+
+  // Pass 1: Identify line count
+  int line_count = 0;
   int position = 0;
-  while (position < src_len) {
+  while (position != -1 && position < src_len) {
     position = Runtime::StringMatch(src, new_line, position);
     if (position != -1) {
-      SetElement(array, array_index++, Handle<Smi>(Smi::FromInt(position++)));
-    } else {
-      break;
+      position++;
     }
+    // Even if the last line misses a line end, it is counted
+    line_count++;
   }
 
-  // If the script does not end with a line ending add the final end position
-  // as just past the last line ending.
-  if (array_index == 0 ||
-      (Smi::cast(array->GetElement(array_index - 1))->value() != src_len - 1)) {
-    SetElement(array, array_index++, Handle<Smi>(Smi::FromInt(src_len)));
+  // 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));
   }
+  ASSERT(array_index == line_count);
 
-  Handle<FixedArray> fixed_array = Factory::NewFixedArray(0);
-  set_line_ends(*AddKeysFromJSArray(fixed_array, array));
-  ASSERT(line_ends()->IsFixedArray());
+  Handle<JSArray> object = Factory::NewJSArrayWithElements(array);
+  set_line_ends(*object);
+  ASSERT(line_ends()->IsJSArray());
 }
 
 
 // Convert code position into line number
 int Script::GetLineNumber(int code_pos) {
   InitLineEnds();
-  FixedArray* line_ends_array = FixedArray::cast(line_ends());
+  JSArray* line_ends_array = JSArray::cast(line_ends());
+  const int line_ends_len = (Smi::cast(line_ends_array->length()))->value();
 
   int line = -1;
-  if (code_pos <= (Smi::cast(line_ends_array->get(0)))->value()) {
+  if (line_ends_len > 0 &&
+      code_pos <= (Smi::cast(line_ends_array->GetElement(0)))->value()) {
     line = 0;
   } else {
-    const int line_ends_length = line_ends_array->length();
-    for (int i = 1; i < line_ends_length; ++i) {
-      if ((Smi::cast(line_ends_array->get(i - 1)))->value() < code_pos &&
-          code_pos <= (Smi::cast(line_ends_array->get(i)))->value()) {
+    for (int i = 1; i < line_ends_len; ++i) {
+      if ((Smi::cast(line_ends_array->GetElement(i - 1)))->value() < code_pos &&
+          code_pos <= (Smi::cast(line_ends_array->GetElement(i)))->value()) {
         line = i;
         break;
       }