Leverage Lasse's StringSearch object to speed up calculations of script ...

src/handles.cc

Index: src/handles.cc
===================================================================
--- src/handles.cc	(revision 5845)
+++ src/handles.cc	(working copy)
@@ -36,6 +36,7 @@
 #include "execution.h"
 #include "global-handles.h"
 #include "natives.h"
+#include "string-search.h"
 #include "runtime.h"
 #include "stub-cache.h"
 
@@ -508,22 +509,21 @@
 }
 
 
-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"));
+template <typename SourceChar>
+static Handle<FixedArray> CalculateLineEnds(Vector<const SourceChar> src,
+                                            bool with_last_line) {
+  const int src_len = src.length();
+  StringSearch<char, SourceChar> search(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);
+    position = search.Search(src, position);
     if (position != -1) {
       position++;
-    }
-    if (position != -1) {
       line_count++;
-    } else if (with_imaginary_last_new_line) {
+    } else if (with_last_line) {
       // Even if the last line misses a line end, it is counted.
       line_count++;
     }
@@ -534,10 +534,10 @@
   int array_index = 0;
   position = 0;
   while (position != -1 && position < src_len) {
-    position = Runtime::StringMatch(src, new_line, position);
+    position = search.Search(src, position);
     if (position != -1) {
       array->set(array_index++, Smi::FromInt(position++));
-    } else if (with_imaginary_last_new_line) {
+    } else if (with_last_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));
@@ -548,7 +548,21 @@
   return array;
 }
 
+Handle<FixedArray> CalculateLineEnds(Handle<String> src,
+                                     bool with_last_line) {
+  if (!src->IsFlat()) FlattenString(src);
+  AssertNoAllocation no_heap_allocation;  // ensure vectors stay valid
+  // Extract flattened substring of cons string before determining asciiness.
+  String* seq_src = *src;
+  if (seq_src->IsConsString()) seq_src = ConsString::cast(seq_src)->first();
+  // Dispatch on type of strings.
+  if (seq_src->IsAsciiRepresentation()) {
+    return CalculateLineEnds(seq_src->ToAsciiVector(), with_last_line);
+  }
+  return CalculateLineEnds(seq_src->ToUC16Vector(), with_last_line);
+}
 
+
 // Convert code position into line number.
 int GetScriptLineNumber(Handle<Script> script, int code_pos) {
   InitScriptLineEnds(script);