From 63f333999c495d3959a4e9d78c01338da1e16671 Mon Sep 17 00:00:00 2001
From: "sandholm@chromium.org"
 <sandholm@chromium.org@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Thu, 18 Nov 2010 08:45:17 +0000
Subject: [PATCH] Leverage Lasse's StringSearch object to speed up calculations
 of script line ends. Review URL: http://codereview.chromium.org/5100002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5846 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/handles.cc | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/handles.cc b/src/handles.cc
index 1364951..38d5adc 100644
--- a/src/handles.cc
+++ b/src/handles.cc
@@ -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 @@ void InitScriptLineEnds(Handle<Script> script) {
 }
 
 
-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 @@ Handle<FixedArray> CalculateLineEnds(Handle<String> src,
   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));
@@ -548,6 +548,20 @@ Handle<FixedArray> CalculateLineEnds(Handle<String> src,
   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) {
-- 
2.7.4