From c7c90acf3fb5863010c608bda3f9dc2106a3d3dd Mon Sep 17 00:00:00 2001
From: Dan Abramov <dan.abramov@gmail.com>
Date: Wed, 14 Jan 2015 19:08:33 +0300
Subject: [PATCH] Store ranges instead of line indexes for performance

---
 lib/6to5/generation/whitespace.js | 16 +++------
 lib/6to5/util.js                  | 60 +++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 12 deletions(-)

diff --git a/lib/6to5/generation/whitespace.js b/lib/6to5/generation/whitespace.js
index c7dda860da..6d16536f26 100644
--- a/lib/6to5/generation/whitespace.js
+++ b/lib/6to5/generation/whitespace.js
@@ -1,6 +1,7 @@
 module.exports = Whitespace;
 
-var _ = require("lodash");
+var _    = require("lodash");
+var util = require("../util");
 
 function Whitespace(tokens, comments) {
   this.tokens = _.sortBy(tokens.concat(comments), "start");
@@ -61,14 +62,5 @@ Whitespace.prototype.getNewlinesBetween = function (startToken, endToken) {
   var start = startToken ? startToken.loc.end.line : 1;
   var end   = endToken.loc.start.line;
 
-  var lines = 0;
-
-  for (var line = start; line < end; line++) {
-    if (!_.contains(this.used, line)) {
-      this.used.push(line);
-      lines++;
-    }
-  }
-
-  return lines;
-};
+  return util.mergeIntegerRange(this.used, start, end);
+};
\ No newline at end of file
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index 66af587e4f..23d9ec9227 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -204,6 +204,66 @@ exports.repeat = function (width, cha) {
   return result;
 };
 
+exports.mergeIntegerRange = function (ranges, start, end) {
+  var pointsAdded = 0;
+  var insertIndex;
+  var rangeIndex;
+  var point;
+  var range;
+  var matchingRange;
+  var rangeImmediatelyToLeft;
+  var rangeImmediatelyToRight;
+
+  for (point = start; point < end; point++) {
+    matchingRange = null;
+    rangeImmediatelyToLeft = null;
+    rangeImmediatelyToRight = null;
+    insertIndex = ranges.length;
+
+    for (rangeIndex = 0; rangeIndex < ranges.length; rangeIndex++) {
+      range = ranges[rangeIndex];
+
+      if (point >= range.start && point <= range.end) {
+        matchingRange = range;
+        break;
+      }
+
+      if (point < range.start) {
+        insertIndex = rangeIndex;
+      }
+
+      if (point === range.end + 1) {
+        rangeImmediatelyToLeft = range;
+      }
+
+      if (point === range.start - 1) {
+        rangeImmediatelyToRight = range;
+      }
+    }
+
+    if (matchingRange)
+      continue;
+
+    pointsAdded++;
+
+    if (rangeImmediatelyToLeft && rangeImmediatelyToRight) {
+      ranges.splice(ranges.indexOf(rangeImmediatelyToRight), 1);
+      rangeImmediatelyToLeft.end = rangeImmediatelyToRight.end;
+    } else if (rangeImmediatelyToLeft) {
+      rangeImmediatelyToLeft.end = point;
+    } else if (rangeImmediatelyToRight) {
+      rangeImmediatelyToRight.start = point;
+    } else {
+      ranges.splice(insertIndex, 0, {
+        start: point,
+        end: point
+      });
+    }
+  }
+
+  return pointsAdded;
+};
+
 exports.normaliseAst = function (ast, comments, tokens) {
   if (ast && ast.type === "Program") {
     return t.file(ast, comments || [], tokens || []);