Backport mozilla#308 onto 0.6.1

Author: benthemonkey

lib/util.js

@@ -66,6 +66,43 @@ function urlGenerate(aParsedUrl) {
 }
 exports.urlGenerate = urlGenerate;
 
+var MAX_CACHED_INPUTS = 32;
+
+/**
+ * Takes some function `f(input) -> result` and returns a memoized version of
+ * `f`.
+ *
+ * We keep at most `MAX_CACHED_INPUTS` memoized results of `f` alive. The
+ * memoization is a dumb-simple, linear least-recently-used cache.
+ */
+function lruMemoize(f) {
+  var cache = [];
+
+  return function(input) {
+    for (var i = 0; i < cache.length; i++) {
+      if (cache[i].input === input) {
+        var temp = cache[0];
+        cache[0] = cache[i];
+        cache[i] = temp;
+        return cache[0].result;
+      }
+    }
+
+    var result = f(input);
+
+    cache.unshift({
+      input,
+      result,
+    });
+
+    if (cache.length > MAX_CACHED_INPUTS) {
+      cache.pop();
+    }
+
+    return result;
+  };
+}
+
 /**
  * Normalizes a path, or the path portion of a URL:
  *
@@ -77,7 +114,7 @@ exports.urlGenerate = urlGenerate;
  *
  * @param aPath The path or url to normalize.
  */
-function normalize(aPath) {
+var normalize = lruMemoize(function normalize(aPath) {
   var path = aPath;
   var url = urlParse(aPath);
   if (url) {
@@ -87,8 +124,25 @@ function normalize(aPath) {
     path = url.path;
   }
   var isAbsolute = exports.isAbsolute(path);
+  // Split the path into parts between `/` characters. This is much faster than
+  // using `.split(/\/+/g)`.
+  var parts = [];
+  var start = 0;
+  var i = 0;
+  while (true) {
+    start = i;
+    i = path.indexOf("/", start);
+    if (i === -1) {
+      parts.push(path.slice(start));
+      break;
+    } else {
+      parts.push(path.slice(start, i));
+      while (i < path.length && path[i] === "/") {
+        i++;
+      }
+    }
+  }
 
-  var parts = path.split(/\/+/);
   for (var part, up = 0, i = parts.length - 1; i >= 0; i--) {
     part = parts[i];
     if (part === '.') {
@@ -119,7 +173,7 @@ function normalize(aPath) {
     return urlGenerate(url);
   }
   return path;
-}
+});
 exports.normalize = normalize;
 
 /**