From 9beb729d9ff106359a26d1fb41f4e349a013d711 Mon Sep 17 00:00:00 2001
From: Anthony Lieuallen <alieuall@google.com>
Date: Sat, 3 Apr 2010 02:21:16 +0800
Subject: [PATCH] Fixes #1089

* Define a general purpose memoize decorator, use it for GM_isGreasemonkeyable() and convert2RegExp().
---
 content/convert2RegExp.js |  1 +
 content/utils.js          | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/content/convert2RegExp.js b/content/convert2RegExp.js
index 4fae6d263..13bf0939a 100644
--- a/content/convert2RegExp.js
+++ b/content/convert2RegExp.js
@@ -50,3 +50,4 @@ function convert2RegExp( pattern ) {
   }
   return new RegExp(res + "$", "i");
 }
+convert2RegExp = GM_memoize(convert2RegExp);
diff --git a/content/utils.js b/content/utils.js
index 0e8c2c557..acbeda744 100644
--- a/content/utils.js
+++ b/content/utils.js
@@ -326,6 +326,7 @@ function GM_isGreasemonkeyable(url) {
 
   return false;
 }
+GM_isGreasemonkeyable = GM_memoize(GM_isGreasemonkeyable);
 
 function GM_getEnabled() {
   return GM_prefRoot.getValue("enabled", true);
@@ -334,3 +335,30 @@ function GM_getEnabled() {
 function GM_setEnabled(enabled) {
   GM_prefRoot.setValue("enabled", enabled);
 }
+
+// Decorate a function with a memoization wrapper, with a limited-size cache
+// to reduce peak memory utilization.  Simple usage:
+//
+// function foo(arg1, arg2) { /* complex operation */ }
+// foo = GM_memoize(foo);
+//
+// The memoized function may have any number of arguments, but they must be
+// primitives (able to be used as object keys).
+function GM_memoize(func, limit) {
+  limit = limit || 1000;
+  var cache = {};
+  var keylist = [];
+
+  return function(a) {
+    var args = Array.prototype.slice.call(arguments);
+    if (args in cache) return cache[args];
+
+    var result = func.apply(null, args);
+
+    cache[args] = result;
+    keylist.push(args);
+    while (keylist.length > limit) keylist.shift();
+
+    return result;
+  }
+}