decodeURI and decodeURIComponent speedup

src/uri.js

Index: src/uri.js
===================================================================
--- src/uri.js	(revision 6653)
+++ src/uri.js	(working copy)
@@ -90,11 +90,13 @@
 }
 
 
-function URIHexCharsToCharCode(ch1, ch2) {
-  if (HexValueOf(ch1) == -1 || HexValueOf(ch2) == -1) {
+function URIHexCharsToCharCode(code1, code2) {
+  var n = HexValueOf(code1);
+  var m = HexValueOf(code2);

[Vyacheslav Egorov (Chromium), 2011/02/07 10:32:35]

Please give more meaningful names to this variables.

For example: high and low.

+  if (n == -1 || m == -1) {
     throw new $URIError("URI malformed");
   }
-  return HexStrToCharCode(ch1 + ch2);
+  return n * 16 + m;

[Vyacheslav Egorov (Chromium), 2011/02/07 10:32:35]

Have you considered using

(high << 4) | low 

instead of

n * 16 + m?

It might be slightly faster.

 }
 
 
@@ -196,7 +198,7 @@
     var ch = uri.charAt(k);
     if (ch == '%') {
       if (k + 2 >= uriLength) throw new $URIError("URI malformed");
-      var cc = URIHexCharsToCharCode(uri.charAt(++k), uri.charAt(++k));
+      var cc = URIHexCharsToCharCode(uri.charCodeAt(++k), uri.charCodeAt(++k));
       if (cc >> 7) {
         var n = 0;
         while (((cc << ++n) & 0x80) != 0) ;
@@ -206,7 +208,7 @@
         if (k + 3 * (n - 1) >= uriLength) throw new $URIError("URI malformed");
         for (var i = 1; i < n; i++) {
           if (uri.charAt(++k) != '%') throw new $URIError("URI malformed");
-          octets[i] = URIHexCharsToCharCode(uri.charAt(++k), uri.charAt(++k));
+          octets[i] = URIHexCharsToCharCode(uri.charCodeAt(++k), uri.charCodeAt(++k));
         }
         index = URIDecodeOctets(octets, result, index);
       } else {
@@ -325,9 +327,7 @@
 }
 
 
-function HexValueOf(c) {
-  var code = c.charCodeAt(0);
-
+function HexValueOf(code) {
   // 0-9
   if (code >= 48 && code <= 57) return code - 48;
   // A-F
@@ -356,18 +356,6 @@
 }
 
 
-// Converts hex string to char code. Not efficient.
-function HexStrToCharCode(s) {
-  var m = 0;
-  var r = 0;
-  for (var i = s.length - 1; i >= 0; --i) {
-    r = r + (HexValueOf(s.charAt(i)) << m);
-    m = m + 4;
-  }
-  return r;
-}
-
-
 // Returns true if all digits in string s are valid hex numbers
 function IsValidHex(s) {
   for (var i = 0; i < s.length; ++i) {