Add optimized _OneByteString.toLowerCase.

sdk/lib/io/http_headers.dart

Index: sdk/lib/io/http_headers.dart
diff --git a/sdk/lib/io/http_headers.dart b/sdk/lib/io/http_headers.dart
index 5dd5c55fd064e50f44e9c3e7d43047a2c3dc0518..b695f05b1fb73315e46b0408b48e4dc60ceefbb9 100644
--- a/sdk/lib/io/http_headers.dart
+++ b/sdk/lib/io/http_headers.dart
@@ -28,10 +28,10 @@ class _HttpHeaders implements HttpHeaders {
     }
   }
 
-  List<String> operator[](String name) => _headers[name.toLowerCase()];
+  List<String> operator[](String name) => _headers[_toLowerCase(name)];
 
   String value(String name) {
-    name = name.toLowerCase();
+    name = _toLowerCase(name);
     List<String> values = _headers[name];
     if (values == null) return null;
     if (values.length > 1) {
@@ -42,7 +42,7 @@ class _HttpHeaders implements HttpHeaders {
 
   void add(String name, value) {
     _checkMutable();
-    _addAll(name.toLowerCase(), value);
+    _addAll(_toLowerCase(name), value);
   }
 
   void _addAll(String name, value) {
@@ -55,14 +55,14 @@ class _HttpHeaders implements HttpHeaders {
 
   void set(String name, Object value) {
     _checkMutable();
-    name = name.toLowerCase();
+    name = _toLowerCase(name);
     _headers.remove(name);
     _addAll(name, value);
   }
 
   void remove(String name, Object value) {
     _checkMutable();
-    name = name.toLowerCase();
+    name = _toLowerCase(name);
     List<String> values = _headers[name];
     if (values != null) {
       int index = values.indexOf(value);
@@ -75,7 +75,7 @@ class _HttpHeaders implements HttpHeaders {
 
   void removeAll(String name) {
     _checkMutable();
-    name = name.toLowerCase();
+    name = _toLowerCase(name);
     _headers.remove(name);
   }
 
@@ -329,7 +329,7 @@ class _HttpHeaders implements HttpHeaders {
         break;
 
       case HttpHeaders.CONNECTION:
-        var lowerCaseValue = value.toLowerCase();
+        var lowerCaseValue = _toLowerCase(value);
         if (lowerCaseValue == 'close') {
           _persistentConnection = false;
         } else if (lowerCaseValue == 'keep-alive') {
@@ -361,7 +361,7 @@ class _HttpHeaders implements HttpHeaders {
   }
 
   void _set(String name, String value) {
-    assert(name == name.toLowerCase());
+    assert(name == _toLowerCase(name));
     List<String> values = new List<String>();
     _headers[name] = values;
     values.add(value);
@@ -518,6 +518,26 @@ class _HttpHeaders implements HttpHeaders {
     }
     return cookies;
   }
+
+  static String _toLowerCase(String str) {
+    int toLowerCase(int byte) {
+      final int aCode = "A".codeUnitAt(0);

[kevmoo, 2014/03/24 17:50:16]

Is this only run the first time the method is called?

Would it be better to be class-level or top-level final?

[Anders Johnsen, 2014/03/24 19:02:59]

When looking at the SSA of the VM, it's heavily inlined. But I'll consider
creating an all-static class with these constants.

[kevmoo, 2014/03/24 19:04:05]

If they are only used in http_headers, just leave 'em in this class.

[Anders Johnsen, 2014/03/24 19:05:04]

Yeah, but so far there is two places it's used (parser as well), and I just
tried to scan through, and found several other places. I should fix.

[Søren Gjesse, 2014/03/25 07:54:25]

Yes, as you have noticed we have the _CharCodes constants in http_parser.dart.
We should consolidate all of these.

+      final int zCode = "Z".codeUnitAt(0);
+      final int delta = "a".codeUnitAt(0) - aCode;
+      return (aCode <= byte && byte <= zCode) ? byte + delta : byte;
+    }
+
+    final length = str.length;
+    var result = new List(length);
+    for (int i = 0; i < length; i++) {
+      int codeUnit = str.codeUnitAt(i);
+      if (codeUnit > 127) {
+        throw new HttpException("HTTP header must be in ASCII encoding");
+      }
+      result[i] = toLowerCase(codeUnit);

[Søren Gjesse, 2014/03/25 07:54:25]

I don't see the need to a function call here (even though it most likely is
inlined).

[Anders Johnsen, 2014/03/25 13:33:40]

Pulled out and shared across all of IO.

+    }
+    return new String.fromCharCodes(result);
+  }
 }