buffer: optimize Buffer.byteLength

Buffer.byteLength is important for speed because it is called whenever a
new Buffer is created from a string.

This commit optimizes Buffer.byteLength execution by:
- moving base64 length calculation into JS-land, which is now much
  faster
- remove redundant code and streamline the UTF8 length calculation

It also adds a benchmark and better tests.

PR-URL: https://github.com/nodejs/io.js/pull/1713
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

1 files changed, 5 insertions, 11 deletions

diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index bd022792125..fca08599e50 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -541,17 +541,11 @@ void WriteDoubleBE(const FunctionCallbackInfo<Value>& args) {
 }
 
 
-void ByteLength(const FunctionCallbackInfo<Value> &args) {
-  Environment* env = Environment::GetCurrent(args);
-
-  if (!args[0]->IsString())
-    return env->ThrowTypeError("Argument must be a string");
-
-  Local<String> s = args[0]->ToString(env->isolate());
-  enum encoding e = ParseEncoding(env->isolate(), args[1], UTF8);
+void ByteLengthUtf8(const FunctionCallbackInfo<Value> &args) {
+  CHECK(args[0]->IsString());
 
-  uint32_t size = StringBytes::Size(env->isolate(), s, e);
-  args.GetReturnValue().Set(size);
+  // Fast case: avoid StringBytes on UTF8 string. Jump to v8.
+  args.GetReturnValue().Set(args[0].As<String>()->Utf8Length());
 }
 
 
@@ -745,7 +739,7 @@ void Initialize(Handle<Object> target,
 
   env->SetMethod(target, "setupBufferJS", SetupBufferJS);
 
-  env->SetMethod(target, "byteLength", ByteLength);
+  env->SetMethod(target, "byteLengthUtf8", ByteLengthUtf8);
   env->SetMethod(target, "compare", Compare);
   env->SetMethod(target, "fill", Fill);
   env->SetMethod(target, "indexOfBuffer", IndexOfBuffer);