buffer: improve creation performance.

Improves performance of allocating unsafe buffers, creating buffers from
an existing ArrayBuffer and creating .slice(...) from existing Buffer by
avoiding deoptimizing change of prototype after Uint8Array allocation
in favor of ES6 native subclassing.

This is done through an internal ES6 class that extends Uint8Array and
is used for allocations, but the regular Buffer function is exposed, so
calling Buffer(...) with or without `new` continues to work as usual
and prototype chains are also preserved.

Performance wins for .slice are +120% (2.2x), and, consequently, for
unsafe allocations up to +95% (1.9x) for small buffers, and for safe
allocations (zero-filled) up to +30% (1.3x).

PR-URL: https://github.com/nodejs/node/pull/6893
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>

1 files changed, 0 insertions, 28 deletions

diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index b8accf517c..388decac4a 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -427,33 +427,6 @@ void CreateFromString(const FunctionCallbackInfo<Value>& args) {
 }
 
 
-void CreateFromArrayBuffer(const FunctionCallbackInfo<Value>& args) {
-  Environment* env = Environment::GetCurrent(args);
-  if (!args[0]->IsArrayBuffer())
-    return env->ThrowTypeError("argument is not an ArrayBuffer");
-  Local<ArrayBuffer> ab = args[0].As<ArrayBuffer>();
-
-  size_t ab_length = ab->ByteLength();
-  size_t offset;
-  size_t max_length;
-
-  CHECK_NOT_OOB(ParseArrayIndex(args[1], 0, &offset));
-  CHECK_NOT_OOB(ParseArrayIndex(args[2], ab_length - offset, &max_length));
-
-  if (offset >= ab_length)
-    return env->ThrowRangeError("'offset' is out of bounds");
-  if (max_length > ab_length - offset)
-    return env->ThrowRangeError("'length' is out of bounds");
-
-  Local<Uint8Array> ui = Uint8Array::New(ab, offset, max_length);
-  Maybe<bool> mb =
-      ui->SetPrototype(env->context(), env->buffer_prototype_object());
-  if (!mb.FromMaybe(false))
-    return env->ThrowError("Unable to set Object prototype");
-  args.GetReturnValue().Set(ui);
-}
-
-
 template <encoding encoding>
 void StringSlice(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
@@ -1244,7 +1217,6 @@ void Initialize(Local<Object> target,
 
   env->SetMethod(target, "setupBufferJS", SetupBufferJS);
   env->SetMethod(target, "createFromString", CreateFromString);
-  env->SetMethod(target, "createFromArrayBuffer", CreateFromArrayBuffer);
 
   env->SetMethod(target, "byteLengthUtf8", ByteLengthUtf8);
   env->SetMethod(target, "compare", Compare);