buffer: only check if instance is Uint8Array

Native Buffer method calls do not require anything from the prototype. So it is unnecessary to check if the Object's prototype is equal to Buffer.prototype. This fixes an issue that prevents Buffer from being inherited the ES5 way. Now the following will work: function A(n) { const b = new Buffer(n); Object.setPrototypeOf(b, A.prototype); return b; } Object.setPrototypeOf(A.prototype, Buffer.prototype); Object.setPrototypeOf(A, Buffer); console.log(new A(4)); Fix: #2882 PR-URL: #3080 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

Author: trevnorris

src/node_buffer.cc

@@ -163,24 +163,20 @@ void CallbackInfo::WeakCallback(Isolate* isolate, Local<Object> object) {
 // Buffer methods
 
 boolHasInstance(Local<Value> val) {
-return val->IsObject() && HasInstance(val.As<Object>());
+return val->IsUint8Array();
 }
 
 
 boolHasInstance(Local<Object> obj) {
-if (!obj->IsUint8Array())
-returnfalse;
- Local<Uint8Array> array = obj.As<Uint8Array>();
- Environment* env = Environment::GetCurrent(array->GetIsolate());
-return array->GetPrototype()->StrictEquals(env->buffer_prototype_object());
+return obj->IsUint8Array();
 }
 
 
 char* Data(Local<Value> val) {
-CHECK(val->IsObject());
-// Use a fully qualified name here to work around a bug in gcc 4.2.
-// It mistakes an unadorned call to Data() for the v8::String::Data type.
-returnnode::Buffer::Data(val.As<Object>());
+CHECK(val->IsUint8Array());
+Local<Uint8Array> ui = val.As<Uint8Array>();
+ArrayBuffer::Contents ab_c = ui->Buffer()->GetContents();
+returnstatic_cast<char*>(ab_c.Data()) + ui->ByteOffset();
 }
 
 
@@ -193,8 +189,9 @@ char* Data(Local<Object> obj) {
 
 
 size_tLength(Local<Value> val) {
-CHECK(val->IsObject());
-returnLength(val.As<Object>());
+CHECK(val->IsUint8Array());
+ Local<Uint8Array> ui = val.As<Uint8Array>();
+return ui->ByteLength();
 }
 
 

test/parallel/test-buffer-inheritance.js

@@ -0,0 +1,38 @@
+'use strict';
+
+constcommon=require('../common');
+constassert=require('assert');
+
+
+functionT(n){
+constui8=newUint8Array(n);
+Object.setPrototypeOf(ui8,T.prototype);
+returnui8;
+}
+Object.setPrototypeOf(T.prototype,Buffer.prototype);
+Object.setPrototypeOf(T,Buffer);
+
+T.prototype.sum=functionsum(){
+letcntr=0;
+for(leti=0;i<this.length;i++)
+cntr+=this[i];
+returncntr;
+};
+
+
+constvals=[newT(4),T(4)];
+
+vals.forEach(function(t){
+assert.equal(t.constructor,T);
+assert.equal(t.__proto__,T.prototype);
+assert.equal(t.__proto__.__proto__,Buffer.prototype);
+
+t.fill(5);
+letcntr=0;
+for(leti=0;i<t.length;i++)
+cntr+=t[i];
+assert.equal(t.length*5,cntr);
+
+// Check this does not throw
+t.toString();
+});