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buffer: only check if instance is Uint8Array
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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>
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trevnorris authored and jasnell committed Oct 8, 2015
1 parent d5a1b1a commit 651a5b5
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Showing 2 changed files with 47 additions and 12 deletions.
21 changes: 9 additions & 12 deletions src/node_buffer.cc
Original file line number Diff line number Diff line change
Expand Up @@ -163,24 +163,20 @@ void CallbackInfo::WeakCallback(Isolate* isolate, Local<Object> object) {
// Buffer methods

bool HasInstance(Local<Value> val) {
return val->IsObject() && HasInstance(val.As<Object>());
return val->IsUint8Array();
}


bool HasInstance(Local<Object> obj) {
if (!obj->IsUint8Array())
return false;
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.
return node::Buffer::Data(val.As<Object>());
CHECK(val->IsUint8Array());
Local<Uint8Array> ui = val.As<Uint8Array>();
ArrayBuffer::Contents ab_c = ui->Buffer()->GetContents();
return static_cast<char*>(ab_c.Data()) + ui->ByteOffset();
}


Expand All @@ -193,8 +189,9 @@ char* Data(Local<Object> obj) {


size_t Length(Local<Value> val) {
CHECK(val->IsObject());
return Length(val.As<Object>());
CHECK(val->IsUint8Array());
Local<Uint8Array> ui = val.As<Uint8Array>();
return ui->ByteLength();
}


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38 changes: 38 additions & 0 deletions test/parallel/test-buffer-inheritance.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
'use strict';

const common = require('../common');
const assert = require('assert');


function T(n) {
const ui8 = new Uint8Array(n);
Object.setPrototypeOf(ui8, T.prototype);
return ui8;
}
Object.setPrototypeOf(T.prototype, Buffer.prototype);
Object.setPrototypeOf(T, Buffer);

T.prototype.sum = function sum() {
let cntr = 0;
for (let i = 0; i < this.length; i++)
cntr += this[i];
return cntr;
};


const vals = [new T(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);
let cntr = 0;
for (let i = 0; i < t.length; i++)
cntr += t[i];
assert.equal(t.length * 5, cntr);

// Check this does not throw
t.toString();
});

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