Investigate proper instanceof Buffer support

[feross]

I saw a potential way to get instanceof Buffer working in a module by @dcodeIO: https://github.com/dcodeIO/node-BufferView/blob/master/BufferView.js

    // Extend DataView and clear all instance methods to be sure
    BufferView.prototype = Object.create(DataView.prototype);
    (function() { for (var i in BufferView.prototype) delete BufferView.prototype[i]; })();

[dcodeIO]

Unfortunately, the delete statement there usually does nothing, as all of the properties exist deeper in the prototype chain. It's literally just there for the case that there is one.

From MDN:

If the object inherits a property from a prototype, and doesn't have the
property itself, the property can't be deleted by referencing the object.
You can, however, delete it directly on the prototype.

function Foo(){}
Foo.prototype.bar = 42;
var foo = new Foo();

// returns true, but with no effect, 
// since bar is an inherited property
delete foo.bar;           

[feross]

I pushed an attempt to fix instanceof to this branch: https://github.com/feross/buffer/tree/fix-instanceof

[feross]

The instanceof fix I pushed seems to work, but there's a big performance hit in non-V8 engines. This is unacceptable, so I won't be merging it. I'll leave it here in case anyone has ideas for how to proceed.

[feross]

New possible solution: nodejs/node#106 (comment)

[feross]

instanceof Buffer works correctly in buffer v3.5.0 now!

This fixes the last remaining incompatibility with the node Buffer! And since Buffer in node v4.0.0 is based on Uint8Array as well, we're on exactly the same page now!

There's a 50% performance hit on the 16 byte buffer test (new Buffer(16)) in non-V8 engines (much better than my previous experiments to get this working). For the 16KB large buffer test (new Buffer(1600)), the hit is only 25%, since the difference is drowned out by the zeroing out operation. I expect this to get better over time since subclassing arrays is supported by ES6 now. 👍

[dcousens]

@feross any reason why node 4.0.0 couldn't be using the same Buffer code as this library? (hell, why not the same library).

[feross]

Well, they do a bunch of calls directly into C++. I think one reason they do that is so they can disable the behavior where new typed array memory must be zeroed-out for security reasons in the browser environment. In node, they can do without that and get perf improvements.

Maybe there are more reasons...