An Introduction to JS-Ctypes

Andrea Giammarchi andrea.giammarchi at
Sat Sep 17 19:34:47 PDT 2011

Brendan I wrote I did it on purpose trying to predict what JS devs will do
once will bring ctypes like syntax.

I wrote the object with properties only assigned too indeed but as is for
functions expressions usually created everywhere by common developers rather
than reused where possible I bet devs will do the same if that will land in

I will file the bench at mozilla soon, thanks.

On Sat, Sep 17, 2011 at 8:43 PM, Brendan Eich <brendan at> wrote:

> On Sep 17, 2011, at 2:34 PM, Andrea Giammarchi wrote:
> > Also I have explicitly slowed down the logic creating a "classic" literal
> JS object per each loop iteration ... still, way too slow performances so
> whatever js-ctypes has been created for, something went wrong, imo
> Why are you doing that? I mean this, from your ctypes.perf.html:
>    for (var t = new Date, i = 0, length = npoints.length; i < length; i +=
> 2) {
>        window.lastPoint = {x: npoints[i], y: npoints[i + 1]};
>    }
> Don't make an object per loop iteration, instead assign to .x and .y
> separately.
> Anyway, the ctypes performance bug you're reporting does not predict binary
> data perf. Ctypes as a privileged FFI for SpiderMonkey, based on Python
> ctypes, was just brought up recently (in the life of SpiderMonkey). The JITs
> do not optimize for it as they do for typed arrays. Please file it at
> with your testcase. Thanks,
> /be
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