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Re: [squeak-dev] Questionable comment

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Eliot Miranda-2

Re: [squeak-dev] Questionable comment

Hi Chris,

On Wed, Aug 19, 2015 at 1:06 PM, Chris Cunningham <[hidden email]> wrote:

well, not questionable - bad.

(in ByteArray)

long64At: index
"Answer a 64-bit integer in Smalltalk order (little-endian)."
| n1 n2 |
n1 := self unsignedLongAt: index bigEndian: true.
n2 := self unsignedLongAt: index+4 bigEndian: true.

These are obviously bigEndian now, nto litte-endian.

Does this mean Smalltalk order (or now Squeak order) has changed?

This is not for general purpose. The method is part of VMMaker. Let's take it to vm-dev.

It's a simple mistake. If you look at long64At:put: you'll see the comment is correct:

long64At: index put: val

"I store 64-bit integers in Smalltalk (little-endian) order."

self unsignedLongAt: index put: (val bitAnd: 16rFFFFFFFF) bigEndian: false.

self unsignedLongAt: index+4 put: (val bitShift: -32) bigEndian: false.

^val

Thanks for finding this!

-cbc

_,,,^..^,,,_

best, Eliot

cbc

Fwd: [squeak-dev] Questionable comment

sorry, wrong list. Will do it right in future. Mostly.

-cbc

---------- Forwarded message ----------
From: Chris Cunningham <[hidden email]>
Date: Fri, Aug 21, 2015 at 4:16 PM
Subject: Re: [squeak-dev] Questionable comment
To: The general-purpose Squeak developers list <[hidden email]>

Hi Eliot,

On Thu, Aug 20, 2015 at 9:25 PM, Eliot Miranda <[hidden email]> wrote:

Hi Chris,

On Wed, Aug 19, 2015 at 1:06 PM, Chris Cunningham <[hidden email]> wrote:
well, not questionable - bad.

(in ByteArray)

long64At: index
"Answer a 64-bit integer in Smalltalk order (little-endian)."
| n1 n2 |
n1 := self unsignedLongAt: index bigEndian: true.
n2 := self unsignedLongAt: index+4 bigEndian: true.

These are obviously bigEndian now, nto litte-endian.

Does this mean Smalltalk order (or now Squeak order) has changed?

This is not for general purpose. The method is part of VMMaker. Let's take it to vm-dev.
It's a simple mistake. If you look at long64At:put: you'll see the comment is correct:

Yes. I had loaded the VMMaker to look at the ARM jit code (I'm working on an ARM simulator - fun project), and then forgot I had it loaded. then later, I needed to pull 64-bit integers out of a structure (while writing a KAFKA interface) and stumbled on this. I think a generalized 64 bit put/access would be useful, and maybe even a general 128 bit too (although I have no need for it at this time).

long64At: index put: val
"I store 64-bit integers in Smalltalk (little-endian) order."
self unsignedLongAt: index put: (val bitAnd: 16rFFFFFFFF) bigEndian: false.
self unsignedLongAt: index+4 put: (val bitShift: -32) bigEndian: false.
^val

I'm now confused. Not only is the comment wrong, but it looks like the code is wrong. The get (#long64At:) is actually getting the 64-bit integer in big-endian order (as witnessed by the two sub-calls, too), while the put it truly doing it in little-endian format.

Or am I missing something?

-cbc

Thanks for finding this!

-cbc

--
_,,,^..^,,,_
best, Eliot

timrowledge

Re: Fwd: [squeak-dev] Questionable comment

On 21-08-2015, at 4:58 PM, Chris Cunningham <[hidden email]> wrote:
> Yes. I had loaded the VMMaker to look at the ARM jit code (I'm working on an ARM simulator - fun project),

Do tell...

tim
--
tim Rowledge; [hidden email]; http://www.rowledge.org/tim
Useful random insult:- An early example of the Peter Principle.