Flatten/Unflatten boolean cluster

[Eugen Graf]

Hello, I would parse a boolean cluster but get some problems(Look attachment). Should I realy make a workaround with Cluster->Array or are there another ways to solve it?

I want also interpret a boolean element as a boolean(=1 Bit) not as a Byte.

Thank you, Eugen

[gb119]

QUOTE(Eugen Graf @ May 30 2007, 07:35 PM)

Hello, I would parse a boolean cluster but get some problems(Look attachment). Should I realy make a workaround with Cluster->Array or are there another ways to solve it?

I want also interpret a boolean element as a boolean(=1 Bit) not as a Byte.

Thank you, Eugen

Flatten to string essentially gives you a straight memory dump of the data with (for versions < 8.0 by default and optionally for >=8.0) a separate ouptut that can describe the structure of the data. Sometime around LabVIEW 4.x/5.x the in-memory storage of a boolean was changed from one bit to one byte, so when you flatten a cluster of 8 booleans you do indeed get 8 bytes back. I'd hazard a guess that the change was done because RAM wasn't quite so critical and memory alignment issues were more so, so it made sense to reserve a whole byte even though only the lsb is used.

I'm not entirely sure I understand what you are trying to do, but if you have 8.2.x or perhaps 8.x, then in the Utility folder of your vi.lib there will be a VariantDataType.llb which has subvis for interpreting variant data-types without getting your hands dirty looking at the flattened data.

[Eugen Graf]

QUOTE(Gavin Burnell @ May 30 2007, 10:22 PM)

I'm not entirely sure I understand what you are trying to do, but if you have 8.2.x or perhaps 8.x, then in the Utility folder of your vi.lib there will be a VariantDataType.llb which has subvis for interpreting variant data-types without getting your hands dirty looking at the flattened data.

I have to parse any data. The transmition-protocol is ready defined.

http://forums.lavag.org/index.php?act=attach&type=post&id=5970

So I made me typedefs for every package type. This one is the status package.

http://forums.lavag.org/index.php?act=attach&type=post&id=5971

My unflatten.vi should parse this package.

http://forums.lavag.org/index.php?act=attach&type=post&id=5972

Thank for your answer. I don't really know if I can use here Variant.llb. And I have LV 8.0.

Eugen

[gb119]

QUOTE(Eugen Graf @ May 30 2007, 09:38 PM)

I have to parse any data. The transmition-protocol is ready defined.

[...]

QUOTE(Eugen Graf @ May 30 2007, 09:38 PM)

Thank for your answer. I don't really know if I can use here Variant.llb. And I have

LV

8.0.

Eugen

So it looks like your data originates from outside LabVIEW - in which case I'm afraid there is no easy way - you need to convert your data to an array of unsigned ints (looks like your protocol aligns on 2 byte boundaries, so U16 will work) and with the individual elements. You can quite easily do U16->array booleans->cast to your type def.

Here's an example of a U8 cast to an 8 element cluster of booleans.

http://forums.lavag.org/index.php?act=attach&type=post&id=5973

[Eugen Graf]

QUOTE(Eugen Graf @ May 30 2007, 08:35 PM)

... a workaround with Cluster->Array or are there another ways to solve it? ...

QUOTE(Gavin Burnell @ May 30 2007, 11:15 PM)

...

You can quite easily do U16->array booleans->cast to your type def.

Here's an example of a U8 cast to an 8 element cluster of booleans.

...

I really assumed it.

Eugen

[Eugen Graf]

Ok, my solution is following.

More ideas?

Eugen

[Mellroth]

QUOTE(Gavin Burnell @ May 30 2007, 10:22 PM)

...Sometime around LabVIEW 4.x/5.x the in-memory storage of a boolean was changed from one bit to one byte, so when you flatten a cluster of 8 booleans you do indeed get 8 bytes back. I'd hazard a guess that the change was done because RAM wasn't quite so critical and memory alignment issues were more so, so it made sense to reserve a whole byte even though only the lsb is used...

If I remember correctly, LabVIEW (<5.0) used different representations for scalars and arrays.

A boolean array was stored with each boolean as a bit, but boolean scalars were stored as I16 (U16?) values.

/J