moving single into a double 1

[autolab]

I am writing a Delphi app to read/write data files created by an old DOS app written in C ( Armor Systems - Advantage).
I am stuck trying to read a field used to figure mark-up percentages. They are storing this field in "Motorola model" which I assume means "Big Endian" order. Their instructions are to:
1. read the data as a long
2. swap the bytes to "Little Endian"
3. move into a double
4. multiply this by 0.0001

I assume Delphi's LongInt is the equivalent of C's Long. When I enter 30.00 in the DOS software, it stores $000493E0
in the file field. Converting this to Little Endian gives $E0930400. At this point I am lost. Can anyone help point me in the right direction?

 

[Ronin441]

Evidently the big/little endian swap has somehow been done for you. This may have to do with the way you're reading the value in.

$000493E0 is decimal 300,000. Multiply this by 0.0001, and you're left with 30.

You're right: Long is the same as LongInt. So it seems all you have to do is read the number, and then do the multiply by 0.0001 to scale it. -- Doug Burbidge mailto:dougburbidge@yahoo.com

http://home.iprimus.com.au/dougburbidge/

 

[autolab]

Doug Burbidge, thank you for your help. Here is what threw me off track and I still have not figured it out. If I do a hex file dump of the data file, the data is stored as $000493E0. If I read it into a LongInt variable(x) in Delphi and do a IntToHex(x), I get $E0930400. I solved the problem by creating a function to swap the bytes around. It seems the file has the data stored in Little Endian but the Delphi function IntToHex returns Big Endian. I would have expected Delphi to always return Little Endian since it is running on an Intel processor. Any thoughts on this?

Again thanls for your help.
Wes Grueninger

 

[Ronin441]

Hmm. Your number is stored big-endian in the file. When you do the read into your LongInt, I think Delphi is expecting to find a little-endian number (as you point out, this is the default for intel architecture). So I think it is here that the mistranslation occurs. -- Doug Burbidge mailto:dougburbidge@yahoo.com

http://home.iprimus.com.au/dougburbidge/