Re: Reading Float Data from a binary file into ada

On Tuesday 30 January 2007 16:55, Jean-Pierre Rosen wrote:
frikk a écrit :
Hello everyone! I am having a problem that I would love some help
with.

Essentially I was given a Visual Basic program that dumps a binary
configuration file with all of the variables in a set. The variables
are each 32 bit floats, with the first 16 bits being the integer part
and the second 16 bits being a representation of the fraction (I'm not
sure if this is stanard - but its just how VB dumps the data).

Hmm... This looks like a fixed point representation, not a floating
point one.

There is the same kind of representation in the tiff format,
The "type RATIONAL" two LONGs : the first represent the numerator of the
fraction, the second the denominator.

The
binary dump is basically a copy of the way VB stores the data in
memory. I need to be able to use this data in ada. There is a C
counterpart to this that makes use of a 'union' to grab the data 1
byte (8 bits) at a time, put them into a char array of size 4, then
use a 32 bit float to reference the data. Is there somehow I can do
this in ada as well?

In general, Unchecked_Conversion is your friend when you need two
different views, at differing levels of abstraction, of the same data.

I remember doing some Unchecked_Conversion to read a proprietary tiff file
some time ago. But only to find the LONGs and then after I was just doing a
simple division to get the result.

Basically I need to be able to read in the binary data byte by byte
but store it into a 32 bit Float.

It may be helpfull to know some value in advance like a magic number.

However, if you do an unchecked_conversion to Float, it will certainly
not work, because your data don't look at all like floats!

--
Ali
.

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