[F-Script-talk] Re: F-script and binary data file

[Philippe M. <pm...@ac...>]

Le 17 mai 05 =E0 07:37, Nicholas Crosbie a =E9crit :

> I'm new to both F-Script and Cocoa. How (using
> F-Script) would I map the contents of a BINARY data
> file to objects. My BINARY file has HEADER, TEXT,
> DATA, and ANALYSIS segments; the HEADER segment includes
> ASCII-encoded integers indicating the byte offsets for
> the start and end of each segment.
>
> Any help would be GREATLY appreciated.

A typical way to handle this in Cocoa is to use the NSData class (see =20=

http://developer.apple.com/documentation/Cocoa/Conceptual/BinaryData/=20
index.html)

Below is an example that shows how you can get at the bytes of a =20
binary file from F-Script:

I have a text file (which, after all, is also a binary data file) on =20
my desktop named "test.txt".
Here is how I can read it from F-Script using NSData:

"Load the content of my file into an NSData object"
data :=3D NSData =
dataWithContentsOfFile:'/Users/pmougin/Desktop/test.txt'.

"Allocate a buffer large enough to contain all the bytes of my data"
buf :=3D FSPointer malloc:data length.

"Put my data in the buffer"
data getBytes:buf.

"Cast the pointer to my buffer to an unsigned char * (see the =20
Objective-C manual for an explanation about run-time type encoding)"
buf setType:'C'.

"I can now get at the bytes in my buffer"
buf at:0

The last instruction return a number with a value of 72, which is the =20=

ASCII code for the letter "H", which is expected because my file =20
start with the word "Hello". To get the value of the 2th byte you do =20
"buf at:1", which in my case returns 101, the ASCII code for the =20
letter "e", etc.

When you are done with the buffer, don't forget to send it a free =20
message (i.e. "buf free") in order to dispose it. Alternatively you =20
can do "buf setFreeWhenDone:YES" after creating the buffer (or =20
later). The system will then take care of disposing the buffer when =20
you are done with it.

Best,

Philippe Mougin=