OpenEuphoria

I need a snippet of EU code?

• Posted by Johnny Kinsey <jkinsey at MINDSPRING.COM> Mar 04, 1998
• 837 views

Help
I need help with coding the File function's in Win32 API.  Like the
CopyFile, DeleteFile and others.  The main prob. that I am having is how do
you find out how much memory to allocate for a C structure.  I have read the
platform.doc that comes with the beta 2.0 ver. of EU and I have the
win32.hlp for the different functions in the Win32 API so now what else do I
need I can't find any where in the Docs above for the memory requirements of
each structure.  Do I just keep adding 4 bytes until it works for each
parameter in the C function.  This seems kinda iffy because what if I
overwrite the OS in memory then what.  Please someone give me some direction
on this.  Here is the section in the platform.doc that I am referring to.

------ Platform.doc -------------

You can read and write members of C structures using peek and poke, or peek4
and poke4. You can allocate space for structures using allocate().  You must
calculate the offset of a member of a C structure. This is usually easy,
because anything in C that needs 4 or fewer bytes will be assigned 4 bytes
in the structure. Thus C int's, char's, unsigned int's, pointers to
anything, etc. will all take 4 bytes. If the C declaration looks like:


// Warning C code ahead!

struct example {

int a; // offset 0

char *b; // offset 4

char c; // offset 8

long d; // offset 12

};


To allocate space for "struct example" you would need:


atom p


p = allocate(16) -- size of "struct example"


The address that you get from allocate is always at least 4-byte aligned.
This is useful, since WIN32 structures are supposed to start on a 4-byte
boundary. Fields within a C structure that are 4-bytes or more in size must
start on a 4-byte boundary in memory. 2-byte fields must start on a 2-byte
boundary. To achieve this you may have to leave small gaps within the
structure. In practice it is not hard to align most structures since 90% of
the fields are 4-byte pointers or 4-byte integers.  You can set the fields
using something like:


poke4(p + 0, a)

poke4(p + 4, b)

poke4(p + 8, c)

poke4(p +12, d)


You can read a field with something like:


d = peek4(p+12)


Tip: for readability, make up Euphoria constants for the numbers 0,4,8 and
12.

e.g.

constant A = 0,

B = 4,

C = 8,

D = 12


Then you can write:


d = peek4(p + D)

------- Platform.doc ---------------------

Or am I completely screwed up.  I would very much like to write a wrapper
for these common file functions and one for updating and changing the
windows registry if possible.  Any help on this would be much appreciated.

Thanks

JKinsey