FILE structure - porting C DLL into other languages

[jparus]

Hello,
can anybody explain me how to port FILE structure into other languages.
I have an DLL library and functions in this library take FILE* as a
parameter. I want to make an interface into Delphi, thus I must
"export" function names and parameters of the function. It is easy for
usual data types and structures but I don't know how to port FILE
structure.

Tahnks.

Jindra

[Xavier]

jp****@gmail.co m wrote:

Hello,
can anybody explain me how to port FILE structure into other languages.
I have an DLL library and functions in this library take FILE* as a
parameter. I want to make an interface into Delphi, thus I must
"export" function names and parameters of the function. It is easy for
usual data types and structures but I don't know how to port FILE
structure.

Tahnks.

Jindra

look at stream in your IDE help system

Xavier

[Vladimir S. Oka]

On Thursday 16 March 2006 08:41, jp****@gmail.co m opined (in
<11************ *********@i40g2 000cwc.googlegr oups.com>):

Hello,
can anybody explain me how to port FILE structure into other
languages. I have an DLL library and functions in this library take
FILE* as a parameter. I want to make an interface into Delphi, thus I
must "export" function names and parameters of the function. It is
easy for usual data types and structures but I don't know how to port
FILE structure.

You should look into the C implementation used to create the library,
and see how exactly is FILE declared there. You'll then hopefully have
enough information to map the fields to whatever Delphi requires. You
will most likely need an interface layer for this.

--
BR, Vladimir

Recent research has tended to show that the Abominable No-Man
is being replaced by the Prohibitive Procrastinator.
-- C.N. Parkinson

[Keith Thompson]

"Vladimir S. Oka" <no****@btopenw orld.com> writes:

On Thursday 16 March 2006 08:41, jp****@gmail.co m opined (in
<11************ *********@i40g2 000cwc.googlegr oups.com>):

can anybody explain me how to port FILE structure into other
languages. I have an DLL library and functions in this library take
FILE* as a parameter. I want to make an interface into Delphi, thus I
must "export" function names and parameters of the function. It is
easy for usual data types and structures but I don't know how to port
FILE structure.

You should look into the C implementation used to create the library,
and see how exactly is FILE declared there. You'll then hopefully have
enough information to map the fields to whatever Delphi requires. You
will most likely need an interface layer for this.

I don't know whether that's the best approach (partly because I know
very little about Delphi).

C programs in general don't use the FILE structure itself. They only
use pointers to FILE structures (type FILE*). Think of a FILE* as an
opaque type that happens to be implemented as a pointer. The only
valid values of type FILE* are NULL and values returned by functions
such as fopen(). The only valid things to do with FILE* values are to
compare them to NULL or to each other, or to pass them to functions.

The internals of the FILE structure itself are entirely
system-specific. Don't do anything that depends on those internals
unless you absolutely have to.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Al Balmer]

On 16 Mar 2006 00:41:50 -0800, jp****@gmail.co m wrote:

Hello,
can anybody explain me how to port FILE structure into other languages.
I have an DLL library and functions in this library take FILE* as a
parameter. I want to make an interface into Delphi, thus I must
"export" function names and parameters of the function. It is easy for
usual data types and structures but I don't know how to port FILE
structure.

You really don't want to port the FILE structure. You want to look at
what the I/O is doing, then do the same thing in Delphi.

--
Al Balmer
Sun City, AZ

[Flash Gordon]

Keith Thompson wrote:

"Vladimir S. Oka" <no****@btopenw orld.com> writes:

On Thursday 16 March 2006 08:41, jp****@gmail.co m opined (in
<11************ *********@i40g2 000cwc.googlegr oups.com>):

can anybody explain me how to port FILE structure into other
languages. I have an DLL library and functions in this library take
FILE* as a parameter. I want to make an interface into Delphi, thus I
must "export" function names and parameters of the function. It is
easy for usual data types and structures but I don't know how to port
FILE structure. You should look into the C implementation used to create the library,
and see how exactly is FILE declared there. You'll then hopefully have
enough information to map the fields to whatever Delphi requires. You
will most likely need an interface layer for this.

I don't know whether that's the best approach (partly because I know
very little about Delphi).

I do know Delphi and cannot think of a good reason for doing it.
C programs in general don't use the FILE structure itself. They only
use pointers to FILE structures (type FILE*). Think of a FILE* as an
opaque type that happens to be implemented as a pointer. The only
valid values of type FILE* are NULL and values returned by functions
such as fopen(). The only valid things to do with FILE* values are to
compare them to NULL or to each other, or to pass them to functions.

The internals of the FILE structure itself are entirely
system-specific. Don't do anything that depends on those internals
unless you absolutely have to.

I agree with you completely.

The OP should either use the IO built in to Delphi with is perfectly
adequate for most tasks of if he *really* needs to access C streams
write wrapper functions in an extended version of C (extensions being
required for calling conventions) to do what is required.

The details are off topic here. Probably one of the Boreland groups
would be a good place, since Boreland do a C (and C++) compiler as well
as Delphi (although you can use other C compilers for this).
--
Flash Gordon, living in interesting times.
Web site - http://home.flash-gordon.me.uk/
comp.lang.c posting guidelines and intro:
http://clc-wiki.net/wiki/Intro_to_clc

[santosh]

Keith Thompson wrote:

C programs in general don't use the FILE structure itself. They only
use pointers to FILE structures (type FILE*). Think of a FILE* as an
opaque type that happens to be implemented as a pointer. The only
valid values of type FILE* are NULL and values returned by functions
such as fopen(). The only valid things to do with FILE* values are to
compare them to NULL or to each other, or to pass them to functions.

Is it meaningful to compare two FILE * values with each other?

[Keith Thompson]

"santosh" <sa*********@gm ail.com> writes:

Keith Thompson wrote:

C programs in general don't use the FILE structure itself. They only
use pointers to FILE structures (type FILE*). Think of a FILE* as an
opaque type that happens to be implemented as a pointer. The only
valid values of type FILE* are NULL and values returned by functions
such as fopen(). The only valid things to do with FILE* values are to
compare them to NULL or to each other, or to pass them to functions.

Is it meaningful to compare two FILE * values with each other?

As far as I know, yes. Why wouldn't it be?

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[santosh]

Keith Thompson wrote:

"santosh" <sa*********@gm ail.com> writes:

Keith Thompson wrote:

C programs in general don't use the FILE structure itself. They only
use pointers to FILE structures (type FILE*). Think of a FILE* as an
opaque type that happens to be implemented as a pointer. The only
valid values of type FILE* are NULL and values returned by functions
such as fopen(). The only valid things to do with FILE* values are to
compare them to NULL or to each other, or to pass them to functions.

Is it meaningful to compare two FILE * values with each other?

As far as I know, yes. Why wouldn't it be?

Sorry if I don't make sense, but I'm still a beginner in C. What I
meant was, in the context of user code, as opposed to the C library
implementation, does it make sense to compare two different FILE *
values? For example you open two files and get two FILE * values as a
result. What would be the meaning in comparing them, even though it may
be valid?

[Jordan Abel]

On 2006-03-21, santosh <sa*********@gm ail.com> wrote:

Keith Thompson wrote:

"santosh" <sa*********@gm ail.com> writes:

> Keith Thompson wrote:
>> C programs in general don't use the FILE structure itself. They only
>> use pointers to FILE structures (type FILE*). Think of a FILE* as an
>> opaque type that happens to be implemented as a pointer. The only
>> valid values of type FILE* are NULL and values returned by functions
>> such as fopen(). The only valid things to do with FILE* values are to
>> compare them to NULL or to each other, or to pass them to functions.
>
> Is it meaningful to compare two FILE * values with each other?

As far as I know, yes. Why wouldn't it be?

Sorry if I don't make sense, but I'm still a beginner in C. What I
meant was, in the context of user code, as opposed to the C library
implementation, does it make sense to compare two different FILE *
values? For example you open two files and get two FILE * values as a
result. What would be the meaning in comparing them, even though it may
be valid?

If one part of your code isn't telling the other whether they're the
same FILE * or not.