Osamu Shigematsu wrote:
>
> Eric, thank you very much for your advice.
>
> > > (1) With constructor, we can init member vaules.
> >
> > This can be done in C. Think about the
> > fopen/fread/fwrite/fgets/fprintf
> > etc functions. Don't they work like this?
>
> Um, how can I do that? With struct, there is no constructor, so I have no
> idea to do that...
Have a look at libsndfile. In the public header file there is
a definition like:
typedef void *SNDFILE ;
This is basically a pointer to some structure however, the user
of the library knows nothing about what the pointer is pointing
to.
Inside the library there is a typedef as follows:
typedef struct
{ /* whole pile of stuff in this struct. */
/* It often changes between releases of the library. */
} SNDFILE_PRIVATE ;
In libsndfile, sf_open_read(), and sf_open_write() functions act
as constructors. The both look something like this:
SNDFILE *sf_open_read (char *filename)
{ SNDFILE_PRIVATE *ptr ;
ptr = malloc (sizeof (SNDFILE_PRIVATE)) ;
/* Do a whole pile of initialisation here. */
return (SNDFILE*) ptr ;
}
The SNDFILE* pointer is then used much like a class object. Instead
of using a C++ calling convention of
sndfile.sf_function (param1, param2, ...) ;
you do
sf_function (sndfile, param1, param2, ...) ;
> > > (2) With destructor, we can dispose resources, such as
> > memory block which
> > > had been allocated with operator new, or malloc(). Of
> > course, we can close
> > > file, too.
> >
> > Isn't this what fclose does?
>
> Yes, but I have to all fclose() when I want to close the file. With
> destructor file will be automatically close when object is removed.
Beware of compilers/languages bearing gifts :-). I use C because it
gives me complete control over what the program does. It doesn't
generate destructors etc unless I specifically tell it to. If I
want a more high level language I would choose Python (with C
extensions if necessary).
> > > (3) To make member values private, we can check the value
> > is valid range.
> >
> > The user of the above fxxxx function knows nothing of what is
> > contained
> > in whatever the FILE* pointer points to.
>
> But, we can access struct FILE* directly.
Well, yes you can, but it is very much discouraged. In my libsndfile
implementation above, accessing data in the struct that SNDFILE* points
to is very much more difficult. It would require you to include the
private header files from the library sources.
I also seem to remember someone recent stating that if they had a C++
class library where they wanted to access the private data members
they just did:
#define private public
before including the header file.
> > Have you tried using diff and patch? These two utilities should make
> > your life very much easier.
>
> I don't know about both diff and patch. Is this available on Macintosh or
> Windoze?
Ahhh, I keep forgeting there are a whole pile of people on this list
who don't use Unix :-). These are widely available on all Unix machines
I have ever seen. I think pathc and diff are also available for Win32
but I'm not sure where.
However, this thread seems to have wandered quite some way off the
subject of MP3 encoders/decoders. If you would like to take it further
maybe we should do it off list.
Erik
--
+-------------------------------------------------+
Erik de Castro Lopo [EMAIL PROTECTED]
+-------------------------------------------------+
"Using Java as a general purpose application development language
is like going big game hunting armed with Nerf weapons."
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