style question

[Serve La]

When I write a medium to large sized C application I tend to create
structures first, then makeStruct and freeStruct functions that dynamically
allocate/free the struct and then I create a bunch of functions that operate
on the struct. Example:

typedef struct ccHashTab
{
.....
} ccHashTab;

ccHashTab * ccMakeHash(unsi gned int size, hash h, comp c);
void ccFreeHashTab(c cHashTab *table);
void *ccHashFindSym( ccHashTab *table, void *symbol);
......

This is a bit the object-oriented way, because I never touch the struct
members directly, only inside the hash functions.
Now I'm wondering if this is a style that other C programmers use in their
work or if they're using something different. I just want to know some
opinions, maybe I'll get some new insights.

[Malcolm]

"Serve La" <ik@veranderhet al.com> wrote in message

Of course the burning question, then is, why not use C++ instead of > >

C then?
Huh?
Because OO is not bound to C++

C++ classes are only really useful when you have inheritance relationships
between them. If you are not going to base your design on a class hierarchy,
a C implementation will generally be cleaner and easier to understand and
maintain.

[E. Robert Tisdale]

Serve La wrote:

E. Robert Tisdale wrote:

ccHashTab ccHashTab_creat e(unsigned int size, hash h, comp c);

places *no* "burden" on the application program.
It works well no matter how complicated the data structure.

People have been doing this sort of thing for a very long time.
Take a look, for example, at The ANSI C Numerical Class Library

http://www.netwood.net/~edwin/svmtl/

It allows you to construct vector and matrix objects from either
automatic or free storage. You might also look at
The GNU Scientific Library (GSL)

http://sources.redhat.com/gsl/
I can't unzip those.

They are compressed UNIX tape archives.
You can probably use Stuffit

http://www.stuffit.com/win/expander/index.html

to uncompress and extract the directory.
Could you give an example?

Here's a fairly complicated struct that I now allocate in a function:

typedef struct Inner {
ITypeInfo *info;
TYPEATTR *attr;
BSTR name;
int index;
} Inner;

typedef struct SomeStruct {
GUID libid;
ITypeLib *lib;
Inner *info;
UINT ntypeinfo;
BSTR filename;
BSTR helpstring;
BSTR helpfilename;
UINT currentiter;
} SomeStruct;

#ifdef NCL_REVEAL
/* Reveal type definitions after applications are thoroughly tested. */

typedef struct { /* submatrix class definition */
/* private: */
ncl_dchandle H;
ncl_offset O;
ncl_extent N1;
ncl_stride S1;
ncl_extent N2;
ncl_stride S2;
ncl_______ _;
} ncl_dcsubmatrix ;
/* A submatrix does not own the array storage that it references. */
/* It does not allocate any array storage when it is constructed */
/* nor does it deallocate any array storage when it is destroyed. */

#else /* NCL_REVEAL */
/* Conceal type definitions until applications are thoroughly tested. */

#define NCL_DCSUBMATRIX _SIZE NCL_SUBMATRIX_S IZE
typedef int ncl_dchidden_su bmatrix[NCL_DCSUBMATRIX _SIZE/sizeof(int)];

typedef struct { /* submatrix class definition */
/* private: */
ncl_dchidden_su bmatrix M;
} ncl_dcsubmatrix ;
/* A submatrix does not own the array storage that it references. */
/* It does not allocate any array storage when it is constructed */
/* nor does it deallocate any array storage when it is destroyed. */

#endif /* NCL_REVEAL */

inline static
ncl_dcsubmatrix /* automatic storage constructor */
(ncl_dcsubm_cre ate)(
ncl_dchandle h, ncl_offset o,
ncl_extent m, ncl_stride s2,
ncl_extent n, ncl_stride s1) {
ncl_dcsubmatrix M;
ncl_dcsubm_init (&M, h, o, m, s2, n, s1);
return M; }

inline static
void /* automatic storage destructor */
(ncl_dcsubm_des troy)(ncl_dcsub matrix* pM) {
pM->_ = ~ncl_other; }

inline static
ncl_dcsubmatrix * /* free storage constructor */
(ncl_dcsubm_new )(
ncl_dchandle h, ncl_offset o,
ncl_extent m, ncl_stride s2,
ncl_extent n, ncl_stride s1) {
ncl_dcsubmatrix * pM
= (ncl_dcsubmatri x*)malloc(sizeo f(ncl_dcsubmatr ix));
if (pM)
ncl_dcsubm_init (pM, h, o, m, s2, n, s1);
return pM; }

inline static
void /* free storage destructor */
(ncl_dcsubm_del ete)(ncl_dcsubm atrix* pM) {
ncl_dcsubm_dest roy(pM);
free((void*)pM) ; }

[Jack Klein]

On Fri, 12 Sep 2003 22:40:33 +0200, "Serve La" <ik@veranderhet al.com>
wrote in comp.lang.c:

When I write a medium to large sized C application I tend to create
structures first, then makeStruct and freeStruct functions that dynamically
allocate/free the struct and then I create a bunch of functions that operate
on the struct. Example:

typedef struct ccHashTab
{
....
} ccHashTab;

One style comment. I personally don't like the practice of using a
struct tag and a typedef for the same structure. One or the other,
please, but not both.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++ ftp://snurse-l.org/pub/acllc-c++/faq

[E. Robert Tisdale]

Jack Klein wrote:

Serve La wrote:

When I write a medium to large sized C application,
I tend to create structures first then makeStruct and freeStruct
functions that dynamically allocate/free the struct and then
I create a bunch of functions that operate on the struct. Example:

typedef struct ccHashTab {
// ...
} ccHashTab;

One style comment.
I personally don't like the practice
of using a struct tag and a typedef for the same structure.
One or the other, please, but not both.

Can you give us a clue why you don't like it?

[Richard Heathfield]

Jack Klein wrote:

On Fri, 12 Sep 2003 22:40:33 +0200, "Serve La" <ik@veranderhet al.com>
wrote in comp.lang.c:

When I write a medium to large sized C application I tend to create
structures first, then makeStruct and freeStruct functions that
dynamically allocate/free the struct and then I create a bunch of
functions that operate on the struct. Example:

typedef struct ccHashTab
{
....
} ccHashTab;

One style comment. I personally don't like the practice of using a
struct tag and a typedef for the same structure. One or the other,
please, but not both.

Hmmm, disagreeing with Jack Klein for a second consecutive article. This is
getting worrying.

Jack -- as you say, it's a style point. I use structure tags for all structs
nowadays, partly in the usual cluon economy drive, so that I don't have to
remember when I need a tag and when I don't, but also to reduce by a tiny
amount the maintenance work involved in making a struct self-referential,
at the expense of a slightly larger amount of work up front!

On the other hand, I like typedefs. Again, I use them for all structs
nowadays. I like the idea of being able to abstract away the structness of
a struct. I am of the opinion that it makes my programs more pleasant to
read, for many people at least, and perhaps even for most people.

--
Richard Heathfield : bi****@eton.pow ernet.co.uk
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton

[Serve La]

"Malcolm" <ma*****@55bank .freeserve.co.u k> wrote in message
news:bk******** **@newsg4.svr.p ol.co.uk...

"Serve La" <ik@veranderhet al.com> wrote in message

Of course the burning question, then is, why not use C++ instead of >

C then?

Huh?
Because OO is not bound to C++

C++ classes are only really useful when you have inheritance relationships
between them. If you are not going to base your design on a class

hierarchy, a C implementation will generally be cleaner and easier to understand and
maintain.

I agree with that and I'll even add inheriting to the list. Only if you want
to override functions then C is not easy to use anymore. Handling virtual
function tables yourself is not easy and maintainable anymore.

[Serve La]

"Jack Klein" <ja*******@spam cop.net> wrote in message
news:im******** *************** *********@4ax.c om...

typedef struct ccHashTab
{
....
} ccHashTab;

One style comment. I personally don't like the practice of using a
struct tag and a typedef for the same structure. One or the other,
please, but not both.

I was expecting that somebody would say that :)
But I have chosen this style because I don't see any problems with it only
advantages.

Why was C designed this way? That you have to declare a struct as a struct,
enum as an enum.....

[The Real OS/2 Guy]

On Fri, 12 Sep 2003 20:40:33 UTC, "Serve La" <ik@veranderhet al.com>
wrote:

When I write a medium to large sized C application I tend to create
structures first, then makeStruct and freeStruct functions that dynamically
allocate/free the struct and then I create a bunch of functions that operate
on the struct. Example:

That's the way I work since the first days of programming I've ever
done (and that was long before C were existent.
With C there is more help to encapsulate things. Think OO, but write
procedual.

1. a header file that holds the external interfaces.
- an abstract type name
- function prototypes
2.. a translation unit that holds the data descriptions and the
functions used to get anything done.

--
Tschau/Bye
Herbert

eComStation 1.1 Deutsch Beta ist verügbar

[Serve La]

"E. Robert Tisdale" <E.************ **@jpl.nasa.gov > wrote in message
news:3F******** ******@jpl.nasa .gov...

typedef struct { /* submatrix class definition */
/* private: */
ncl_dchandle H;
ncl_offset O;
ncl_extent N1;
ncl_stride S1;
ncl_extent N2;
ncl_stride S2;
ncl_______ _;
} ncl_dcsubmatrix ;

Ah, ok, but this struct has only valuetypes that can be easily copied. What
you said was "It works well no matter how complicated the data structure"
What if a struct contains pointers or other structs that contain pointers?

[Arthur J. O'Dwyer]

On Sun, 14 Sep 2003, Serve La wrote:

"Jack Klein" <ja*******@spam cop.net> wrote...

typedef struct ccHashTab
{
....
} ccHashTab;
One style comment. I personally don't like the practice of using a
struct tag and a typedef for the same structure. One or the other,
please, but not both.

I was expecting that somebody would say that :)
But I have chosen this style because I don't see any problems
with it only advantages.

(Personally, I don't often use typedefs. But in the rare case I do,
I try to give the struct tag and the typedef-name *different*
identifiers; perhaps 'typedef struct Foo_tag { } Foo;', for example.
It's less confusing than having the same identifier mean different
things in different namespaces, IMHO.)

Why was C designed this way? That you have to declare a struct
as a struct, enum as an enum.....

I do believe you've just answered your own question. :)

-Arthur