Re: [J-T-C] struct defs

[jean-frederic clere]

Andy Armstrong wrote:
> 
> GOMEZ Henri wrote:
> >
> > >The reason would be to keep the implementation details of the structure
> > >private so that people aren't tempted to access the fields
> > >directly. All
> > >the caller gets is an opaque handle. Think of it as 'objects lite' for
> > >C.
> >
> > I could understand the OO construction if we were using C++
> > but in strict K&R when you need to have access elements in
> > a struct you need to know about them ?)
> >
> > The goal is to have functions defs in .c and data defs in .h
> > preparing scandoc task
> >
> > So what about that repartition ?
> 
> No, I think it's right as it stands. Just because we're working in C
> doesn't mean we can't do encapsulation. This is a perfectly valid idiom
> to express the concept of some.c and some.h working together to
> implement a 'class' which is only accessed through a functional
> interface. The encapsulation benefits are the same as for Java or C++.
> For one thing it means that the implementation in some.c can change
> without impacting client code.
> 
> I haven't looked at any of the specific cases you're talking about, but
> in general I would say that this is good programming style.

An example (partial only, toto should be allocated in stinternal.c):

st.c:
+++
struct jk_map;                                                                  
typedef struct jk_map jk_map_t;                                                 
                                                                                
main()                                                                          
{                                                                               
jk_map_t *toto;                                                                 
                                                                                
        printtoto(toto);                                                        
}                                                                               
+++

stinternal.c:
+++
                                                                                
struct jk_map;                                                                  
typedef struct jk_map jk_map_t;                                                 
                                                                                
#define SMALL_POOL_SIZE 32                                                      
                                                                                
struct jk_map {                                                                 
    int p;                                                                      
    char buf[SMALL_POOL_SIZE];                                                  
                                                                                
    char **names;                                                               
    void **values;                                                              
                                                                                
    unsigned capacity;                                                          
    unsigned size;                                                              
};                                                                              
                                                                                
                                                                                
printtoto(jk_map_t *toto)                                                       
{                                                                               
                                                                                
        printf("%d\n",toto->size);                                              
}                                                                               
+++

The part 
+++
struct jk_map;                                                                  
typedef struct jk_map jk_map_t;                                                 
+++
Could be in an include st.h. used both by st.c and stinternal.c, but the jk_map
structure elements are only accessible in stinternal.c

An other point is that I prefer homogeneous code and I plan to use the following
for APR:
#ifdef HAS_APR
typedef apr_socket jk_socket;
#else
typedef int jk_socket;
#endif

> 
> --
> Andy Armstrong, Tagish