CODEWITHSUNDEEP
c
bsky
bsky

Reputation: 20222

C place interface in header file while hiding the functions which implement it

I want to make an interface to a system call handler but I don't want to declare the functions implementing it in the header file as well.

I want them to be static, within the syscall.c (the source file) rather than being declared in syscall..h (the header file).

Is there any way of achieving this? Also, do you know of any C books touching upon this subject?

//container of pointers to the functions executing the system call
typedef struct
{
   void     (*halt)     (void);
   void     (*exit)     (int status);
   pid_t    (*exec)     (const char *file);
   int      (*wait)     (pid_t pid);
   bool     (*create)   (const char *file, int initial_size);
   bool     (*remove)   (const char *file);
   int      (*open)     (const char *file);
   int      (*filesize) (int fd);
   int      (*read)     (int fd, void *buffer, int length);
   int      (*write)    (int fd, const void *buffer, int length);
   void     (*seek)     (int fd, int position);
   int      (*tell)     (int fd);
   void     (*close)    (int fd);
}td_sys_call_handler;



//points to system call handling functions
static td_sys_call_handler syscall_redirect =
{
  .halt     = fu_halt,
  .exit     = fu_exit,
  .exec     = fu_exec,
  .wait     = process_wait,
  .create   = fu_create,
  .remove   = fu_remove,
  .open     = fu_open,
  .filesize = fu_file_filesize,
  .read     = fu_read,
  .write    = fu_write,
  .seek     = fu_file_seek,
  .tell     = fu_file_tell,
  .close    = fu_file_close,
};

Upvotes: 2

Views: 66

Answers (1)

Wyzard
Wyzard

Reputation: 34563

In the header, declare:

extern td_sys_call_handler syscall_redirect;

and in the implementation (syscall.c), just define the structure as a normal global variable — but don't make it static. (A static variable has internal linkage, so it can't be referred to by other modules, but the whole point of this structure is for other modules to use it.)

Upvotes: 4

Related Questions