using struct type X as pointer in struct X.

worldmagic · 10-28-2003, 05:25 AM

Hello.

Can I "predeclerate" a struct type so I can use it in the struct itself ?

Example:

<code>

typedef struct {
void* myData;
myDataList* next;
myDataList* prev;
} myDataList;

</code>

The abow is an example, this is realy what I want to do:

<code>

void ImAnCallBack( myCBConfig* data, char* rawTcpData );

typedef struct {
char* cmd; // Command to match
char* data; // Additional data to callback
void (void* callback)( myCBConfig*, char* rawTcpData); // Callback to call
} myCBConfig;

</code>

I will create a list of myCBConfig. When I get a command on TCP (text) I will match it against myCBConfig.cmd and for every match in my list I will call myCBConfig.callback.

Any good ideas how to make this work?

Ps. Im building a IRC library .Ds =)

ToniT · 10-28-2003, 02:06 PM

Why wouldn't you give a name for your structs.

Code:

struct myCBConfig {
char* cmd; // Command to match
char* data; // Additional data to callback
void (*callback)(struct myCBConfig*, char* rawTcpData); // Callback to call
};

If you want to use typedef instead of struct name, you can write

Code:

typedef struct myCBConfig myCBConfig;

.

For more cleaner approach, I would write (YMMV)

Code:

struct myCBConfig;
typedef void CBFunction(struct myCBConfig*,char*);

struct myCBConfig {
  char* cmd; // Command to match
  char* data; // Additional data to callback
  CBFunction *callback;
};

A sample usage of this code would be

Code:

void aCBfunction(struct myCBConfig*cf,char *foo) {
  printf("Im useless..\n");
}

int main(void) {
  struct myCBConfig f;
  char c;
  f.callback=aCBfunction;
  f.callback(&f,&c);
  return 0;
}

The same thing in C++ would be

Code:

#include <cstdio>
class myCallback {
public:
  char* cmd; // Command to match
  char* data; // Additional data to callback
  virtual void operator()(char *rawTcpData)=0; //Callback to call
};

class aCallback : public myCallback {
void operator()(char *foo) { printf("Im useless..\n"); }
};

int main(void) {
  aCallback cb;
  myCallback &f=cb;
  char c;
  f(&c);
  return 0;
}