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Re: Is this kosher wrt Generic?

From "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups comp.lang.c
Subject Re: Is this kosher wrt Generic?
Date 2019-11-29 14:35 -0800
Organization Aioe.org NNTP Server
Message-ID <qrs6ft$13to$1@gioia.aioe.org> (permalink)
References (3 earlier) <8f6ba3a5-3385-45f8-bfc6-342f6cbd54d4@googlegroups.com> <5e3b0d5e-5e2c-4acd-8111-346e859e3e51@googlegroups.com> <7c6d2fae-86af-4660-932a-64bccef28b4a@googlegroups.com> <qKAwF.44683$vV6.25665@fx17.am4> <qpvett$drj$1@dont-email.me>

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On 11/6/2019 1:45 PM, David Brown wrote:
> On 06/11/2019 15:26, Bart wrote:
>> On 06/11/2019 13:56, Thiago Adams wrote:
>>> On Wednesday, November 6, 2019 at 10:33:11 AM UTC-3, Thiago Adams wrote:
[...]
>> Class-based (or method-based) is simpler, and the choice is made on 
>> the first parameter only. Take this example in fantasy C:
>>
>>     typedef struct {
>>          void SayMyName(bart &s) {puts("Bart");}
>>     } bart;
>>
>>     typedef struct {
>>          void SayMyName(lisa &s) {puts("Lisa");}
>>     } lisa;
>>
>>     bart B;
>>     lisa L;
>>
>>     B.SayMyName();       // Bart
>>     L.SayMyName();       // Lisa
>>
>>     bart.SayMyName(B);   // Bart
>>     lisa.SayMyName(L);   // Lisa
> 
> 
> You can get a fair amount of that today in C, though it is a little more 
> verbose:
> 
> #include <stdio.h>
> 
> typedef struct bart {
>      void (*SayMyName)(struct bart*);
> } bart;
> 
> void bart_SayMyName(struct bart* s) { puts("Bart"); }
> #define bart_init { bart_SayMyName }
> 
> typedef struct lisa {
>      void (*SayMyName)(struct lisa*);
> } lisa;
> 
> void lisa_SayMyName(struct lisa * s) { puts("Lisa"); }
> #define lisa_init { lisa_SayMyName }
> 
> bart B = bart_init;
> lisa L = lisa_init;
> 
> void foo(void) {
>      B.SayMyName(&B);
>      L.SayMyName(&L);
> 
>      bart_SayMyName(&B);
>      lisa_SayMyName(&L);
> }
> 
> 
> Not perfect, but some people find such constructs useful.
> 

Indeed, not perfect but can be made to work. Fwiw, here is a hack that I 
created in the past:

https://pastebin.com/raw/f52a443b1
_______________________________________
/* Interfaces
____________________________________________________________________*/
#include <stddef.h>


struct object_prv_vtable {
   int (*fp_destroy) (void* const);
};


struct device_prv_vtable {
   int (*fp_read) (void* const, void*, size_t);
   int (*fp_write) (void* const, void const*, size_t);
};


struct device_vtable {
   struct object_prv_vtable const object;
   struct device_prv_vtable const device;
};


struct device {
   struct device_vtable const* vtable;
};


#define object_destroy(mp_self) ( \
   (mp_self)->vtable->object.fp_destroy((mp_self)) \
)


#define device_read(mp_self, mp_buf, mp_size) ( \
   (mp_self)->vtable->device.fp_read((mp_self), (mp_buf), (mp_size)) \
)


#define device_write(mp_self, mp_buf, mp_size) ( \
   (mp_self)->vtable->device.fp_write((mp_self), (mp_buf), (mp_size)) \
)






/* Sample Header (usb_drive.h)
____________________________________________________________________*/
#if ! defined(USB_HEADER_H)
#define USB_HEADER_H


extern int usb_drive_create(struct device** const);


#endif







/* Sample Impl (usb_drive.c)
____________________________________________________________________*/
/* #include "usb_drive.c" */
#include <stdio.h>
#include <stdlib.h>


struct usb_drive {
   struct device device;
   /* whatever */
};


static int usb_drive_object_destroy(void* const);
static int usb_drive_device_read(void* const, void*, size_t);
static int usb_drive_device_write(void* const, void const*, size_t);


static struct device_vtable const g_table = {
   { /* object */
     usb_drive_object_destroy
   },

   { /* device */
     usb_drive_device_read,
     usb_drive_device_write
   }
};


int usb_drive_create(
  struct device** const pself
) {
   struct usb_drive* const self = malloc(sizeof(*self));
   if (self) {
     self->device.vtable = &g_table;
     *pself = &self->device;
     return 0;
   }
   return -1;
}


int usb_drive_object_destroy(
  void* const self_
) {
   struct usb_drive* const self = self_;
   printf("usb_drive_object_destroy(%p)\n", (void*)self);
   free(self_);
   return 0;
}


int usb_drive_device_read(
  void* const self_,
  void* buf,
  size_t size
) {
   struct usb_drive* const self = self_;
   printf("usb_drive_device_read(%p, %p, %lu)\n",
     (void*)self, buf, (unsigned long)size);
   return 0;
}


int usb_drive_device_write(
  void* const self_,
  void const* buf,
  size_t size
) {
   struct usb_drive* const self = self_;
   printf("usb_drive_device_write(%p, %p, %lu)\n",
     (void*)self, buf, (unsigned long)size);
   return 0;
}







/* Sample Application
____________________________________________________________________*/
void read_write(
  struct device* const self
) {
   char buf[100];

   device_read(self, buf, 50);

   device_write(self, buf, 5);
}


int main(void) {
   struct device* a_device;

   if (! usb_drive_create(&a_device)) {
     read_write(a_device);

     object_destroy(a_device);
   }

   return 0;
}
_______________________________________

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Thread

Is this kosher wrt Generic? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-04 22:55 -0800
  Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 08:12 +0100
    Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-05 03:52 -0800
      Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 13:12 +0100
        Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-05 04:24 -0800
          Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 13:33 +0100
            Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-05 04:57 -0800
              Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 14:08 +0100
                Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-05 05:21 -0800
                Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 14:27 +0100
                Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-05 05:42 -0800
                Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 14:51 +0100
                Re: Is this kosher wrt Generic? Bart <bc@freeuk.com> - 2019-11-05 14:49 +0000
                Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 15:53 +0100
                Re: Is this kosher wrt Generic? Bart <bc@freeuk.com> - 2019-11-05 15:59 +0000
                Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 17:11 +0100
                Re: Is this kosher wrt Generic? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-11-05 09:19 -0800
                Re: Is this kosher wrt Generic? Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-11-05 07:00 -0800
                Re: Is this kosher wrt Generic? David Brown <david.brown@hesbynett.no> - 2019-11-05 16:30 +0100
                Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 15:31 +0100
              Re: Is this kosher wrt Generic? Ian Collins <ian-news@hotmail.com> - 2019-11-06 10:34 +1300
                Re: Is this kosher wrt Generic? Bart <bc@freeuk.com> - 2019-11-05 22:16 +0000
                Re: Is this kosher wrt Generic? Ian Collins <ian-news@hotmail.com> - 2019-11-06 11:34 +1300
                Re: Is this kosher wrt Generic? Bart <bc@freeuk.com> - 2019-11-05 23:12 +0000
                Re: Is this kosher wrt Generic? Ian Collins <ian-news@hotmail.com> - 2019-11-06 12:29 +1300
                Re: Is this kosher wrt Generic? David Brown <david.brown@hesbynett.no> - 2019-11-06 10:17 +0100
                Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-06 10:56 +0100
                Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-06 10:02 +0100
                Re: Is this kosher wrt Generic? Bart <bc@freeuk.com> - 2019-11-06 10:43 +0000
                Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-06 04:56 -0800
                Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-06 14:05 +0100
                Re: Is this kosher wrt Generic? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-08 21:03 -0800
                Re: Is this kosher wrt Generic? Ian Collins <ian-news@hotmail.com> - 2019-11-10 08:45 +1300
                Re: Is this kosher wrt Generic? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 16:35 -0800
                Re: Is this kosher wrt Generic? David Brown <david.brown@hesbynett.no> - 2019-11-29 12:41 +0100
                Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-29 04:08 -0800
                Re: Is this kosher wrt Generic? Bart <bc@freeuk.com> - 2019-11-29 13:01 +0000
                Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-29 06:43 -0800
                Re: Is this kosher wrt Generic? Bart <bc@freeuk.com> - 2019-11-29 17:31 +0000
                Re: Is this kosher wrt Generic? David Brown <david.brown@hesbynett.no> - 2019-11-29 14:31 +0100
                Re: Is this kosher wrt Generic? Öö Tiib <ootiib@hot.ee> - 2019-11-30 13:16 -0800
                Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-12-02 03:31 -0800
                Re: Is this kosher wrt Generic? Öö Tiib <ootiib@hot.ee> - 2019-12-02 23:30 -0800
                Re: Is this kosher wrt Generic? Ian Collins <ian-news@hotmail.com> - 2019-12-01 12:10 +1300
                Re: Is this kosher wrt Generic? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-11 09:35 -0800
              Re: Is this kosher wrt Generic? Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-11-05 22:49 +0000
            Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-05 05:12 -0800
              Re: Is this kosher wrt Generic? Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-05 14:20 +0100
    Re: Is this kosher wrt Generic? guinness.tony@gmail.com - 2019-11-05 16:19 -0800
    Re: Is this kosher wrt Generic? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-06 00:06 -0800
  Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-05 03:19 -0800
    Re: Is this kosher wrt Generic? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-05 22:38 -0800
      Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-06 04:50 -0800
        Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-06 05:32 -0800
          Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-06 05:56 -0800
            Re: Is this kosher wrt Generic? Bart <bc@freeuk.com> - 2019-11-06 14:26 +0000
              Re: Is this kosher wrt Generic? Thiago Adams <thiago.adams@gmail.com> - 2019-11-06 09:04 -0800
              Re: Is this kosher wrt Generic? David Brown <david.brown@hesbynett.no> - 2019-11-06 22:45 +0100
                Re: Is this kosher wrt Generic? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-29 14:35 -0800
                Re: Is this kosher wrt Generic? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-29 23:23 +0000
                Re: Is this kosher wrt Generic? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-29 19:08 -0800
                Re: Is this kosher wrt Generic? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-29 19:12 -0800
                Re: Is this kosher wrt Generic? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-30 10:44 +0000
            Re: Is this kosher wrt Generic? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-09 23:21 -0800
            Re: Is this kosher wrt Generic? "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2019-11-09 23:22 -0800

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