/* catch.h -- more exception handling in C (non-thread safe)
 * $Id: catch.h,v 1.5 2023/05/18 13:45:48 oj14ozun Exp $
 *
 * Lisp-like jumping up up the call-stack to specific blocks:
 *
 *     int foo() {
 *        throw(bar);
 *     }
 *     
 *     int main() {
 *        catch(bar) {
 *          foo();
 *        }
 *     }
 *
 * See http://clhs.lisp.se/Body/s_catch.htm.
 *     
 * To initialise, add
 *
 *   struct catch_stack *catch_tos = NULL;
 *
 * to your main file. */

#ifndef _CATCH_H
#define _CATCH_H

#include <setjmp.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>

struct catch_stack {
     sigjmp_buf frame;
     char *name;
     struct catch_stack *prev;
     bool done;
};

extern struct catch_stack *catch_tos;

#define __catch(fid, _name)					\
     for (struct catch_stack fid = {				\
	       .name = _name,					\
	       .prev = catch_tos,				\
	  }; (!fid.done && !setjmp(fid.frame)) ?		\
	    (catch_tos = &fid, 1) : (catch_tos = fid.prev, 0);	\
	  fid.done = true)

#define catch(name) __catch(_catch_ ## __COUNTER__ ## name, #name)

/* Implicit-catch, deriving the function name */
#define icatch catch(__func__)

#define throw(_name)				\
     do {					\
	  struct catch_stack *i = catch_tos;	\
	  while (i) {				\
	       if (!strcmp(#_name, i->name)) {	\
		    catch_tos = i;		\
		    longjmp(i->frame, 1);	\
		    abort();			\
	       }				\
	       i = i->prev;			\
	  }					\
	  abort();				\
     } while (0)

#endif