c_cpp 尝试goto状态转换表达式引擎

Posted 2021-05-14

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

/*
 * Prototype for cell based vm
 * uses only arrays and blocks of 32-bit signed integer.
*/

// macro to get length of cells machine
#define CellMachine_LEN(cm) (cm->head - cm->cells)




enum CellCode {
	CellCode_STOP,
	CellCode_END,
	CellCode_INT,
	CellCode_SUM
};

struct CellMachine {
	int size;
	int* base;
	int* head;
	const int* end;
	int* cells;
};

struct CellMachine* CellMachine_new(int size)
{
	struct CellMachine* mach = malloc(sizeof(struct CellMachine));
	mach->size = size;
	mach->cells = malloc(sizeof(int) * size);
	mach->head = mach->cells;
	mach->end = mach->head + size;
	mach->base = mach->cells;
	memset(mach->cells, 0, size * sizeof(int));
	return mach;
}

void CellMachine_reset(struct CellMachine* mach)
{
	mach->base = mach->cells;
	mach->head = mach->cells;
}


// Method that runs code on the machine.
void CellMachine_run(struct CellMachine* mach, int* code)
{
	CellMachine_reset(mach);
	goto START_STATE;
START_STATE:
     switch(*code++)
     {
     	case CellCode_STOP:
     	     goto STOP_STATE;
     	case CellCode_SUM:
     	     goto SUM_STATE;
     	case CellCode_END:
     	     fprintf(stderr, "Error got end code but no expression to end\n");
     	     return;
     	default:
     	     goto ERR_STATE;

     }
SUM_STATE:
     switch(*code++)
     {
     	case CellCode_STOP:
     	     goto STOP_STATE;
     	case CellCode_INT:
     	     *(mach->head++) = *code++;
     	     *(mach->head++) = *code++;
     	     goto SUM_STATE;
     	case CellCode_END:
     	     goto START_STATE;
     	default:
     	    goto ERR_STATE;
     }
STOP_STATE:
     printf("Reached stop code\n");
     return;
ERR_STATE:
     fprintf(stderr, "Reached unknowned error code: %d \n", *(code - 1));
     return;
}

void CellMachine_del(struct CellMachine* mach)
{
	free(mach->cells);
	free(mach);
}



int main(int argc, char const *argv[])
{
	struct CellMachine* machine = CellMachine_new(10);
	CellMachine_del(machine);
	return 0;
}