4.7  Un programme, trois implantations

• Addition avec un ATmega328p.
• Pas d’utilisation de la pile, de l’assembleur en quelque sorte, code factorisé :

  int main(void)
  {
  buffer[MAX_BUFFER]='\0';
  
  goto start;
  
  number_get:
  if(base>strlen(digits)) goto *next;
  number=0;
  _number_get:
  char c=serial_get();
  char *f=strchr(digits,c);
  int pos=f?f-digits:-1;
  if(f==NULL || pos>=base) goto *next;
  number *= base;
  number += pos;
  serial_put(c);
  goto _number_get;
  
  number_put:
  if(base>strlen(digits)) goto *next;
  char *p=buffer+MAX_BUFFER;
  unsigned int copy=number;
  _number_put:
  int digit=copy%base;
  *--p=digits[digit];
  copy /= base;
  if(copy && p>buffer) goto _number_put;
  serial_print(p);
  goto *next;
  
  start:
  serial_init(9600);
  serial_print("Addition Calculator\n");
  goto read_first_number;
  
  read_first_number:
  serial_print("first number: ");
  next=&&read_second_number;
  goto number_get;
  
  read_second_number:
  op1=number;
  serial_print("\nsecond number: ");
  next=&&make_addition;
  goto number_get;
  
  make_addition:
  op2=number;
  number=op1+op2;
  serial_print("\naddition: ");
  next=&&end;
  goto number_put;
  
  end:
  serial_print("\n");
  
  return 0;
  }
  

• Programmation structurée en fonctions, utilisation minimale de la libc :

  int number_get(int base){
  if(base>strlen(digits)) return 0;
  int number=0;
  while(1){
    char c=serial_get();
    char *f=strchr(digits,c);
    int pos=f?f-digits:-1;
    if(f==NULL || pos>=base) break;
    number *= base;
    number += pos;
    serial_put(c);
    }
  return number;
  }
  
  void number_put(unsigned int number,int base){
  if(base>strlen(digits)) return;
  if(number){
    int digit=number%base;
    number_put(number/base,base);
    serial_put(digits[digit]);
    }
  return;
  }
  
  int main(void)
  {
  serial_init(9600);
  serial_print("Addition Calculator\n");
  serial_print("first number: ");
  unsigned int op1=number_get(BASE);
  serial_print("\nsecond number: ");
  unsigned int op2=number_get(BASE);
  unsigned int result=op1+op2;
  serial_print("\naddition: ");
  number_put(result,BASE);
  serial_print("\n");
  return 0;
  }
  

• Utilisation lourde de la libc :

  int main(void)
  {
  unsigned int op1,op2;
  stdio_init(9600);
  printf("Addition Calculator\n");
  printf("first number: ");
  scanf("%d",&op1);
  printf("\nsecond number: ");
  scanf("%d",&op2);
  unsigned int result=op1+op2;
  printf("\naddition: %d\n",result);
  return 0;
  }
  

• Listez dans les 3 cas les ressources du microcontrôleur mobilisées.