pd.if.org Git - lice/blob - tests/cgoto.c

   1 // labels as values (computed goto)
   2
   3 int main(void) {
   4     // implement a small dispatch table of instructions for a mini
   5     // state machine, to test computed goto
   6
   7     // test state
   8     int instruction_0_state = 0;
   9     int instruction_1_state = 0;
  10     int instruction_2_state = 0;
  11
  12     unsigned char bytecode[] = {0x01, 0x05, 0x01, 0x02, 0x02, 0x03};
  13     unsigned char *pc        = bytecode;
  14
  15     void *dispatch[] = {
  16         0,
  17         &&instruction_0,
  18         &&instruction_1,
  19         &&instruction_2
  20     };
  21
  22     #define DISPATCH(INDEX)      \
  23         do {                     \
  24             pc += (INDEX);       \
  25             goto *dispatch[*pc]; \
  26         } while (0)
  27
  28     // machine loop
  29     do {
  30
  31         instruction_0:
  32             instruction_0_state += *(pc + 1);
  33             DISPATCH(2);
  34
  35         instruction_1:
  36             instruction_1_state ++;
  37             DISPATCH(1);
  38
  39         instruction_2:
  40             instruction_2_state --;
  41             break;
  42
  43     } while (1);
  44
  45     expecti(instruction_0_state, 7);
  46     expecti(instruction_1_state, 1);
  47     expecti(instruction_2_state, -1);
  48
  49     return 0;
  50 }