brainfuck interpreter

brainfuck.c

// by SeungheonOh 2020
#include <stdio.h>
#include <stdlib.h>

int main() {
  unsigned char heap[30000] = { 0 }, cloop = 0, *ptr = heap;
  char doloop = 0, *loops[30000], *loopretp[30000] = { 0 }, *lptr, *innerptr, c;

  while(1) {
    if(!doloop) scanf("%c", &c);
    else { c = *(lptr++); }

    switch(c) {
      case '>': ++ptr; break;
      case '<': --ptr; break;
      case '+': ++*ptr; break;
      case '-': --*ptr; break;
      case '.': printf("%c", *ptr); break;
      case ',': scanf("%c", ptr); break;
      case '[': 
        innerptr = lptr;
        lptr = loops[++cloop] = malloc(30000);
        int loopstart = 1;
        while(loopstart != 0) {
          if(cloop == 1)scanf("%c", lptr++); 
          else *(lptr++) = *(innerptr++);
          if(*(lptr-1) == '[') loopstart++;
          else if(*(lptr-1) == ']') loopstart--;
        }
        loopretp[cloop] = innerptr;
        if(!*ptr) {
          lptr = loopretp[cloop];
          free(loops[cloop--]);
          break;
        }
        lptr = loops[cloop];
        doloop = 1;
        break;
      case ']': 
        if(*ptr) lptr = loops[cloop]; 
        else {
          if(cloop <= 1)doloop = 0;
          else lptr = loopretp[cloop];
          free(loops[cloop--]);
        }
        break;
      default: break;
    }
  }
}