c言語でBrainf*ckインタプリタ

2018/09/29 追記

https://qiita.com/kasari/items/043764c4b3ba87a547e3#comment-5d5261c37687129f69a8
実装にバグがあったため一部修正しました。ご指摘ありがとうございました。

#include <stdio.h>
#define CODESIZE 1024
#define MEMSIZE 1024

typedef struct Code {
  char code;
  struct Code *addr;
} Code;

int debug = 0;

Code codes[CODESIZE];
char memory[MEMSIZE];

void step(Code *cp, char *mp) {
  int i;
  char ch;
  printf("code: %c (%p)\nmp: %d(%c) (%p)\n", cp->code, cp, *mp, *mp,  mp);
  printf("memory: ");
  for (i=0; i<8; i++) {
    printf("%d(%c) ",memory[i], memory[i]);
  }
  scanf("%c", &ch);
  printf("\n\n");
}

void getSource(char *fileName) {
  char ch;
  Code *cp = codes;
  FILE *f = fopen(fileName, "r");
  while ((ch=getc(f)) != EOF) {
    switch (ch) {
    case '>':
    case '<':
    case '+':
    case '-':
    case '.':
    case ',':
    case '[': 
    case ']':
      (cp++)->code = ch;
    }
  }
  fclose(f);
}

void analyze() {
  int index = 0;
  Code* stack[20];
  Code *cp = codes;
  for (;cp->code != 0; cp++) {
    if (cp->code == '[') {
      stack[index++] = cp;
    } else if (cp->code == ']') {
      index--;
      stack[index]->addr = cp+1;
      cp->addr = stack[index];
    }
  }

  if (debug) {
    for (cp=codes; cp->code!=0; cp++) {
      printf("%p    code: %c    addr: %p\n", cp, cp->code, cp->addr);
    }
  }
}

void execute() {
  Code *cp = codes;
  char *mp = memory;

  while (cp->code != 0) {
    if (debug) step(cp, mp);

    switch (cp->code) {
    case '>': mp++; break;
    case '<': mp--; break;
    case '+': (*mp)++; break;
    case '-': (*mp)--; break;
    case '.': putchar(*mp); break;
    case ',': *mp = getchar(); break;
    case '[': if (*mp == 0) {cp = cp->addr; continue;} else break;
    case ']': cp = cp->addr; continue;
    }
    cp++;
  }
}

int main(int argc, char *argv[]) {
  if (argc == 3) debug = 1;
  getSource(argv[1]);
  analyze();
  execute();
  return 0;
}