user: 提供的汇编代码用C语言表示会是什么样子：

```asm
<marker_length>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x50,%rsp
  mov    %rdi,-0x38(%rbp)
  mov    %rsi,-0x40(%rbp)
  mov    %edx,-0x44(%rbp)
  mov    %ecx,-0x48(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x8(%rbp)
  xor    %eax,%eax
  movq   $0x0,-0x18(%rbp)
  mov    -0x40(%rbp),%rax
  mov    (%rax),%rax
  mov    %rax,-0x20(%rbp)
  mov    -0x40(%rbp),%rax
  mov    (%rax),%rdx
  mov    -0x44(%rbp),%eax
  cltq
  add    %rdx,%rax
  mov    %rax,-0x10(%rbp)
  jmp    L103
L49:
  mov    -0x20(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x28,%al
  je     L39
  mov    -0x20(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x29,%al
  jne    L108
L39:
  movq   $0x0,-0x18(%rbp)
  jmp    L96
L108:
  mov    -0x48(%rbp),%eax
  cltq
  add    %rax,-0x18(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x1,%rax
  mov    %rax,-0x20(%rbp)
L103:
  mov    -0x20(%rbp),%rax
  cmp    %rax,-0x10(%rbp)
  ja     L49
L96:
  cmpq   $0x0,-0x18(%rbp)
  je     L73
  mov    -0x20(%rbp),%rdx
  mov    -0x40(%rbp),%rax
  mov    %rdx,(%rax)
  mov    -0x18(%rbp),%rax
  jmp    L95
L73:
  mov    -0x40(%rbp),%rax
  mov    (%rax),%rax
  mov    %rax,-0x20(%rbp)
  mov    -0x40(%rbp),%rax
  mov    (%rax),%rdx
  mov    -0x44(%rbp),%eax
  cltq
  add    %rdx,%rax
  mov    %rax,-0x10(%rbp)
  jmp    L2
L119:
  mov    -0x20(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  cmp    $0x28,%al
  jne    L16
  mov    -0x20(%rbp),%rax
  add    $0x1,%rax
  mov    %rax,-0x20(%rbp)
  lea    -0x20(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <read_int_from_string@plt>
  mov    %eax,-0x28(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x1,%rax
  mov    %rax,-0x20(%rbp)
  lea    -0x20(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <read_int_from_string@plt>
  mov    %eax,-0x24(%rbp)
  mov    -0x20(%rbp),%rax
  add    $0x1,%rax
  mov    %rax,-0x20(%rbp)
  mov    -0x24(%rbp),%ecx
  mov    -0x28(%rbp),%edx
  lea    -0x20(%rbp),%rsi
  mov    -0x38(%rbp),%rax
  mov    %rax,%rdi
  call   <marker_length>
  mov    -0x48(%rbp),%edx
  movslq %edx,%rdx
  imul   %rdx,%rax
  add    %rax,-0x18(%rbp)
  mov    -0x20(%rbp),%rax
  sub    $0x1,%rax
  mov    %rax,-0x20(%rbp)
  jmp    L3
L16:
  mov    -0x48(%rbp),%eax
  cltq
  add    %rax,-0x18(%rbp)
L3:
  mov    -0x20(%rbp),%rax
  add    $0x1,%rax
  mov    %rax,-0x20(%rbp)
L2:
  mov    -0x20(%rbp),%rax
  cmp    %rax,-0x10(%rbp)
  ja     L119
  mov    -0x20(%rbp),%rdx
  mov    -0x40(%rbp),%rax
  mov    %rdx,(%rax)
  mov    -0x18(%rbp),%rax
L95:
  mov    -0x8(%rbp),%rdx
  sub    %fs:0x28,%rdx
  je     L5
  call   <__stack_chk_fail@plt>
L5:
  leave
  ret
```

assistant: ```c
unsigned long marker_length(char str[], unsigned long *start_i, int a, int b) {
  unsigned long length = 0;
  unsigned long i, l;
  int nested_a, nested_b;
  for (i = *start_i, l = *start_i + a; i < l; i++) {
    if (str[i] == '(' || str[i] == ')') {
      length = 0;
      break;
    } else {
      length += b;
    }
  }
  if (length) {
    *start_i = i;
    return length;
  }
  for (i = *start_i, l = *start_i + a; i < l; i++) {
    if (str[i] == '(') {
      i += 1;
      nested_a = read_int_from_string(str, &i);
      i += 1;
      nested_b = read_int_from_string(str, &i);
      i += 1;
      length += marker_length(str, &i, nested_a, nested_b) * b;
      i -= 1;
    } else {
      length += b;
    }
  }
  *start_i = i;
  return length;
}
```