user: 提供的汇编代码用C语言表示会是什么样子：

```asm
<dn_expand>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x38(%rbp)
  mov    %rsi,-0x40(%rbp)
  mov    %rdx,-0x48(%rbp)
  mov    %rcx,-0x50(%rbp)
  mov    %r8d,-0x54(%rbp)
  movl   $0xffffffff,-0x24(%rbp)
  movl   $0x0,-0x20(%rbp)
  mov    -0x50(%rbp),%rax
  mov    %rax,-0x10(%rbp)
  mov    -0x48(%rbp),%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x54(%rbp),%eax
  cltq
  lea    0x0(,%rax,4),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x8(%rbp)
  jmp    L212
L156:
  mov    -0x28(%rbp),%eax
  and    $0xc0,%eax
  test   %eax,%eax
  je     L168
  cmp    $0xc0,%eax
  je     L162
  jmp    L56
L168:
  mov    -0x10(%rbp),%rax
  cmp    -0x50(%rbp),%rax
  je     L27
  mov    -0x10(%rbp),%rax
  cmp    -0x8(%rbp),%rax
  jb     L221
  mov    $0xffffffff,%eax
  jmp    L258
L221:
  mov    -0x10(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    %rdx,-0x10(%rbp)
  movl   $0x2e,(%rax)
L27:
  mov    -0x28(%rbp),%eax
  cltq
  lea    0x0(,%rax,4),%rdx
  mov    -0x10(%rbp),%rax
  add    %rdx,%rax
  cmp    %rax,-0x8(%rbp)
  ja     L220
  mov    $0xffffffff,%eax
  jmp    L258
L220:
  mov    -0x28(%rbp),%eax
  add    $0x1,%eax
  add    %eax,-0x20(%rbp)
  jmp    L101
L245:
  mov    -0x18(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    %rdx,-0x18(%rbp)
  mov    (%rax),%eax
  mov    %eax,-0x1c(%rbp)
  cmpl   $0x2e,-0x1c(%rbp)
  jne    L135
  mov    -0x28(%rbp),%eax
  cltq
  add    $0x2,%rax
  lea    0x0(,%rax,4),%rdx
  mov    -0x10(%rbp),%rax
  add    %rdx,%rax
  cmp    %rax,-0x8(%rbp)
  ja     L165
  mov    $0xffffffff,%eax
  jmp    L258
L165:
  mov    -0x10(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    %rdx,-0x10(%rbp)
  movl   $0x5c,(%rax)
L135:
  mov    -0x10(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    %rdx,-0x10(%rbp)
  mov    -0x1c(%rbp),%edx
  mov    %edx,(%rax)
  mov    -0x18(%rbp),%rax
  cmp    -0x40(%rbp),%rax
  jb     L101
  mov    $0xffffffff,%eax
  jmp    L258
L101:
  subl   $0x1,-0x28(%rbp)
  cmpl   $0x0,-0x28(%rbp)
  jns    L245
  jmp    L212
L162:
  cmpl   $0x0,-0x24(%rbp)
  jns    L25
  mov    -0x18(%rbp),%rax
  sub    -0x48(%rbp),%rax
  sar    $0x2,%rax
  add    $0x1,%eax
  mov    %eax,-0x24(%rbp)
L25:
  mov    -0x28(%rbp),%eax
  shl    $0x8,%eax
  and    $0x3f00,%eax
  mov    %eax,%edx
  mov    -0x18(%rbp),%rax
  mov    (%rax),%eax
  movzbl %al,%eax
  or     %edx,%eax
  cltq
  lea    0x0(,%rax,4),%rdx
  mov    -0x38(%rbp),%rax
  add    %rdx,%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x18(%rbp),%rax
  cmp    -0x38(%rbp),%rax
  jb     L37
  mov    -0x18(%rbp),%rax
  cmp    -0x40(%rbp),%rax
  jb     L198
L37:
  mov    $0xffffffff,%eax
  jmp    L258
L198:
  addl   $0x2,-0x20(%rbp)
  mov    -0x20(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x40(%rbp),%rax
  sub    -0x38(%rbp),%rax
  sar    $0x2,%rax
  cmp    %rax,%rdx
  jl     L212
  mov    $0xffffffff,%eax
  jmp    L258
L56:
  mov    $0xffffffff,%eax
  jmp    L258
L212:
  mov    -0x18(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    %rdx,-0x18(%rbp)
  mov    (%rax),%eax
  mov    %eax,-0x28(%rbp)
  cmpl   $0x0,-0x28(%rbp)
  jne    L156
  mov    -0x10(%rbp),%rax
  movl   $0x0,(%rax)
  cmpl   $0x0,-0x24(%rbp)
  jns    L120
  mov    -0x18(%rbp),%rax
  sub    -0x48(%rbp),%rax
  sar    $0x2,%rax
  mov    %eax,-0x24(%rbp)
L120:
  mov    -0x24(%rbp),%eax
L258:
  pop    %rbp
  ret
```

assistant: ```c
int dn_expand(u_char *msg, u_char *eomorig, u_char *comp_dn, u_char *exp_dn, int length) {
  u_char *cp, *dn;
  int n, c;
  u_char *eom;
  int len = -1, checked = 0;
  dn = exp_dn;
  cp = comp_dn;
  eom = exp_dn + length;
  while (n = *cp++) {
    switch (n & 0xc0) {
    case 0:
      if (dn != exp_dn) {
        if (dn >= eom)
          return (-1);
        *dn++ = '.';
      }
      if (dn + n >= eom)
        return (-1);
      checked += n + 1;
      while (--n >= 0) {
        if ((c = *cp++) == '.') {
          if (dn + n + 2 >= eom)
            return (-1);
          *dn++ = '\\';
        }
        *dn++ = c;
        if (cp >= eomorig)
          return (-1);
      }
      break;
    case 0xc0:
      if (len < 0)
        len = cp - comp_dn + 1;
      cp = msg + (((n & 0x3f) << 8) | (*cp & 0xff));
      if (cp < msg || cp >= eomorig)
        return (-1);
      checked += 2;
      if (checked >= eomorig - msg)
        return (-1);
      break;
    default:
      return (-1);
    }
  }
  *dn = '\0';
  if (len < 0)
    len = cp - comp_dn;
  return (len);
}
```