user: 这段汇编代码用C语言表示是什么样的:

```asm
<calculate_packet_size>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  mov    %rdi,-0x8(%rbp)
  mov    -0x8(%rbp),%rax
  movzbl (%rax),%eax
  test   %al,%al
  jne    L248
  mov    -0x8(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  test   %al,%al
  jne    L248
  mov    -0x8(%rbp),%rax
  add    $0x2,%rax
  movzbl (%rax),%eax
  cmp    $0x1,%al
  je     L475
L248:
  mov    $0x0,%eax
  jmp    L400
L475:
  mov    -0x8(%rbp),%rax
  add    $0x3,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  test   %eax,%eax
  je     L326
  test   %eax,%eax
  js     L449
  cmp    $0xef,%eax
  jg     L449
  cmp    $0xb3,%eax
  jl     L449
  sub    $0xb3,%eax
  cmp    $0x3c,%eax
  ja     L449
  mov    %eax,%eax
  lea    0x0(,%rax,4),%rdx
  lea    D8(%rip),%rax
  mov    (%rdx,%rax,1),%eax
  cltq
  lea    D8(%rip),%rdx
  add    %rdx,%rax
  notrack jmp *%rax
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0xc4,%eax
  cmp    $0x44,%eax
  jne    L175
  mov    -0x8(%rbp),%rax
  add    $0x6,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x4,%eax
  test   %eax,%eax
  je     L175
  mov    -0x8(%rbp),%rax
  add    $0x8,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x4,%eax
  test   %eax,%eax
  je     L175
  mov    -0x8(%rbp),%rax
  add    $0x9,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x1,%eax
  test   %eax,%eax
  je     L175
  mov    -0x8(%rbp),%rax
  add    $0xc,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x3,%eax
  cmp    $0x3,%eax
  jne    L175
  mov    -0x8(%rbp),%rax
  add    $0xd,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x7,%eax
  add    $0xe,%eax
  jmp    L400
L175:
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0xf1,%eax
  cmp    $0x21,%eax
  jne    L383
  mov    -0x8(%rbp),%rax
  add    $0x6,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x1,%eax
  test   %eax,%eax
  je     L383
  mov    -0x8(%rbp),%rax
  add    $0x8,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x1,%eax
  test   %eax,%eax
  je     L383
  mov    -0x8(%rbp),%rax
  add    $0x9,%rax
  movzbl (%rax),%eax
  test   %al,%al
  jns    L383
  mov    -0x8(%rbp),%rax
  add    $0xb,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x1,%eax
  test   %eax,%eax
  je     L383
  mov    $0xc,%eax
  jmp    L400
L383:
  mov    $0x0,%eax
  jmp    L400
  mov    -0x8(%rbp),%rax
  add    $0xa,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x20,%eax
  test   %eax,%eax
  je     L483
  mov    -0x8(%rbp),%rax
  add    $0xb,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x3,%eax
  test   %eax,%eax
  je     L96
  mov    $0x4c,%eax
  jmp    L400
L96:
  mov    $0xc,%eax
  jmp    L400
L483:
  mov    $0x0,%eax
  jmp    L400
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0xf0,%eax
  cmp    $0x10,%eax
  jne    L461
  mov    -0x8(%rbp),%rax
  add    $0x7,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x1,%eax
  test   %eax,%eax
  je     L461
  mov    $0xa,%eax
  jmp    L400
L461:
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0xf0,%eax
  cmp    $0x20,%eax
  jne    L422
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x1,%eax
  test   %eax,%eax
  jne    L422
  mov    -0x8(%rbp),%rax
  add    $0x6,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x2,%eax
  test   %eax,%eax
  je     L422
  mov    $0x9,%eax
  jmp    L400
L422:
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0xf0,%eax
  cmp    $0x20,%eax
  jne    L360
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x1,%eax
  test   %eax,%eax
  je     L360
  mov    -0x8(%rbp),%rax
  add    $0x9,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x2,%eax
  test   %eax,%eax
  je     L360
  mov    $0xc,%eax
  jmp    L400
L360:
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0xf0,%eax
  cmp    $0x40,%eax
  jne    L291
  mov    -0x8(%rbp),%rax
  add    $0x8,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x40,%eax
  test   %eax,%eax
  jne    L116
  mov    $0x9,%eax
  jmp    L400
L116:
  mov    $0xb,%eax
  jmp    L400
L291:
  mov    $0x0,%eax
  jmp    L400
  mov    -0x8(%rbp),%rax
  add    $0x5,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  and    $0x40,%eax
  test   %eax,%eax
  je     L313
  mov    $0x8,%eax
  jmp    L400
L313:
  mov    $0x0,%eax
  jmp    L400
  mov    $0x4,%eax
  jmp    L400
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  shl    $0x8,%eax
  mov    %eax,%edx
  mov    -0x8(%rbp),%rax
  add    $0x5,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  add    %edx,%eax
  add    $0x6,%eax
  jmp    L400
  mov    -0x8(%rbp),%rax
  add    $0x4,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  shl    $0x8,%eax
  mov    %eax,%edx
  mov    -0x8(%rbp),%rax
  add    $0x5,%rax
  movzbl (%rax),%eax
  movzbl %al,%eax
  add    %edx,%eax
  add    $0x6,%eax
  jmp    L400
L326:
  mov    $0x0,%eax
  jmp    L400
L449:
  mov    $0x0,%eax
L400:
  pop    %rbp
  ret
```

assistant: ```c
unsigned int calculate_packet_size(const unsigned char *buffer) {
  if (buffer[0] != 0 || buffer[1] != 0 || buffer[2] != 1)
    return 0;
  switch (buffer[3]) {
  case 0xBA:
    if ((buffer[4] & 0xc4) == 0x44 && (buffer[6] & 4) == 4 && (buffer[8] & 4) == 4 && (buffer[9] & 1) == 1 && (buffer[12] & 3) == 3)
      return (buffer[13] & 0x7) + 14;
    if ((buffer[4] & 0xF1) == 0x21 && (buffer[6] & 1) == 1 && (buffer[8] & 1) == 1 && (buffer[9] & 0x80) == 0x80 && (buffer[11] & 1) == 1)
      return 12;
    return 0;
  case 0xB3:
    if ((buffer[10] & 0x20) == 0x20) {
      if ((buffer[11] & 3) != 0)
        return 12 + 64;
      return 12;
    }
    return 0;
  case 0xB5:
    if ((buffer[4] & 0xF0) == 0x10 && (buffer[7] & 1) == 1)
      return 10;
    if ((buffer[4] & 0xF0) == 0x20 && (buffer[4] & 1) == 0 && (buffer[6] & 2) == 2)
      return 9;
    if ((buffer[4] & 0xF0) == 0x20 && (buffer[4] & 1) == 1 && (buffer[9] & 2) == 2)
      return 12;
    if ((buffer[4] & 0xF0) == 0x40) {
      if ((buffer[8] & 0x40) == 0)
        return 9;
      else
        return 11;
    }
    return 0;
  case 0xB8:
    if ((buffer[5] & 0x40) == 0x40)
      return 8;
    return 0;
  case 0xB9:
    return 4;
  case 0xBD:
  case 0xC0 ... 0xDF:
  case 0xE0 ... 0xEF:
    return (buffer[4] << 8) + buffer[5] + 6;
  case 0xBB:
  case 0xBE:
  case 0xBF:
    return (buffer[4] << 8) + buffer[5] + 6;
  case 0:
    return 0;
  default:
    return 0;
  }
}
```