user: 请显示与下面列出的汇编代码相匹配的C语言实现：

```asm
<des_decrypt>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x40,%rsp
  mov    %rdi,-0x28(%rbp)
  mov    %esi,-0x2c(%rbp)
  mov    %rdx,-0x38(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x8(%rbp)
  xor    %eax,%eax
  movb   $0x0,-0x1f(%rbp)
  cmpq   $0x0,-0x38(%rbp)
  jne    L78
  mov    -0x2c(%rbp),%eax
  jmp    L97
L78:
  mov    -0x2c(%rbp),%eax
  sub    $0x2,%eax
  and    $0x7,%eax
  test   %eax,%eax
  jne    L16
  cmpl   $0x11,-0x2c(%rbp)
  jg     L46
L16:
  mov    $0xffffffff,%eax
  jmp    L97
L46:
  subl   $0x8,-0x2c(%rbp)
  mov    -0x2c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  lea    -0x10(%rbp),%rax
  mov    $0x8,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  movl   $0x2,-0x1c(%rbp)
  jmp    L101
L137:
  movb   $0x3,-0x1d(%rbp)
  lea    -0x10(%rbp),%rcx
  lea    -0x18(%rbp),%rax
  mov    $0x8,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  lea    -0x10(%rbp),%rax
  mov    $0x8,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  movzbl -0x1d(%rbp),%edx
  mov    -0x38(%rbp),%rax
  lea    0x8(%rax),%rsi
  mov    -0x38(%rbp),%rax
  mov    %rcx,%r8
  mov    $0x0,%ecx
  mov    %rax,%rdi
  call   <EuroDes@plt>
  movb   $0x0,-0x1e(%rbp)
  jmp    L17
L125:
  movzbl -0x1e(%rbp),%edx
  mov    -0x1c(%rbp),%eax
  add    %edx,%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  mov    %eax,%edx
  movzbl -0x1e(%rbp),%eax
  cltq
  movzbl -0x18(%rbp,%rax,1),%eax
  mov    %edx,%ecx
  xor    %eax,%ecx
  movzbl -0x1e(%rbp),%edx
  mov    -0x1c(%rbp),%eax
  add    %edx,%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  mov    %ecx,%edx
  mov    %dl,(%rax)
  movzbl -0x1e(%rbp),%eax
  add    $0x1,%eax
  mov    %al,-0x1e(%rbp)
L17:
  cmpb   $0x7,-0x1e(%rbp)
  jbe    L125
  addl   $0x8,-0x1c(%rbp)
L101:
  mov    -0x1c(%rbp),%eax
  cmp    -0x2c(%rbp),%eax
  jl     L137
  movl   $0x2,-0x1c(%rbp)
  jmp    L62
L122:
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%eax
  xor    %al,-0x1f(%rbp)
  addl   $0x1,-0x1c(%rbp)
L62:
  mov    -0x1c(%rbp),%eax
  cmp    -0x2c(%rbp),%eax
  jl     L122
  cmpb   $0x0,-0x1f(%rbp)
  je     L39
  mov    $0xffffffff,%eax
  jmp    L97
L39:
  mov    -0x2c(%rbp),%eax
L97:
  mov    -0x8(%rbp),%rdx
  sub    %fs:0x28,%rdx
  je     L133
  call   <__stack_chk_fail@plt>
L133:
  leave
  ret
```

assistant: ```c
int des_decrypt(unsigned char *buffer, int len, unsigned char *deskey) {
  char ivec[8];
  char nextIvec[8];
  int i;
  unsigned char checksum = 0;
  if (!deskey)
    return len;
  if ((len - 2) % 8 || (len - 2) < 16)
    return -1;
  len -= 8;
  memcpy(nextIvec, buffer + len, 8);
  for (i = 2; i < len; i += 8) {
    unsigned char j;
    const unsigned char flags = (1 << 0) | (1 << 1);
    memcpy(ivec, nextIvec, 8);
    memcpy(nextIvec, buffer + i, 8);
    EuroDes(deskey, deskey + 8, flags, 0, buffer + i);
    for (j = 0; j < 8; j++)
      buffer[i + j] ^= ivec[j];
  }
  for (i = 2; i < len; i++)
    checksum ^= buffer[i];
  if (checksum)
    return -1;
  return len;
}
```