user: 这段汇编代码用C语言表示是什么样的:

```asm
<insert>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x30,%rsp
  mov    %rdi,-0x18(%rbp)
  mov    %esi,-0x1c(%rbp)
  mov    %edx,-0x20(%rbp)
  mov    %ecx,-0x24(%rbp)
  cmpl   $0xb,-0x24(%rbp)
  setle  %al
  movzbl %al,%eax
  mov    %eax,%edi
  mov    $0x0,%eax
  call   <assert@plt>
  mov    -0x20(%rbp),%eax
  not    %eax
  shr    $0x1f,%eax
  movzbl %al,%eax
  mov    %eax,%edi
  mov    $0x0,%eax
  call   <assert@plt>
  mov    -0x24(%rbp),%eax
  not    %eax
  shr    $0x1f,%eax
  movzbl %al,%eax
  mov    %eax,%edi
  mov    $0x0,%eax
  call   <assert@plt>
  mov    -0x20(%rbp),%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  cmp    $0x42,%eax
  setle  %al
  movzbl %al,%eax
  mov    %eax,%edi
  mov    $0x0,%eax
  call   <assert@plt>
  mov    -0x20(%rbp),%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  cltd
  shr    $0x1d,%edx
  add    %edx,%eax
  and    $0x7,%eax
  sub    %edx,%eax
  mov    %eax,%edx
  mov    $0x8,%eax
  sub    %edx,%eax
  cltd
  shr    $0x1d,%edx
  add    %edx,%eax
  and    $0x7,%eax
  sub    %edx,%eax
  mov    %eax,-0xc(%rbp)
  mov    -0x1c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0xc(%rbp),%eax
  mov    %eax,%ecx
  shl    %cl,%rdx
  mov    %rdx,%rax
  mov    %rax,-0x8(%rbp)
  mov    -0x8(%rbp),%rax
  shr    $0x10,%rax
  mov    %al,-0xf(%rbp)
  mov    -0x8(%rbp),%rax
  shr    $0x8,%rax
  mov    %al,-0xe(%rbp)
  mov    -0x8(%rbp),%rax
  mov    %al,-0xd(%rbp)
  mov    -0xc(%rbp),%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  cmp    $0x10,%eax
  jle    L19
  mov    -0x20(%rbp),%eax
  lea    0x7(%rax),%edx
  test   %eax,%eax
  cmovs  %edx,%eax
  sar    $0x3,%eax
  movslq %eax,%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rdx),%ecx
  movzbl -0xf(%rbp),%edx
  movslq %eax,%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  or     %ecx,%edx
  mov    %dl,(%rax)
  mov    -0x20(%rbp),%eax
  lea    0x7(%rax),%edx
  test   %eax,%eax
  cmovs  %edx,%eax
  sar    $0x3,%eax
  movslq %eax,%rdx
  lea    0x1(%rdx),%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rdx),%ecx
  movzbl -0xe(%rbp),%edx
  cltq
  lea    0x1(%rax),%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  or     %ecx,%edx
  mov    %dl,(%rax)
  mov    -0x20(%rbp),%eax
  lea    0x7(%rax),%edx
  test   %eax,%eax
  cmovs  %edx,%eax
  sar    $0x3,%eax
  movslq %eax,%rdx
  lea    0x2(%rdx),%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rdx),%ecx
  movzbl -0xd(%rbp),%edx
  cltq
  lea    0x2(%rax),%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  or     %ecx,%edx
  mov    %dl,(%rax)
  jmp    L21
L19:
  mov    -0xc(%rbp),%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  cmp    $0x8,%eax
  jle    L25
  mov    -0x20(%rbp),%eax
  lea    0x7(%rax),%edx
  test   %eax,%eax
  cmovs  %edx,%eax
  sar    $0x3,%eax
  movslq %eax,%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rdx),%ecx
  movzbl -0xe(%rbp),%edx
  movslq %eax,%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  or     %ecx,%edx
  mov    %dl,(%rax)
  mov    -0x20(%rbp),%eax
  lea    0x7(%rax),%edx
  test   %eax,%eax
  cmovs  %edx,%eax
  sar    $0x3,%eax
  movslq %eax,%rdx
  lea    0x1(%rdx),%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rdx),%ecx
  movzbl -0xd(%rbp),%edx
  cltq
  lea    0x1(%rax),%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  or     %ecx,%edx
  mov    %dl,(%rax)
  jmp    L21
L25:
  mov    -0x20(%rbp),%eax
  lea    0x7(%rax),%edx
  test   %eax,%eax
  cmovs  %edx,%eax
  sar    $0x3,%eax
  movslq %eax,%rcx
  mov    -0x18(%rbp),%rdx
  add    %rcx,%rdx
  movzbl (%rdx),%ecx
  movzbl -0xd(%rbp),%edx
  movslq %eax,%rsi
  mov    -0x18(%rbp),%rax
  add    %rsi,%rax
  or     %ecx,%edx
  mov    %dl,(%rax)
L21:
  nop
  leave
  ret
```

assistant: ```c
void insert(s, x, start, length) char *s;
int x;
int start, length;
{
  unsigned char cl;
  unsigned char cc;
  unsigned char cr;
  unsigned long y;
  int shift;
  assert(length <= 11);
  assert(start >= 0);
  assert(length >= 0);
  assert(start + length <= 66);
  shift = ((8 - ((start + length) % 8)) % 8);
  y = (long)x << shift;
  cl = (y >> 16) & 0xff;
  cc = (y >> 8) & 0xff;
  cr = y & 0xff;
  if (shift + length > 16) {
    s[start / 8] |= cl;
    s[start / 8 + 1] |= cc;
    s[start / 8 + 2] |= cr;
  } else if (shift + length > 8) {
    s[start / 8] |= cc;
    s[start / 8 + 1] |= cr;
  } else {
    s[start / 8] |= cr;
  }
}
```