user: Demonstrate the C code that generates the assembly output below:

```asm
<uint64Pack>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x20,%rsp
  mov    %rdi,-0x8(%rbp)
  mov    %rsi,-0x10(%rbp)
  mov    %rdx,-0x18(%rbp)
  mov    %rcx,-0x20(%rbp)
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x4(%rax),%rdx
  mov    -0x18(%rbp),%rcx
  mov    -0x10(%rbp),%rax
  mov    %rcx,%rsi
  mov    %rax,%rdi
  call   <size_buffer@plt>
  mov    -0x8(%rbp),%rax
  mov    (%rax),%eax
  mov    $0x38,%edx
  mov    %edx,%ecx
  sar    %cl,%eax
  mov    %eax,%edi
  mov    -0x10(%rbp),%rax
  mov    (%rax),%rsi
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x1(%rax),%rcx
  mov    -0x20(%rbp),%rdx
  mov    %rcx,(%rdx)
  add    %rsi,%rax
  mov    %edi,%edx
  mov    %dl,(%rax)
  mov    -0x8(%rbp),%rax
  mov    (%rax),%eax
  mov    $0x30,%edx
  mov    %edx,%ecx
  sar    %cl,%eax
  mov    %eax,%edi
  mov    -0x10(%rbp),%rax
  mov    (%rax),%rsi
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x1(%rax),%rcx
  mov    -0x20(%rbp),%rdx
  mov    %rcx,(%rdx)
  add    %rsi,%rax
  mov    %edi,%edx
  mov    %dl,(%rax)
  mov    -0x8(%rbp),%rax
  mov    (%rax),%eax
  mov    $0x28,%edx
  mov    %edx,%ecx
  sar    %cl,%eax
  mov    %eax,%edi
  mov    -0x10(%rbp),%rax
  mov    (%rax),%rsi
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x1(%rax),%rcx
  mov    -0x20(%rbp),%rdx
  mov    %rcx,(%rdx)
  add    %rsi,%rax
  mov    %edi,%edx
  mov    %dl,(%rax)
  mov    -0x8(%rbp),%rax
  mov    (%rax),%eax
  mov    $0x20,%edx
  mov    %edx,%ecx
  sar    %cl,%eax
  mov    %eax,%edi
  mov    -0x10(%rbp),%rax
  mov    (%rax),%rsi
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x1(%rax),%rcx
  mov    -0x20(%rbp),%rdx
  mov    %rcx,(%rdx)
  add    %rsi,%rax
  mov    %edi,%edx
  mov    %dl,(%rax)
  mov    -0x8(%rbp),%rax
  mov    (%rax),%eax
  shr    $0x18,%eax
  mov    %eax,%edi
  mov    -0x10(%rbp),%rax
  mov    (%rax),%rsi
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x1(%rax),%rcx
  mov    -0x20(%rbp),%rdx
  mov    %rcx,(%rdx)
  add    %rsi,%rax
  mov    %edi,%edx
  mov    %dl,(%rax)
  mov    -0x8(%rbp),%rax
  mov    (%rax),%eax
  sar    $0x10,%eax
  mov    %eax,%edi
  mov    -0x10(%rbp),%rax
  mov    (%rax),%rsi
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x1(%rax),%rcx
  mov    -0x20(%rbp),%rdx
  mov    %rcx,(%rdx)
  add    %rsi,%rax
  mov    %edi,%edx
  mov    %dl,(%rax)
  mov    -0x8(%rbp),%rax
  mov    (%rax),%eax
  sar    $0x8,%eax
  mov    %eax,%edi
  mov    -0x10(%rbp),%rax
  mov    (%rax),%rsi
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x1(%rax),%rcx
  mov    -0x20(%rbp),%rdx
  mov    %rcx,(%rdx)
  add    %rsi,%rax
  mov    %edi,%edx
  mov    %dl,(%rax)
  mov    -0x8(%rbp),%rax
  mov    (%rax),%esi
  mov    -0x10(%rbp),%rax
  mov    (%rax),%rdi
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  lea    0x1(%rax),%rcx
  mov    -0x20(%rbp),%rdx
  mov    %rcx,(%rdx)
  add    %rdi,%rax
  mov    %esi,%edx
  mov    %dl,(%rax)
  mov    $0x4,%eax
  leave
  ret
```

assistant: ```c
size_t uint64Pack(const uint64_t *data, char **buffer, size_t *size, size_t *pos) {
  size_buffer(buffer, size, *pos + sizeof(uint64_t));
  (*buffer)[(*pos)++] = (*data >> 56) & 0xFF;
  (*buffer)[(*pos)++] = (*data >> 48) & 0xFF;
  (*buffer)[(*pos)++] = (*data >> 40) & 0xFF;
  (*buffer)[(*pos)++] = (*data >> 32) & 0xFF;
  (*buffer)[(*pos)++] = (*data >> 24) & 0xFF;
  (*buffer)[(*pos)++] = (*data >> 16) & 0xFF;
  (*buffer)[(*pos)++] = (*data >> 8) & 0xFF;
  (*buffer)[(*pos)++] = (*data >> 0) & 0xFF;
  return sizeof(uint64_t);
}
```