user: 请从给定的汇编指令推导出C源代码：

```asm
<my_crc32c_sse42>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x30,%rsp
  mov    %rdi,-0x28(%rbp)
  mov    %rsi,-0x30(%rbp)
  mov    -0x28(%rbp),%rax
  mov    %rax,-0x10(%rbp)
  movl   $0xffffffff,-0x18(%rbp)
  movq   $0x0,-0x8(%rbp)
  jmp    L61
L62:
  mov    -0x10(%rbp),%rax
  mov    (%rax),%edx
  mov    -0x18(%rbp),%eax
  mov    %edx,%esi
  mov    %eax,%edi
  call   <my_asm_crc32_u64@plt>
  mov    %eax,-0x18(%rbp)
  addq   $0x10,-0x10(%rbp)
  addq   $0x1,-0x8(%rbp)
L61:
  mov    -0x30(%rbp),%rax
  shr    $0x2,%rax
  cmp    %rax,-0x8(%rbp)
  jb     L62
  mov    -0x18(%rbp),%eax
  mov    %eax,-0x14(%rbp)
  andq   $0x3,-0x30(%rbp)
  cmpq   $0x7,-0x30(%rbp)
  ja     L18
  mov    -0x30(%rbp),%rax
  lea    0x0(,%rax,4),%rdx
  lea    D15(%rip),%rax
  mov    (%rdx,%rax,1),%eax
  cltq
  lea    D15(%rip),%rdx
  add    %rdx,%rax
  notrack jmp *%rax
  mov    -0x10(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    %rdx,-0x10(%rbp)
  mov    (%rax),%edx
  mov    -0x14(%rbp),%eax
  mov    %edx,%esi
  mov    %eax,%edi
  call   <my_asm_crc32_u8@plt>
  mov    %eax,-0x14(%rbp)
  mov    -0x10(%rbp),%rax
  mov    (%rax),%edx
  mov    -0x14(%rbp),%eax
  mov    %edx,%esi
  mov    %eax,%edi
  call   <my_asm_crc32_u16@plt>
  mov    %eax,-0x14(%rbp)
  addq   $0x8,-0x10(%rbp)
  mov    -0x10(%rbp),%rax
  mov    (%rax),%edx
  mov    -0x14(%rbp),%eax
  mov    %edx,%esi
  mov    %eax,%edi
  call   <my_asm_crc32_u32@plt>
  mov    %eax,-0x14(%rbp)
  jmp    L38
  mov    -0x10(%rbp),%rax
  lea    0x4(%rax),%rdx
  mov    %rdx,-0x10(%rbp)
  mov    (%rax),%edx
  mov    -0x14(%rbp),%eax
  mov    %edx,%esi
  mov    %eax,%edi
  call   <my_asm_crc32_u8@plt>
  mov    %eax,-0x14(%rbp)
  mov    -0x10(%rbp),%rax
  mov    (%rax),%edx
  mov    -0x14(%rbp),%eax
  mov    %edx,%esi
  mov    %eax,%edi
  call   <my_asm_crc32_u16@plt>
  mov    %eax,-0x14(%rbp)
  jmp    L38
  mov    -0x10(%rbp),%rax
  mov    (%rax),%edx
  mov    -0x14(%rbp),%eax
  mov    %edx,%esi
  mov    %eax,%edi
  call   <my_asm_crc32_u32@plt>
  mov    %eax,-0x14(%rbp)
  addq   $0x10,-0x10(%rbp)
  mov    -0x10(%rbp),%rax
  mov    (%rax),%edx
  mov    -0x14(%rbp),%eax
  mov    %edx,%esi
  mov    %eax,%edi
  call   <my_asm_crc32_u8@plt>
  mov    %eax,-0x14(%rbp)
  jmp    L38
L18:
  nop
  jmp    L38
  nop
L38:
  mov    -0x14(%rbp),%eax
  not    %eax
  leave
  ret
```

assistant: ```c
uint32_t my_crc32c_sse42(const uint8_t *buf, size_t len) {
  const uint8_t *p = buf;
  uint64_t crc64bit = 0xFFFFFFFF;
  for (size_t i = 0; i < len / sizeof(uint64_t); i++) {
    crc64bit = my_asm_crc32_u64(crc64bit, *(uint64_t *)p);
    p += sizeof(uint64_t);
  }
  uint32_t crc32bit = (uint32_t)crc64bit;
  len &= sizeof(uint64_t) - 1;
  switch (len) {
  case 7:
    crc32bit = my_asm_crc32_u8(crc32bit, *p++);
  case 6:
    crc32bit = my_asm_crc32_u16(crc32bit, *(uint16_t *)p);
    p += 2;
  case 4:
    crc32bit = my_asm_crc32_u32(crc32bit, *(uint32_t *)p);
    break;
  case 3:
    crc32bit = my_asm_crc32_u8(crc32bit, *p++);
  case 2:
    crc32bit = my_asm_crc32_u16(crc32bit, *(uint16_t *)p);
    break;
  case 5:
    crc32bit = my_asm_crc32_u32(crc32bit, *(uint32_t *)p);
    p += 4;
  case 1:
    crc32bit = my_asm_crc32_u8(crc32bit, *p);
    break;
  case 0:
    break;
  default:
    break;
  }
  return ~crc32bit;
}
```