user: 请从给定的汇编指令推导出C源代码：

```asm
<gendifferentialtime>:
  endbr64
  mov    %edx,%r8d
  movzbl 0xb(%rsi),%ecx
  movzbl 0xa(%rsi),%edx
  mov    %ecx,%eax
  shr    $0x4,%al
  movzbl %al,%eax
  imul   $0x64,%eax,%eax
  and    $0xf,%ecx
  lea    (%rcx,%rcx,4),%ecx
  lea    (%rax,%rcx,2),%eax
  mov    %edx,%ecx
  shr    $0x4,%cl
  movzbl %cl,%ecx
  add    %ecx,%eax
  movzbl 0x9(%rsi),%ecx
  movzbl 0x8(%rsi),%r9d
  and    $0xf,%edx
  imul   $0x2710,%edx,%edx
  mov    %ecx,%esi
  shr    $0x4,%sil
  movzbl %sil,%esi
  imul   $0x3e8,%esi,%esi
  add    %esi,%edx
  and    $0xf,%ecx
  imul   $0x64,%ecx,%ecx
  add    %ecx,%edx
  mov    %r9d,%ecx
  shr    $0x4,%cl
  movzbl %cl,%ecx
  lea    (%rcx,%rcx,4),%ecx
  lea    (%rdx,%rcx,2),%edx
  and    $0xf,%r9d
  add    %r9d,%edx
  add    %r8d,%edx
  js     L12
  cmp    $0x1517f,%edx
  jle    L10
  sub    $0x15180,%edx
  lea    0x1(%rax),%ecx
  sub    $0x3e7,%eax
  cmp    $0x3e7,%ecx
  cmovle %ecx,%eax
  jmp    L10
L12:
  add    $0x15180,%edx
  lea    0x3e7(%rax),%ecx
  sub    $0x1,%eax
  cmovs  %ecx,%eax
L10:
  movslq %edx,%rcx
  imul   $0x66666667,%rcx,%rcx
  sar    $0x22,%rcx
  mov    %edx,%esi
  sar    $0x1f,%esi
  sub    %esi,%ecx
  movslq %ecx,%r8
  imul   $0x66666667,%r8,%r8
  sar    $0x22,%r8
  mov    %ecx,%esi
  sar    $0x1f,%esi
  sub    %esi,%r8d
  lea    (%r8,%r8,4),%r9d
  add    %r9d,%r9d
  mov    %ecx,%esi
  sub    %r9d,%esi
  shl    $0x4,%esi
  lea    (%rcx,%rcx,4),%ecx
  add    %ecx,%ecx
  sub    %ecx,%edx
  add    %esi,%edx
  mov    %dl,(%rdi)
  movslq %r8d,%rcx
  imul   $0x66666667,%rcx,%rcx
  sar    $0x22,%rcx
  mov    %r8d,%edx
  sar    $0x1f,%edx
  sub    %edx,%ecx
  movslq %ecx,%rdx
  imul   $0x66666667,%rdx,%rdx
  sar    $0x22,%rdx
  mov    %ecx,%esi
  sar    $0x1f,%esi
  sub    %esi,%edx
  lea    (%rdx,%rdx,4),%r9d
  add    %r9d,%r9d
  mov    %ecx,%esi
  sub    %r9d,%esi
  shl    $0x4,%esi
  lea    (%rcx,%rcx,4),%r9d
  add    %r9d,%r9d
  mov    %r8d,%ecx
  sub    %r9d,%ecx
  add    %esi,%ecx
  mov    %cl,0x1(%rdi)
  movslq %edx,%rcx
  imul   $0x66666667,%rcx,%rcx
  sar    $0x22,%rcx
  mov    %edx,%esi
  sar    $0x1f,%esi
  sub    %esi,%ecx
  lea    (%rcx,%rcx,4),%esi
  add    %esi,%esi
  sub    %esi,%edx
  mov    %edx,%ecx
  movslq %eax,%rdx
  imul   $0x66666667,%rdx,%rdx
  sar    $0x22,%rdx
  mov    %eax,%esi
  sar    $0x1f,%esi
  sub    %esi,%edx
  lea    (%rdx,%rdx,4),%esi
  add    %esi,%esi
  sub    %esi,%eax
  shl    $0x4,%eax
  add    %ecx,%eax
  mov    %al,0x2(%rdi)
  movslq %edx,%rax
  imul   $0x66666667,%rax,%rax
  sar    $0x22,%rax
  mov    %edx,%ecx
  sar    $0x1f,%ecx
  sub    %ecx,%eax
  movslq %eax,%rcx
  imul   $0x66666667,%rcx,%rcx
  sar    $0x22,%rcx
  mov    %eax,%esi
  sar    $0x1f,%esi
  sub    %esi,%ecx
  lea    (%rcx,%rcx,4),%esi
  add    %esi,%esi
  mov    %eax,%ecx
  sub    %esi,%ecx
  shl    $0x4,%ecx
  lea    (%rax,%rax,4),%eax
  add    %eax,%eax
  sub    %eax,%edx
  lea    (%rcx,%rdx,1),%eax
  mov    %al,0x3(%rdi)
  ret
```

assistant: ```c
void gendifferentialtime(unsigned char timebytes[4], const unsigned char *cur, int dt) {
  int newday;
  int newsec;
  newday = (cur[11] >> 4) * 100 + (cur[11] & 0x0F) * 10 + (cur[10] >> 4);
  newsec = (cur[10] & 0x0F) * 10000 + (cur[9] >> 4) * 1000 + (cur[9] & 0x0F) * 100 + (cur[8] >> 4) * 10 + (cur[8] & 0x0F);
  newsec += dt;
  if (newsec < 0) {
    newsec += 86400;
    --newday;
    if (newday < 0) {
      newday += 1000;
    }
  } else if (newsec >= 86400) {
    newsec -= 86400;
    ++newday;
    if (newday >= 1000) {
      newday -= 1000;
    }
  }
  timebytes[0] = newsec % 10;
  newsec /= 10;
  timebytes[0] += (newsec % 10) << 4;
  newsec /= 10;
  timebytes[1] = newsec % 10;
  newsec /= 10;
  timebytes[1] += (newsec % 10) << 4;
  newsec /= 10;
  timebytes[2] = newsec % 10;
  timebytes[2] += (newday % 10) << 4;
  newday /= 10;
  timebytes[3] = newday % 10;
  newday /= 10;
  timebytes[3] += (newday % 10) << 4;
}
```