user: 提供的汇编代码用C语言表示会是什么样子：

```asm
<cBytesLshiftfromlentolen>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x28,%rsp
  mov    %rsi,%r10
  mov    %edx,0x18(%rsp)
  mov    %rcx,0x10(%rsp)
  mov    %edi,%r12d
  sar    $0x3,%r12d
  mov    %edi,%eax
  sar    $0x1f,%eax
  shr    $0x1d,%eax
  lea    (%rdi,%rax,1),%r9d
  and    $0x7,%r9d
  sub    %eax,%r9d
  test   $0x7,%dil
  je     L64
  mov    %edi,%r11d
  test   %r9d,%r9d
  jle    L73
  mov    %edi,%ecx
  and    $0x7,%ecx
  mov    $0xff,%eax
  shr    %cl,%eax
  mov    %eax,0xc(%rsp)
L121:
  test   %r12d,%r12d
  jle    L100
  mov    0x10(%rsp),%rbx
  mov    %rbx,%rax
  lea    -0x1(%r12),%edx
  lea    0x1(%rbx,%rdx,1),%rdx
L21:
  movb   $0x0,(%rax)
  add    $0x1,%rax
  cmp    %rdx,%rax
  jne    L21
L100:
  sub    %r12d,%r8d
  mov    %r8d,0x1c(%rsp)
  cmp    $0x1,%r8d
  jle    L119
  lea    -0x2(%r8),%r15d
  mov    $0x0,%r8d
  mov    $0x0,%eax
  mov    %r11d,%r14d
  and    $0x7,%r14d
  mov    %r9d,%r13d
  neg    %r13d
  movslq %r12d,%rbp
  add    0x10(%rsp),%rbp
  mov    $0x8,%ebx
  sub    %r9d,%ebx
  jmp    L112
L64:
  lea    -0x1(%r8),%edx
  mov    $0x0,%r8d
  mov    %rsi,%rcx
  mov    %r12d,%esi
  mov    0x10(%rsp),%rdi
  call   <cBytesReplacefromtowithstartingAt@plt>
  jmp    L101
L73:
  mov    %r9d,%ecx
  neg    %ecx
  mov    $0xff,%eax
  shl    %cl,%eax
  mov    %eax,0xc(%rsp)
  jmp    L121
L82:
  mov    %rdx,%r8
L112:
  movzbl (%r10,%r8,1),%edi
  movzbl %dil,%esi
  mov    0xc(%rsp),%edx
  and    %esi,%edx
  mov    %r14d,%ecx
  shl    %cl,%edx
  and    0xc(%rsp),%esi
  mov    %r13d,%ecx
  shr    %cl,%esi
  test   %r9d,%r9d
  cmovs  %esi,%edx
  or     %eax,%edx
  mov    %dl,0x0(%rbp,%r8,1)
  movzbl %dil,%edi
  mov    %edi,%eax
  mov    %ebx,%ecx
  shr    %cl,%eax
  lea    0x1(%r8),%rdx
  cmp    %r8,%r15
  jne    L82
L27:
  mov    0x1c(%rsp),%esi
  sub    $0x1,%esi
  mov    $0x0,%edx
  cmp    0x18(%rsp),%esi
  jge    L20
  movslq %esi,%rdx
  movzbl (%r10,%rdx,1),%edx
L20:
  test   %r9d,%r9d
  js     L87
  and    0xc(%rsp),%edx
  mov    %r11d,%ecx
  and    $0x7,%ecx
  shl    %cl,%edx
L79:
  add    %esi,%r12d
  movslq %r12d,%r12
  or     %eax,%edx
  mov    0x10(%rsp),%rax
  mov    %dl,(%rax,%r12,1)
L101:
  add    $0x28,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L119:
  mov    $0x0,%eax
  jmp    L27
L87:
  and    0xc(%rsp),%edx
  mov    %r9d,%ecx
  neg    %ecx
  shr    %cl,%edx
  jmp    L79
```

assistant: ```c
int cBytesLshiftfromlentolen(int shiftCount, unsigned char *pFrom, int lenFrom, unsigned char *pTo, int lenTo) {
  int limit;
  int lastIx;
  int i;
  int carry;
  int byteShift;
  int rShift;
  int mask;
  int digit;
  int bitShift;
  byteShift = ((int)shiftCount >> 3);
  bitShift = shiftCount % 8;
  if (bitShift == 0) {
    return cBytesReplacefromtowithstartingAt(pTo, byteShift, lenTo - 1, pFrom, 0);
  }
  carry = 0;
  rShift = bitShift - 8;
  mask = (((0 - bitShift) < 0) ? ((unsigned)255 >> -(0 - bitShift)) : ((unsigned)255 << (0 - bitShift)));
  limit = byteShift - 1;
  for (i = 0; i <= limit; i += 1) {
    pTo[i] = 0;
  }
  limit = (lenTo - byteShift) - 2;
  ;
l1:;
  for (i = 0; i <= limit; i += 1) {
    digit = pFrom[i];
    pTo[i + byteShift] = ((((bitShift < 0) ? ((unsigned)(digit & mask) >> -bitShift) : ((unsigned)(digit & mask) << bitShift))) | carry);
    carry = ((rShift < 0) ? ((unsigned)digit >> -rShift) : ((unsigned)digit << rShift));
  }
  lastIx = limit + 1;
  if (lastIx > (lenFrom - 1)) {
    digit = 0;
  } else {
    digit = pFrom[lastIx];
  }
  pTo[lastIx + byteShift] = ((((bitShift < 0) ? ((unsigned)(digit & mask) >> -bitShift) : ((unsigned)(digit & mask) << bitShift))) | carry);
  carry = ((rShift < 0) ? ((unsigned)digit >> -rShift) : ((unsigned)digit << rShift));
  ;
l2:;
}
```