user: Converte this assembly snippet into its equivalent C code:

```asm
<tracer_crc16>:
  endbr64
  cmp    $0x1,%esi
  jle    L91
  mov    (%rdi),%eax
  mov    0x4(%rdi),%edx
  lea    0x8(%rdi),%r8
  cmp    $0x2,%esi
  je     L25
  lea    -0x3(%rsi),%ecx
  lea    0xc(%rdi,%rcx,4),%rdi
  nopw   0x0(%rax,%rax,1)
L54:
  mov    (%r8),%ecx
  mov    %edx,%r9d
  add    $0x4,%r8
  lea    (%rax,%rax,1),%esi
  and    $0x80,%r9d
  cmp    $0x1,%r9d
  mov    %ecx,%r9d
  sbb    $0xffffffff,%esi
  and    $0x80,%r9d
  add    %edx,%edx
  cmp    $0x1,%r9d
  lea    (%rcx,%rcx,1),%r9d
  sbb    $0xffffffff,%edx
  test   $0x80,%al
  je     L96
  xor    $0x10,%esi
  xor    $0x41,%edx
L96:
  mov    %edx,%r10d
  lea    (%rsi,%rsi,1),%eax
  and    $0x80,%r10d
  cmp    $0x1,%r10d
  sbb    $0xffffffff,%eax
  and    $0x80,%r9d
  add    %edx,%edx
  cmp    $0x1,%r9d
  lea    0x0(,%rcx,4),%r9d
  sbb    $0xffffffff,%edx
  and    $0x80,%esi
  je     L83
  xor    $0x10,%eax
  xor    $0x41,%edx
L83:
  mov    %edx,%r10d
  lea    (%rax,%rax,1),%esi
  and    $0x80,%r10d
  cmp    $0x1,%r10d
  sbb    $0xffffffff,%esi
  and    $0x80,%r9d
  add    %edx,%edx
  cmp    $0x1,%r9d
  lea    0x0(,%rcx,8),%r9d
  sbb    $0xffffffff,%edx
  test   $0x80,%al
  je     L46
  xor    $0x10,%esi
  xor    $0x41,%edx
L46:
  mov    %edx,%r10d
  lea    (%rsi,%rsi,1),%eax
  and    $0x80,%r10d
  cmp    $0x1,%r10d
  sbb    $0xffffffff,%eax
  and    $0x80,%r9d
  add    %edx,%edx
  cmp    $0x1,%r9d
  mov    %ecx,%r9d
  sbb    $0xffffffff,%edx
  shl    $0x4,%r9d
  and    $0x80,%esi
  je     L68
  xor    $0x10,%eax
  xor    $0x41,%edx
L68:
  mov    %edx,%r10d
  lea    (%rax,%rax,1),%esi
  and    $0x80,%r10d
  cmp    $0x1,%r10d
  sbb    $0xffffffff,%esi
  and    $0x80,%r9d
  add    %edx,%edx
  cmp    $0x1,%r9d
  mov    %ecx,%r9d
  sbb    $0xffffffff,%edx
  shl    $0x5,%r9d
  test   $0x80,%al
  je     L103
  xor    $0x10,%esi
  xor    $0x41,%edx
L103:
  mov    %edx,%r10d
  lea    (%rsi,%rsi,1),%eax
  and    $0x80,%r10d
  cmp    $0x1,%r10d
  sbb    $0xffffffff,%eax
  and    $0x80,%r9d
  add    %edx,%edx
  cmp    $0x1,%r9d
  mov    %ecx,%r9d
  sbb    $0xffffffff,%edx
  shl    $0x6,%r9d
  and    $0x80,%esi
  je     L66
  xor    $0x10,%eax
  xor    $0x41,%edx
L66:
  mov    %edx,%r10d
  lea    (%rax,%rax,1),%esi
  and    $0x80,%r10d
  cmp    $0x1,%r10d
  sbb    $0xffffffff,%esi
  and    $0x80,%r9d
  add    %edx,%edx
  cmp    $0x1,%r9d
  sbb    $0xffffffff,%edx
  shl    $0x7,%ecx
  test   $0x80,%al
  je     L56
  xor    $0x10,%esi
  xor    $0x41,%edx
L56:
  mov    %edx,%r9d
  lea    (%rsi,%rsi,1),%eax
  movzbl %cl,%ecx
  and    $0x80,%r9d
  cmp    $0x1,%r9d
  sbb    $0xffffffff,%eax
  add    %edx,%edx
  cmp    $0x1,%ecx
  sbb    $0xffffffff,%edx
  and    $0x80,%esi
  je     L28
  xor    $0x10,%eax
  xor    $0x41,%edx
L28:
  cmp    %r8,%rdi
  jne    L54
L25:
  shl    $0x8,%eax
  or     %edx,%eax
  ret
L91:
  mov    $0xdead,%eax
  ret
```

assistant: ```c
uint16_t tracer_crc16(uint8_t *buf, uint16_t len) {
  uint8_t crc_i, crc_j, r1, r2, r3, r4;
  uint16_t crc;
  if (len < 2)
    return 0xdead;
  r1 = *buf;
  buf++;
  r2 = *buf;
  buf++;
  for (crc_i = 0; crc_i < len - 2; crc_i++) {
    r3 = *buf;
    buf++;
    for (crc_j = 0; crc_j < 8; crc_j++) {
      r4 = r1;
      r1 = (r1 << 1);
      if ((r2 & 0x80) != 0) {
        r1++;
      }
      r2 = r2 << 1;
      if ((r3 & 0x80) != 0) {
        r2++;
      }
      r3 = r3 << 1;
      if ((r4 & 0x80) != 0) {
        r1 = r1 ^ 0x10;
        r2 = r2 ^ 0x41;
      }
    }
  }
  crc = r1;
  crc = crc << 8 | r2;
  return (crc);
}
```