user: Translate the below assembly code into C programming language:

```asm
<checksum>:
  endbr64
  mov    $0xfe,%eax
  push   %rbx
  mov    %edi,%ebx
  mov    %rsi,%rdi
  sub    %ecx,%eax
  mov    %edx,%esi
  movzbl %dl,%edx
  sub    %edx,%eax
  cmp    $0x4,%ecx
  je     L38
  cmp    $0x2,%ecx
  jg     L20
L98:
  movzbl %bh,%edx
  sub    %edx,%eax
  movzbl %bl,%edx
  sub    %edx,%eax
  test   %esi,%esi
  jle    L93
  lea    -0x1(%rsi),%edx
  cmp    $0xe,%edx
  jbe    L147
  mov    %esi,%ecx
  pxor   %xmm0,%xmm0
  pxor   %xmm4,%xmm4
  mov    %rdi,%rdx
  shr    $0x4,%ecx
  pxor   %xmm3,%xmm3
  sub    $0x1,%ecx
  shl    $0x4,%rcx
  lea    0x10(%rdi,%rcx,1),%rcx
  nopl   0x0(%rax,%rax,1)
L150:
  movdqu (%rdx),%xmm1
  add    $0x10,%rdx
  movdqa %xmm1,%xmm2
  punpckhbw %xmm4,%xmm1
  punpcklbw %xmm4,%xmm2
  movdqa %xmm2,%xmm5
  punpckhwd %xmm3,%xmm2
  punpcklwd %xmm3,%xmm5
  psubd  %xmm5,%xmm0
  psubd  %xmm2,%xmm0
  movdqa %xmm1,%xmm2
  punpckhwd %xmm3,%xmm1
  punpcklwd %xmm3,%xmm2
  psubd  %xmm2,%xmm0
  psubd  %xmm1,%xmm0
  cmp    %rcx,%rdx
  jne    L150
  movdqa %xmm0,%xmm1
  psrldq $0x8,%xmm1
  paddd  %xmm1,%xmm0
  movdqa %xmm0,%xmm1
  psrldq $0x4,%xmm1
  paddd  %xmm1,%xmm0
  movd   %xmm0,%edx
  add    %edx,%eax
  mov    %esi,%edx
  and    $0xfffffff0,%edx
  mov    %edx,%ecx
  add    %rcx,%rdi
  cmp    %edx,%esi
  je     L93
L158:
  movzbl (%rdi),%ecx
  sub    %ecx,%eax
  lea    0x1(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x1(%rdi),%ecx
  sub    %ecx,%eax
  lea    0x2(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x2(%rdi),%ecx
  sub    %ecx,%eax
  lea    0x3(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x3(%rdi),%ecx
  sub    %ecx,%eax
  lea    0x4(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x4(%rdi),%ecx
  sub    %ecx,%eax
  lea    0x5(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x5(%rdi),%ecx
  sub    %ecx,%eax
  lea    0x6(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x6(%rdi),%ecx
  sub    %ecx,%eax
  lea    0x7(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x7(%rdi),%ecx
  sub    %ecx,%eax
  lea    0x8(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x8(%rdi),%ecx
  sub    %ecx,%eax
  lea    0x9(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0x9(%rdi),%ecx
  sub    %ecx,%eax
  lea    0xa(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0xa(%rdi),%ecx
  sub    %ecx,%eax
  lea    0xb(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0xb(%rdi),%ecx
  sub    %ecx,%eax
  lea    0xc(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0xc(%rdi),%ecx
  sub    %ecx,%eax
  lea    0xd(%rdx),%ecx
  cmp    %ecx,%esi
  jle    L93
  movzbl 0xd(%rdi),%ecx
  add    $0xe,%edx
  sub    %ecx,%eax
  cmp    %edx,%esi
  jle    L93
  movzbl 0xe(%rdi),%edx
  sub    %edx,%eax
L93:
  movzbl %al,%eax
  pop    %rbx
  ret
  nopl   0x0(%rax,%rax,1)
L38:
  mov    %ebx,%edx
  shr    $0x18,%edx
  sub    %edx,%eax
L20:
  mov    %ebx,%edx
  sar    $0x10,%edx
  movzbl %dl,%edx
  sub    %edx,%eax
  jmp    L98
L147:
  xor    %edx,%edx
  jmp    L158
```

assistant: ```c
int checksum(addr, buf, len, size)
int addr;
char buf[];
int len;
int size;
{
  char *cp = buf;
  int sum = 0xff - 1 - size - (len & 0xff);
  int i;
  if (size == 4)
    sum -= (addr >> 24) & 0xff;
  if (size >= 3)
    sum -= (addr >> 16) & 0xff;
  sum -= (addr >> 8) & 0xff;
  sum -= addr & 0xff;
  for (i = 0; i < len; ++i) {
    sum -= *cp++ & 0xff;
  }
  return sum & 0xff;
}
```