user: What is the c source code of the assembly code below:

```asm
<avg_420_downsample_ag_rb_vectors_sse2>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %rdi,-0x38(%rbp)
  mov    %rsi,-0x40(%rbp)
  mov    %rdx,-0x48(%rbp)
  movl   $0x0,-0x30(%rbp)
  movl   $0x0,-0x2c(%rbp)
  movl   $0x0,-0x28(%rbp)
  movl   $0x0,-0x24(%rbp)
  movl   $0x0,-0x20(%rbp)
  movl   $0x0,-0x1c(%rbp)
  movl   $0x0,-0x18(%rbp)
  movl   $0x0,-0x14(%rbp)
  mov    -0x40(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  mov    (%rdx),%rsi
  mov    (%rax),%rdi
  call   <_mm_avg_epu16@plt>
  mov    %rax,-0x30(%rbp)
  mov    -0x40(%rbp),%rax
  lea    0x10(%rax),%rdx
  mov    -0x38(%rbp),%rax
  add    $0x10,%rax
  mov    (%rdx),%rsi
  mov    (%rax),%rdi
  call   <_mm_avg_epu16@plt>
  mov    %rax,-0x28(%rbp)
  mov    -0x30(%rbp),%rax
  mov    $0x8d,%esi
  mov    %rax,%rdi
  call   <_mm_shuffle_epi32@plt>
  mov    %rax,-0x30(%rbp)
  mov    -0x28(%rbp),%rax
  mov    $0x8d,%esi
  mov    %rax,%rdi
  call   <_mm_shuffle_epi32@plt>
  mov    %rax,-0x28(%rbp)
  mov    -0x28(%rbp),%rdx
  mov    -0x30(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <_mm_unpacklo_epi64@plt>
  mov    %rax,-0x20(%rbp)
  mov    -0x28(%rbp),%rdx
  mov    -0x30(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <_mm_unpackhi_epi64@plt>
  mov    %rax,-0x18(%rbp)
  mov    -0x18(%rbp),%rdx
  mov    -0x20(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <_mm_avg_epu16@plt>
  mov    %rax,%rdx
  mov    -0x48(%rbp),%rax
  mov    %rdx,(%rax)
  mov    -0x40(%rbp),%rax
  lea    0x8(%rax),%rdx
  mov    -0x38(%rbp),%rax
  add    $0x8,%rax
  mov    (%rdx),%rsi
  mov    (%rax),%rdi
  call   <_mm_avg_epu16@plt>
  mov    %rax,-0x30(%rbp)
  mov    -0x40(%rbp),%rax
  lea    0x18(%rax),%rdx
  mov    -0x38(%rbp),%rax
  add    $0x18,%rax
  mov    (%rdx),%rsi
  mov    (%rax),%rdi
  call   <_mm_avg_epu16@plt>
  mov    %rax,-0x28(%rbp)
  mov    -0x30(%rbp),%rax
  mov    $0x8d,%esi
  mov    %rax,%rdi
  call   <_mm_shuffle_epi32@plt>
  mov    %rax,-0x30(%rbp)
  mov    -0x28(%rbp),%rax
  mov    $0x8d,%esi
  mov    %rax,%rdi
  call   <_mm_shuffle_epi32@plt>
  mov    %rax,-0x28(%rbp)
  mov    -0x28(%rbp),%rdx
  mov    -0x30(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <_mm_unpacklo_epi64@plt>
  mov    %rax,-0x20(%rbp)
  mov    -0x28(%rbp),%rdx
  mov    -0x30(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <_mm_unpackhi_epi64@plt>
  mov    %rax,-0x18(%rbp)
  mov    -0x48(%rbp),%rax
  lea    0x8(%rax),%rbx
  mov    -0x18(%rbp),%rdx
  mov    -0x20(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <_mm_avg_epu16@plt>
  mov    %rax,(%rbx)
  nop
  mov    -0x8(%rbp),%rbx
  leave
  ret
```

assistant: ```c
extern void avg_420_downsample_ag_rb_vectors_sse2(__m128i *in_4_v16i_current_ag_rb_vectors_1, __m128i *in_4_v16i_current_ag_rb_vectors_2, __m128i *out_2_v16i_avg_420_ag_rb_vectors) {
  __m128i scratch1 = {0x0LL, 0x0LL};
  __m128i scratch2 = {0x0LL, 0x0LL};
  __m128i scratch3 = {0x0LL, 0x0LL};
  __m128i scratch4 = {0x0LL, 0x0LL};
  (scratch1) = _mm_avg_epu16(in_4_v16i_current_ag_rb_vectors_1[0], in_4_v16i_current_ag_rb_vectors_2[0]);
  (scratch2) = _mm_avg_epu16(in_4_v16i_current_ag_rb_vectors_1[2], in_4_v16i_current_ag_rb_vectors_2[2]);
  (scratch1) = _mm_shuffle_epi32((scratch1), 0x8D);
  (scratch2) = _mm_shuffle_epi32((scratch2), 0x8D);
  (scratch3) = _mm_unpacklo_epi64((scratch1), (scratch2));
  (scratch4) = _mm_unpackhi_epi64((scratch1), (scratch2));
  out_2_v16i_avg_420_ag_rb_vectors[0] = _mm_avg_epu16((scratch3), (scratch4));
  (scratch1) = _mm_avg_epu16(in_4_v16i_current_ag_rb_vectors_1[1], in_4_v16i_current_ag_rb_vectors_2[1]);
  (scratch2) = _mm_avg_epu16(in_4_v16i_current_ag_rb_vectors_1[3], in_4_v16i_current_ag_rb_vectors_2[3]);
  (scratch1) = _mm_shuffle_epi32((scratch1), 0x8D);
  (scratch2) = _mm_shuffle_epi32((scratch2), 0x8D);
  (scratch3) = _mm_unpacklo_epi64((scratch1), (scratch2));
  (scratch4) = _mm_unpackhi_epi64((scratch1), (scratch2));
  out_2_v16i_avg_420_ag_rb_vectors[1] = _mm_avg_epu16((scratch3), (scratch4));
}
```