user: What would the C source look like for the assembly code provided here:

```asm
<scale2x3>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %rdi,%rbx
  mov    %esi,%ebp
  mov    %rdx,0x30(%rsp)
  mov    %ecx,%r12d
  mov    %r8d,%r13d
  mov    %r9d,%r14d
  mov    0x88(%rsp),%r15d
  cmpl   $0x1,0x80(%rsp)
  seta   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    %r12d,0x28(%rsp)
  mov    %r12d,%ecx
  mov    %rcx,0x8(%rsp)
  lea    0x0(%rbp,%rbp,1),%r12d
  mov    %r12d,%esi
  mov    %rsi,0x10(%rsp)
  mov    %ebp,%r10d
  mov    %r10,0x18(%rsp)
  lea    (%rbx,%rsi,1),%rdx
  lea    (%rbx,%r10,1),%rsi
  sub    $0x8,%rsp
  push   %r15
  push   %r14
  push   %r13
  mov    0x50(%rsp),%rax
  lea    (%rax,%rcx,1),%r9
  mov    %rax,%r8
  mov    %rax,%rcx
  mov    %rbx,%rdi
  call   <stage_scale2x3@plt>
  lea    (%r12,%rbp,1),%edx
  mov    %rdx,0x40(%rsp)
  add    %rdx,%rbx
  mov    %rbx,0x58(%rsp)
  add    $0x20,%rsp
  mov    0x80(%rsp),%edx
  sub    $0x2,%edx
  je     L3
  mov    %edx,%r12d
  mov    0x28(%rsp),%edi
  add    %edi,%edi
  mov    %edi,%edi
  mov    %rdi,0x28(%rsp)
  mov    0x30(%rsp),%rbp
L0:
  mov    0x28(%rsp),%rax
  lea    0x0(%rbp,%rax,1),%r9
  mov    %rbp,%rcx
  add    0x8(%rsp),%rbp
  mov    0x10(%rsp),%rax
  lea    (%rax,%rbx,1),%rdx
  mov    0x18(%rsp),%rax
  lea    (%rax,%rbx,1),%rsi
  sub    $0x8,%rsp
  push   %r15
  push   %r14
  push   %r13
  mov    %rbp,%r8
  mov    %rbx,%rdi
  call   <stage_scale2x3@plt>
  add    0x40(%rsp),%rbx
  add    $0x20,%rsp
  sub    $0x1,%r12d
  jne    L0
  mov    0x80(%rsp),%eax
  lea    -0x2(%rax),%eax
  mov    0x8(%rsp),%rdx
  imul   %rax,%rdx
  add    %rdx,0x30(%rsp)
  imul   0x20(%rsp),%rax
  add    %rax,0x38(%rsp)
L3:
  mov    0x8(%rsp),%r8
  mov    0x30(%rsp),%rcx
  add    %rcx,%r8
  mov    0x10(%rsp),%rdx
  mov    0x38(%rsp),%rax
  add    %rax,%rdx
  mov    0x18(%rsp),%rsi
  add    %rax,%rsi
  sub    $0x8,%rsp
  push   %r15
  push   %r14
  push   %r13
  mov    %r8,%r9
  mov    %rax,%rdi
  call   <stage_scale2x3@plt>
  add    $0x68,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
void scale2x3(void *void_dst, unsigned dst_slice, const void *void_src, unsigned src_slice, unsigned pixel, unsigned width, unsigned height, unsigned opt) {
  unsigned char *dst = (unsigned char *)void_dst;
  const unsigned char *src = (const unsigned char *)void_src;
  unsigned count;
  assert(height >= 2);
  count = height;
  stage_scale2x3((dst + (0) * dst_slice), (dst + (1) * dst_slice), (dst + (2) * dst_slice), (src + (0) * src_slice), (src + (0) * src_slice), (src + (1) * src_slice), pixel, width, opt);
  dst = (dst + (3) * dst_slice);
  count -= 2;
  while (count) {
    stage_scale2x3((dst + (0) * dst_slice), (dst + (1) * dst_slice), (dst + (2) * dst_slice), (src + (0) * src_slice), (src + (1) * src_slice), (src + (2) * src_slice), pixel, width, opt);
    dst = (dst + (3) * dst_slice);
    src = (src + (1) * src_slice);
    --count;
  }
  stage_scale2x3((dst + (0) * dst_slice), (dst + (1) * dst_slice), (dst + (2) * dst_slice), (src + (0) * src_slice), (src + (1) * src_slice), (src + (1) * src_slice), pixel, width, opt);
}
```