## Encode a VNC PointerEvent.  See also pointerevent.c, file
        ## `yeso-vnc.md` in pavnotes2, and file
        ## `binary-serialization.md` in pavnotes2.
        .intel_syntax noprefix
        .globl encode_pointer_event
encode_pointer_event:   
        mov rax, [rdi]             # load buffer pointer from buffer struct
        lea rax, [rax + 6]         # add 6 bytes to buffer pointer
        cmp rax, [rdi + 8]         # compare to buffer end pointer
        jae 1f                     # jump to buffer reallocation code if necessary
        mov byte ptr [rax - 6], 5  # store type byte into buffer
        mov rcx, [rsi]             # load button mask field from in-memory struct
        mov [rax - 5], cl          # store buttons byte into buffer
        mov rcx, [rsi + 8]         # load x position from in-memory struct
        mov [rax - 4], ch          # store bytes in big-endian order
        mov [rax - 3], cl          # (there’s probably a better way to byteswap)
        mov rcx, [rsi + 16]        # load y position from in-memory struct
        mov [rax - 2], ch       
        mov [rax - 1], cl       
        mov [rdi], rax             # update buffer pointer
        ret
        ## buffer reallocation code would follow
    1: