//
// New Animated File Format
//

// xxx_xxxx_xxxx_xxx is the number of bytes 1-16384 to follow (0 == 1 byte)

%0xxx_xxxx_xxxx_xxx1 - Copy Bytes - straight copy bytes
%1xxx_xxxx_xxxx_xxx1 - Skip Bytes - skip bytes / move the cursor
%1xxx_xxxx_xxxx_xxx0 - Dictionary Copy Bytes from  frame buffer to frame buffer

%0000_0000_0000_0000- Source Skip -> Source pointer skips to next bank of data
%0000_0000_0000_0010- End of Frame - end of frame
%0000_0000_0000_0110- End of Animation / End of File / no more frames

// other remaining codes, are reserved for future expansion


16 bit opcode

%1 xxx xxxx xxxx xxx 0
%0 xxx xxxx xxxx xxx 0

// X = SRC
// Y = DST

// Source Data Stream Copy
// Dictionary Copy
// xx xxxx xxxx xxxx // up to 16384 length of copy (0 is a copy length of 1 byte, so it's length-1)

// Copy this code to your direct page, please make sure it's aligned to a page
// The buffer is hardcoded to be at $012000, to take advantage of fast reads

// pass in a pointer to the start of the compressed stream
// ldx #offset in source bank
// lda #source bank
// we assume all next bank data is sequential from this first bank, but it
// wouldn't be hard to work from a list of banks, to make the player more
// friendly

//---  this code sits at location $0 in the DP register
//---  DP may be anywhere in bank 0, but make sure it's PAGE aligned
//---- for performance reasons

        org $0
        mx %00
        phb
        sep #$30
        sta <srcbank+1           // self modify the code for mvn
        sta <read_opcode+3       // data stream reader
        sta <dictionary_offset+3 // opcode stream reader
        rep #$31
        ldy #$2000              // it's a new frame, cursor starts at beginning of SHR

        bra     read_opcode

extended_command

        lsr
        bcs :not end of frame

        ldy #$2000
        // check elapsed ticks (need at least 1)

        // For now just inline vsync (preferable to check the number of
        // if jiffy that have elapsed, because if the animation uses more than
        // roughly 10% of the screen we don't want to sync here


        bra read_opcode

:end_of_file
        plb    // restore bank
        rtl

:not_end_of_frame
        beq :end_of_file

        cmp #1
        bne :not_new_bank

        // source data, new bank
        inc <read_opcode+3        // 6
        inc <dictionary_offset+3  // 6

        // start of new bank
        ldx #0

:not_new_bank
       
        ; currently reserved
        bra read_opcode

stream_copy:
        inx
        inx
        lsr
        bcc extended_command
srcbank:
        mvn ss,dd
read_opcode:
        ldal opcode,x
        bpl stream_copy
        inx
        inx
dictionary_copy:
        and #$7FFF
        lsr
        bcs cursor_skip

        sta <temp

        stx <dictionary_offset+1
dictionary_offset
        ldal dictionary_offset
        tax

        lda <temp
        // dictionary copy
        mvn dd,dd

        ldx <dictionary_ofset+1
        inx
        inx

        bra read_opcode

cursor_skip
        sty temp
        adc temp
        tay
        bra read_opcode