Track geometry: GetPlayerIndex

       Name: GetPlayerIndex                                          [Show more]
       Type: Subroutine
   Category: Track geometry
    Summary: Set the index for the player's segment in the track section buffer
             to be 32 segments behind the front segment
  Deep dive: Data structures for the track calculations
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * GetTrackSegment (Part 3 of 3) calls GetPlayerIndex


.GetPlayerIndex

 LDA frontSegmentIndex  \ Set A = the front track segment index * 3 - 96
 SEC                    \
 SBC #96                \ So this is 32 segments before the front track segment
                        \ in the track segment buffer, as each buffer entry has
                        \ three bytes

 BPL zsta1              \ If A < 0, set A = A + 120, so the index number wraps
 CLC                    \ around to the end of the stack
 ADC #120

.zsta1

 STA playerSegmentIndex \ Set playerSegmentIndex to the updated index

 RTS                    \ Return from the subroutine