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ReC98/th04/score[bss].asm

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[Reverse-engineering] [th04/th05] Score variables In which ZUN uses little-endian BCD as the exclusive internal storage for both the current and the high score. Which are then updated using, once again, ridiculously micro-optimized ASM code that uses the venerable x86 BCD instructions. Funded by -Tom-.
2019-03-03 18:41:25 +00:00
; Scores and high scores are exclusively stored in little-endian BCD format
; internally. Points are added via adding regular integers to [score_delta],
; which is then taken "times 10" ([score_delta] += 1 → 10 more on-screen
; points).
[Reverse-engineering] [th02/th04/th05] Score update and display The TH02 version is a piece of cake… … but TH04 starts turning it into this un-decompilable piece of unnecessarily micro-optimized ZUN code. Couldn't have chosen anything better for the first separate ASM translation unit. Aside from now having to convert names of exported *variables* to uppercase for visibility in ASM translation units, the most notable lesson in this was the one about avoiding fixup overflows. From the Borland C++ Version 4.0 User's Guide: "In an assembly language program, a fixup overflow frequently occurs if you have declared an external variable within a segment definition, but this variable actually exists in a different segment." Can't be restated often enough. Completes P0032, funded by zorg.
2019-09-18 16:33:38 +00:00
public _CONTINUES_USED, _SCORE_LEBCD, _HISCORE_LEBCD
public _SCORE_DELTA, _SCORE_DELTA_FRAME
[Reverse-engineering] [th04/th05] Score variables In which ZUN uses little-endian BCD as the exclusive internal storage for both the current and the high score. Which are then updated using, once again, ridiculously micro-optimized ASM code that uses the venerable x86 BCD instructions. Funded by -Tom-.
2019-03-03 18:41:25 +00:00
label _continues_used byte
_score_lebcd db SCORE_DIGITS dup(?)
_hiscore_lebcd db SCORE_DIGITS dup(?)
if GAME eq 4
[Reverse-engineering] [th02/th04/th05] Score update and display The TH02 version is a piece of cake… … but TH04 starts turning it into this un-decompilable piece of unnecessarily micro-optimized ZUN code. Couldn't have chosen anything better for the first separate ASM translation unit. Aside from now having to convert names of exported *variables* to uppercase for visibility in ASM translation units, the most notable lesson in this was the one about avoiding fixup overflows. From the Borland C++ Version 4.0 User's Guide: "In an assembly language program, a fixup overflow frequently occurs if you have declared an external variable within a segment definition, but this variable actually exists in a different segment." Can't be restated often enough. Completes P0032, funded by zorg.
2019-09-18 16:33:38 +00:00
public _SCORE_UNUSED
[Reverse-engineering] [th04/th05] Score variables In which ZUN uses little-endian BCD as the exclusive internal storage for both the current and the high score. Which are then updated using, once again, ridiculously micro-optimized ASM code that uses the venerable x86 BCD instructions. Funded by -Tom-.
2019-03-03 18:41:25 +00:00
_score_unused db ?
endif
_score_delta dd ?
; Amount of points transferred from [score_delta] to [score_lebcd] this frame.
_score_delta_frame dd ?