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https://github.com/deater/dos33fsprogs.git
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64 lines
1.4 KiB
ArmAsm
64 lines
1.4 KiB
ArmAsm
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;====================================
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; do a full lookup, takes much longer
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; used to be a separate function but we inlined it here
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;====================
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; lookup_map
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;====================
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; finds value in space_x.i,space_y.i
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; returns color in A
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; CLOBBERS: A,Y
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lda SPACEX_I ; 3
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sta spacex_label+1 ; self modifying code, LAST_SPACEX_I ; 4
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and #CONST_MAP_MASK_X ; wrap at 64 ; 2
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sta SPACEX_I ; store i patch out ; 3
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tay ; copy to Y for later ; 2
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lda SPACEY_I ; 3
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sta spacey_label+1 ; self modifying code, LAST_SPACEY_I ; 4
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and #CONST_MAP_MASK_Y ; wrap to 64x64 grid ; 2
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sta SPACEY_I ; 3
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asl ; 2
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asl ; 2
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asl ; multiply by 8 ; 2
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clc ; 2
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adc SPACEX_I ; add in X value ; 3
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; only valid if x<8 and y<8
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; SPACEX_I is also in y
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cpy #$8 ; 2
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;============
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; 39
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bcs @ocean_color ; bgt 8 ; 2nt/3
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ldy SPACEY_I ; 3
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cpy #$8 ; 2
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;=============
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; 7
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bcs @ocean_color ; bgt 8 ; 2nt/3
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tay ; 2
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lda flying_map,Y ; load from array ; 4
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bcc @update_cache ; 3
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;============
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; 11
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@ocean_color:
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and #$1f ; 2
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tay ; 2
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lda water_map,Y ; the color of the sea ; 4
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;===========
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; 8
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@update_cache:
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sta map_color_label+1 ; self-modifying ; 4
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;===========
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; 4
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; rts ; 6
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