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some comments
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@ -68,6 +68,8 @@
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;
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!ifndef USES_CLEAR {
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; if an effect doesn't use any clear stages, you can reduce code size
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; by setting USES_CLEAR=0 before including this file
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USES_CLEAR = 1
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}
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@ -82,7 +84,17 @@ hgrlo = $300 ; [$C0 bytes] HGR base addresses
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BoxesX = $200 ; [$30 bytes] starting row for each box
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BoxesY = $230 ; [$30 bytes] starting byte offset for each box
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; high bytes of drawing routines for each stage (actual routine will be page-aligned)
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; High bytes of drawing routines for each stage (actual routines will be page-aligned).
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; To minimize code size, we build drawing routines in this order:
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; - copy01 (STAGE1 template)
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; - copy00 (STAGE0 template)
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; - copy0F..copy09 (OUTER_STAGE template)
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; - copy08..copy02 (MIDDLE_STAGE template)
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; - change some opcodes to turn the 'copy' routines into 'clear' routines
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; - clear0F..clear08 (OUTER_STAGE)
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; - clear07..clear02 (MIDDLE_STAGE)
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; - clear01 (STAGE1)
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; - clear00 (STAGE0)
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clear00 = $64
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clear01 = $65
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clear02 = $66
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@ -117,7 +129,9 @@ copy00 = $82
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copy01 = $83
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; tokens for code generation
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k_rts = 0
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; used as indexes into |codegen_pieces| and |codegen_piece_lengths|,
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; so keep all three in sync
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k_rts = 0 ; must be 0
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k_inx_and_recalc = 1
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k_recalc = 2
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k_recalc_and_iny = 3
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@ -180,7 +194,9 @@ k_right_mask = 17
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bne -
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pla
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jsr GenerateStages
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; drawing routines for each stage are constructed dynamically
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; and stored at copy00..copy0F and clear00..clear0F
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jsr BuildDrawingRoutines
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; set up zero page for drawing phase
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; A=0 here
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@ -194,7 +210,6 @@ k_right_mask = 17
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; X=0 here
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+BUILD_HGR_LOOKUP_TABLES_X_IS_ALREADY_0 hgrlo, hgrhi
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; any was initialized by the BoxStages copy loop
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MainLoop ldx #48
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BoxLoop stx box
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ldy BoxStages-1, x ; for each box, get its current stage
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@ -205,7 +220,7 @@ BoxLoop stx box
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lda BoxesX-1, x
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ldy BoxesY-1, x ; Y = starting byte offset for this box
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tax ; X = starting HGR row for this box
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inc any
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inc any ; was initialized by the BoxStages copy loop
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clc
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j jsr $FD00 ; [SMC] call drawing routine for this stage
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ldx box
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@ -217,10 +232,18 @@ NextBox dex
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bit $C000
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bpl MainLoop
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+
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; execution falls through here
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; These are all the pieces of code we need to construct the drawing routines.
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; There are 32 drawing routines (16 if USES_CLEAR=0), which we construct from
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; four templates (below). Templates use tokens to refer to these code pieces.
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; Note that several pieces overlap in order to minimize code size.
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; Everything from CODEGEN_COPY_START and onward is copied to zero page for
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; the code generation phase on program startup.
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CODEGEN_COPY_START
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!pseudopc 0 {
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RTS0 ; 1 byte
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rts
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rts ; also terminates MainLoop
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RTS0_E
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INX_AND_RECALC ; 16 bytes
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inx
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@ -302,7 +325,7 @@ RIGHT_MASK ; 1 byte
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!byte $FD
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RIGHT_MASK_E
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codegen_piece_lengths
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codegen_piece_lengths ; length of each of the pieces
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!byte RTS0_E-RTS0
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!byte INX_AND_RECALC_E-INX_AND_RECALC
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!byte RECALC_E-RECALC
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@ -322,7 +345,7 @@ codegen_piece_lengths
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!byte LEFT_MASK_E-LEFT_MASK
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!byte RIGHT_MASK_E-RIGHT_MASK
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codegen_pieces
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codegen_pieces ; address of each of the pieces (on zero page, so 1 byte)
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!byte <RTS0
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!byte <INX_AND_RECALC
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!byte <RECALC
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@ -342,6 +365,8 @@ codegen_pieces
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!byte <LEFT_MASK
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!byte <RIGHT_MASK
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; Template for 'stage 0' routine (copy00), which copies the innermost
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; part of the box (labeled '0' in diagram above).
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STAGE0
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!byte k_stage_init
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!byte k_recalc
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@ -349,7 +374,10 @@ STAGE0
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!byte k_maskcopy_pre, k_left_mask, k_maskcopy_post
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!byte k_inx_and_recalc
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!byte k_maskcopy_pre, k_left_mask, k_maskcopy_post
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!byte k_rts
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!byte k_rts ; also serves as an end-of-template marker
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; Template for 'stage 1' routine (copy01), which copies the pixels
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; around the innermost box (labeled '1' in diagram above).
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STAGE1
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!byte k_stage_init
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!byte k_recalc
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@ -361,7 +389,9 @@ STAGE1
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!byte k_copy
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!byte k_inx_and_recalc
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!byte k_copy
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!byte k_rts
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!byte k_rts ; also serves as an end-of-template marker
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; Template for stages 2-8 (copy02..copy08)
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MIDDLE_STAGE
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!byte k_stage_init
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!byte k_recalc_and_iny
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@ -375,7 +405,9 @@ MIDDLE_STAGE
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!byte k_dey2
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!byte k_inx_and_recalc
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!byte k_middle_branches
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!byte k_rts
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!byte k_rts ; also serves as an end-of-template marker
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; Template for stages 9-15 (copy09..copy0F)
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OUTER_STAGE
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!byte k_stage_init
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!byte k_recalc
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@ -394,7 +426,7 @@ OUTER_STAGE
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!byte k_dey2
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!byte k_inx_and_recalc
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!byte k_outer_branches
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!byte k_rts
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!byte k_rts ; also serves as an end-of-template marker
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EdgeRightMasks
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!byte %10000001
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@ -455,7 +487,7 @@ piece_src=*+1
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lda $FD, x ; SMC
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!byte $99,$00 ; STA $4400, Y
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codegen_dst
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!byte copy01
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!byte copy01 ; SMC
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iny
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inx
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piece_length=*+1
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@ -468,7 +500,7 @@ piece_length=*+1
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rts
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}
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GenerateStages
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BuildDrawingRoutines
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; copy codegen data to zero page
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; X=0 here
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- lda CODEGEN_COPY_START, x
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@ -477,7 +509,7 @@ GenerateStages
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bne -
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; generate drawing routines for copy01, then copy00
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jsr GenerateStage1And0
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jsr BuildStage1And0
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; A=0 here
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sta <FIRST_ROW
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@ -499,7 +531,7 @@ GenerateStages
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dec <ROW_COUNT
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dec <ROW_COUNT
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dec <codegen_stage
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bmi GenerateStage1And0
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bmi BuildStage1And0
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lda <codegen_stage
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eor #13
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bne +
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@ -521,8 +553,8 @@ GenerateStages
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bmi ---
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bpl -- ; always branches
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; generate drawing routines for clear01, then clear00, then exit
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GenerateStage1And0
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; generate drawing routines for copy01, copy00 (or clear01, clear00)
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BuildStage1And0
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lda #%10111110
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sta <LEFT_MASK
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lda #<STAGE1
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