mirror of https://github.com/nmlgc/ReC98.git
95 lines
1.1 KiB
NASM
95 lines
1.1 KiB
NASM
; Description:
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; atan2の整数(256度系)版
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;
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; Function
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; int pascal iatan2( int y, int x ) ;
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;
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; Author:
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; 恋塚昭彦
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;
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; History:
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; 92/ 7/29 Initial
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; 93/ 5/29 [M0.18] .CONST->.DATA
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;
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MRETURN macro
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pop BP
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ret 4
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EVEN
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endm
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; int iatan2( int y, int x ) ;
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func IATAN2
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push BP
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mov BP,SP
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; 引数
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@@y = (RETSIZE+2)*2
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@@x = (RETSIZE+1)*2
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mov CX,[BP+@@y]
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mov BP,[BP+@@x]
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mov AX,CX
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or AX,BP
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jz short @@RETURN
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mov AX,CX
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cwd
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xor AX,DX
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sub AX,DX
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mov BX,AX ; BX = abs(y)
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mov AX,BP
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cwd
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xor AX,DX
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sub AX,DX
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mov DX,AX ; DX = abs(x)
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cmp DX,BX ; abs(x) <= abs(y) -> jump
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je short @@L100
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jl short @@L150
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mov AX,BX
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mov BX,DX
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xor DH,DH
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mov DL,AH
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mov AH,AL
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mov AL,DH
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div BX
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mov BX,offset AtanTable8
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xlatb
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jmp short @@L200
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EVEN
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@@L100: mov AL,32
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jmp short @@L200
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EVEN
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@@L150: mov AX,DX
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xor DH,DH
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mov DL,AH
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mov AH,AL
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mov AL,DH
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div BX
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mov BX,offset AtanTable8
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xlatb
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neg AL
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add AL,64
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@@L200:
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xor AH,AH
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or BP,BP
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jge short @@L300
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neg AX
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add AX,128
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@@L300:
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or CX,CX
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jge short @@L400
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neg AL ; ax = 256 - axだけど…省略
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@@L400:
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xor AH,AH
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@@RETURN:
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MRETURN
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endfunc
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