71 lines
1.6 KiB
NASM
71 lines
1.6 KiB
NASM
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; void _HalveUnsArr(a,n)
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;
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; ARGUMENT
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; unsigned *a[];
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; unsigned n;
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;
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; DESCRIPTION
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; Halves the number a (taken as one number of 'n' 16-bit unsigneds).
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;
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; SIDE EFFECTS
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; If number is odd, discards low-order bit.
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;
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; RETURNS
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; None.
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;
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; AUTHOR
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; Andy Anderson 31-JAN-1987 13:30
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; Copyright (C) 1987-90 Greenleaf Software Inc. All Rights Reserved.
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;
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; MODIFICATIONS
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; aa 08-JUL-87 80-bit
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;
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;
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include model.h
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include prologue.h
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include gm.equ
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pseg gmath
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;
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; if large memory model then:
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;
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; parm1_ = ptr to source 1
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; parm3_ = number of words to shift right (divide by 2)
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;
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; for if small model then
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; parm1_ = ptr to source1
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; parm2_ = number of words to shift right (divide by 2)
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;
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;
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cproc _HalveUnsArr,,_hmi
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if _LDATA
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push ds
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lds si,parm1_ ; ptr to a
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mov cx,parm3_ ; get number of words to shift
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else
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mov si,parm1_
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mov cx,parm2_ ; ditto for small model
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endif
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xor bx,bx ; clear flags
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mov bx,cx ; then convert number of word to
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dec bx ; index for loop
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rcl bx,1 ; change byte to word offset
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xor ax,ax ; clear flags
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lp:
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rcr Word Ptr [bx+si],1 ; word and divide it by 2
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dec bx ; and decrease the index (offset)
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dec bx
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loop lp ; for next until done
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; no return values
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if _LDATA
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pop ds
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endif
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cproce
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endps
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END
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