102 lines
3.0 KiB
NASM
102 lines
3.0 KiB
NASM
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; int _DivUnsArrByUns(a, c, n)
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;
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; ARGUMENT
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; unsigned a[] n-word number to divide
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; unsigned c number of divide by
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; int n number of digits
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;
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; DESCRIPTION
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; Divides n-digit number c by b, storing result in c.
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; The (positive) remainder is calculated and returned.
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;
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; SIDE EFFECTS
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; None.
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;
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; RETURNS
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; Remainder.
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;
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; AUTHOR
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; Jared Levy 7/9/89
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; Copyright (C) 1989-90 Greenleaf Software Inc. All Rights Reserved.
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;
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; MODIFICATIONS
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;
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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 dmby1
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cproc _DivUnsArrByUns,,_dmby1
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; load parameters
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if _LDATA
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push es
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les di, parm1_ ; get pointer to source & destination
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mov cx, parm3_ ; get number to divide by
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mov bx, parm4_ ; get number of digits
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else
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mov di, parm1_ ; get pointer to source & destination
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mov ax, ds
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mov es, ax
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mov cx, parm2_ ; get number to divide by
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mov bx, parm3_ ; get number of digits
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endif
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call near ptr dmby1a
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if _LDATA
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pop es
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endif
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cproce
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; the computation routine is separate so it may be called from assembly
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dmby1a:
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dec bx ; digits go from 0 to n-1
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sal bx, 1 ; want bytes rather than words
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;/* skip initial zeroes */
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; for(;(q>0)&&(c[q-1]==0);q--);
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;
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; if (q == 0)
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; return(0);
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; q--; /* q will be used for subscript */
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zeroloop:
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mov ax, word ptr es:[di+bx] ; get digit
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cmp ax, 0 ; is digit zero?
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jne nonzero ; if non-zero, begin divide
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dec bx ; next word
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dec bx
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cmp bx, 0 ; last digit?
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jge zeroloop ; if not, process next digit
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xor ax, ax ; otherwise, remainder 0
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jmp short exit1 ; && division through (0/c=0)
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; bl = (unsigned long) b;
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; while (q>=0) {
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; k = (unsigned long *) &r[q];
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; cl = *k / bl;
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; c[q] = (unsigned) cl;
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; r[q] = (unsigned) (*k - cl * bl);
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; q--;
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; }
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nonzero:
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xor dx,dx ; high word zero in first divide
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divloop:
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div cx ; divide digit
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mov word ptr es:[di+bx], ax ; store quotient digit
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cmp bx, 0 ; last digit?
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je exit2 ; if so, division complete
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dec bx ; next digit
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dec bx
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mov ax, word ptr es:[di+bx] ; get digit
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jmp short divloop ; process digit
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exit2:
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mov ax, dx ; return remainder
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exit1:
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ret
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endps
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end
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