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/*++
Copyright (c) 1989 Microsoft Corporation
Module Name:
recip.c
Abstract:
This module generates reciprocol fractions for implementing integer
division by multiplication.
Author:
David N. Cutler (davec) 13-May-1989
Environment:
User mode.
Revision History:
--*/
#include <stdio.h>
typedef struct _large_integer {
unsigned long LowPart;
long HighPart;
} large_integer;
//long Divisors[] = {2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 0};
long Divisors[] = {10, 10000, 10000000, 86400000, 0};
void
main (argc, argv)
int argc;
char *argv[];
{
large_integer Fraction;
long Index;
long NumberBits;
long Remainder;
long i;
//
// Compute first few reciprocols.
//
for (Index = Divisors[i = 0]; Index != 0L; Index = Divisors[++i]) {
NumberBits = 0L;
Remainder = 1L;
Fraction.LowPart = 0L;
Fraction.HighPart = 0L;
while (Fraction.HighPart >= 0L) {
NumberBits += 1L;
Fraction.HighPart <<= 1L;
if ((Fraction.LowPart & 0x80000000) != 0L) {
Fraction.HighPart += 1L;
}
Fraction.LowPart <<= 1L;
Remainder <<= 1L;
if (Remainder >= Index) {
Remainder -= Index;
Fraction.LowPart |= 1L;
}
}
if (Remainder) {
if ((Fraction.LowPart == -1L) && (Fraction.HighPart == -1L)) {
Fraction.LowPart = 0L;
Fraction.HighPart = 0x80000000;
NumberBits -= 1L;
} else {
if (Fraction.LowPart == -1L) {
Fraction.LowPart = 0L;
Fraction.HighPart += 1L;
} else {
Fraction.LowPart += 1L;
}
}
}
printf("Divisor %2ld, Fraction %8lx, %8lx Shift %ld\n", Index,
Fraction.HighPart, Fraction.LowPart, NumberBits - 64L);
}
return;
}
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