90 lines
1.7 KiB
ActionScript
90 lines
1.7 KiB
ActionScript
package com.hurlant.math
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{
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use namespace bi_internal;
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internal class BarrettReduction implements IReduction
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{
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private var m:BigInteger;
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private var r2:BigInteger;
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private var q3:BigInteger;
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private var mu:BigInteger;
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public function BarrettReduction(m:BigInteger) {
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// setup Barrett
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r2 = new BigInteger;
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q3 = new BigInteger;
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BigInteger.ONE.dlShiftTo(2*m.t, r2);
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mu = r2.divide(m);
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this.m = m;
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}
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public function revert(x:BigInteger):BigInteger
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{
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return x;
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}
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/**
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*
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* @param x
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* @param y
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* @param r = x*y mod m; x != r
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*
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*/
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public function mulTo(x:BigInteger, y:BigInteger, r:BigInteger):void
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{
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x.multiplyTo(y, r);
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reduce(r);
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}
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/**
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*
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* @param x
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* @param r = x^2 mod m; x != r
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*
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*/
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public function sqrTo(x:BigInteger, r:BigInteger):void
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{
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x.squareTo(r);
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reduce(r);
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}
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public function convert(x:BigInteger):BigInteger
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{
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if (x.s<0 || x.t>2*m.t) {
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return x.mod(m);
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} else if (x.compareTo(m)<0) {
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return x;
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} else {
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var r:BigInteger = new BigInteger;
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x.copyTo(r);
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reduce(r);
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return r;
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}
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}
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/**
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*
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* @param x = x mod m (HAC 14.42)
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*
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*/
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public function reduce(lx:BigInteger):void
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{
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var x:BigInteger = lx as BigInteger;
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x.drShiftTo(m.t-1,r2);
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if (x.t>m.t+1) {
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x.t = m.t+1;
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x.clamp();
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}
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mu.multiplyUpperTo(r2, m.t+1, q3);
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m.multiplyLowerTo(q3, m.t+1, r2);
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while (x.compareTo(r2)<0) {
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x.dAddOffset(1, m.t+1);
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}
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x.subTo(r2,x);
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while (x.compareTo(m)>=0) {
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x.subTo(m,x);
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}
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}
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}
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} |