52 lines
1.8 KiB
C#
52 lines
1.8 KiB
C#
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///////////////////////////////////////////////////////////////////////////////
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//
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// Microsoft Research Singularity
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//
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//
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///////////////////////////////////////////////////////////////////////////////
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using System;
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using System.Diagnostics;
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namespace Microsoft.Singularity.Crypto.PublicKey {
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internal class Digit2 {
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internal static Digit Lo(UInt64 x) {
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return unchecked((UInt32)(x & Digit.MaxValue));
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}
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internal static Digit Hi(UInt64 x) {
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Digit hi = unchecked((UInt32)(x >> Digit.BitN));
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return hi;
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}
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internal static void
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Div(UInt64 num, Digit denom, out Digit q, out Digit r) {
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Digit numHi = Hi(num), numLo = Lo(num);
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if (numHi >= denom) { throw new ArgumentException(); }
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q = (Digit)(num / denom);
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r = unchecked(numLo - denom * q);
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Digit rr = unchecked((Digit)(num - denom * q));
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Debug.Assert(rr == r, "internal error");
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}
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internal static void Div(
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UInt64 num
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, Digit denom
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, Reciprocal recip
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, out Digit q
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, out Digit r
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) {
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Digit numHi = Hi(num)
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, numLo = Lo(num)
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, qEst = Digit.MaxValue - recip.EstQuotient(numHi, numLo, 0);
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UInt64 rEst = unchecked(
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((UInt64)(numHi - denom) << Digit.BitN | numLo)
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+ (UInt64)qEst * denom
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);
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q = unchecked((Digit)(Hi(rEst) - qEst));
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r = unchecked(Lo(rEst) + (denom & Hi(rEst)));
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Digit qq, rr;
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Div(num, denom, out qq, out rr);
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Debug.Assert(qq == q && rr == r, "internal error");
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}
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}
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}
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