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package org.testifyproject.bouncycastle.math.raw;
import java.util.Random;
import org.testifyproject.bouncycastle.util.Pack;
public abstract class Mod
{
public static int inverse32(int d)
{
// int x = d + (((d + 1) & 4) << 1); // d.x == 1 mod 2**4
int x = d; // d.x == 1 mod 2**3
x *= 2 - d * x; // d.x == 1 mod 2**6
x *= 2 - d * x; // d.x == 1 mod 2**12
x *= 2 - d * x; // d.x == 1 mod 2**24
x *= 2 - d * x; // d.x == 1 mod 2**48
// assert d * x == 1;
return x;
}
public static void invert(int[] p, int[] x, int[] z)
{
int len = p.length;
if (Nat.isZero(len, x))
{
throw new IllegalArgumentException("'x' cannot be 0");
}
if (Nat.isOne(len, x))
{
System.arraycopy(x, 0, z, 0, len);
return;
}
int[] u = Nat.copy(len, x);
int[] a = Nat.create(len);
a[0] = 1;
int ac = 0;
if ((u[0] & 1) == 0)
{
ac = inversionStep(p, u, len, a, ac);
}
if (Nat.isOne(len, u))
{
inversionResult(p, ac, a, z);
return;
}
int[] v = Nat.copy(len, p);
int[] b = Nat.create(len);
int bc = 0;
int uvLen = len;
for (;;)
{
while (u[uvLen - 1] == 0 && v[uvLen - 1] == 0)
{
--uvLen;
}
if (Nat.gte(uvLen, u, v))
{
Nat.subFrom(uvLen, v, u);
// assert (u[0] & 1) == 0;
ac += Nat.subFrom(len, b, a) - bc;
ac = inversionStep(p, u, uvLen, a, ac);
if (Nat.isOne(uvLen, u))
{
inversionResult(p, ac, a, z);
return;
}
}
else
{
Nat.subFrom(uvLen, u, v);
// assert (v[0] & 1) == 0;
bc += Nat.subFrom(len, a, b) - ac;
bc = inversionStep(p, v, uvLen, b, bc);
if (Nat.isOne(uvLen, v))
{
inversionResult(p, bc, b, z);
return;
}
}
}
}
public static int[] random(int[] p)
{
int len = p.length;
Random rand = new Random();
int[] s = Nat.create(len);
int m = p[len - 1];
m |= m >>> 1;
m |= m >>> 2;
m |= m >>> 4;
m |= m >>> 8;
m |= m >>> 16;
do
{
for (int i = 0; i != len; i++)
{
s[i] = rand.nextInt();
}
s[len - 1] &= m;
}
while (Nat.gte(len, s, p));
return s;
}
public static void add(int[] p, int[] x, int[] y, int[] z)
{
int len = p.length;
int c = Nat.add(len, x, y, z);
if (c != 0)
{
Nat.subFrom(len, p, z);
}
}
public static void subtract(int[] p, int[] x, int[] y, int[] z)
{
int len = p.length;
int c = Nat.sub(len, x, y, z);
if (c != 0)
{
Nat.addTo(len, p, z);
}
}
private static void inversionResult(int[] p, int ac, int[] a, int[] z)
{
if (ac < 0)
{
Nat.add(p.length, a, p, z);
}
else
{
System.arraycopy(a, 0, z, 0, p.length);
}
}
private static int inversionStep(int[] p, int[] u, int uLen, int[] x, int xc)
{
int len = p.length;
int count = 0;
while (u[0] == 0)
{
Nat.shiftDownWord(uLen, u, 0);
count += 32;
}
{
int zeroes = getTrailingZeroes(u[0]);
if (zeroes > 0)
{
Nat.shiftDownBits(uLen, u, zeroes, 0);
count += zeroes;
}
}
for (int i = 0; i < count; ++i)
{
if ((x[0] & 1) != 0)
{
if (xc < 0)
{
xc += Nat.addTo(len, p, x);
}
else
{
xc += Nat.subFrom(len, p, x);
}
}
// assert xc == 0 || xc == 1;
Nat.shiftDownBit(len, x, xc);
}
return xc;
}
private static int getTrailingZeroes(int x)
{
// assert x != 0;
int count = 0;
while ((x & 1) == 0)
{
x >>>= 1;
++count;
}
return count;
}
}
