package org.bouncycastle.math.ec.custom.sec;
import java.math.BigInteger;
import org.bouncycastle.math.raw.Nat;
import org.bouncycastle.math.raw.Nat256;
public class SecP256R1Field
{
private static final long M = 0xFFFFFFFFL;
// 2^256 - 2^224 + 2^192 + 2^96 - 1
static final int[] P = new int[]{ 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000000, 0x00000000, 0x00000000,
0x00000001, 0xFFFFFFFF };
static final int[] PExt = new int[]{ 0x00000001, 0x00000000, 0x00000000, 0xFFFFFFFE, 0xFFFFFFFF,
0xFFFFFFFF, 0xFFFFFFFE, 0x00000001, 0xFFFFFFFE, 0x00000001, 0xFFFFFFFE, 0x00000001, 0x00000001, 0xFFFFFFFE,
0x00000002, 0xFFFFFFFE };
private static final int P7 = 0xFFFFFFFF;
private static final int PExt15 = 0xFFFFFFFF;
public static void add(int[] x, int[] y, int[] z)
{
int c = Nat256.add(x, y, z);
if (c != 0 || (z[7] == P7 && Nat256.gte(z, P)))
{
addPInvTo(z);
}
}
public static void addExt(int[] xx, int[] yy, int[] zz)
{
int c = Nat.add(16, xx, yy, zz);
if (c != 0 || (zz[15] == PExt15 && Nat.gte(16, zz, PExt)))
{
Nat.subFrom(16, PExt, zz);
}
}
public static void addOne(int[] x, int[] z)
{
int c = Nat.inc(8, x, z);
if (c != 0 || (z[7] == P7 && Nat256.gte(z, P)))
{
addPInvTo(z);
}
}
public static int[] fromBigInteger(BigInteger x)
{
int[] z = Nat256.fromBigInteger(x);
if (z[7] == P7 && Nat256.gte(z, P))
{
Nat256.subFrom(P, z);
}
return z;
}
public static void half(int[] x, int[] z)
{
if ((x[0] & 1) == 0)
{
Nat.shiftDownBit(8, x, 0, z);
}
else
{
int c = Nat256.add(x, P, z);
Nat.shiftDownBit(8, z, c);
}
}
public static void multiply(int[] x, int[] y, int[] z)
{
int[] tt = Nat256.createExt();
Nat256.mul(x, y, tt);
reduce(tt, z);
}
public static void multiplyAddToExt(int[] x, int[] y, int[] zz)
{
int c = Nat256.mulAddTo(x, y, zz);
if (c != 0 || (zz[15] == PExt15 && Nat.gte(16, zz, PExt)))
{
Nat.subFrom(16, PExt, zz);
}
}
public static void negate(int[] x, int[] z)
{
if (Nat256.isZero(x))
{
Nat256.zero(z);
}
else
{
Nat256.sub(P, x, z);
}
}
public static void reduce(int[] xx, int[] z)
{
long xx08 = xx[8] & M, xx09 = xx[9] & M, xx10 = xx[10] & M, xx11 = xx[11] & M;
long xx12 = xx[12] & M, xx13 = xx[13] & M, xx14 = xx[14] & M, xx15 = xx[15] & M;
final long n = 6;
xx08 -= n;
long t0 = xx08 + xx09;
long t1 = xx09 + xx10;
long t2 = xx10 + xx11 - xx15;
long t3 = xx11 + xx12;
long t4 = xx12 + xx13;
long t5 = xx13 + xx14;
long t6 = xx14 + xx15;
long t7 = t5 - t0;
long cc = 0;
cc += (xx[0] & M) - t3 - t7;
z[0] = (int)cc;
cc >>= 32;
cc += (xx[1] & M) + t1 - t4 - t6;
z[1] = (int)cc;
cc >>= 32;
cc += (xx[2] & M) + t2 - t5;
z[2] = (int)cc;
cc >>= 32;
cc += (xx[3] & M) + (t3 << 1) + t7 - t6;
z[3] = (int)cc;
cc >>= 32;
cc += (xx[4] & M) + (t4 << 1) + xx14 - t1;
z[4] = (int)cc;
cc >>= 32;
cc += (xx[5] & M) + (t5 << 1) - t2;
z[5] = (int)cc;
cc >>= 32;
cc += (xx[6] & M) + (t6 << 1) + t7;
z[6] = (int)cc;
cc >>= 32;
cc += (xx[7] & M) + (xx15 << 1) + xx08 - t2 - t4;
z[7] = (int)cc;
cc >>= 32;
cc += n;
// assert cc >= 0;
reduce32((int)cc, z);
}
public static void reduce32(int x, int[] z)
{
long cc = 0;
if (x != 0)
{
long xx08 = x & M;
cc += (z[0] & M) + xx08;
z[0] = (int)cc;
cc >>= 32;
if (cc != 0)
{
cc += (z[1] & M);
z[1] = (int)cc;
cc >>= 32;
cc += (z[2] & M);
z[2] = (int)cc;
cc >>= 32;
}
cc += (z[3] & M) - xx08;
z[3] = (int)cc;
cc >>= 32;
if (cc != 0)
{
cc += (z[4] & M);
z[4] = (int)cc;
cc >>= 32;
cc += (z[5] & M);
z[5] = (int)cc;
cc >>= 32;
}
cc += (z[6] & M) - xx08;
z[6] = (int)cc;
cc >>= 32;
cc += (z[7] & M) + xx08;
z[7] = (int)cc;
cc >>= 32;
// assert cc == 0 || cc == 1;
}
if (cc != 0 || (z[7] == P7 && Nat256.gte(z, P)))
{
addPInvTo(z);
}
}
public static void square(int[] x, int[] z)
{
int[] tt = Nat256.createExt();
Nat256.square(x, tt);
reduce(tt, z);
}
public static void squareN(int[] x, int n, int[] z)
{
// assert n > 0;
int[] tt = Nat256.createExt();
Nat256.square(x, tt);
reduce(tt, z);
while (--n > 0)
{
Nat256.square(z, tt);
reduce(tt, z);
}
}
public static void subtract(int[] x, int[] y, int[] z)
{
int c = Nat256.sub(x, y, z);
if (c != 0)
{
subPInvFrom(z);
}
}
public static void subtractExt(int[] xx, int[] yy, int[] zz)
{
int c = Nat.sub(16, xx, yy, zz);
if (c != 0)
{
Nat.addTo(16, PExt, zz);
}
}
public static void twice(int[] x, int[] z)
{
int c = Nat.shiftUpBit(8, x, 0, z);
if (c != 0 || (z[7] == P7 && Nat256.gte(z, P)))
{
addPInvTo(z);
}
}
private static void addPInvTo(int[] z)
{
long c = (z[0] & M) + 1;
z[0] = (int)c;
c >>= 32;
if (c != 0)
{
c += (z[1] & M);
z[1] = (int)c;
c >>= 32;
c += (z[2] & M);
z[2] = (int)c;
c >>= 32;
}
c += (z[3] & M) - 1;
z[3] = (int)c;
c >>= 32;
if (c != 0)
{
c += (z[4] & M);
z[4] = (int)c;
c >>= 32;
c += (z[5] & M);
z[5] = (int)c;
c >>= 32;
}
c += (z[6] & M) - 1;
z[6] = (int)c;
c >>= 32;
c += (z[7] & M) + 1;
z[7] = (int)c;
// c >>= 32;
}
private static void subPInvFrom(int[] z)
{
long c = (z[0] & M) - 1;
z[0] = (int)c;
c >>= 32;
if (c != 0)
{
c += (z[1] & M);
z[1] = (int)c;
c >>= 32;
c += (z[2] & M);
z[2] = (int)c;
c >>= 32;
}
c += (z[3] & M) + 1;
z[3] = (int)c;
c >>= 32;
if (c != 0)
{
c += (z[4] & M);
z[4] = (int)c;
c >>= 32;
c += (z[5] & M);
z[5] = (int)c;
c >>= 32;
}
c += (z[6] & M) + 1;
z[6] = (int)c;
c >>= 32;
c += (z[7] & M) - 1;
z[7] = (int)c;
// c >>= 32;
}
}