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Curve25519 library for Java
package org.whispersystems.curve25519.java;
public class fe_cswap {
//CONVERT #include
//CONVERT #include "fe.h"
/*
Replace (f,g) with (g,f) if b == 1;
replace (f,g) with (f,g) if b == 0.
Preconditions: b in {0,1}.
*/
public static void fe_cswap(int[] f,int[] g,int b)
{
int f0 = f[0];
int f1 = f[1];
int f2 = f[2];
int f3 = f[3];
int f4 = f[4];
int f5 = f[5];
int f6 = f[6];
int f7 = f[7];
int f8 = f[8];
int f9 = f[9];
int g0 = g[0];
int g1 = g[1];
int g2 = g[2];
int g3 = g[3];
int g4 = g[4];
int g5 = g[5];
int g6 = g[6];
int g7 = g[7];
int g8 = g[8];
int g9 = g[9];
int x0 = f0 ^ g0;
int x1 = f1 ^ g1;
int x2 = f2 ^ g2;
int x3 = f3 ^ g3;
int x4 = f4 ^ g4;
int x5 = f5 ^ g5;
int x6 = f6 ^ g6;
int x7 = f7 ^ g7;
int x8 = f8 ^ g8;
int x9 = f9 ^ g9;
b = -b;
x0 &= b;
x1 &= b;
x2 &= b;
x3 &= b;
x4 &= b;
x5 &= b;
x6 &= b;
x7 &= b;
x8 &= b;
x9 &= b;
f[0] = f0 ^ x0;
f[1] = f1 ^ x1;
f[2] = f2 ^ x2;
f[3] = f3 ^ x3;
f[4] = f4 ^ x4;
f[5] = f5 ^ x5;
f[6] = f6 ^ x6;
f[7] = f7 ^ x7;
f[8] = f8 ^ x8;
f[9] = f9 ^ x9;
g[0] = g0 ^ x0;
g[1] = g1 ^ x1;
g[2] = g2 ^ x2;
g[3] = g3 ^ x3;
g[4] = g4 ^ x4;
g[5] = g5 ^ x5;
g[6] = g6 ^ x6;
g[7] = g7 ^ x7;
g[8] = g8 ^ x8;
g[9] = g9 ^ x9;
}
}