content: package im.actor.crypto.primitives.curve25519;
  
  public class fe_mul {
  
  //CONVERT #include "fe.h"
  //CONVERT #include "long.h"
  
  /*
  h = f * g
  Can overlap h with f or g.
  
  Preconditions:
     |f| bounded by 1.65*2^26,1.65*2^25,1.65*2^26,1.65*2^25,etc.
     |g| bounded by 1.65*2^26,1.65*2^25,1.65*2^26,1.65*2^25,etc.
  
  Postconditions:
     |h| bounded by 1.01*2^25,1.01*2^24,1.01*2^25,1.01*2^24,etc.
  */
  
  /*
  Notes on implementation strategy:
  
  Using schoolbook multiplication.
  Karatsuba would save a little in some cost models.
  
  Most multiplications by 2 and 19 are 32-bit precomputations;
  cheaper than 64-bit postcomputations.
  
  There is one remaining multiplication by 19 in the carry chain;
  one *19 precomputation can be merged into this,
  but the resulting data flow is considerably less clean.
  
  There are 12 carries below.
  10 of them are 2-way parallelizable and vectorizable.
  Can get away with 11 carries, but then data flow is much deeper.
  
  With tighter constraints on inputs can squeeze carries into int32.
  */
  
    private static long[] fe_mul1(int[] f,int[] g){
      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 g1_19 = 19 * g1; /* 1.959375*2^29 */
      int g2_19 = 19 * g2; /* 1.959375*2^30; still ok */
      int g3_19 = 19 * g3;
      int g4_19 = 19 * g4;
      int g5_19 = 19 * g5;
      int g6_19 = 19 * g6;
      int g7_19 = 19 * g7;
      int g8_19 = 19 * g8;
      int g9_19 = 19 * g9;
      int f1_2 = 2 * f1;
      int f3_2 = 2 * f3;
      int f5_2 = 2 * f5;
      int f7_2 = 2 * f7;
      int f9_2 = 2 * f9;
      long f0g0    = f0   * (long) g0;
      long f0g1    = f0   * (long) g1;
      long f0g2    = f0   * (long) g2;
      long f0g3    = f0   * (long) g3;
      long f0g4    = f0   * (long) g4;
      long f0g5    = f0   * (long) g5;
      long f0g6    = f0   * (long) g6;
      long f0g7    = f0   * (long) g7;
      long f0g8    = f0   * (long) g8;
      long f0g9    = f0   * (long) g9;
      long f1g0    = f1   * (long) g0;
      long f1g1_2  = f1_2 * (long) g1;
      long f1g2    = f1   * (long) g2;
      long f1g3_2  = f1_2 * (long) g3;
      long f1g4    = f1   * (long) g4;
      long f1g5_2  = f1_2 * (long) g5;
      long f1g6    = f1   * (long) g6;
      long f1g7_2  = f1_2 * (long) g7;
      long f1g8    = f1   * (long) g8;
      long f1g9_38 = f1_2 * (long) g9_19;
      long f2g0    = f2   * (long) g0;
      long f2g1    = f2   * (long) g1;
      long f2g2    = f2   * (long) g2;
      long f2g3    = f2   * (long) g3;
      long f2g4    = f2   * (long) g4;
      long f2g5    = f2   * (long) g5;
      long f2g6    = f2   * (long) g6;
      long f2g7    = f2   * (long) g7;
      long f2g8_19 = f2   * (long) g8_19;
      long f2g9_19 = f2   * (long) g9_19;
      long f3g0    = f3   * (long) g0;
      long f3g1_2  = f3_2 * (long) g1;
      long f3g2    = f3   * (long) g2;
      long f3g3_2  = f3_2 * (long) g3;
      long f3g4    = f3   * (long) g4;
      long f3g5_2  = f3_2 * (long) g5;
      long f3g6    = f3   * (long) g6;
      long f3g7_38 = f3_2 * (long) g7_19;
      long f3g8_19 = f3   * (long) g8_19;
      long f3g9_38 = f3_2 * (long) g9_19;
      long f4g0    = f4   * (long) g0;
      long f4g1    = f4   * (long) g1;
      long f4g2    = f4   * (long) g2;
      long f4g3    = f4   * (long) g3;
      long f4g4    = f4   * (long) g4;
      long f4g5    = f4   * (long) g5;
      long f4g6_19 = f4   * (long) g6_19;
      long f4g7_19 = f4   * (long) g7_19;
      long f4g8_19 = f4   * (long) g8_19;
      long f4g9_19 = f4   * (long) g9_19;
      long f5g0    = f5   * (long) g0;
      long f5g1_2  = f5_2 * (long) g1;
      long f5g2    = f5   * (long) g2;
      long f5g3_2  = f5_2 * (long) g3;
      long f5g4    = f5   * (long) g4;
      long f5g5_38 = f5_2 * (long) g5_19;
      long f5g6_19 = f5   * (long) g6_19;
      long f5g7_38 = f5_2 * (long) g7_19;
      long f5g8_19 = f5   * (long) g8_19;
      long f5g9_38 = f5_2 * (long) g9_19;
      long f6g0    = f6   * (long) g0;
      long f6g1    = f6   * (long) g1;
      long f6g2    = f6   * (long) g2;
      long f6g3    = f6   * (long) g3;
      long f6g4_19 = f6   * (long) g4_19;
      long f6g5_19 = f6   * (long) g5_19;
      long f6g6_19 = f6   * (long) g6_19;
      long f6g7_19 = f6   * (long) g7_19;
      long f6g8_19 = f6   * (long) g8_19;
      long f6g9_19 = f6   * (long) g9_19;
      long f7g0    = f7   * (long) g0;
      long f7g1_2  = f7_2 * (long) g1;
      long f7g2    = f7   * (long) g2;
      long f7g3_38 = f7_2 * (long) g3_19;
      long f7g4_19 = f7   * (long) g4_19;
      long f7g5_38 = f7_2 * (long) g5_19;
      long f7g6_19 = f7   * (long) g6_19;
      long f7g7_38 = f7_2 * (long) g7_19;
      long f7g8_19 = f7   * (long) g8_19;
      long f7g9_38 = f7_2 * (long) g9_19;
      long f8g0    = f8   * (long) g0;
      long f8g1    = f8   * (long) g1;
      long f8g2_19 = f8   * (long) g2_19;
      long f8g3_19 = f8   * (long) g3_19;
      long f8g4_19 = f8   * (long) g4_19;
      long f8g5_19 = f8   * (long) g5_19;
      long f8g6_19 = f8   * (long) g6_19;
      long f8g7_19 = f8   * (long) g7_19;
      long f8g8_19 = f8   * (long) g8_19;
      long f8g9_19 = f8   * (long) g9_19;
      long f9g0    = f9   * (long) g0;
      long f9g1_38 = f9_2 * (long) g1_19;
      long f9g2_19 = f9   * (long) g2_19;
      long f9g3_38 = f9_2 * (long) g3_19;
      long f9g4_19 = f9   * (long) g4_19;
      long f9g5_38 = f9_2 * (long) g5_19;
      long f9g6_19 = f9   * (long) g6_19;
      long f9g7_38 = f9_2 * (long) g7_19;
      long f9g8_19 = f9   * (long) g8_19;
      long f9g9_38 = f9_2 * (long) g9_19;
      long h[] = new long[10];
      h[0] = f0g0+f1g9_38+f2g8_19+f3g7_38+f4g6_19+f5g5_38+f6g4_19+f7g3_38+f8g2_19+f9g1_38;
      h[1] = f0g1+f1g0   +f2g9_19+f3g8_19+f4g7_19+f5g6_19+f6g5_19+f7g4_19+f8g3_19+f9g2_19;
      h[2] = f0g2+f1g1_2 +f2g0   +f3g9_38+f4g8_19+f5g7_38+f6g6_19+f7g5_38+f8g4_19+f9g3_38;
      h[3] = f0g3+f1g2   +f2g1   +f3g0   +f4g9_19+f5g8_19+f6g7_19+f7g6_19+f8g5_19+f9g4_19;
      h[4] = f0g4+f1g3_2 +f2g2   +f3g1_2 +f4g0   +f5g9_38+f6g8_19+f7g7_38+f8g6_19+f9g5_38;
      h[5] = f0g5+f1g4   +f2g3   +f3g2   +f4g1   +f5g0   +f6g9_19+f7g8_19+f8g7_19+f9g6_19;
      h[6] = f0g6+f1g5_2 +f2g4   +f3g3_2 +f4g2   +f5g1_2 +f6g0   +f7g9_38+f8g8_19+f9g7_38;
      h[7] = f0g7+f1g6   +f2g5   +f3g4   +f4g3   +f5g2   +f6g1   +f7g0   +f8g9_19+f9g8_19;
      h[8] = f0g8+f1g7_2 +f2g6   +f3g5_2 +f4g4   +f5g3_2 +f6g2   +f7g1_2 +f8g0   +f9g9_38;
      h[9] = f0g9+f1g8   +f2g7   +f3g6   +f4g5   +f5g4   +f6g3   +f7g2   +f8g1   +f9g0   ;
  
      return h;
    }
  
    public static void fe_mul(int[] h,int[] f,int[] g)
    {
  
      long hr[] = fe_mul1(f, g);
  
      long carry0;
      long carry1;
      long carry2;
      long carry3;
      long carry4;
      long carry5;
      long carry6;
      long carry7;
      long carry8;
      long carry9;
  
    /*
    |h0| <= (1.65*1.65*2^52*(1+19+19+19+19)+1.65*1.65*2^50*(38+38+38+38+38))
      i.e. |h0| <= 1.4*2^60; narrower ranges for h2, h4, h6, h8
    |h1| <= (1.65*1.65*2^51*(1+1+19+19+19+19+19+19+19+19))
      i.e. |h1| <= 1.7*2^59; narrower ranges for h3, h5, h7, h9
    */
  
      carry0 = (hr[0] + (long) (1<<25)) >> 26; hr[1] += carry0; hr[0] -= carry0 << 26;
      carry4 = (hr[4] + (long) (1<<25)) >> 26; hr[5] += carry4; hr[4] -= carry4 << 26;
    /* |h0| <= 2^25 */
    /* |h4| <= 2^25 */
    /* |h1| <= 1.71*2^59 */
    /* |h5| <= 1.71*2^59 */
  
      carry1 = (hr[1] + (long) (1<<24)) >> 25; hr[2] += carry1; hr[1] -= carry1 << 25;
      carry5 = (hr[5] + (long) (1<<24)) >> 25; hr[6] += carry5; hr[5] -= carry5 << 25;
    /* |h1| <= 2^24; from now on fits into int32 */
    /* |h5| <= 2^24; from now on fits into int32 */
    /* |h2| <= 1.41*2^60 */
    /* |h6| <= 1.41*2^60 */
  
      carry2 = (hr[2] + (long) (1<<25)) >> 26; hr[3] += carry2; hr[2] -= carry2 << 26;
      carry6 = (hr[6] + (long) (1<<25)) >> 26; hr[7] += carry6; hr[6] -= carry6 << 26;
    /* |h2| <= 2^25; from now on fits into int32 unchanged */
    /* |h6| <= 2^25; from now on fits into int32 unchanged */
    /* |h3| <= 1.71*2^59 */
    /* |h7| <= 1.71*2^59 */
  
      carry3 = (hr[3] + (long) (1<<24)) >> 25; hr[4] += carry3; hr[3] -= carry3 << 25;
      carry7 = (hr[7] + (long) (1<<24)) >> 25; hr[8] += carry7; hr[7] -= carry7 << 25;
    /* |h3| <= 2^24; from now on fits into int32 unchanged */
    /* |h7| <= 2^24; from now on fits into int32 unchanged */
    /* |h4| <= 1.72*2^34 */
    /* |h8| <= 1.41*2^60 */
  
      carry4 = (hr[4] + (long) (1<<25)) >> 26; hr[5] += carry4; hr[4] -= carry4 << 26;
      carry8 = (hr[8] + (long) (1<<25)) >> 26; hr[9] += carry8; hr[8] -= carry8 << 26;
    /* |h4| <= 2^25; from now on fits into int32 unchanged */
    /* |h8| <= 2^25; from now on fits into int32 unchanged */
    /* |h5| <= 1.01*2^24 */
    /* |h9| <= 1.71*2^59 */
  
      carry9 = (hr[9] + (long) (1<<24)) >> 25; hr[0] += carry9 * 19; hr[9] -= carry9 << 25;
    /* |h9| <= 2^24; from now on fits into int32 unchanged */
    /* |h0| <= 1.1*2^39 */
  
      carry0 = (hr[0] + (long) (1<<25)) >> 26; hr[1] += carry0; hr[0] -= carry0 << 26;
    /* |h0| <= 2^25; from now on fits into int32 unchanged */
    /* |h1| <= 1.01*2^24 */
  
      h[0] = (int)hr[0];
      h[1] = (int)hr[1];
      h[2] = (int)hr[2];
      h[3] = (int)hr[3];
      h[4] = (int)hr[4];
      h[5] = (int)hr[5];
      h[6] = (int)hr[6];
      h[7] = (int)hr[7];
      h[8] = (int)hr[8];
      h[9] = (int)hr[9];
    }
  }
  