content: package org.whispersystems.curve25519.java;
  
  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.
  */
  
  public 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 h0 = hr[0];
    long h1 = hr[1];
    long h2 = hr[2];
    long h3 = hr[3];
    long h4 = hr[4];
    long h5 = hr[5];
    long h6 = hr[6];
    long h7 = hr[7];
    long h8 = hr[8];
    long h9 = hr[9];
  
    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 = (h0 + (long) (1<<25)) >> 26; h1 += carry0; h0 -= carry0 << 26;
    carry4 = (h4 + (long) (1<<25)) >> 26; h5 += carry4; h4 -= carry4 << 26;
    /* |h0| <= 2^25 */
    /* |h4| <= 2^25 */
    /* |h1| <= 1.71*2^59 */
    /* |h5| <= 1.71*2^59 */
  
    carry1 = (h1 + (long) (1<<24)) >> 25; h2 += carry1; h1 -= carry1 << 25;
    carry5 = (h5 + (long) (1<<24)) >> 25; h6 += carry5; h5 -= 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 = (h2 + (long) (1<<25)) >> 26; h3 += carry2; h2 -= carry2 << 26;
    carry6 = (h6 + (long) (1<<25)) >> 26; h7 += carry6; h6 -= 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 = (h3 + (long) (1<<24)) >> 25; h4 += carry3; h3 -= carry3 << 25;
    carry7 = (h7 + (long) (1<<24)) >> 25; h8 += carry7; h7 -= 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 = (h4 + (long) (1<<25)) >> 26; h5 += carry4; h4 -= carry4 << 26;
    carry8 = (h8 + (long) (1<<25)) >> 26; h9 += carry8; h8 -= 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 = (h9 + (long) (1<<24)) >> 25; h0 += carry9 * 19; h9 -= carry9 << 25;
    /* |h9| <= 2^24; from now on fits into int32 unchanged */
    /* |h0| <= 1.1*2^39 */
  
    carry0 = (h0 + (long) (1<<25)) >> 26; h1 += carry0; h0 -= carry0 << 26;
    /* |h0| <= 2^25; from now on fits into int32 unchanged */
    /* |h1| <= 1.01*2^24 */
  
    h[0] = (int)h0;
    h[1] = (int)h1;
    h[2] = (int)h2;
    h[3] = (int)h3;
    h[4] = (int)h4;
    h[5] = (int)h5;
    h[6] = (int)h6;
    h[7] = (int)h7;
    h[8] = (int)h8;
    h[9] = (int)h9;
  }
  
  
  }
  