hl2[2] = hl2[2] ^ c[2];   hl2[3] = hl2[3] ^ c[3];      c[2] ^= hl2[0];   c[3] ^= hl2[1];   c[4] ^= hl2[2];   c[5] ^= hl2[3];}staticvoid mul4(_ntl_ulong *c, const _ntl_ulong *a, const _ntl_ulong *b){   _ntl_ulong hs0[2], hs1[2];   _ntl_ulong hl2[4];   hs0[0] = a[0] ^ a[2];   hs0[1] = a[1] ^ a[3];   hs1[0] = b[0] ^ b[2];   hs1[1] = b[1] ^ b[3];   mul2(c, a, b);   mul2(c+4, a+2, b+2);    mul2(hl2, hs0, hs1);   hl2[0] = hl2[0] ^ c[0] ^ c[4];   hl2[1] = hl2[1] ^ c[1] ^ c[5];   hl2[2] = hl2[2] ^ c[2] ^ c[6];   hl2[3] = hl2[3] ^ c[3] ^ c[7];      c[2] ^= hl2[0];   c[3] ^= hl2[1];   c[4] ^= hl2[2];   c[5] ^= hl2[3];}staticvoid mul5 (_ntl_ulong *c, const _ntl_ulong *a, const _ntl_ulong *b){   _ntl_ulong hs0[3], hs1[3];   _ntl_ulong hl2[6];   hs0[0] = a[0] ^ a[3];    hs0[1] = a[1] ^ a[4];   hs0[2] = a[2];   hs1[0] = b[0] ^ b[3];    hs1[1] = b[1] ^ b[4];   hs1[2] = b[2];   mul3(c, a, b);    mul2(c+6, a+3, b+3);    mul3(hl2, hs0, hs1);   hl2[0] = hl2[0] ^ c[0] ^ c[6];    hl2[1] = hl2[1] ^ c[1] ^ c[7];   hl2[2] = hl2[2] ^ c[2] ^ c[8];   hl2[3] = hl2[3] ^ c[3] ^ c[9];   hl2[4] = hl2[4] ^ c[4];   hl2[5] = hl2[5] ^ c[5];     c[3] ^= hl2[0];   c[4] ^= hl2[1];   c[5] ^= hl2[2];   c[6] ^= hl2[3];   c[7] ^= hl2[4];   c[8] ^= hl2[5];}staticvoid mul6(_ntl_ulong *c, const _ntl_ulong *a, const _ntl_ulong *b){   _ntl_ulong hs0[3], hs1[3];   _ntl_ulong hl2[6];   hs0[0] = a[0] ^ a[3];      hs0[1] = a[1] ^ a[4];   hs0[2] = a[2] ^ a[5];   hs1[0] = b[0] ^ b[3];      hs1[1] = b[1] ^ b[4];   hs1[2] = b[2] ^ b[5];   mul3(c, a, b);      mul3(c+6, a+3, b+3);    mul3(hl2, hs0, hs1);     hl2[0] = hl2[0] ^ c[0] ^ c[6];   hl2[1] = hl2[1] ^ c[1] ^ c[7];   hl2[2] = hl2[2] ^ c[2] ^ c[8];   hl2[3] = hl2[3] ^ c[3] ^ c[9];   hl2[4] = hl2[4] ^ c[4] ^ c[10];   hl2[5] = hl2[5] ^ c[5] ^ c[11];      c[3] ^= hl2[0];   c[4] ^= hl2[1];   c[5] ^= hl2[2];   c[6] ^= hl2[3];   c[7] ^= hl2[4];   c[8] ^= hl2[5];}staticvoid mul7(_ntl_ulong *c, const _ntl_ulong *a, const _ntl_ulong *b){   _ntl_ulong hs0[4], hs1[4];   _ntl_ulong hl2[8];   hs0[0] = a[0] ^ a[4];    hs0[1] = a[1] ^ a[5];   hs0[2] = a[2] ^ a[6];   hs0[3] = a[3];   hs1[0] = b[0] ^ b[4];    hs1[1] = b[1] ^ b[5];   hs1[2] = b[2] ^ b[6];   hs1[3] = b[3];   mul4(c, a, b);    mul3(c+8, a+4, b+4);    mul4(hl2, hs0, hs1);   hl2[0] = hl2[0] ^ c[0] ^ c[8];   hl2[1] = hl2[1] ^ c[1] ^ c[9];   hl2[2] = hl2[2] ^ c[2] ^ c[10];   hl2[3] = hl2[3] ^ c[3] ^ c[11];   hl2[4] = hl2[4] ^ c[4] ^ c[12];   hl2[5] = hl2[5] ^ c[5] ^ c[13];   hl2[6] = hl2[6] ^ c[6];   hl2[7] = hl2[7] ^ c[7];      c[4]  ^= hl2[0];   c[5]  ^= hl2[1];   c[6]  ^= hl2[2];   c[7]  ^= hl2[3];   c[8]  ^= hl2[4];   c[9]  ^= hl2[5];   c[10] ^= hl2[6];   c[11] ^= hl2[7];}staticvoid mul8(_ntl_ulong *c, const _ntl_ulong *a, const _ntl_ulong *b){   _ntl_ulong hs0[4], hs1[4];   _ntl_ulong hl2[8];   hs0[0] = a[0] ^ a[4];    hs0[1] = a[1] ^ a[5];   hs0[2] = a[2] ^ a[6];   hs0[3] = a[3] ^ a[7];   hs1[0] = b[0] ^ b[4];    hs1[1] = b[1] ^ b[5];   hs1[2] = b[2] ^ b[6];   hs1[3] = b[3] ^ b[7];   mul4(c, a, b);    mul4(c+8, a+4, b+4);   mul4(hl2, hs0, hs1);    hl2[0] = hl2[0] ^ c[0] ^ c[8];   hl2[1] = hl2[1] ^ c[1] ^ c[9];   hl2[2] = hl2[2] ^ c[2] ^ c[10];   hl2[3] = hl2[3] ^ c[3] ^ c[11];   hl2[4] = hl2[4] ^ c[4] ^ c[12];   hl2[5] = hl2[5] ^ c[5] ^ c[13];   hl2[6] = hl2[6] ^ c[6] ^ c[14];   hl2[7] = hl2[7] ^ c[7] ^ c[15];      c[4]  ^= hl2[0];   c[5]  ^= hl2[1];   c[6]  ^= hl2[2];   c[7]  ^= hl2[3];   c[8]  ^= hl2[4];   c[9]  ^= hl2[5];   c[10] ^= hl2[6];   c[11] ^= hl2[7];}staticvoid KarMul(_ntl_ulong *c, const _ntl_ulong *a, const _ntl_ulong *b, long len, _ntl_ulong *stk){   if (len <= 8) {      switch (len) {         case 1: mul1(c, a[0], b[0]); break;         case 2: mul2(c, a, b); break;         case 3: mul3(c, a, b); break;         case 4: mul4(c, a, b); break;         case 5: mul5(c, a, b); break;         case 6: mul6(c, a, b); break;         case 7: mul7(c, a, b); break;         case 8: mul8(c, a, b); break;      }      return;   }   long ll, lh, i, ll2, lh2;   const _ntl_ulong *a0, *a1, *b0, *b1;   _ntl_ulong *a01, *b01, *h;   lh = len >> 1;   ll = (len+1) >> 1;   ll2 = ll << 1;   lh2 = lh << 1;   a01 = stk;  stk += ll+1;   b01 = stk;  stk += ll+1;   h = stk; stk += ll2+1;   a0 = a;   a1 = a+ll;   b0 = b;   b1 = b+ll;   KarMul(c, a0, b0, ll, stk);   KarMul(c+ll2, a1, b1, lh, stk);   for (i = 0; i < lh; i++) {      a01[i] = a[i] ^ a[i+ll];      b01[i] = b[i] ^ b[i+ll];   }   if (lh < ll) {      a01[lh] = a[lh];      b01[lh] = b[lh];   }   KarMul(h, a01, b01, ll, stk);   for (i = 0; i < ll2; i++)      h[i] ^= c[i];   for (i = 0; i < lh2; i++)      h[i] ^= c[i+ll2];   for (i = 0; i < ll2; i++)      c[i+ll] ^= h[i];}void mul(GF2X& c, const GF2X& a, const GF2X& b){   long sa = a.xrep.length();   long sb = b.xrep.length();   if (sa <= 0 || sb <= 0) {      clear(c);      return;   }    _ntl_ulong a0 = a.xrep[0];   _ntl_ulong b0 = b.xrep[0];   if (sb == 1 && b0 == 1) {      c = a;      return;   }   if (sa == 1 && a0 == 1) {      c = b;      return;   }   if (&a == &b) {      sqr(c, a);      return;   }   if (sa == sb && sa <= 8) {      // we treat these cases specially for efficiency reasons      switch (sa) {         case 1: {            _ntl_ulong v[2];            if (!(a0 >> NTL_BITS_PER_LONG/2))               mul_half(v, b0, a0);            else if (!(b0 >> NTL_BITS_PER_LONG/2))               mul_half(v, a0, b0);            else               mul1(v, a0, b0);            if (v[1]) {               c.xrep.SetLength(2);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];            }            else {               c.xrep.SetLength(1);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];            }         }         return;         case 2: {            _ntl_ulong v[4];            mul2(v, &a.xrep[0], &b.xrep[0]);            if (v[3]) {               c.xrep.SetLength(4);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];            }            else {               c.xrep.SetLength(3);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];            }         }         return;         case 3: {            _ntl_ulong v[6];            mul3(v, &a.xrep[0], &b.xrep[0]);            if (v[5]) {               c.xrep.SetLength(6);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];            }            else {               c.xrep.SetLength(5);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];            }         }         return;         case 4: {            _ntl_ulong v[8];            mul4(v, &a.xrep[0], &b.xrep[0]);            if (v[7]) {               c.xrep.SetLength(8);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];            }            else {               c.xrep.SetLength(7);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];            }         }         return;         case 5: {            _ntl_ulong v[10];            mul5(v, &a.xrep[0], &b.xrep[0]);            if (v[9]) {               c.xrep.SetLength(10);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];               cp[8] = v[8];               cp[9] = v[9];            }            else {               c.xrep.SetLength(9);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];               cp[8] = v[8];            }         }         return;         case 6: {            _ntl_ulong v[12];            mul6(v, &a.xrep[0], &b.xrep[0]);            if (v[11]) {               c.xrep.SetLength(12);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];               cp[8] = v[8];               cp[9] = v[9];               cp[10] = v[10];               cp[11] = v[11];            }            else {               c.xrep.SetLength(11);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];               cp[8] = v[8];               cp[9] = v[9];               cp[10] = v[10];            }         }         return;          case 7: {            _ntl_ulong v[14];            mul7(v, &a.xrep[0], &b.xrep[0]);            if (v[13]) {               c.xrep.SetLength(14);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];               cp[8] = v[8];               cp[9] = v[9];               cp[10] = v[10];               cp[11] = v[11];               cp[12] = v[12];               cp[13] = v[13];            }            else {               c.xrep.SetLength(13);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];               cp[8] = v[8];               cp[9] = v[9];               cp[10] = v[10];               cp[11] = v[11];               cp[12] = v[12];            }         }         return;          case 8: {            _ntl_ulong v[16];            mul8(v, &a.xrep[0], &b.xrep[0]);            if (v[15]) {               c.xrep.SetLength(16);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];               cp[8] = v[8];               cp[9] = v[9];               cp[10] = v[10];               cp[11] = v[11];               cp[12] = v[12];               cp[13] = v[13];               cp[14] = v[14];               cp[15] = v[15];            }            else {               c.xrep.SetLength(15);               _ntl_ulong *cp = &c.xrep[0];               cp[0] = v[0];               cp[1] = v[1];               cp[2] = v[2];               cp[3] = v[3];               cp[4] = v[4];               cp[5] = v[5];               cp[6] = v[6];               cp[7] = v[7];               cp[8] = v[8];               cp[9] = v[9];               cp[10] = v[10];               cp[11] = v[11];               cp[12] = v[12];               cp[13] = v[13];               cp[14] = v[14];            }         }         return;       }   }   // another special case:  one of the two inputs   // has length 1 (and maybe 1/2).   if (sa == 1) {      c.xrep.SetLength(sb + 1);      _ntl_ulong *cp = c.xrep.elts();      const _ntl_ulong *bp = b.xrep.elts();      long i;      _ntl_ulong carry;      _ntl_ulong v[2];      carry = 0;      if (a0 >> NTL_BITS_PER_LONG/2) {         for (i = 0; i < sb; i++) {            mul1(v, bp[i], a0);            cp[i] = carry ^ v[0];            carry = v[1];         }      }      else {         for (i = 0; i < sb; i++) {            mul_half(v, bp[i], a0);            cp[i] = carry ^ v[0];            carry = v[1];         }      }      cp[sb] = carry;      c.normalize();      return;   }   if (sb == 1) {      c.xrep.SetLength(sa + 1);      _ntl_ulong *cp = c.xrep.elts();      const _ntl_ulong *ap = a.xrep.elts();      long i;      _ntl_ulong carry;      _ntl_ulong v[2];      carry = 0;      if (b0 >> NTL_BITS_PER_LONG/2) {         for (i = 0; i < sa; i++) {            mul1(v, ap[i], b0);            cp[i] = carry ^ v[0];            carry = v[1];         }      }      else {         for (i = 0; i < sa; i++) {            mul_half(v, ap[i], b0);            cp[i] = carry ^ v[0];            carry = v[1];         }      }      cp[sa] = carry;      c.normalize();      return;   }   // finally: the general case      static WordVector mem;   static WordVector stk;   static WordVector vec;   const _ntl_ulong *ap, *bp;   _ntl_ulong *cp;   long sc = sa + sb;   long in_mem = 0;   if (&a == &c || &b == &c) {      mem.SetLength(sc);      cp = mem.elts();