int invmodp(_MIPD_ big a,big p,big z)
{
#ifdef MR_OS_THREADS
miracl *mr_mip=get_mip();
#endif
big u,v,x1,x2;
MR_IN(213);
u=mr_mip->w1; v=mr_mip->w2; x1=mr_mip->w3; x2=mr_mip->w4;
copy(a,u);
copy(p,v);
convert(_MIPP_ 1,x1);
zero(x2);
while (size(u)!=1 && size(v)!=1)
{
while (remain(_MIPP_ u,2)==0)
{
subdiv(_MIPP_ u,2,u);
if (remain(_MIPP_ x1,2)!=0) add(_MIPP_ x1,p,x1);
subdiv(_MIPP_ x1,2,x1);
}
while (remain(_MIPP_ v,2)==0)
{
subdiv(_MIPP_ v,2,v);
if (remain(_MIPP_ x2,2)!=0) add(_MIPP_ x2,p,x2);
subdiv(_MIPP_ x2,2,x2);
}
if (mr_compare(u,v)>=0)
{
mr_psub(_MIPP_ u,v,u);
subtract(_MIPP_ x1,x2,x1);
}
else
{
mr_psub(_MIPP_ v,u,v);
subtract(_MIPP_ x2,x1,x2);
}
}
if (size(u)==1) copy(x1,z);
else copy(x2,z);
if (size(z)<0) add(_MIPP_ z,p,z);
MR_OUT
return 1; /* note - no checking that gcd=1 */
}
int xgcd(_MIPD_ big x,big y,big xd,big yd,big z)
{ /* greatest common divisor by Euclids method *
* extended to also calculate xd and yd where *
* z = x.xd + y.yd = gcd(x,y) *
* if xd, yd not distinct, only xd calculated *
* z only returned if distinct from xd and yd *
* xd will always be positive, yd negative */
int s,n,iter;
mr_small r,a,b,c,d;
mr_small q,m,sr;
#ifdef MR_FP
mr_small dres;
#endif
#ifdef mr_dltype
union doubleword uu,vv;
mr_large u,v,lr;
#else
mr_small u,v,lr;
#endif
BOOL last,dplus=TRUE;
big t;
#ifdef MR_OS_THREADS
miracl *mr_mip=get_mip();
#endif
if (mr_mip->ERNUM) return 0;
MR_IN(30)
#ifdef MR_COUNT_OPS
fpx++;
#endif
copy(x,mr_mip->w1);
copy(y,mr_mip->w2);
s=exsign(mr_mip->w1);
insign(PLUS,mr_mip->w1);
insign(PLUS,mr_mip->w2);
convert(_MIPP_ 1,mr_mip->w3);
zero(mr_mip->w4);
last=FALSE;
a=b=c=d=0;
iter=0;
while (size(mr_mip->w2)!=0)
{
if (b==0)
{ /* update mr_mip->w1 and mr_mip->w2 */
divide(_MIPP_ mr_mip->w1,mr_mip->w2,mr_mip->w5);
t=mr_mip->w1,mr_mip->w1=mr_mip->w2,mr_mip->w2=t; /* swap(mr_mip->w1,mr_mip->w2) */
multiply(_MIPP_ mr_mip->w4,mr_mip->w5,mr_mip->w0);
add(_MIPP_ mr_mip->w3,mr_mip->w0,mr_mip->w3);
t=mr_mip->w3,mr_mip->w3=mr_mip->w4,mr_mip->w4=t; /* swap(xd,yd) */
iter++;
}
else
{
/* printf("a= %I64u b= %I64u c= %I64u d= %I64u \n",a,b,c,d); */
mr_pmul(_MIPP_ mr_mip->w1,c,mr_mip->w5); /* c*w1 */
mr_pmul(_MIPP_ mr_mip->w1,a,mr_mip->w1); /* a*w1 */
mr_pmul(_MIPP_ mr_mip->w2,b,mr_mip->w0); /* b*w2 */
mr_pmul(_MIPP_ mr_mip->w2,d,mr_mip->w2); /* d*w2 */
if (!dplus)
{
mr_psub(_MIPP_ mr_mip->w0,mr_mip->w1,mr_mip->w1); /* b*w2-a*w1 */
mr_psub(_MIPP_ mr_mip->w5,mr_mip->w2,mr_mip->w2); /* c*w1-d*w2 */
}
else
{
mr_psub(_MIPP_ mr_mip->w1,mr_mip->w0,mr_mip->w1); /* a*w1-b*w2 */
mr_psub(_MIPP_ mr_mip->w2,mr_mip->w5,mr_mip->w2); /* d*w2-c*w1 */
}
mr_pmul(_MIPP_ mr_mip->w3,c,mr_mip->w5);
mr_pmul(_MIPP_ mr_mip->w3,a,mr_mip->w3);
mr_pmul(_MIPP_ mr_mip->w4,b,mr_mip->w0);
mr_pmul(_MIPP_ mr_mip->w4,d,mr_mip->w4);
if (a==0) copy(mr_mip->w0,mr_mip->w3);
else mr_padd(_MIPP_ mr_mip->w3,mr_mip->w0,mr_mip->w3);
mr_padd(_MIPP_ mr_mip->w4,mr_mip->w5,mr_mip->w4);
}
if (mr_mip->ERNUM || size(mr_mip->w2)==0) break;
n=(int)mr_mip->w1->len;
if (n==1)
{
last=TRUE;
u=mr_mip->w1->w[0];
v=mr_mip->w2->w[0];
}
else
{
m=mr_mip->w1->w[n-1]+1;
#ifndef MR_SIMPLE_BASE
if (mr_mip->base==0)
{
#endif
#ifndef MR_NOFULLWIDTH
#ifdef mr_dltype
/* use double length type if available */
if (n>2 && m!=0)
{ /* squeeze out as much significance as possible */
uu.h[MR_TOP]=muldvm(mr_mip->w1->w[n-1],mr_mip->w1->w[n-2],m,&sr);
uu.h[MR_BOT]=muldvm(sr,mr_mip->w1->w[n-3],m,&sr);
vv.h[MR_TOP]=muldvm(mr_mip->w2->w[n-1],mr_mip->w2->w[n-2],m,&sr);
vv.h[MR_BOT]=muldvm(sr,mr_mip->w2->w[n-3],m,&sr);
}
else
{
uu.h[MR_TOP]=mr_mip->w1->w[n-1];
uu.h[MR_BOT]=mr_mip->w1->w[n-2];
vv.h[MR_TOP]=mr_mip->w2->w[n-1];
vv.h[MR_BOT]=mr_mip->w2->w[n-2];
if (n==2) last=TRUE;
}
u=uu.d;
v=vv.d;
#else
if (m==0)
{
u=mr_mip->w1->w[n-1];
v=mr_mip->w2->w[n-1];
}
else
{
u=muldvm(mr_mip->w1->w[n-1],mr_mip->w1->w[n-2],m,&sr);
v=muldvm(mr_mip->w2->w[n-1],mr_mip->w2->w[n-2],m,&sr);
}
#endif
#endif
#ifndef MR_SIMPLE_BASE
}
else
{
#ifdef mr_dltype
if (n>2)
{ /* squeeze out as much significance as possible */
u=muldiv(mr_mip->w1->w[n-1],mr_mip->base,mr_mip->w1->w[n-2],m,&sr);
u=u*mr_mip->base+muldiv(sr,mr_mip->base,mr_mip->w1->w[n-3],m,&sr);
v=muldiv(mr_mip->w2->w[n-1],mr_mip->base,mr_mip->w2->w[n-2],m,&sr);
v=v*mr_mip->base+muldiv(sr,mr_mip->base,mr_mip->w2->w[n-3],m,&sr);
}
else
{
u=(mr_large)mr_mip->base*mr_mip->w1->w[n-1]+mr_mip->w1->w[n-2];
v=(mr_large)mr_mip->base*mr_mip->w2->w[n-1]+mr_mip->w2->w[n-2];
last=TRUE;
}
#else
u=muldiv(mr_mip->w1->w[n-1],mr_mip->base,mr_mip->w1->w[n-2],m,&sr);
v=muldiv(mr_mip->w2->w[n-1],mr_mip->base,mr_mip->w2->w[n-2],m,&sr);
#endif
}
#endif
}
dplus=TRUE;
a=1; b=0; c=0; d=1;
forever
{ /* work only with most significant piece */
if (last)
{
if (v==0) break;
q=qdiv(u,v);
if (q==0) break;
}
else
{
if (dplus)
{
if ((mr_small)(v-c)==0 || (mr_small)(v+d)==0) break;
q=qdiv(u+a,v-c);
if (q==0) break;
if (q!=qdiv(u-b,v+d)) break;
}
else
{
if ((mr_small)(v+c)==0 || (mr_small)(v-d)==0) break;
q=qdiv(u-a,v+c);
if (q==0) break;
if (q!=qdiv(u+b,v-d)) break;
}
}
if (q==1)
{
if ((mr_small)(b+d) >= MAXBASE) break;
r=a+c; a=c; c=r;
r=b+d; b=d; d=r;
lr=u-v; u=v; v=lr;
}
else
{
if (q>=MR_DIV(MAXBASE-b,d)) break;
r=a+q*c; a=c; c=r;
r=b+q*d; b=d; d=r;
lr=u-q*v; u=v; v=lr;
}
iter++;
dplus=!dplus;
}
iter%=2;
}
if (s==MINUS) iter++;
if (iter%2==1) subtract(_MIPP_ y,mr_mip->w3,mr_mip->w3);
if (xd!=yd)
{
negify(x,mr_mip->w2);
mad(_MIPP_ mr_mip->w2,mr_mip->w3,mr_mip->w1,y,mr_mip->w4,mr_mip->w4);
copy(mr_mip->w4,yd);
}
copy(mr_mip->w3,xd);
if (z!=xd && z!=yd) copy(mr_mip->w1,z);
MR_OUT
return (size(mr_mip->w1));
}
static void mr_select(_MIPD_ big x,int d,big y,big z)
{ /* perform required add or subtract operation */
int sx,sy,sz,jf,xgty;
#ifdef MR_FLASH
if (mr_notint(x) || mr_notint(y))
{
mr_berror(_MIPP_ MR_ERR_INT_OP);
return;
}
#endif
sx=exsign(x);
sy=exsign(y);
sz=0;
x->len&=MR_OBITS; /* force operands to be positive */
y->len&=MR_OBITS;
xgty=mr_compare(x,y);
jf=(1+sx)+(1+d*sy)/2;
switch (jf)
{ /* branch according to signs of operands */
case 0:
if (xgty>=0)
mr_padd(_MIPP_ x,y,z);
else
mr_padd(_MIPP_ y,x,z);
sz=MINUS;
break;
case 1:
if (xgty<=0)
{
mr_psub(_MIPP_ y,x,z);
sz=PLUS;
}
else
{
mr_psub(_MIPP_ x,y,z);
sz=MINUS;
}
break;
case 2:
if (xgty>=0)
{
mr_psub(_MIPP_ x,y,z);
sz=PLUS;
}
else
{
mr_psub(_MIPP_ y,x,z);
sz=MINUS;
}
break;
case 3:
if (xgty>=0)
mr_padd(_MIPP_ x,y,z);
else
mr_padd(_MIPP_ y,x,z);
sz=PLUS;
break;
}
if (sz<0) z->len^=MR_MSBIT; /* set sign of result */
if (x!=z && sx<0) x->len^=MR_MSBIT; /* restore signs to operands */
if (y!=z && y!=x && sy<0) y->len^=MR_MSBIT;
}