/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/

/* AMCL BIG number class */ 

package org.apache.milagro.amcl.XXX;
import org.apache.milagro.amcl.RAND;

public class BIG {

	public static final int CHUNK=32; /* Set word size */

	public static final int NLEN=(1+((8*CONFIG_BIG.MODBYTES-1)/CONFIG_BIG.BASEBITS));
	public static final int DNLEN=2*NLEN;
	public static final int BMASK=(((int)1<<CONFIG_BIG.BASEBITS)-1);

	public static final int HBITS=CONFIG_BIG.BASEBITS/2;
	public static final int HMASK=(((int)1<<HBITS)-1);
	public static final int NEXCESS = ((int)1<<(CHUNK-CONFIG_BIG.BASEBITS-1));
	public static final int BIGBITS=(CONFIG_BIG.MODBYTES*8);

	protected int[] w=new int[NLEN];

/* Constructors */

	public BIG()
	{
		for (int i=0;i<NLEN;i++)
			w[i]=0;
	}

	public BIG(int x)
	{
		w[0]=x;
		for (int i=1;i<NLEN;i++)
			w[i]=0;
	}

	public BIG(BIG x)
	{
		for (int i=0;i<NLEN;i++)
			w[i]=x.w[i];
	}

	public BIG(DBIG x)
	{
		for (int i=0;i<NLEN;i++)
			w[i]=x.w[i];
	}

	public BIG(int[] x)
	{
		for (int i=0;i<NLEN;i++)
			w[i]=x[i];
	}

	public int get(int i)
	{
		return w[i];
	}

	public void set(int i,int x)
	{
		w[i]=x;
	} 

/* Conditional swap of two bigs depending on d using XOR - no branches */
	public void cswap(BIG b,int d)
	{
		int i;
		int t,c=d;
		c=~(c-1);

		for (i=0;i<NLEN;i++)
		{
			t=c&(w[i]^b.w[i]);
			w[i]^=t;
			b.w[i]^=t;
		}
	}

	public void cmove(BIG g,int d)
	{
		int i;
		int b=-d;

		for (i=0;i<NLEN;i++)
		{
			w[i]^=(w[i]^g.w[i])&b;
		}
	}

    public static int cast_to_chunk(int x)
	{
		return (int)x;
	}

/* normalise BIG - force all digits < 2^BASEBITS */
	public long norm() {
		int d,carry=0;
		for (int i=0;i<NLEN-1;i++)
		{
			d=w[i]+carry;
			w[i]=d&BMASK;
			carry=d>>CONFIG_BIG.BASEBITS;
		}
		w[NLEN-1]=(w[NLEN-1]+carry);
		return (long)(w[NLEN-1]>>((8*CONFIG_BIG.MODBYTES)%CONFIG_BIG.BASEBITS));  
	}

/* return number of bits */
	public int nbits() {
		BIG t=new BIG(this);
		int bts,k=NLEN-1;
		int c;
		t.norm();
		while (k>=0 && t.w[k]==0) k--;
		if (k<0) return 0;
		bts=CONFIG_BIG.BASEBITS*k;
		c=t.w[k];
		while (c!=0) {c/=2; bts++;}
		return bts;
	}

	public String toRawString()
	{
		BIG b=new BIG(this);
		String s="(";
		for (int i=0;i<NLEN-1;i++)
		{
			s+=Integer.toHexString(b.w[i]); s+=",";
		}
		s+=Integer.toHexString(b.w[NLEN-1]); s+=")";
		return s;
	}

/* Convert to Hex String */
	public String toString() {
		BIG b;
		String s="";
		int len=nbits();

		if (len%4==0) len/=4;
		else {len/=4; len++;}
		if (len<CONFIG_BIG.MODBYTES*2) len=CONFIG_BIG.MODBYTES*2;

		for (int i=len-1;i>=0;i--)
		{
			b=new BIG(this);
			b.shr(i*4);
			s+=Integer.toHexString(b.w[0]&15);
		}
		return s;
	}

	public static int[] muladd(int x,int y,int c,int r)
	{
		int[] tb=new int[2];
		long prod=(long)x*y+c+r;	
		tb[1]=(int)prod&BMASK;
		tb[0]=(int)(prod>>CONFIG_BIG.BASEBITS);
		return tb;
	}

/* this*=x, where x is >NEXCESS */
	public int pmul(int c)
	{
		int ak,carry=0;
		int[] cr=new int[2];

		for (int i=0;i<NLEN;i++)
		{
			ak=w[i];
			w[i]=0;
			cr=muladd(ak,c,carry,w[i]);
			carry=cr[0];
			w[i]=cr[1];
		}
		return carry;
	}

/* return this*c and catch overflow in DBIG */
	public DBIG pxmul(int c)
	{
		DBIG m=new DBIG(0);	
		int[] cr=new int[2];	
		int carry=0;
		for (int j=0;j<NLEN;j++)
		{
			cr=muladd(w[j],c,carry,m.w[j]);
			carry=cr[0];
			m.w[j]=cr[1];
		}
		m.w[NLEN]=carry;		
		return m;
	}

/* divide by 3 */
	public int div3()
	{	
		int ak,base,carry=0;
		norm();
		base=((int)1<<CONFIG_BIG.BASEBITS);
		for (int i=NLEN-1;i>=0;i--)
		{
			ak=(carry*base+w[i]);
			w[i]=ak/3;
			carry=ak%3;
		}
		return (int)carry;
	}

/* return a*b where result fits in a BIG */
	public static BIG smul(BIG a,BIG b)
	{
		int carry;
		BIG c=new BIG(0);
		int[] cr=new int[2];			
		for (int i=0;i<NLEN;i++)
		{
			carry=0;
			for (int j=0;j<NLEN;j++)
			{
				if (i+j<NLEN) 
				{
					cr=muladd(a.w[i],b.w[j],carry,c.w[i+j]);
					carry=cr[0];
					c.w[i+j]=cr[1];
				}
			}
		}
		return c;
	}

/* return a*b as DBIG */
/* Inputs must be normed */
	public static DBIG mul(BIG a,BIG b)
	{
		long t,co;
		DBIG c=new DBIG(0);

		long[] d=new long[NLEN];
		long s;
		int i,k;

		for (i=0;i<NLEN;i++)
			d[i]=(long)a.w[i]*b.w[i];

		s=d[0];
		t=s; c.w[0]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;

		for (k=1;k<NLEN;k++)
		{
			s+=d[k]; t=co+s; for (i=k;i>=1+k/2;i--) t+=(long)(a.w[i]-a.w[k-i])*(b.w[k-i]-b.w[i]); c.w[k]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;
		}
		for (k=NLEN;k<2*NLEN-1;k++)
		{
			s-=d[k-NLEN]; t=co+s; for (i=NLEN-1;i>=1+k/2;i--) t+=(long)(a.w[i]-a.w[k-i])*(b.w[k-i]-b.w[i]); c.w[k]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;
		}
		c.w[2*NLEN-1]=(int)co;

		return c;
	}

/* return a^2 as DBIG */
/* Input must be normed */
	public static DBIG sqr(BIG a)
	{
		int i,j,last;
		long t,co;
		DBIG c=new DBIG(0);

		t=(long)a.w[0]*a.w[0]; 
		c.w[0]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;

		for (j=1;j<NLEN-1; )
		{
			t=(long)a.w[j]*a.w[0]; for (i=1; i<(j+1)/2; i++) {t+=(long)a.w[j-i]*a.w[i];} t+=t;  t+=co; 
			c.w[j]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;
			j++;
			t=(long)a.w[j]*a.w[0]; for (i=1; i<(j+1)/2; i++) {t+=(long)a.w[j-i]*a.w[i];} t+=t; t+=co; t+=(long)a.w[j/2]*a.w[j/2]; 
			c.w[j]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;
			j++;
		}

		for (j=NLEN-1+NLEN%2;j<DNLEN-3; )
		{
			t=(long)a.w[NLEN-1]*a.w[j-NLEN+1]; for (i=j-NLEN+2; i<(j+1)/2; i++) {t+=(long)a.w[j-i]*a.w[i];} t+=t; t+=co; 
			c.w[j]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;
			j++;
			t=(long)a.w[NLEN-1]*a.w[j-NLEN+1]; for (i=j-NLEN+2; i<(j+1)/2; i++) {t+=(long)a.w[j-i]*a.w[i];} t+=t; t+=co; t+=(long)a.w[j/2]*a.w[j/2]; 
			c.w[j]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;
			j++;
		}

		t=(long)a.w[NLEN-2]*a.w[NLEN-1];
		t+=t; t+=co;
		c.w[DNLEN-3]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;
	
		t=(long)a.w[NLEN-1]*a.w[NLEN-1]+co; 
		c.w[DNLEN-2]=(int)t&BMASK; co=t>>CONFIG_BIG.BASEBITS;
		c.w[DNLEN-1]=(int)co;

		return c;
	}

	static BIG monty(BIG m,int MC,DBIG d)
	{
		BIG b;
		long t,c,s;
		int i,k;
		long[] dd=new long[NLEN];
		int[] v=new int[NLEN];
		b=new BIG(0);

		t=d.w[0]; v[0]=((int)t*MC)&BMASK; t+=(long)v[0]*m.w[0]; c=(t>>CONFIG_BIG.BASEBITS)+d.w[1]; s=0;

		for (k=1;k<NLEN;k++)
		{
			t=c+s+(long)v[0]*m.w[k];
			for (i=k-1;i>k/2;i--) t+=(long)(v[k-i]-v[i])*(m.w[i]-m.w[k-i]);
			v[k]=((int)t*MC)&BMASK; t+=(long)v[k]*m.w[0]; c=(t>>CONFIG_BIG.BASEBITS)+d.w[k+1];
			dd[k]=(long)v[k]*m.w[k]; s+=dd[k];
		}
		for (k=NLEN;k<2*NLEN-1;k++)
		{
			t=c+s;
			for (i=NLEN-1;i>=1+k/2;i--) t+=(long)(v[k-i]-v[i])*(m.w[i]-m.w[k-i]);
			b.w[k-NLEN]=(int)t&BMASK; c=(t>>CONFIG_BIG.BASEBITS)+d.w[k+1]; s-=dd[k-NLEN+1];
		}
		b.w[NLEN-1]=(int)c&BMASK;	
		return b;		
	}

	public static int ssn(BIG r,BIG a,BIG m)
	{
		int n=NLEN-1;
		m.w[0]=(m.w[0]>>1)|((m.w[1]<<(CONFIG_BIG.BASEBITS-1))&BMASK);
		r.w[0]=a.w[0]-m.w[0];
		int carry=r.w[0]>>CONFIG_BIG.BASEBITS;
		r.w[0]&=BMASK;
		for (int i=1;i<n;i++) {
			m.w[i]=(m.w[i]>>1)|((m.w[i+1]<<(CONFIG_BIG.BASEBITS-1))&BMASK);
			r.w[i]=a.w[i]-m.w[i]+carry;
			carry=r.w[i]>>CONFIG_BIG.BASEBITS;
			r.w[i]&=BMASK;
		}
		m.w[n]>>=1;
		r.w[n]=a.w[n]-m.w[n]+carry;
		return (int)((r.w[n]>>(CHUNK-1))&1);
	}


/****************************************************************************/
	public void xortop(long x)
	{
		w[NLEN-1]^=x;
	}

/* set x = x mod 2^m */
	public void mod2m(int m)
	{
		int i,wd,bt;
		wd=m/CONFIG_BIG.BASEBITS;
		bt=m%CONFIG_BIG.BASEBITS;
		w[wd]&=((cast_to_chunk(1)<<bt)-1);
		for (i=wd+1;i<NLEN;i++) w[i]=0;
	}

/* return n-th bit */
	public int bit(int n)
	{
		if ((w[n/CONFIG_BIG.BASEBITS]&(cast_to_chunk(1)<<(n%CONFIG_BIG.BASEBITS)))>0) return 1;
		else return 0;
	}

/* Shift right by less than a word */
	public int fshr(int k) {
		int r=(int)(w[0]&((cast_to_chunk(1)<<k)-1)); /* shifted out part */
		for (int i=0;i<NLEN-1;i++)
			w[i]=(w[i]>>k)|((w[i+1]<<(CONFIG_BIG.BASEBITS-k))&BMASK);
		w[NLEN-1]=w[NLEN-1]>>k;
		return r;
	}

/* Shift right by less than a word */
	public int fshl(int k) {
		w[NLEN-1]=((w[NLEN-1]<<k))|(w[NLEN-2]>>(CONFIG_BIG.BASEBITS-k));
		for (int i=NLEN-2;i>0;i--)
			w[i]=((w[i]<<k)&BMASK)|(w[i-1]>>(CONFIG_BIG.BASEBITS-k));
		w[0]=(w[0]<<k)&BMASK; 
		return (int)(w[NLEN-1]>>((8*CONFIG_BIG.MODBYTES)%CONFIG_BIG.BASEBITS)); /* return excess - only used in FF.java */
	}

/* test for zero */
	public boolean iszilch() {
		for (int i=0;i<NLEN;i++)
			if (w[i]!=0) return false;
		return true; 
	}

/* set to zero */
	public void zero()
	{
		for (int i=0;i<NLEN;i++)
			w[i]=0;
	}

/* set to one */
	public void one()
	{
		w[0]=1;
		for (int i=1;i<NLEN;i++)
			w[i]=0;
	}

/* Test for equal to one */
	public boolean isunity()
	{
		for (int i=1;i<NLEN;i++)
			if (w[i]!=0) return false;
		if (w[0]!=1) return false;
		return true;
	}

/* Copy from another BIG */
	public void copy(BIG x)
	{
		for (int i=0;i<NLEN;i++)
			w[i]=x.w[i];
	}

	public void copy(DBIG x)
	{
		for (int i=0;i<NLEN;i++)
			w[i]=x.w[i];
	}

/* general shift right */
	public void shr(int k) {
		int n=k%CONFIG_BIG.BASEBITS;
		int m=k/CONFIG_BIG.BASEBITS;	
		for (int i=0;i<NLEN-m-1;i++)
			w[i]=(w[m+i]>>n)|((w[m+i+1]<<(CONFIG_BIG.BASEBITS-n))&BMASK);
		if (NLEN>m) w[NLEN-m-1]=w[NLEN-1]>>n;
		for (int i=NLEN-m;i<NLEN;i++) w[i]=0;
	}

/* general shift left */
	public void shl(int k) {
		int n=k%CONFIG_BIG.BASEBITS;
		int m=k/CONFIG_BIG.BASEBITS;

		w[NLEN-1]=((w[NLEN-1-m]<<n));
		if (NLEN>=m+2) w[NLEN-1]|=(w[NLEN-m-2]>>(CONFIG_BIG.BASEBITS-n));

		for (int i=NLEN-2;i>m;i--)
			w[i]=((w[i-m]<<n)&BMASK)|(w[i-m-1]>>(CONFIG_BIG.BASEBITS-n));
		w[m]=(w[0]<<n)&BMASK;
		for (int i=0;i<m;i++) w[i]=0;
	}

/* return this+x */
	public BIG plus(BIG x) {
		BIG s=new BIG(0);
		for (int i=0;i<NLEN;i++)
			s.w[i]=w[i]+x.w[i];	
		return s;
	}

/* this+=x */
	public void add(BIG x) {
		for (int i=0;i<NLEN;i++)
			w[i]+=x.w[i];
	}

/* this|=x */
	public void or(BIG x) {
		for (int i=0;i<NLEN;i++)
			w[i]|=x.w[i];
	}

/* this+=x, where x is int */
	public void inc(int x) {
		norm();
		w[0]+=x;
	}

/* this+=x, where x is long */
	public void incl(long x) {
		norm();
		w[0]+=x;
	}	

/* return this.x */
	public BIG minus(BIG x) {
		BIG d=new BIG(0);
		for (int i=0;i<NLEN;i++)
			d.w[i]=w[i]-x.w[i];
		return d;
	}

/* this-=x */
	public void sub(BIG x) {
		for (int i=0;i<NLEN;i++)
			w[i]-=x.w[i];
	}

/* reverse subtract this=x-this */
	public void rsub(BIG x) {
		for (int i=0;i<NLEN;i++)
			w[i]=x.w[i]-w[i];
	}

/* this-=x where x is int */
	public void dec(int x) {
		norm();
		w[0]-=x;
	}

/* this*=x, where x is small int<NEXCESS */
	public void imul(int c)
	{
		for (int i=0;i<NLEN;i++) w[i]*=c;
	}

/* convert this BIG to byte array */
	public void tobytearray(byte[] b,int n)
	{
		BIG c=new BIG(this);
		c.norm();

		for (int i=CONFIG_BIG.MODBYTES-1;i>=0;i--)
		{
			b[i+n]=(byte)c.w[0];
			c.fshr(8);
		}
	}

/* convert from byte array to BIG */
	public static BIG frombytearray(byte[] b,int n)
	{
		BIG m=new BIG(0);

		for (int i=0;i<CONFIG_BIG.MODBYTES;i++)
		{
			m.fshl(8); m.w[0]+=(int)b[i+n]&0xff;
			//m.inc((int)b[i]&0xff);
		}
		return m; 
	}

	public void toBytes(byte[] b)
	{
		tobytearray(b,0);
	}

	public static BIG fromBytes(byte[] b)
	{
		return frombytearray(b,0);
	}

/* Compare a and b, return 0 if a==b, -1 if a<b, +1 if a>b. Inputs must be normalised */
	public static int comp(BIG a,BIG b)
	{
		for (int i=NLEN-1;i>=0;i--)
		{
			if (a.w[i]==b.w[i]) continue;
			if (a.w[i]>b.w[i]) return 1;
			else  return -1;
		}
		return 0;
	}

/* Arazi and Qi inversion mod 256 */
	public static int invmod256(int a)
	{
		int U,t1,t2,b,c;
		t1=0;
		c=(a>>1)&1;  
		t1+=c;
		t1&=1;
		t1=2-t1;
		t1<<=1;
		U=t1+1;

// i=2
		b=a&3;
		t1=U*b; t1>>=2;
		c=(a>>2)&3;
		t2=(U*c)&3;
		t1+=t2;
		t1*=U; t1&=3;
		t1=4-t1;
		t1<<=2;
		U+=t1;

// i=4
		b=a&15;
		t1=U*b; t1>>=4;
		c=(a>>4)&15;
		t2=(U*c)&15;
		t1+=t2;
		t1*=U; t1&=15;
		t1=16-t1;
		t1<<=4;
		U+=t1;

		return U;
	}

/* a=1/a mod 2^256. This is very fast! */
	public void invmod2m()
	{
		int i;
		BIG U=new BIG(0);
		BIG b=new BIG(0);
		BIG c=new BIG(0);

		U.inc(invmod256(lastbits(8)));

		for (i=8;i<BIGBITS;i<<=1)
		{
			U.norm();
			b.copy(this); b.mod2m(i);
			BIG t1=BIG.smul(U,b); 
			t1.shr(i);

			c.copy(this); c.shr(i); c.mod2m(i);

			BIG t2=BIG.smul(U,c); t2.mod2m(i);

			t1.add(t2);
			t1.norm();
			b=BIG.smul(t1,U); t1.copy(b);
			t1.mod2m(i);

			t2.one(); t2.shl(i); t1.rsub(t2); t1.norm();

			t1.shl(i);
			U.add(t1);
		}
		U.mod2m(BIGBITS);
		copy(U);
		norm();
	}

/* reduce this mod m */
	public void mod(BIG m1)
	{
		int k=0;  
		BIG r=new BIG(0);
		BIG m=new BIG(m1);

		norm();
		if (comp(this,m)<0) return;
		do
		{
			m.fshl(1);
			k++;
		} while (comp(this,m)>=0);

		while (k>0)
		{
			m.fshr(1);

			r.copy(this);
			r.sub(m);
			r.norm();
			cmove(r,(int)(1-((r.w[NLEN-1]>>(CHUNK-1))&1)));
			k--;
		}
	}

/* divide this by m */
	public void div(BIG m1)
	{
		int d,k=0;
		norm();
		BIG e=new BIG(1);
		BIG m=new BIG(m1);
		BIG b=new BIG(this);
		BIG r=new BIG(0);
		zero();

		while (comp(b,m)>=0)
		{
			e.fshl(1);
			m.fshl(1);
			k++;
		}

		while (k>0)
		{
			m.fshr(1);
			e.fshr(1);

			r.copy(b);
			r.sub(m);
			r.norm();
			d=(int)(1-((r.w[NLEN-1]>>(CHUNK-1))&1));
			b.cmove(r,d);
			r.copy(this);
			r.add(e);
			r.norm();
			cmove(r,d);
			k--;
		}
	}

/* return parity */
	public int parity()
	{
		return (int)(w[0]%2);
	}

/* return n last bits */
	public int lastbits(int n)
	{
		int msk=(1<<n)-1;
		norm();
		return ((int)w[0])&msk;
	}

/* get 8*CONFIG_BIG.MODBYTES size random number */
	public static BIG random(RAND rng)
	{
		BIG m=new BIG(0);
		int i,b,j=0,r=0;

/* generate random BIG */ 
		for (i=0;i<8*CONFIG_BIG.MODBYTES;i++)   
		{
			if (j==0) r=rng.getByte();
			else r>>=1;

			b=r&1;
			m.shl(1); m.w[0]+=b;// m.inc(b);
			j++; j&=7; 
		}
		return m;
	}

/* Create random BIG in portable way, one bit at a time */
	public static BIG randomnum(BIG q,RAND rng) 
	{
		DBIG d=new DBIG(0);
		int i,b,j=0,r=0;
		for (i=0;i<2*q.nbits();i++)
		{
			if (j==0) r=rng.getByte();
			else r>>=1;

			b=r&1;
			d.shl(1); d.w[0]+=b;// m.inc(b);
			j++; j&=7; 
		}
		BIG m=d.mod(q);
		return m;
	}

/* return a*b mod m */
	public static BIG modmul(BIG a1,BIG b1,BIG m)
	{
		BIG a=new BIG(a1);
		BIG b=new BIG(b1);
		a.mod(m);
		b.mod(m);
		DBIG d=mul(a,b);
		return d.mod(m);
	}

/* return a^2 mod m */
	public static BIG modsqr(BIG a1,BIG m)
	{
		BIG a=new BIG(a1);
		a.mod(m);
		DBIG d=sqr(a);
		return d.mod(m);
	}

/* return -a mod m */
	public static BIG modneg(BIG a1,BIG m)
	{
		BIG a=new BIG(a1);
		a.mod(m);
		return m.minus(a);
	}

/* return this^e mod m */
	public BIG powmod(BIG e1,BIG m)
	{
		BIG e=new BIG(e1);
		int bt;
		norm();
		e.norm();
		BIG a=new BIG(1);
		BIG z=new BIG(e);
		BIG s=new BIG(this);
		while (true)
		{
			bt=z.parity();
			z.fshr(1);
			if (bt==1) a=modmul(a,s,m);
			if (z.iszilch()) break;
			s=modsqr(s,m);
		}
		return a;
	}

/* Jacobi Symbol (this/p). Returns 0, 1 or -1 */
	public int jacobi(BIG p)
	{
		int n8,k,m=0;
		BIG t=new BIG(0);
		BIG x=new BIG(0);
		BIG n=new BIG(0);
		BIG zilch=new BIG(0);
		BIG one=new BIG(1);
		if (p.parity()==0 || comp(this,zilch)==0 || comp(p,one)<=0) return 0;
		norm();
		x.copy(this);
		n.copy(p);
		x.mod(p);

		while (comp(n,one)>0)
		{
			if (comp(x,zilch)==0) return 0;
			n8=n.lastbits(3);
			k=0;
			while (x.parity()==0)
			{
				k++;
				x.shr(1);
			}
			if (k%2==1) m+=(n8*n8-1)/8;
			m+=(n8-1)*(x.lastbits(2)-1)/4;
			t.copy(n);
			t.mod(x);
			n.copy(x);
			x.copy(t);
			m%=2;

		}
		if (m==0) return 1;
		else return -1;
	}

/* this=1/this mod p. Binary method */
	public void invmodp(BIG p)
	{
		mod(p);
		BIG u=new BIG(this);
		BIG v=new BIG(p);
		BIG x1=new BIG(1);
		BIG x2=new BIG(0);
		BIG t=new BIG(0);
		BIG one=new BIG(1);

		while (comp(u,one)!=0 && comp(v,one)!=0)
		{
			while (u.parity()==0)
			{
				u.fshr(1);
				if (x1.parity()!=0)
				{
					x1.add(p);
					x1.norm();
				}
				x1.fshr(1);
			}
			while (v.parity()==0)
			{
				v.fshr(1);
				if (x2.parity()!=0)
				{
					x2.add(p);
					x2.norm();
				}
				x2.fshr(1);
			}
			if (comp(u,v)>=0)
			{
				u.sub(v);
				u.norm();
				if (comp(x1,x2)>=0) x1.sub(x2);
				else
				{
					t.copy(p);
					t.sub(x2);
					x1.add(t);
				}
				x1.norm();
			}
			else
			{
				v.sub(u);
				v.norm();
				if (comp(x2,x1)>=0) x2.sub(x1);
				else
				{
					t.copy(p);
					t.sub(x1);
					x2.add(t);
				}
				x2.norm();
			}
		}
		if (comp(u,one)==0) copy(x1);
		else copy(x2);
	}
}