232 lines
7.1 KiB
C
232 lines
7.1 KiB
C
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/***************************************************************************
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*
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Copyright 2013 CertiVox UK Ltd. *
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*
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This file is part of CertiVox MIRACL Crypto SDK. *
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*
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The CertiVox MIRACL Crypto SDK provides developers with an *
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extensive and efficient set of cryptographic functions. *
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For further information about its features and functionalities please *
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refer to http://www.certivox.com *
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*
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* The CertiVox MIRACL Crypto SDK is free software: you can *
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redistribute it and/or modify it under the terms of the *
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GNU Affero General Public License as published by the *
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Free Software Foundation, either version 3 of the License, *
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or (at your option) any later version. *
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*
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* The CertiVox MIRACL Crypto SDK is distributed in the hope *
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that it will be useful, but WITHOUT ANY WARRANTY; without even the *
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implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. *
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See the GNU Affero General Public License for more details. *
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*
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* You should have received a copy of the GNU Affero General Public *
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License along with CertiVox MIRACL Crypto SDK. *
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If not, see <http://www.gnu.org/licenses/>. *
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*
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You can be released from the requirements of the license by purchasing *
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a commercial license. Buying such a license is mandatory as soon as you *
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develop commercial activities involving the CertiVox MIRACL Crypto SDK *
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without disclosing the source code of your own applications, or shipping *
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the CertiVox MIRACL Crypto SDK with a closed source product. *
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*
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***************************************************************************/
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/*
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* MIRACL arithmetic routines 3 - simple powers and roots
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* mrarth3.c
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*/
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#include <stdlib.h>
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#include "miracl.h"
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void expint(_MIPD_ int b,int n,big x)
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{ /* sets x=b^n */
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unsigned int bit,un;
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#ifdef MR_OS_THREADS
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miracl *mr_mip=get_mip();
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#endif
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if (mr_mip->ERNUM) return;
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convert(_MIPP_ 1,x);
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if (n==0) return;
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MR_IN(50)
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if (n<0)
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{
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mr_berror(_MIPP_ MR_ERR_NEG_POWER);
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MR_OUT
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return;
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}
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if (b==2) expb2(_MIPP_ n,x);
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else
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{
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bit=1;
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un=(unsigned int)n;
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while (un>=bit) bit<<=1;
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bit>>=1;
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while (bit>0)
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{ /* ltr method */
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multiply(_MIPP_ x,x,x);
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if ((bit&un)!=0) premult(_MIPP_ x,b,x);
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bit>>=1;
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}
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}
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MR_OUT
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}
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void power(_MIPD_ big x,long n,big z,big w)
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{ /* raise big number to int power w=x^n *
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* (mod z if z and w distinct) */
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mr_small norm;
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#ifdef MR_OS_THREADS
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miracl *mr_mip=get_mip();
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#endif
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copy(x,mr_mip->w5);
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zero(w);
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if(mr_mip->ERNUM || size(mr_mip->w5)==0) return;
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convert(_MIPP_ 1,w);
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if (n==0L) return;
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MR_IN(17)
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if (n<0L)
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{
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mr_berror(_MIPP_ MR_ERR_NEG_POWER);
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MR_OUT
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return;
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}
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if (w==z) forever
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{ /* "Russian peasant" exponentiation */
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if (n%2!=0L)
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multiply(_MIPP_ w,mr_mip->w5,w);
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n/=2L;
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if (mr_mip->ERNUM || n==0L) break;
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multiply(_MIPP_ mr_mip->w5,mr_mip->w5,mr_mip->w5);
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}
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else
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{
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norm=normalise(_MIPP_ z,z);
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divide(_MIPP_ mr_mip->w5,z,z);
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forever
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{
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if (mr_mip->user!=NULL) (*mr_mip->user)();
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if (n%2!=0L) mad(_MIPP_ w,mr_mip->w5,mr_mip->w5,z,z,w);
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n/=2L;
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if (mr_mip->ERNUM || n==0L) break;
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mad(_MIPP_ mr_mip->w5,mr_mip->w5,mr_mip->w5,z,z,mr_mip->w5);
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}
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if (norm!=1)
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{
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#ifdef MR_FP_ROUNDING
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mr_sdiv(_MIPP_ z,norm,mr_invert(norm),z);
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#else
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mr_sdiv(_MIPP_ z,norm,z);
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#endif
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divide(_MIPP_ w,z,z);
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}
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}
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MR_OUT
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}
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BOOL nroot(_MIPD_ big x,int n,big w)
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{ /* extract lower approximation to nth root *
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* w=x^(1/n) returns TRUE for exact root *
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* uses Newtons method */
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int sx,dif,s,p,d,lg2,lgx,rem;
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BOOL full;
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#ifdef MR_OS_THREADS
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miracl *mr_mip=get_mip();
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#endif
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if (mr_mip->ERNUM) return FALSE;
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if (size(x)==0 || n==1)
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{
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copy(x,w);
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return TRUE;
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}
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MR_IN(16)
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if (n<1) mr_berror(_MIPP_ MR_ERR_BAD_ROOT);
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sx=exsign(x);
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if (n%2==0 && sx==MINUS) mr_berror(_MIPP_ MR_ERR_NEG_ROOT);
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if (mr_mip->ERNUM)
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{
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MR_OUT
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return FALSE;
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}
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insign(PLUS,x);
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lgx=logb2(_MIPP_ x);
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if (n>=lgx)
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{ /* root must be 1 */
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insign(sx,x);
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convert(_MIPP_ sx,w);
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MR_OUT
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if (lgx==1) return TRUE;
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else return FALSE;
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}
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expb2(_MIPP_ 1+(lgx-1)/n,mr_mip->w2); /* guess root as 2^(log2(x)/n) */
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s=(-(((int)x->len-1)/n)*n);
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mr_shift(_MIPP_ mr_mip->w2,s/n,mr_mip->w2);
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lg2=logb2(_MIPP_ mr_mip->w2)-1;
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full=FALSE;
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if (s==0) full=TRUE;
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d=0;
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p=1;
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while (!mr_mip->ERNUM)
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{ /* Newtons method */
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copy(mr_mip->w2,mr_mip->w3);
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mr_shift(_MIPP_ x,s,mr_mip->w4);
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mr_mip->check=OFF;
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power(_MIPP_ mr_mip->w2,n-1,mr_mip->w6,mr_mip->w6);
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mr_mip->check=ON;
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divide(_MIPP_ mr_mip->w4,mr_mip->w6,mr_mip->w2);
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rem=size(mr_mip->w4);
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subtract(_MIPP_ mr_mip->w2,mr_mip->w3,mr_mip->w2);
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dif=size(mr_mip->w2);
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subdiv(_MIPP_ mr_mip->w2,n,mr_mip->w2);
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add(_MIPP_ mr_mip->w2,mr_mip->w3,mr_mip->w2);
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p*=2;
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if(p<lg2+d*mr_mip->lg2b) continue;
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if (full && mr_abs(dif)<n)
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{ /* test for finished */
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while (dif<0)
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{
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rem=0;
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decr(_MIPP_ mr_mip->w2,1,mr_mip->w2);
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mr_mip->check=OFF;
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power(_MIPP_ mr_mip->w2,n,mr_mip->w6,mr_mip->w6);
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mr_mip->check=ON;
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dif=mr_compare(x,mr_mip->w6);
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}
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copy(mr_mip->w2,w);
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insign(sx,w);
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insign(sx,x);
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MR_OUT
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if (rem==0 && dif==0) return TRUE;
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else return FALSE;
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}
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else
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{ /* adjust precision */
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d*=2;
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if (d==0) d=1;
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s+=d*n;
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if (s>=0)
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{
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d-=s/n;
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s=0;
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full=TRUE;
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}
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mr_shift(_MIPP_ mr_mip->w2,d,mr_mip->w2);
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}
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p/=2;
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}
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MR_OUT
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return FALSE;
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}
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