219 lines
7.1 KiB
C
219 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 euclidean mediant rounding routine
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* mrround.c
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*/
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#include "miracl.h"
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#ifdef MR_FP
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#include <math.h>
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#endif
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#ifdef MR_FLASH
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static int euclid(_MIPD_ big x,int num)
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{ /* outputs next c.f. quotient from gcd(w5,w6) */
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mr_small sr,m;
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#ifdef MR_FP
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mr_small dres;
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#endif
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mr_small lr,lq;
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big t;
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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 (num==0)
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{
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mr_mip->oldn=(-1);
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mr_mip->carryon=FALSE;
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mr_mip->last=FALSE;
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if (mr_compare(mr_mip->w6,mr_mip->w5)>0)
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{ /* ensure w5>w6 */
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t=mr_mip->w5,mr_mip->w5=mr_mip->w6,mr_mip->w6=t;
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return (mr_mip->q=0);
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}
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}
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else if (num==mr_mip->oldn || mr_mip->q<0) return mr_mip->q;
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mr_mip->oldn=num;
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if (mr_mip->carryon) goto middle;
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start:
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if (size(mr_mip->w6)==0) return (mr_mip->q=(-1));
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mr_mip->ndig=(int)mr_mip->w5->len;
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mr_mip->carryon=TRUE;
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mr_mip->a=1;
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mr_mip->b=0;
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mr_mip->c=0;
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mr_mip->d=1;
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if (mr_mip->ndig==1)
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{
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mr_mip->last=TRUE;
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mr_mip->u=mr_mip->w5->w[0];
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mr_mip->v=mr_mip->w6->w[0];
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}
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else
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{
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m=mr_mip->w5->w[mr_mip->ndig-1]+1;
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if (mr_mip->base==0)
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{
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#ifndef MR_NOFULLWIDTH
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if (m==0)
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{
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mr_mip->u=mr_mip->w5->w[mr_mip->ndig-1];
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mr_mip->v=mr_mip->w6->w[mr_mip->ndig-1];
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}
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else
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{
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mr_mip->u=muldvm(mr_mip->w5->w[mr_mip->ndig-1],mr_mip->w5->w[mr_mip->ndig-2],m,&sr);
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mr_mip->v=muldvm(mr_mip->w6->w[mr_mip->ndig-1],mr_mip->w6->w[mr_mip->ndig-2],m,&sr);
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}
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#endif
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}
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else
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{
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mr_mip->u=muldiv(mr_mip->w5->w[mr_mip->ndig-1],mr_mip->base,mr_mip->w5->w[mr_mip->ndig-2],m,&sr);
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mr_mip->v=muldiv(mr_mip->w6->w[mr_mip->ndig-1],mr_mip->base,mr_mip->w6->w[mr_mip->ndig-2],m,&sr);
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}
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}
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mr_mip->ku=mr_mip->u;
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mr_mip->kv=mr_mip->v;
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middle:
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forever
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{ /* work only with most significant piece */
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if (mr_mip->last)
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{
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if (mr_mip->v==0) return (mr_mip->q=(-1));
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lq=MR_DIV(mr_mip->u,mr_mip->v);
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}
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else
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{
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if (((mr_mip->v+mr_mip->c)==0) || ((mr_mip->v+mr_mip->d)==0)) break;
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lq=MR_DIV((mr_mip->u+mr_mip->a),(mr_mip->v+mr_mip->c));
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if (lq!=MR_DIV((mr_mip->u+mr_mip->b),(mr_mip->v+mr_mip->d))) break;
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}
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if (lq>=(mr_small)(MR_TOOBIG/mr_abs(mr_mip->d))) break;
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mr_mip->q=(int)lq;
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mr_mip->r=mr_mip->a-mr_mip->q*mr_mip->c;
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mr_mip->a=mr_mip->c;
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mr_mip->c=mr_mip->r;
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mr_mip->r=mr_mip->b-mr_mip->q*mr_mip->d;
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mr_mip->b=mr_mip->d;
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mr_mip->d=mr_mip->r;
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lr=mr_mip->u-lq*mr_mip->v;
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mr_mip->u=mr_mip->v;
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mr_mip->v=lr;
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return mr_mip->q;
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}
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mr_mip->carryon=FALSE;
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if (mr_mip->b==0)
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{ /* update w5 and w6 */
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mr_mip->check=OFF;
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divide(_MIPP_ mr_mip->w5,mr_mip->w6,mr_mip->w7);
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mr_mip->check=ON;
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if (mr_lent(mr_mip->w7)>mr_mip->nib) return (mr_mip->q=(-2));
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t=mr_mip->w5,mr_mip->w5=mr_mip->w6,mr_mip->w6=t; /* swap(w5,w6) */
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copy(mr_mip->w7,x);
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return (mr_mip->q=size(x));
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}
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else
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{
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mr_mip->check=OFF;
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premult(_MIPP_ mr_mip->w5,mr_mip->c,mr_mip->w7);
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premult(_MIPP_ mr_mip->w5,mr_mip->a,mr_mip->w5);
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premult(_MIPP_ mr_mip->w6,mr_mip->b,mr_mip->w0);
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premult(_MIPP_ mr_mip->w6,mr_mip->d,mr_mip->w6);
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add(_MIPP_ mr_mip->w5,mr_mip->w0,mr_mip->w5);
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add(_MIPP_ mr_mip->w6,mr_mip->w7,mr_mip->w6);
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mr_mip->check=ON;
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}
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goto start;
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}
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void mround(_MIPD_ big num,big den,flash z)
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{ /* reduces and rounds the fraction num/den into z */
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int s;
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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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if (size(num)==0)
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{
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zero(z);
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return;
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}
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MR_IN(34)
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if (size(den)==0)
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{
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mr_berror(_MIPP_ MR_ERR_FLASH_OVERFLOW);
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MR_OUT
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return;
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}
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copy(num,mr_mip->w5);
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copy(den,mr_mip->w6);
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s=exsign(mr_mip->w5)*exsign(mr_mip->w6);
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insign(PLUS,mr_mip->w5);
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insign(PLUS,mr_mip->w6);
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if (mr_compare(mr_mip->w5,mr_mip->w6)==0)
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{
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convert(_MIPP_ s,z);
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MR_OUT
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return;
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}
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if (size(mr_mip->w6)==1)
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{
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if ((int)mr_mip->w5->len>mr_mip->nib)
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{
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mr_berror(_MIPP_ MR_ERR_FLASH_OVERFLOW);
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MR_OUT
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return;
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}
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copy(mr_mip->w5,z);
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insign(s,z);
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MR_OUT
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return;
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}
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build(_MIPP_ z,euclid);
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insign(s,z);
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MR_OUT
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}
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#endif
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