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     40 
     41 /*
     42 //               Intel(R) Integrated Performance Primitives
     43 //                   Cryptographic Primitives (ippcp)
     44 //
     45 //  Contents:
     46 //     ippsSub_BN()
     47 //
     48 */
     49 
     50 #include "owndefs.h"
     51 #include "owncp.h"
     52 #include "pcpbn.h"
     53 #include "pcptool.h"
     54 
     55 
     56 /*F*
     57 //    Name: ippsSub_BN
     58 //
     59 // Purpose: Subtract BigNums.
     60 //
     61 // Returns:                Reason:
     62 //    ippStsNullPtrErr        pA  == NULL
     63 //                            pB  == NULL
     64 //                            pR  == NULL
     65 //    ippStsContextMatchErr   !BN_VALID_ID(pA)
     66 //                            !BN_VALID_ID(pB)
     67 //                            !BN_VALID_ID(pR)
     68 //    ippStsOutOfRangeErr     pR can not hold result
     69 //    ippStsNoErr             no errors
     70 //
     71 // Parameters:
     72 //    pA    source BigNum
     73 //    pB    source BigNum
     74 //    pR    resultant BigNum
     75 //
     76 *F*/
     77 IPPFUN(IppStatus, ippsSub_BN, (IppsBigNumState* pA, IppsBigNumState* pB, IppsBigNumState* pR))
     78 {
     79    IPP_BAD_PTR3_RET(pA, pB, pR);
     80 
     81    pA = (IppsBigNumState*)( IPP_ALIGNED_PTR(pA, BN_ALIGNMENT) );
     82    IPP_BADARG_RET(!BN_VALID_ID(pA), ippStsContextMatchErr);
     83    pB = (IppsBigNumState*)( IPP_ALIGNED_PTR(pB, BN_ALIGNMENT) );
     84    IPP_BADARG_RET(!BN_VALID_ID(pB), ippStsContextMatchErr);
     85    pR = (IppsBigNumState*)( IPP_ALIGNED_PTR(pR, BN_ALIGNMENT) );
     86    IPP_BADARG_RET(!BN_VALID_ID(pR), ippStsContextMatchErr);
     87 
     88    {
     89       cpSize nsA = BN_SIZE(pA);
     90       cpSize nsB = BN_SIZE(pB);
     91       cpSize nsR = BN_ROOM(pR);
     92       IPP_BADARG_RET(nsR < IPP_MAX(nsA, nsB), ippStsOutOfRangeErr);
     93 
     94       {
     95          BNU_CHUNK_T* pDataR = BN_NUMBER(pR);
     96 
     97          IppsBigNumSGN sgnA = BN_SIGN(pA);
     98          IppsBigNumSGN sgnB = BN_SIGN(pB);
     99          BNU_CHUNK_T* pDataA = BN_NUMBER(pA);
    100          BNU_CHUNK_T* pDataB = BN_NUMBER(pB);
    101 
    102          BNU_CHUNK_T carry;
    103 
    104          if(sgnA!=sgnB) {
    105             if(nsA < nsB) {
    106                SWAP(nsA, nsB);
    107                SWAP_PTR(BNU_CHUNK_T, pDataA, pDataB);
    108             }
    109 
    110             carry = cpAdd_BNU(pDataR, pDataA, pDataB, nsB);
    111             if(nsA>nsB)
    112                carry = cpInc_BNU(pDataR+nsB, pDataA+nsB, nsA-nsB, carry);
    113             if(carry) {
    114                if(nsR > nsA)
    115                   pDataR[nsA++] = carry;
    116                else
    117                   IPP_ERROR_RET(ippStsOutOfRangeErr);
    118             }
    119             BN_SIGN(pR) = sgnA;
    120          }
    121 
    122          else {
    123             int cmpRes= cpCmp_BNU(pDataA, nsA, pDataB, nsB);
    124 
    125             if(0==cmpRes) {
    126                ZEXPAND_BNU(pDataR,0, nsR);
    127                BN_SIZE(pR) = 1;
    128                BN_SIGN(pR) = ippBigNumPOS;
    129                return ippStsNoErr;
    130             }
    131 
    132             if(0>cmpRes) {
    133                SWAP(nsA, nsB);
    134                SWAP_PTR(BNU_CHUNK_T, pDataA, pDataB);
    135             }
    136 
    137             carry = cpSub_BNU(pDataR, pDataA, pDataB, nsB);
    138             if(nsA>nsB)
    139                cpDec_BNU(pDataR+nsB, pDataA+nsB, nsA-nsB, carry);
    140 
    141             BN_SIGN(pR) = cmpRes>0? sgnA : INVERSE_SIGN(sgnA);
    142          }
    143 
    144          FIX_BNU(pDataR, nsA);
    145          BN_SIZE(pR) = nsA;
    146 
    147          return ippStsNoErr;
    148       }
    149    }
    150 }
    151