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/* 
//     Intel(R) Integrated Performance Primitives. Cryptography Primitives.
//     Operations over GF(p).
// 
//     Context:
//        ippsGFpSub_PE()
// 
*/
#include "owndefs.h"
#include "owncp.h"

#include "pcpgfpstuff.h"
#include "pcpgfpxstuff.h"
#include "pcptool.h"

/*F*
// Name: ippsGFpSub_PE
//
// Purpose: Subtract of GF element and parent GF element
//
// Returns:                   Reason:
//    ippStsNullPtrErr              NULL == pGFp
//                                  NULL == pA
//                                  NULL == pR
//                                  NULL == pParentB
//
//    ippStsContextMatchErr         invalid pGFp->idCtx
//                                  invalid pA->idCtx
//                                  invalid pR->idCtx
//                                  invalid pParentB->idCtx
//
//    ippStsOutOfRangeErr           GFPE_ROOM() != GFP_FELEN()
//
//    ippStsBadArgErr               pGFp does not specify prime field
//
//    ippStsNoErr                   no error
//
// Parameters:
//    pA         Pointer to the context of the first finite field element.
//    pParentB   Pointer to the context of the second finite field element.
//    pR         Pointer to the context of the result finite field element.
//    pGFp       Pointer to the context of the finite field.
//
*F*/

IPPFUN(IppStatus, ippsGFpSub_PE,(const IppsGFpElement* pA, const IppsGFpElement* pParentB,
                                 IppsGFpElement* pR, IppsGFpState* pGFp))
{
   IPP_BAD_PTR4_RET(pA, pParentB, pR, pGFp);
   pGFp = (IppsGFpState*)( IPP_ALIGNED_PTR(pGFp, GFP_ALIGNMENT) );
   IPP_BADARG_RET( !GFP_TEST_ID(pGFp), ippStsContextMatchErr );
   IPP_BADARG_RET( !GFPE_TEST_ID(pA), ippStsContextMatchErr );
   IPP_BADARG_RET( !GFPE_TEST_ID(pParentB), ippStsContextMatchErr );
   IPP_BADARG_RET( !GFPE_TEST_ID(pR), ippStsContextMatchErr );
   {
      gsModEngine* pGFE = GFP_PMA(pGFp);
      IPP_BADARG_RET( GFP_IS_BASIC(pGFE), ippStsBadArgErr )
      IPP_BADARG_RET( (GFPE_ROOM(pA)!=GFP_FELEN(pGFE)) || (GFPE_ROOM(pR)!=GFP_FELEN(pGFE)), ippStsOutOfRangeErr);
      IPP_BADARG_RET( (GFPE_ROOM(pParentB)!=GFP_FELEN(GFP_PARENT(pGFE))), ippStsOutOfRangeErr);

      cpGFpxSub_GFE(GFPE_DATA(pR), GFPE_DATA(pA), GFPE_DATA(pParentB), pGFE);
      return ippStsNoErr;
   }
}