ext/ipp/sources/ippcp/pcpgfpecbufsize.c

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/*
//     Intel(R) Integrated Performance Primitives. Cryptography Primitives.
//     EC over GF(p^m) definitinons
//
//     Context:
//        ippsGFpECScratchBufferSize()
//
*/

#include "owndefs.h"
#include "owncp.h"
#include "pcpgfpecstuff.h"
#include "pcpeccp.h"

/*F*
// Name: ippsGFpScratchBufferSize
//
// Purpose: Gets the size of the scratch buffer.
//
// Returns:                   Reason:
//    ippStsNullPtrErr          pEC == NULL
//                              pBufferSize == NULL
//    ippStsContextMatchErr     invalid pEC->idCtx
//    ippStsBadArgErr           0>=nScalars
//                              nScalars>6
//    ippStsNoErr               no error
//
// Parameters:
//    nScalars        Number of scalar values.
//    pEC             Pointer to the context of the elliptic curve
//    pBufferSize     Pointer to the calculated buffer size in bytes.
//
*F*/

IPPFUN(IppStatus, ippsGFpECScratchBufferSize,(int nScalars, const IppsGFpECState* pEC, int* pBufferSize))
{
   IPP_BAD_PTR2_RET(pEC, pBufferSize);
   pEC = (IppsGFpECState*)( IPP_ALIGNED_PTR(pEC, ECGFP_ALIGNMENT) );
   IPP_BADARG_RET( !ECP_TEST_ID(pEC), ippStsContextMatchErr );

   IPP_BADARG_RET( (0>=nScalars)||(nScalars>IPP_MAX_EXPONENT_NUM), ippStsBadArgErr);

   {
      /* select constant size of window */
      const int w = 5;
      /* number of table entries */
      const int nPrecomputed = 1<<(w-1);  /* because of signed digit representation of scalar is uses */

      int pointDataSize = ECP_POINTLEN(pEC)*sizeof(BNU_CHUNK_T);

      *pBufferSize = nScalars * pointDataSize*nPrecomputed + CACHE_LINE_SIZE;

      return ippStsNoErr;
   }
}