ext/ipp/sources/ippcp/pcpgfpecsetpointoctstring.c

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/*
//
//  Purpose:
//     Intel(R) Integrated Performance Primitives. Cryptography Primitives.
//     EC over GF(p) Operations
//
//     Context:
//        ippsGFpECSetPointOctString()
//
*/

#include "pcpgfpecessm2.h"
#include "pcpgfpecstuff.h"

/*F*
//    Name: ippsGFpECSetPointOctString
//
// Purpose: Converts x||y octstring into a point on EC
//
// Returns:                   Reason:
//    ippStsNullPtrErr           pPoint == NULL / pEC == NULL / pStr == NULL
//    ippStsContextMatchErr      pEC, pPoint invalid context
//    ippStsNotSupportedModeErr  pGFE->extdegree > 1
//    ippStsSizeErr              strLen is not equal to double GFp element
//    ippStsOutOfRangeErr        X or Y from the string exceeds the EC's field modulus or the point does not belong to the EC
//    ippStsNoErr                no errors
//
// Parameters:
//    pStr     pointer to the string to read from
//    strLen   length of the string
//    pPoint   pointer to output point
//    pEC      EC ctx
//
*F*/
IPPFUN(IppStatus, ippsGFpECSetPointOctString, (const Ipp8u* pStr,
   int strLen, IppsGFpECPoint* pPoint, IppsGFpECState* pEC)) {
   IPP_BAD_PTR3_RET(pPoint, pEC, pStr);
   IPP_BADARG_RET(pEC->idCtx != idCtxGFPEC, ippStsContextMatchErr);
   IPP_BADARG_RET(!pEC->subgroup, ippStsContextMatchErr);
   IPP_BADARG_RET(1 < pEC->pGF->pGFE->extdegree, ippStsNotSupportedModeErr);

   {
      gsModEngine* pGFE = pEC->pGF->pGFE;
      int elemLen = BITS2WORD8_SIZE(pGFE->modBitLen);
      IPP_BADARG_RET(strLen != elemLen * 2, ippStsSizeErr);

      {
         IppStatus ret;
         IppsGFpElement ptX, ptY;
         cpGFpElementConstruct(&ptX, cpGFpGetPool(1, pGFE), pGFE->modLen);
         cpGFpElementConstruct(&ptY, cpGFpGetPool(1, pGFE), pGFE->modLen);

         ret = ippsGFpSetElementOctString(pStr, elemLen, &ptX, pEC->pGF);
         if (ippStsNoErr == ret) {
            pStr += elemLen;
            ret = ippsGFpSetElementOctString(pStr, elemLen, &ptY, pEC->pGF);
         }
         if (ippStsNoErr == ret) {
            ret = ippsGFpECSetPoint(&ptX, &ptY, pPoint, pEC);
         }

         cpGFpReleasePool(2, pGFE); /* release ptX and ptY from the pool */

         return ret;
      }
   }
}