ippsGenCRCOptPoly_8u
Computes optimization table for
ippsCRC_8u
.Syntax
IppStatus ippsGenCRCOptPoly_8u(Ipp64u*
poly
, Ipp8u optPoly[128]
);
Include Files
ippe.h
Domain Dependencies
ippcore.h
Libraries
ippe.lib
Parameters
- poly
- CRC polynomial with explicit leading 1. Indicates CRC length: 8/16/24/32 bits.
- optPoly
- The initialized data table (NULL, by default).
Description
The
ippsGenCRCOptPoly_8u
function is auxiliary for ippsCRC_8u
and computes a table for low-level optimization in ippsCRC_8u
. You can use this function in the
initialization procedure of the application. Low-level
ippsCRC_8u
optimization requires special tables for every poly
value. This function
calls the optimized code only for the fixed set of polynomials by default and
returns the ippStsNoErr
status. If such
table is not available for poly
, it calculates CRC using non-optimized code and returns the
ippStsNonOptimalPathSelected
warning. To compute CRC for an arbitrary polynomial with low-level
optimization, you need to initialize the
optPoly
table first with the
ippsGenCRCOptPoly_8u
function and transfer optPoly
into ippsCRC_8u
.Example
// Computing the table for the function that does not support CRC16 with the 0x8005 polynomial. int main() { Ipp8u* src = "123456789"; IppStatus status; Ipp32u CRC; Ipp64u poly = 0x18005; Ipp32u init = 0; Ipp8u optPoly[128]; //function returns ippStsNonOptimalPathSelected status = ippsCRC_8u(src, 9, poly, NULL, init, &CRC); printf("status = '%s'\n", ippGetStatusString(status)); printf("CRC=0x%x\n", CRC); //function returns ippStsNoErr and //calls optimized code status = ippsGenCRCOptPoly_8u(poly, optPoly); status = ippsCRC_8u(src, 9, poly, optPoly, init, &CRC); printf("status = '%s'\n", ippGetStatusString(status)); printf("CRC=0x%x\n", CRC); return 0; }
The result:
status = 'The function is inefficient due to the combination of input parameters' CRC=0xfee8 status = 'ippStsNoErr: No errors' CRC=0xfee8
// Computing CRC6 int main() { Ipp8u* src = "123456789"; IppStatus status; Ipp32u CRC; Ipp64u poly = 0x61;//CRC6 polynomial; Ipp32u init = 0x0; Ipp8u optPoly[128]; //Function calculates crc8/crc16/crc24/crc32 //Shift 2 bits left, CRC6 -> CRC8 poly <<= 2; status = ippsGenCRCOptPoly_8u(poly, optPoly); status = ippsCRC_8u(src, 9, poly, optPoly, init, &CRC); printf("status = %d, '%s'\n", status, ippGetStatusString(status)); //Shift 2 bits right, CRC8 -> CRC6 printf("crc6=%x\n", CRC >> 2); return 0; }
Return Values
- ippStsNoErr
- Indicates no error.
- ippStsNullPtrErr
- Indicates an error if the pointer to the source vector isNULL.
- ippStsAlgTypeErr
- Indicates an error if the most significant 1 bit is in the wrong position.