#include <stddef.h>
#include <stdint.h>
#include "crc64.h"
uint64_t	crc_tab64[256];
/*
 * void init_crc64_tab( void );
 *
 * For optimal speed, the CRC64 calculation uses a table with pre-calculated
 * bit patterns which are used in the XOR operations in the program. This table
 * is generated during compilation of the library and added to the library as a
 * table with constant values.
 */
void init_crc64_tab( uint64_t poly ) {

	uint64_t i;
	uint64_t j;
	uint64_t c;
	uint64_t crc;

	for (i=0; i<256; i++) {

		crc = 0;
		c   = i << 56;

		for (j=0; j<8; j++) {

			if ( ( crc ^ c ) & 0x8000000000000000ull ) crc = ( crc << 1 ) ^ poly;
			else                                       crc =   crc << 1;

			c = c << 1;
		}

		crc_tab64[i] = crc;
	}

}  /* init_crc64_tab */

/*
 * uint64_t crc_64_ecma( const unsigned char *input_str, size_t num_bytes );
 *
 * The function crc_64() calculates in one pass the 64 bit CRC value
 * for a byte string that is passed to the function together with a parameter
 * indicating the length.
 * This is used for CRC64-ECMA and CRC64-ISO
 */

uint64_t crc_64(const unsigned char *input_str, size_t num_bytes)
{
	uint64_t crc;
	const unsigned char *ptr;
	size_t a;
	crc = CRC_START_64;
	ptr = input_str;
	if ( ptr != NULL ) {
		for (a=0; a<num_bytes; a++) {
		crc = (crc << 8) ^ crc_tab64[ ((crc >> 56) ^ (uint64_t) *ptr++) & 0x00000000000000FFull ];
	}
	return crc;
}  /* crc_64 */


/*
 * The function crc_64_inv() calculates in one pass the CRC64 64 bit CRC
 * value for a byte string that is passed to the function together with a
 * parameter indicating the length.
 * This is used for CRC64-WE
 */

uint64_t crc_64_inv( const unsigned char *input_str, size_t num_bytes ) {

	uint64_t crc;
	const unsigned char *ptr;
	size_t a;

	crc = CRC_START_64_INV;
	ptr = input_str;

	if ( ptr != NULL ) for (a=0; a<num_bytes; a++) {

		crc = (crc << 8) ^ crc_tab64[ ((crc >> 56) ^ (uint64_t) *ptr++) & 0x00000000000000FFull ];
	}

	return crc ^ 0xFFFFFFFFFFFFFFFFull;

}  /* crc_64_inv */