simple_checksum.cpp File Reference

#include <cstdint>
#include <cstring>
#include <cmath>
#include <limits>

Go to the source code of this file.

Macros
#define	POLYNOMIAL   0xEDB88320

Functions
void	init_crc32_table (uint32_t *crc32_table)
void	simple_checksum (const double *vector, const int *length, double *hash)

Macro Definition Documentation

POLYNOMIAL

#define POLYNOMIAL   0xEDB88320

Definition at line 32 of file simple_checksum.cpp.

Function Documentation

init_crc32_table()

void init_crc32_table

(

uint32_t *

crc32_table

)

Definition at line 34 of file simple_checksum.cpp.

                                             {
    for (uint32_t i = 0; i < 256; i++) {
        uint32_t crc = i;
        for (uint32_t j = 0; j < 8; j++) {
            crc = (crc >> 1) ^ (POLYNOMIAL * (crc & 1));
        }
        crc32_table[i] = crc;
    }
} 

simple_checksum()

void simple_checksum	(	const double *	vector,
		const int *	length,
		double *	hash )

Definition at line 43 of file simple_checksum.cpp.

                                                                            {
    uint32_t crc32_table[256];
    uint32_t crc = 0xFFFFFFFF; // initial value
 
        init_crc32_table(crc32_table);
 
        for (size_t i = 0; i < *length; i++) {
        uint64_t value = *(uint64_t*)&vector[i]; // Conversion of double to uint64_t
        
        for (size_t j = 0; j < sizeof(value); j++) {
            uint8_t byte = value & 0xFF; // byte extraction
            crc = (crc >> 8) ^ crc32_table[(crc ^ byte) & 0xFF];
            value >>= 8; // shift for the next byte
        }
     }
     *hash = (double) (crc ^ 0xFFFFFFFF);
  }