simple_checksum.cpp

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//Copyright>    OpenRadioss
//Copyright>    Copyright (C) 1986-2025 Altair Engineering Inc.
//Copyright>
//Copyright>    This program is free software: you can redistribute it and/or modify
//Copyright>    it under the terms of the GNU Affero General Public License as published by
//Copyright>    the Free Software Foundation, either version 3 of the License, or
//Copyright>    (at your option) any later version.
//Copyright>
//Copyright>    This program is distributed in the hope that it will be useful,
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//Copyright>    along with this program.  If not, see <https://www.gnu.org/licenses/>.
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//Copyright>    Commercial Alternative: Altair Radioss Software
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// ----------------------------------------------------------------------------------------------------------------------
 
#include <cstdint>
#include <cstring>  // For memcpy
#include <cmath>    // For std::isnan
#include <limits>   // For std::numeric_limits
 
extern "C" {
 
#define POLYNOMIAL 0xEDB88320  // standard polynomial for CRC32
 
void init_crc32_table(uint32_t *crc32_table) {
    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;
    }
} 
void simple_checksum(const double* vector, const int* length, double* hash) {
    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);
  }
}