inline void PIRServer::decompose_to_plaintexts_ptr()

in pir_server.cpp [375:410]

• 24 lines of code
• 5 McCabe index (conditional complexity)

inline void PIRServer::decompose_to_plaintexts_ptr(const Ciphertext &encrypted, Plaintext *plain_ptr, int logt) {

    vector<Plaintext> result;
    auto coeff_count = params_.poly_modulus_degree();
    auto coeff_mod_count = params_.coeff_modulus().size();
    auto encrypted_count = encrypted.size();

    uint64_t t1 = 1 << logt;  //  t1 <= t. 

    uint64_t t1minusone =  t1 -1; 
    // A triple for loop. Going over polys, moduli, and decomposed index.

    for (int i = 0; i < encrypted_count; i++) {
        const uint64_t *encrypted_pointer = encrypted.data(i);
        for (int j = 0; j < coeff_mod_count; j++) {
            // populate one poly at a time.
            // create a polynomial to store the current decomposition value
            // which will be copied into the array to populate it at the current
            // index.
            double logqj = log2(params_.coeff_modulus()[j].value());
            //int expansion_ratio = ceil(logqj + exponent - 1) / exponent;
            int expansion_ratio =  ceil(logqj / logt); 
            // cout << "local expansion ratio = " << expansion_ratio << endl;
            uint64_t curexp = 0;
            for (int k = 0; k < expansion_ratio; k++) {
                // Decompose here
                for (int m = 0; m < coeff_count; m++) {
                    plain_ptr[i * coeff_mod_count * expansion_ratio
                        + j * expansion_ratio + k][m] =
                        (*(encrypted_pointer + m + (j * coeff_count)) >> curexp) & t1minusone;
                }
                curexp += logt;
            }
        }
    }
}