74 lines
2.1 KiB
C++
74 lines
2.1 KiB
C++
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#include "Rabin_fingerprint.hpp"
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Rabin_fingerprint::Rabin_fingerprint(uint32_t p, size_t window_size_in_bits) {
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set_modulo_polynomial(p);
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set_shift_polynomial(window_size_in_bits);
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}
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void Rabin_fingerprint::set_modulo_polynomial (uint32_t p) {
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polynomial = p & ((uint32_t)pow(2, 31)-1);
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}
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void Rabin_fingerprint::set_shift_polynomial (size_t window_size_in_bits) {
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#ifndef NDEBUG
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if (polynomial == 0)
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throw std::logic_error("Call set_modulo_polynomial first, as this function depends on the polynomial variable being set.");
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#endif
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shift_polynomial = 1;
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// NOTE: We shift the bit 1 space too long, since we are removing the bit that has been pushed outside the window
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for (size_t i = 0; i < window_size_in_bits; i++) {
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shift_polynomial <<= 1;
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if ((shift_polynomial & (uint32_t)pow(2, 31)) != 0)
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shift_polynomial ^= polynomial;
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}
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}
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void Rabin_fingerprint::push_char (char c) {
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std::bitset<8> b(c);
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for (char i = 7; i >= 0; i--) {
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push_bit((bool)b[i]);
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}
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}
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void Rabin_fingerprint::push_bit (bool b) {
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fingerprint <<= 1;
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fingerprint |= b;
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if ((fingerprint & (uint32_t)pow(2, 31)) != 0)
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fingerprint ^= polynomial;
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}
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void Rabin_fingerprint::shift_bit (bool b) {
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#ifndef NDEBUG
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if (shift_polynomial == 0)
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throw std::logic_error("Call set_shift_polynomial first, as this function depends on the shift_polynomial variable being set.");
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#endif
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if (b)
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fingerprint ^= shift_polynomial;
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}
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void Rabin_fingerprint::slide_char (char c_in, char c_out) {
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std::bitset<8> b_in(c_in);
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std::bitset<8> b_out(c_out);
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for (char i = 7; i >= 0; i--) {
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slide_bit((bool)b_in[i], (bool)b_out[i]);
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}
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}
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/* #include <iostream> */
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void Rabin_fingerprint::slide_bit (bool b_in, bool b_out) {
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/* std::cout << "bitset b(c): " << b << std::endl; */
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/* std::cout << "push bit " << b[i] << std::endl; */
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/* std::cout << "push bit " << b_in << std::endl; */
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push_bit(b_in);
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/* std::cout << "shift bit " << b_out << std::endl; */
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shift_bit(b_out);
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}
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uint32_t Rabin_fingerprint::get_fingerprint () {
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return fingerprint;
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}
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