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reset() cleared the hash array but left the `first` flag false, so a calculator reused after reset() took the XOR update path on its next add() instead of the initialisation path. This produced an incorrect hash for any pearson object that was reset and reused. Reset `first` to true in reset() so a reset calculator behaves like a freshly constructed one. Add test_pearson_reset regression test. Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com>
190 lines
6.8 KiB
C++
190 lines
6.8 KiB
C++
/******************************************************************************
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The MIT License(MIT)
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Embedded Template Library.
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https://github.com/ETLCPP/etl
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https://www.etlcpp.com
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Copyright(c) 2015 John Wellbelove
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files(the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions :
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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******************************************************************************/
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#include "unit_test_framework.h"
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#include <iomanip>
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#include <iterator>
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#include <stdint.h>
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#include <string>
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#include <vector>
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#include "etl/endianness.h"
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#include "etl/pearson.h"
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const size_t HASH_SIZE = 8;
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typedef etl::pearson<HASH_SIZE>::value_type hash_t;
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//***************************************************************************
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/// Pearson lookup table
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/// \ingroup pearson
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//***************************************************************************
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namespace etl
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{
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static const uint8_t PEARSON_LOOKUP[] = {
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228, 39, 61, 95, 227, 187, 0, 197, 31, 189, 161, 222, 34, 15, 221, 246, 19, 234, 6, 50, 113, 3, 91, 63, 77, 245, 144, 2, 183,
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196, 25, 226, 97, 126, 48, 59, 217, 4, 100, 145, 12, 88, 203, 149, 80, 154, 38, 27, 224, 218, 158, 115, 202, 79, 53, 83, 242, 36,
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139, 131, 136, 191, 42, 170, 23, 99, 156, 51, 143, 60, 233, 206, 62, 108, 17, 67, 81, 71, 93, 195, 26, 231, 247, 96, 24, 200, 176,
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209, 152, 212, 138, 165, 75, 185, 130, 248, 125, 110, 10, 116, 201, 90, 69, 204, 85, 251, 78, 157, 47, 184, 169, 141, 134, 230, 89, 21,
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146, 46, 55, 128, 148, 207, 216, 11, 114, 199, 103, 102, 166, 244, 5, 104, 225, 160, 132, 28, 172, 65, 121, 140, 153, 119, 198, 210, 58,
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87, 117, 177, 33, 22, 13, 37, 49, 174, 109, 40, 73, 211, 18, 167, 164, 252, 168, 74, 30, 173, 35, 98, 66, 193, 94, 175, 86, 54,
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179, 122, 220, 151, 192, 29, 133, 254, 155, 127, 240, 232, 190, 180, 8, 68, 236, 20, 137, 92, 219, 208, 52, 250, 147, 142, 111, 112, 120,
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45, 135, 255, 123, 229, 57, 182, 243, 124, 186, 253, 7, 237, 9, 16, 70, 171, 235, 107, 223, 118, 215, 178, 194, 181, 43, 188, 106, 105,
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64, 241, 84, 238, 159, 44, 32, 76, 213, 163, 150, 101, 129, 14, 249, 205, 214, 1, 41, 56, 162, 72, 239, 82};
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}
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//***************************************************************************
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// Comparison calculator based on Wikipedia example.
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// https://en.wikipedia.org/wiki/Pearson_hashing
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//***************************************************************************
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template <typename TContainer>
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hash_t Pearson_Compare(const TContainer& data)
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{
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hash_t hash;
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hash.fill(0);
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for (size_t j = 0UL; j < HASH_SIZE; ++j)
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{
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uint8_t subhash = etl::PEARSON_LOOKUP[(static_cast<size_t>(data[0]) + j) % 256];
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for (size_t i = 1UL; i < data.size(); ++i)
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{
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subhash = etl::PEARSON_LOOKUP[subhash ^ data[i]];
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}
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hash[j] = subhash;
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}
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return hash;
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}
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//***************************************************************************
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// Output stream for hash_t
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//***************************************************************************
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std::ostream& operator<<(std::ostream& os, const hash_t& hash)
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{
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for (size_t i = 0UL; i < hash.size(); ++i)
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{
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os << int(hash[i]) << " ";
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}
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return os;
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}
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namespace
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{
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SUITE(test_pearson)
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{
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//*************************************************************************
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TEST(test_pearson_constructor)
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{
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std::string data("123456789");
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hash_t compare = Pearson_Compare(data);
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hash_t hash = etl::pearson<HASH_SIZE>(data.begin(), data.end());
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CHECK(compare == hash);
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}
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//*************************************************************************
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TEST(test_pearson_add_values)
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{
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std::string data("123456789");
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etl::pearson<HASH_SIZE> pearson_calculator;
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for (size_t i = 0UL; i < data.size(); ++i)
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{
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pearson_calculator.add(static_cast<uint8_t>(data[i]));
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}
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hash_t compare = Pearson_Compare(data);
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hash_t hash = pearson_calculator;
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CHECK(compare == hash);
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}
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//*************************************************************************
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TEST(test_pearson_add_range)
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{
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std::string data("123456789");
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etl::pearson<HASH_SIZE> pearson_calculator;
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pearson_calculator.add(data.begin(), data.end());
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hash_t compare = Pearson_Compare(data);
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hash_t hash = pearson_calculator.value();
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CHECK(compare == hash);
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}
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//*************************************************************************
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TEST(test_pearson_reset)
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{
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std::string data("123456789");
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etl::pearson<HASH_SIZE> pearson_calculator;
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// Use the calculator, then reset it and reuse it for the same data.
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pearson_calculator.add(data.begin(), data.end());
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pearson_calculator.reset();
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pearson_calculator.add(data.begin(), data.end());
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hash_t compare = Pearson_Compare(data);
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hash_t hash = pearson_calculator.value();
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// A reset calculator must produce the same hash as a fresh one.
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CHECK(compare == hash);
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}
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//*************************************************************************
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TEST(test_pearson_add_range_endian)
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{
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std::vector<uint8_t> data1 = {0x01U, 0x02U, 0x03U, 0x04U, 0x05U, 0x06U, 0x07U, 0x08U};
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std::vector<uint32_t> data2;
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if (etl::endianness::value() == etl::endian::little)
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{
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data2 = {0x04030201UL, 0x08070605UL};
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}
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else
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{
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data2 = {0x01020304UL, 0x05060708UL};
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}
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std::vector<uint8_t> data3 = {0x08U, 0x07U, 0x06U, 0x05U, 0x04U, 0x03U, 0x02U, 0x01U};
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hash_t hash1 = etl::pearson<HASH_SIZE>(data1.begin(), data1.end());
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hash_t hash2 = etl::pearson<HASH_SIZE>((uint8_t*)&data2[0], (uint8_t*)(&data2[0] + data2.size()));
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CHECK(hash1 == hash2);
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hash_t hash3 = etl::pearson<HASH_SIZE>(data3.rbegin(), data3.rend());
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CHECK(hash1 == hash3);
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}
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}
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} // namespace
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