CRC16_test.cc

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#include "catch.hpp"
#include "CRC16.hh"
 
#include "narrow.hh"
#include "xrange.hh"
 
#include <array>
#include <bit>
 
using namespace openmsx;
 
TEST_CASE("CRC16")
{
        CRC16 crc;
        REQUIRE(crc.getValue() == 0xFFFF);
 
        // Test a simple sequence
        SECTION("'3 x A1' in a loop") {
                repeat(3, [&] { crc.update(0xA1); });
                CHECK(crc.getValue() == 0xCDB4);
        }
        SECTION("'3 x A1' in one chunk") {
                static constexpr std::array<uint8_t, 3> buf = { 0xA1, 0xA1, 0xA1 };
                crc.update(buf);
                CHECK(crc.getValue() == 0xCDB4);
        }
        SECTION("'3 x A1' via init") {
                crc.init({0xA1, 0xA1, 0xA1});
                CHECK(crc.getValue() == 0xCDB4);
        }
 
        // Internally the block-update method works on chunks of 8 bytes,
        // so also try a few bigger examples
        //   not (an integer) multiple of 8
        SECTION("'123456789' in a loop") {
                for (char c : {'1', '2', '3', '4', '5', '6', '7', '8', '9'}) crc.update(c);
                CHECK(crc.getValue() == 0x29B1);
        }
        SECTION("'123456789' in one chunk") {
                static constexpr const char* const digits = "123456789";
                crc.update(std::span{std::bit_cast<const uint8_t*>(digits), 9});
                CHECK(crc.getValue() == 0x29B1);
        }
        // same as disk sector size
        SECTION("512 bytes") {
                std::array<uint8_t, 512> buf;
                for (auto i : xrange(512)) buf[i] = narrow_cast<uint8_t>(i & 255);
                SECTION("in a loop") {
                        for (char c : buf) crc.update(c);
                        CHECK(crc.getValue() == 0x56EE);
                }
                SECTION("in one chunk") {
                        crc.update(buf);
                        CHECK(crc.getValue() == 0x56EE);
                }
        }
 
        // Tests for init<..>()
        // It's possible to pass up-to 4 parameters. Verify that this gives
        // the same result as the other 2 CRC calculation methods.
        SECTION("'11' in a loop") {
                for (uint8_t c : {uint8_t(0x11)}) crc.update(c);
                CHECK(crc.getValue() == 0xE3E0);
        }
        SECTION("'11' in one chunk") {
                static constexpr std::array<uint8_t, 1> buf = {0x11};
                crc.update(buf);
                CHECK(crc.getValue() == 0xE3E0);
        }
        SECTION("'11' via init") {
                crc.init({0x11});
                CHECK(crc.getValue() == 0xE3E0);
        }
 
        SECTION("'11 22' in a loop") {
                for (uint8_t c : {uint8_t(0x11), uint8_t(0x22)}) crc.update(c);
                CHECK(crc.getValue() == 0x296D);
        }
        SECTION("'11 22' in one chunk") {
                static constexpr std::array<uint8_t, 2> buf = {0x11, 0x22};
                crc.update(buf);
                CHECK(crc.getValue() == 0x296D);
        }
        SECTION("'11 22' via init") {
                crc.init({0x11, 0x22});
                CHECK(crc.getValue() == 0x296D);
        }
 
        SECTION("'11 22 33' in a loop") {
                for (uint8_t c : {uint8_t(0x11), uint8_t(0x22), uint8_t(0x33)}) crc.update(c);
                CHECK(crc.getValue() == 0xDE7B);
        }
        SECTION("'11 22 33' in one chunk") {
                static constexpr std::array<uint8_t, 3> buf = {0x11, 0x22, 0x33};
                crc.update(buf);
                CHECK(crc.getValue() == 0xDE7B);
        }
        SECTION("'11 22 33' via init") {
                crc.init({0x11, 0x22, 0x33});
                CHECK(crc.getValue() == 0xDE7B);
        }
 
        SECTION("'11 22 33 44' in a loop") {
                for (uint8_t c : {uint8_t(0x11), uint8_t(0x22), uint8_t(0x33), uint8_t(0x44)}) crc.update(c);
                CHECK(crc.getValue() == 0x59F3);
        }
        SECTION("'11 22 33 44' in one chunk") {
                static constexpr std::array<uint8_t, 4> buf = {0x11, 0x22, 0x33, 0x44};
                crc.update(buf);
                CHECK(crc.getValue() == 0x59F3);
        }
        SECTION("'11 22 33 44' via init") {
                crc.init({0x11, 0x22, 0x33, 0x44});
                CHECK(crc.getValue() == 0x59F3);
        }
}
 
 
#if 0
 
// Functions to inspect the quality of the generated code
 
uint16_t test_init()
{
        // I verified that gcc is capable of optimizing this to 'return 0xcdb4'.
        CRC16 crc;
        crc.init({0xA1, 0xA1, 0xA1});
        return crc.getValue();
}
 
#endif