monero/tests/unit_tests/mul_div.cpp

// Copyright (c) 2014-2019, The Monero Project
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// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers

#include "gtest/gtest.h"

#include "int-util.h"

namespace
{
  TEST(mul128, handles_zero)
  {
    uint64_t hi, lo;

    lo = mul128(0, 0, &hi);
    ASSERT_EQ(lo, 0);
    ASSERT_EQ(hi, 0);

    lo = mul128(7, 0, &hi);
    ASSERT_EQ(lo, 0);
    ASSERT_EQ(hi, 0);

    lo = mul128(0, 7, &hi);
    ASSERT_EQ(lo, 0);
    ASSERT_EQ(hi, 0);
  }

  TEST(mul128, handles_one)
  {
    uint64_t hi, lo;

    lo = mul128(1, 1, &hi);
    ASSERT_EQ(lo, 1);
    ASSERT_EQ(hi, 0);

    lo = mul128(7, 1, &hi);
    ASSERT_EQ(lo, 7);
    ASSERT_EQ(hi, 0);

    lo = mul128(1, 7, &hi);
    ASSERT_EQ(lo, 7);
    ASSERT_EQ(hi, 0);
  }

  TEST(mul128_without_carry, multiplies_correctly)
  {
    uint64_t hi, lo;

    lo = mul128(0x3333333333333333, 5, &hi);
    ASSERT_EQ(lo, 0xffffffffffffffff);
    ASSERT_EQ(hi, 0);

    lo = mul128(5, 0x3333333333333333, &hi);
    ASSERT_EQ(lo, 0xffffffffffffffff);
    ASSERT_EQ(hi, 0);

    lo = mul128(0x1111111111111111, 0x1111111111111111, &hi);
    ASSERT_EQ(lo, 0x0fedcba987654321);
    ASSERT_EQ(hi, 0x0123456789abcdf0);;
  }

  TEST(mul128_with_carry_1_only, multiplies_correctly)
  {
    uint64_t hi, lo;

    lo = mul128(0xe0000000e0000000, 0xe0000000e0000000, &hi);
    ASSERT_EQ(lo, 0xc400000000000000);
    ASSERT_EQ(hi, 0xc400000188000000);
  }

  TEST(mul128_with_carry_2_only, multiplies_correctly)
  {
    uint64_t hi, lo;

    lo = mul128(0x10000000ffffffff, 0x10000000ffffffff, &hi);
    ASSERT_EQ(lo, 0xdffffffe00000001);
    ASSERT_EQ(hi, 0x0100000020000000);
  }

  TEST(mul128_with_carry_1_and_2, multiplies_correctly)
  {
    uint64_t hi, lo;

    lo = mul128(0xf1f2f3f4f5f6f7f8, 0xf9f0fafbfcfdfeff, &hi);
    ASSERT_EQ(lo, 0x52118e5f3b211008);
    ASSERT_EQ(hi, 0xec39104363716e59);

    lo = mul128(0xffffffffffffffff, 0xffffffffffffffff, &hi);
    ASSERT_EQ(lo, 0x0000000000000001);
    ASSERT_EQ(hi, 0xfffffffffffffffe);
  }

  TEST(div128_32, handles_zero)
  {
    uint32_t reminder;
    uint64_t hi;
    uint64_t lo;

    reminder = div128_32(0, 0, 7, &hi, &lo);
    ASSERT_EQ(reminder, 0);
    ASSERT_EQ(hi, 0);
    ASSERT_EQ(lo, 0);

    // Division by zero is UB, so can be tested correctly
  }

  TEST(div128_32, handles_one)
  {
    uint32_t reminder;
    uint64_t hi;
    uint64_t lo;

    reminder = div128_32(0, 7, 1, &hi, &lo);
    ASSERT_EQ(reminder, 0);
    ASSERT_EQ(hi, 0);
    ASSERT_EQ(lo, 7);

    reminder = div128_32(7, 0, 1, &hi, &lo);
    ASSERT_EQ(reminder, 0);
    ASSERT_EQ(hi, 7);
    ASSERT_EQ(lo, 0);
  }

  TEST(div128_32, handles_if_dividend_less_divider)
  {
    uint32_t reminder;
    uint64_t hi;
    uint64_t lo;

    reminder = div128_32(0, 1383746, 1645825, &hi, &lo);
    ASSERT_EQ(reminder, 1383746);
    ASSERT_EQ(hi, 0);
    ASSERT_EQ(lo, 0);
  }

  TEST(div128_32, handles_if_dividend_dwords_less_divider)
  {
    uint32_t reminder;
    uint64_t hi;
    uint64_t lo;

    reminder = div128_32(0x5AD629E441074F28, 0x0DBCAB2B231081F1, 0xFE735CD6, &hi, &lo);
    ASSERT_EQ(reminder, 0xB9C924E9);
    ASSERT_EQ(hi, 0x000000005B63C274);
    ASSERT_EQ(lo, 0x9084FC024383E48C);
  }

  TEST(div128_32, works_correctly)
  {
    uint32_t reminder;
    uint64_t hi;
    uint64_t lo;

    reminder = div128_32(2, 0, 2, &hi, &lo);
    ASSERT_EQ(reminder, 0);
    ASSERT_EQ(hi, 1);
    ASSERT_EQ(lo, 0);

    reminder = div128_32(0xffffffffffffffff, 0, 0xffffffff, &hi, &lo);
    ASSERT_EQ(reminder, 0);
    ASSERT_EQ(hi, 0x0000000100000001);
    ASSERT_EQ(lo, 0);

    reminder = div128_32(0xffffffffffffffff, 5846, 0xffffffff, &hi, &lo);
    ASSERT_EQ(reminder, 5846);
    ASSERT_EQ(hi, 0x0000000100000001);
    ASSERT_EQ(lo, 0);

    reminder = div128_32(0xffffffffffffffff - 1, 0, 0xffffffff, &hi, &lo);
    ASSERT_EQ(reminder, 0xfffffffe);
    ASSERT_EQ(hi, 0x0000000100000000);
    ASSERT_EQ(lo, 0xfffffffefffffffe);

    reminder = div128_32(0x2649372534875028, 0xaedbfedc5adbc739, 0x27826534, &hi, &lo);
    ASSERT_EQ(reminder, 0x1a6dc2e5);
    ASSERT_EQ(hi, 0x00000000f812c1f8);
    ASSERT_EQ(lo, 0xddf2fdb09bc2e2e9);
  }
}