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MINIFICPP-1383 fix intdiv_ceil #918

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MINIFICPP-1383 fix intdiv_ceil #918

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c3205e7
MINIFICPP-1383 intdiv_ceil: disable negative numbers
szaszm Oct 1, 2020
fcdecd3
MINIFICPP-1383 fix negative numbers, constexpr
szaszm Oct 1, 2020
585e874
MINIFICPP-1383 add more tests
szaszm Oct 2, 2020
b11f101
MINIFICPP-1383 check that constexpr division by zero doesn't compile
adebreceni Oct 7, 2020
c26cf15
MINIFICPP-1383 test does_compile test utility
szaszm Oct 7, 2020
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7 changes: 4 additions & 3 deletions libminifi/include/utils/GeneralUtils.h
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Expand Up @@ -42,10 +42,11 @@ using std::make_unique;
#endif /* < C++14 */

template<typename T, typename = typename std::enable_if<std::is_integral<T>::value>::type>
T intdiv_ceil(T numerator, T denominator) {
gsl_Expects(denominator != 0);
constexpr T intdiv_ceil(T numerator, T denominator) {
// note: division and remainder is 1 instruction on x86
return numerator / denominator + (numerator % denominator > 0);
return gsl_Expects(denominator != 0), ((numerator >= 0) != (denominator > 0)
? numerator / denominator // negative result rounds towards zero, i.e. up
: numerator / denominator + (numerator % denominator != 0));
}

using gsl::owner;
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44 changes: 32 additions & 12 deletions libminifi/test/unit/GeneralUtilsTest.cpp
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Expand Up @@ -32,18 +32,38 @@ TEST_CASE("GeneralUtils::make_unique", "[make_unique]") {
REQUIRE("test string" == *pstr);
}

TEST_CASE("GeneralUtils::intdiv_ceil", "[intdiv_ceil]") {
REQUIRE(0 == utils::intdiv_ceil(0, 1));
REQUIRE(0 == utils::intdiv_ceil(0, 2));
REQUIRE(1 == utils::intdiv_ceil(1, 2));
REQUIRE(1 == utils::intdiv_ceil(1, 3));
REQUIRE(1 == utils::intdiv_ceil(3, 3));
REQUIRE(2 == utils::intdiv_ceil(4, 3));
REQUIRE(2 == utils::intdiv_ceil(4, 3));
REQUIRE(0 == utils::intdiv_ceil(-1, 3));
REQUIRE(-1 == utils::intdiv_ceil(-3, 3));
REQUIRE(-1 == utils::intdiv_ceil(-4, 3));
}
// intdiv_ceil
static_assert(0 == utils::intdiv_ceil(0, 1), "");
static_assert(0 == utils::intdiv_ceil(0, 2), "");
static_assert(1 == utils::intdiv_ceil(1, 2), "");
static_assert(1 == utils::intdiv_ceil(1, 3), "");
static_assert(1 == utils::intdiv_ceil(3, 3), "");
static_assert(2 == utils::intdiv_ceil(4, 3), "");
static_assert(2 == utils::intdiv_ceil(5, 3), "");
static_assert(0 == utils::intdiv_ceil(-1, 3), "");
static_assert(-1 == utils::intdiv_ceil(-3, 3), "");
static_assert(-1 == utils::intdiv_ceil(-4, 3), "");
static_assert(2 == utils::intdiv_ceil(-4, -3), "");
static_assert(2 == utils::intdiv_ceil(-5, -3), "");
static_assert(0 == utils::intdiv_ceil(1, -3), "");
static_assert(-1 == utils::intdiv_ceil(5, -3), "");
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static_assert(3 == utils::intdiv_ceil(6, 2), "");
static_assert(-3 == utils::intdiv_ceil(-6, 2), "");
static_assert(-3 == utils::intdiv_ceil(6, -2), "");
static_assert(3 == utils::intdiv_ceil(-6, -2), "");
static_assert(0 == utils::intdiv_ceil(0, -10), "");

template<int N, int D, typename = void>
struct does_compile : std::false_type {};

template<int N, int D>
struct does_compile<N, D,
// we must force evaluation so decltype won't do
typename std::enable_if<(utils::intdiv_ceil(N, D), true)>::type> : std::true_type {};

static_assert(does_compile<2, 3>::value, "does_compile should work");
static_assert(!does_compile<1, 0>::value, "constexpr division by zero shouldn't compile");


TEST_CASE("GeneralUtils::exchange", "[exchange]") {
int a = 1;
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