libcruft-util/test/hash/table.cpp

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#include "hash/table.hpp"
#include "tap.hpp"
#include "introspection.hpp"
///////////////////////////////////////////////////////////////////////////////
/// Exhaustively test the table hash output for:
/// * uniqueness
/// * equal counts of bit values at each bit offset
template <typename ValueT>
void test_type (cruft::TAP::logger &tap)
{
// Exhaustively list the hash outputs for u08. The result is sorted
// because it simplifies upcoming tests and we don't care about mapping it
// back to the original values.
std::vector<ValueT> results;
std::iota (
std::begin (results),
std::end (results),
0
);
std::transform (
std::begin (results),
std::end (results),
std::begin (results),
cruft::hash::table<ValueT> {}
);
std::sort (std::begin (results), std::end (results));
// Ensure all values are unique.
{
auto const pos = std::adjacent_find (std::begin (results), std::end (results));
tap.expect (
pos == std::end (results),
"no equal elements, %!",
cruft::type_name<ValueT> ()
);
}
// Ensure that at each bit offset we have equal numbers of high and low
// values across the table results.
{
bool success = true;
std::vector<int> bits;
for (std::size_t i = 0; i < sizeof (ValueT) * 8; ++i) {
bits.clear ();
for (auto const v: results)
bits.push_back ((v >> i) & 0x1);
auto const zeros = std::count (std::begin (bits), std::end (bits), 0);
auto const ones = std::count (std::begin (bits), std::end (bits), 1);
if (zeros != ones) {
success = false;
break;
}
}
tap.expect (
success,
"equal counts at bit positions, %!",
cruft::type_name<ValueT> ()
);
}
}
///////////////////////////////////////////////////////////////////////////////
int main ()
{
cruft::TAP::logger tap;
test_type<u08> (tap);
test_type<u16> (tap);
test_type<u32> (tap);
test_type<u64> (tap);
return tap.status ();
}