static void hexstrTest() {
unsigned char buf[6] = {1, 2, 33, 255, 0, 18};
unsigned char buf2[6] = {0};
AutoFree s(_MemToHex(&buf));
utassert(str::Eq(s, "010221ff0012"));
bool ok = _HexToMem(s, &buf2);
utassert(ok);
utassert(memeq(buf, buf2, sizeof(buf)));
FILETIME ft1, ft2;
GetSystemTimeAsFileTime(&ft1);
s.Set(_MemToHex(&ft1));
_HexToMem(s, &ft2);
DWORD diff = FileTimeDiffInSecs(ft1, ft2);
utassert(0 == diff);
utassert(FileTimeEq(ft1, ft2));
s.Set(str::MemToHex(nullptr, 0));
utassert(str::Eq(s, ""));
ok = str::HexToMem(s, nullptr, 0);
utassert(ok);
}
// return t1 - t2 in seconds
static int SystemTimeDiffInSecs(SYSTEMTIME& t1, SYSTEMTIME& t2) {
FILETIME ft1, ft2;
SystemTimeToFileTime(&t1, &ft1);
SystemTimeToFileTime(&t2, &ft2);
return FileTimeDiffInSecs(ft1, ft2);
}