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larku / RakNet

RakNet is a cross platform, open source, C++ networking engine for game programmers.
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how to understand "bool CCRakNetSlidingWindow::GreaterThan(DatagramSequenceNumberType a, DatagramSequenceNumberType b)" ? #46

Closed yandaren closed 6 years ago

yandaren commented 6 years ago

in the CCRakNetSlidingWindow,

bool CCRakNetSlidingWindow::GreaterThan(DatagramSequenceNumberType a, DatagramSequenceNumberType b)
{
    // a > b?
    const DatagramSequenceNumberType halfSpan =(DatagramSequenceNumberType) (((DatagramSequenceNumberType)(const uint32_t)-1)/(DatagramSequenceNumberType)2);
    return b!=a && b-a>halfSpan;
}
// ----------------------------------------------------------------------------------------------------------------------------
bool CCRakNetSlidingWindow::LessThan(DatagramSequenceNumberType a, DatagramSequenceNumberType b)
{
    // a < b?
    const DatagramSequenceNumberType halfSpan = ((DatagramSequenceNumberType)(const uint32_t)-1)/(DatagramSequenceNumberType)2;
    return b!=a && b-a<halfSpan;
}

what the 'hafSpan' mean, i just can't understand the comparison algorithm mean ?