EventHandler.cxx

Go to the documentation of this file.

 
#include "openlcb/EventHandler.hxx"
#include "openlcb/WriteHelper.hxx"
 
namespace openlcb
{
 
EventRegistry::EventRegistry()
{
}
 
EventRegistry::~EventRegistry()
{
}
 
// static
unsigned EventRegistry::align_mask(EventId *event, unsigned size)
{
    // example: size = 140. highest bit set is bit 7
    // example2: size = 256. highest bit set is bit 8, but it is power-of-two.
    HASSERT(event);
    if (size <= 1)
    {
        return 0;
    }
    // should be 7 in both examples
    unsigned log2 = sizeof(size) * 8 - __builtin_clz(size - 1) - 1;
    uint64_t new_event, rounded_range;
    do
    {
        ++log2;                       // 8 in both examples
        rounded_range = 1ULL << log2; // 256
        new_event = *event & (~(rounded_range - 1));
        // we have to be careful for overflowing uint64 in new_event =
        // rounded_range
    } while (log2 < 64 &&
             ((new_event + (rounded_range - 1)) < (*event + (size - 1))));
    if (log2 >= 64)
    {
        new_event = 0;
        log2 = 64;
    }
    // The rounding is successful.
    *event = new_event;
    return log2;
}
 
} /* namespace openlcb */