/// <summary>
/// Moves the enumerator that is assumed to be sorted by departure time to the first connection with a departure time larger than or equal to the given departure time.
/// </summary>
public static bool MoveToDepartureTime(this ConnectionsDb.Enumerator enumerator,
uint departureTime)
{
if (enumerator == null)
{
throw new ArgumentNullException("enumerator");
}
if (enumerator.Count == 0)
{ // not possible to search and there's no need.
return(false);
}
// do a binary search.
uint lower = 0;
uint upper = enumerator.Count - 1;
// check bound.
enumerator.MoveTo(upper);
if (enumerator.DepartureTime < departureTime)
{ // no connection with a departure time after the given departure time.
return(false);
}
// check lowest.
enumerator.MoveTo(lower);
if (enumerator.DepartureTime >= departureTime)
{ // the first connection is already the one with a departure time after the given departure time.
return(true);
}
while (upper - lower > 1)
{
var position = (uint)((lower + upper) / 2);
enumerator.MoveTo(position);
if (enumerator.DepartureTime >= departureTime)
{ // position >= than target position.
upper = position;
}
else
{ // position > than target position.
lower = position;
}
}
enumerator.MoveTo(upper);
return(true);
}
/// <summary>
/// Moves the given enumerator to the connection right before the current connection on the same trip.
/// </summary>
/// <remarks>This requires the connections to be sorted by departure time.</remarks>
/// <returns></returns>
public static bool MoveToPreviousConnection(this ConnectionsDb.Enumerator enumerator)
{
if (enumerator == null)
{
throw new ArgumentNullException("enumerator");
}
if (enumerator.Count == 0)
{ // not possible to search and there's no need.
return(false);
}
var trip = enumerator.TripId;
while (enumerator.MovePrevious())
{
if (enumerator.TripId == trip)
{
return(true);
}
}
return(false);
}
