/// <summary>
/// </summary>
/// <param name="indexCoverage"></param>
public IndexedEdgeSet(IndexCoverage indexCoverage = IndexCoverage.Basic)
{
this.IndexCoverage = indexCoverage;
_indexes = Enum.GetValues(typeof(IndexCoverage))
.OfType <IndexCoverage>()
.Where(c => this.IndexCoverage.HasFlag(c) && c.HasSingleFlag());
}
// Selects the best index in the supplied IndexCoverage for the given set.
// Returns a tuple<index, remaining bitfield>
/// <summary>
///
/// </summary>
/// <param name="coverage"></param>
/// <param name="mask"></param>
/// <returns></returns>
public static Tuple <IndexCoverage, TripleMask> SelectIndex(this IndexCoverage coverage, TripleMask mask)
{
if (mask == TripleMask.None)
{
return(Tuple.Create(IndexCoverage.None, TripleMask.None));
}
// The prefered order of indices.
byte[] pref = { 10, 13, 12, 11, 5, 4, 7, 6, 8, 9, 0, 2, 1, 3 };
// The bitmask for each index.
byte[] table = { 1, 2, 4, 8, 3, 5, 9, 6, 10, 12, 7, 11, 13, 14 };
int i;
for (i = 0; i < 14; i++)
{
if (((int)mask & table[pref[i]]) == table[pref[i]] && coverage.HasFlag((IndexCoverage)(1 << pref[i])))
{
break;
}
}
return(Tuple.Create((IndexCoverage)(1 << pref[i]), (TripleMask)((int)mask & ~table[pref[i]])));
}
/// <summary>
///
/// </summary>
/// <param name="ic"></param>
/// <returns></returns>
public static TripleMask ToMask(this IndexCoverage ic)
{
Debug.Assert((ic & (ic - 1)) == 0, "Only one flag can be set.");
byte[] table = { 1, 2, 4, 8, 3, 5, 9, 6, 10, 12, 7, 11, 13, 14 };
return((TripleMask)table[(int)Math.Log((int)ic, 2)]);
}
/// <summary>
///
/// </summary>
/// <param name="coverage"></param>
/// <param name="s"></param>
/// <param name="p"></param>
/// <param name="o"></param>
/// <param name="c"></param>
/// <returns></returns>
public static Tuple <IndexCoverage, TripleMask> SelectIndex(this IndexCoverage coverage, INode s, INode p,
INode o, INode c)
{
var requested = TripleMask.None;
if (s != null)
{
requested |= TripleMask.Subject;
}
if (p != null)
{
requested |= TripleMask.Predicate;
}
if (o != null)
{
requested |= TripleMask.Object;
}
if (c != null)
{
requested |= TripleMask.Context;
}
return(coverage.SelectIndex(requested));
}
/// <summary>
///
/// </summary>
/// <param name="coverage"></param>
/// <returns></returns>
public static bool HasSingleFlag(this IndexCoverage coverage)
{
var x = (int)coverage;
return((x != 0) && ((x & (x - 1)) == 0));
}
/// <summary> /// /// </summary> /// <param name="coverage"></param> /// <param name="triple"></param> /// <returns></returns> public static Tuple <IndexCoverage, TripleMask> SelectIndex(this IndexCoverage coverage, Edge triple) => coverage.SelectIndex(triple.Subject, triple.Predicate, triple.Object, triple.Context);
