public virtual Bookmark <ValueTuple <K, V> >?PositionAt(K k)
{
SBookmark <K, V>?bmk = null;
var cb = root;
while (cb != null)
{
var bpos = cb.PositionFor(k, out bool b);
bmk = new SBookmark <K, V>(cb, bpos, bmk);
if (bpos == cb.count)
{
var inr = cb as SInner <K, V>;
if (inr == null)
{
return(null);
}
cb = inr.gtr;
}
else
{
cb = (cb.Slot(bpos).Item2 ?? throw new Exception("??")) as SBucket <K, V>;
}
}
return((bmk == null)?null:new SDictBookmark <K, V>(bmk));
}
public static SBookmark <K, V>?Next(SBookmark <K, V>?stk, SDict <K, V>?tree = null)
{
SBucket <K, V>? b;
ValueTuple <K, object?> d;
if (stk == null) // following Create or Reset
{
// if Tree is empty return null
if (tree == null || tree.root == null || tree.Length == 0)
{
return(null);
}
// The first entry is root.slots[0] or below
stk = new SBookmark <K, V>(tree.root, 0, null);
d = tree.root.Slot(0);
b = d.Item2 as SBucket <K, V>;
}
else // guaranteed to be at a LEAF
{
var stkPos = stk._bpos;
if (++stkPos == stk._bucket.count) // this is the right test for a leaf
{
// at end of current bucket: pop till we aren't
for (; ;)
{
if (++stkPos <= stk._bucket.count)// this is the right test for a non-leaf; redundantly ok for first time (leaf)
{
break;
}
stk = stk._parent;
if (stk == null)
{
break;
}
stkPos = stk._bpos;
}
// we may run out of the BTree
if (stk == null)
{
return(null);
}
}
stk = new SBookmark <K, V>(stk._bucket, stkPos, stk._parent);
if (stk._bpos == stk._bucket.count)
{ // will only happen for a non-leaf
b = ((SInner <K, V>)stk._bucket).gtr;
d = new ValueTuple <K, object?>(default(K), null); // or compiler complains
}
else // might be leaf or not
{
d = stk._bucket.Slot(stkPos);
b = d.Item2 as SBucket <K, V>;
}
}
while (b != null) // now ensure we are at a leaf
{
stk = new SBookmark <K, V>(b, 0, stk);
d = stk._bucket.Slot(0);
b = d.Item2 as SBucket <K, V>;
}
return(stk);
}
public SBookmark(SBucket <K, V> b, int bp, SBookmark <K, V>?n)
{
_bucket = b; _bpos = bp; _parent = n;
}
internal SDictBookmark(SBookmark <K, V> bmk) : base(bmk.position())
{
_bmk = bmk;
}
public override Bookmark <ValueTuple <K, V> >?First()
{
return((SBookmark <K, V> .Next(null, this) is SBookmark <K, V> b)?
new SDictBookmark <K, V>(b):null);
}