protected IEnumerable <HexSpan> GetValidSpansReverse(HexBuffer buffer, HexPosition start, HexPosition lowerBounds)
{
var pos = start;
bool fullSpan = true;
for (;;)
{
var span = buffer.GetPreviousValidSpan(pos, lowerBounds, fullSpan);
if (span == null)
{
break;
}
var newStart = HexPosition.Max(lowerBounds, span.Value.Start);
var newEnd = HexPosition.Min(pos + 1, span.Value.End);
if (newStart < newEnd)
{
yield return(HexSpan.FromBounds(newStart, newEnd));
}
if (span.Value.Start == 0)
{
break;
}
pos = span.Value.Start - 1;
fullSpan = false;
}
}