internal virtual void AdvanceWord(int targetWordNum)
{
Debug.Assert(targetWordNum > WordNum);
int delta = targetWordNum - WordNum;
if (delta <= AllOnesLength + DirtyLength + 1)
{
SkipDirtyBytes(delta - 1);
}
else
{
SkipDirtyBytes();
Debug.Assert(DirtyLength == 0);
if (delta > IndexThreshold_Renamed)
{
// use the index
int i = ForwardBinarySearch(targetWordNum);
int position = (int)Positions.Get(i);
if (position > @in.Position) // if the binary search returned a backward offset, don't move
{
WordNum = (int)WordNums.Get(i) - 1;
@in.Position = position;
SequenceNum = i * IndexInterval - 1;
}
}
while (true)
{
if (!ReadSequence())
{
return;
}
delta = targetWordNum - WordNum;
if (delta <= AllOnesLength + DirtyLength + 1)
{
if (delta > 1)
{
SkipDirtyBytes(delta - 1);
}
break;
}
SkipDirtyBytes();
}
}
NextWord();
}
internal virtual int ForwardBinarySearch(int targetWordNum)
{
// advance forward and double the window at each step
int indexSize = (int)WordNums.Size();
int lo = SequenceNum / IndexInterval, hi = lo + 1;
Debug.Assert(SequenceNum == -1 || WordNums.Get(lo) <= WordNum);
Debug.Assert(lo + 1 == WordNums.Size() || WordNums.Get(lo + 1) > WordNum);
while (true)
{
if (hi >= indexSize)
{
hi = indexSize - 1;
break;
}
else if (WordNums.Get(hi) >= targetWordNum)
{
break;
}
int newLo = hi;
hi += (hi - lo) << 1;
lo = newLo;
}
// we found a window containing our target, let's binary search now
while (lo <= hi)
{
int mid = (int)((uint)(lo + hi) >> 1);
int midWordNum = (int)WordNums.Get(mid);
if (midWordNum <= targetWordNum)
{
lo = mid + 1;
}
else
{
hi = mid - 1;
}
}
Debug.Assert(WordNums.Get(hi) <= targetWordNum);
Debug.Assert(hi + 1 == WordNums.Size() || WordNums.Get(hi + 1) > targetWordNum);
return(hi);
}