private void WriteBlock()
{
Debug.Assert(BlockChunks > 0);
FieldsIndexOut.WriteVInt(BlockChunks);
// The trick here is that we only store the difference from the average start
// pointer or doc base, this helps save bits per value.
// And in order to prevent a few chunks that would be far from the average to
// raise the number of bits per value for all of them, we only encode blocks
// of 1024 chunks at once
// See LUCENE-4512
// doc bases
int avgChunkDocs;
if (BlockChunks == 1)
{
avgChunkDocs = 0;
}
else
{
avgChunkDocs = (int)Math.Round((float)(BlockDocs - DocBaseDeltas[BlockChunks - 1]) / (BlockChunks - 1));
}
FieldsIndexOut.WriteVInt(TotalDocs - BlockDocs); // docBase
FieldsIndexOut.WriteVInt(avgChunkDocs);
int docBase = 0;
long maxDelta = 0;
for (int i = 0; i < BlockChunks; ++i)
{
int delta = docBase - avgChunkDocs * i;
maxDelta |= MoveSignToLowOrderBit(delta);
docBase += DocBaseDeltas[i];
}
int bitsPerDocBase = PackedInts.BitsRequired(maxDelta);
FieldsIndexOut.WriteVInt(bitsPerDocBase);
PackedInts.Writer writer = PackedInts.GetWriterNoHeader(FieldsIndexOut, PackedInts.Format.PACKED, BlockChunks, bitsPerDocBase, 1);
docBase = 0;
for (int i = 0; i < BlockChunks; ++i)
{
long delta = docBase - avgChunkDocs * i;
Debug.Assert(PackedInts.BitsRequired(MoveSignToLowOrderBit(delta)) <= writer.BitsPerValue());
writer.Add(MoveSignToLowOrderBit(delta));
docBase += DocBaseDeltas[i];
}
writer.Finish();
// start pointers
FieldsIndexOut.WriteVLong(FirstStartPointer);
long avgChunkSize;
if (BlockChunks == 1)
{
avgChunkSize = 0;
}
else
{
avgChunkSize = (MaxStartPointer - FirstStartPointer) / (BlockChunks - 1);
}
FieldsIndexOut.WriteVLong(avgChunkSize);
long startPointer = 0;
maxDelta = 0;
for (int i = 0; i < BlockChunks; ++i)
{
startPointer += StartPointerDeltas[i];
long delta = startPointer - avgChunkSize * i;
maxDelta |= MoveSignToLowOrderBit(delta);
}
int bitsPerStartPointer = PackedInts.BitsRequired(maxDelta);
FieldsIndexOut.WriteVInt(bitsPerStartPointer);
writer = PackedInts.GetWriterNoHeader(FieldsIndexOut, PackedInts.Format.PACKED, BlockChunks, bitsPerStartPointer, 1);
startPointer = 0;
for (int i = 0; i < BlockChunks; ++i)
{
startPointer += StartPointerDeltas[i];
long delta = startPointer - avgChunkSize * i;
Debug.Assert(PackedInts.BitsRequired(MoveSignToLowOrderBit(delta)) <= writer.BitsPerValue());
writer.Add(MoveSignToLowOrderBit(delta));
}
writer.Finish();
}
