private static byte[] BuildHeader(ulong count, ulong featuresSize, IList <LayerMeta> layers, PackedHilbertRTree index)
{
// TODO: size might not be enough, need to be adaptive
var builder = new FlatBufferBuilder(1024);
// TODO: can be different per layer...
var columns = layers.First().Columns;
VectorOffset?columnsOffset = null;
if (columns != null)
{
var columnsArray = columns
.Select(c => Column.CreateColumn(builder, builder.CreateString(c.Name), c.Type))
.ToArray();
columnsOffset = Column.CreateSortedVectorOfColumn(builder, columnsArray);
}
var layerOffsets = layers
.Select(l =>
{
Layer.StartLayer(builder);
if (columnsOffset.HasValue)
{
Layer.AddColumns(builder, columnsOffset.Value);
}
Layer.AddGeometryType(builder, l.GeometryType);
var layerOffset = Layer.EndLayer(builder);
return(layerOffset);
}).ToArray();
var layersOffset = Header.CreateLayersVector(builder, layerOffsets);
Header.StartHeader(builder);
Header.AddLayers(builder, layersOffset);
if (index != null)
{
Header.AddIndexNodesCount(builder, index.NumNodes);
}
Header.AddFeaturesCount(builder, count);
Header.AddFeaturesSize(builder, featuresSize);
var offset = Header.EndHeader(builder);
builder.FinishSizePrefixed(offset.Value);
return(builder.DataBuffer.ToSizedArray());
}