private static byte[] BuildHeader(ulong count, GeometryType geometryType, IList <ColumnMeta> columns, PackedRTree index)
{
var builder = new FlatBufferBuilder(4096);
VectorOffset?columnsOffset = null;
if (columns != null)
{
var columnsArray = columns
.Select(c => Column.CreateColumn(builder, builder.CreateString(c.Name), c.Type))
.ToArray();
columnsOffset = Header.CreateColumnsVector(builder, columnsArray);
}
Header.StartHeader(builder);
Header.AddGeometryType(builder, geometryType);
if (columnsOffset.HasValue)
{
Header.AddColumns(builder, columnsOffset.Value);
}
//if (index != null)
Header.AddIndexNodeSize(builder, 0);
Header.AddFeaturesCount(builder, count);
var offset = Header.EndHeader(builder);
builder.FinishSizePrefixed(offset.Value);
return(builder.DataBuffer.ToSizedArray());
}
public static IEnumerable <IFeature> Deserialize(Stream stream, Envelope rect = null)
{
var reader = new BinaryReader(stream);
var magicBytes = reader.ReadBytes(8);
if (!magicBytes.SequenceEqual(Constants.MagicBytes))
{
throw new Exception("Not a FlatGeobuf file");
}
var headerSize = reader.ReadInt32();
var header = Header.GetRootAsHeader(new ByteBuffer(reader.ReadBytes(headerSize)));
var count = header.FeaturesCount;
var nodeSize = header.IndexNodeSize;
var geometryType = header.GeometryType;
IList <ColumnMeta> columns = null;
if (header.ColumnsLength > 0)
{
columns = new List <ColumnMeta>();
for (int i = 0; i < header.ColumnsLength; i++)
{
var column = header.Columns(i).Value;
columns.Add(new ColumnMeta()
{
Name = column.Name, Type = column.Type
});
}
}
if (nodeSize > 0)
{
long offset = 8 + 4 + headerSize;
var size = PackedRTree.CalcSize(count, nodeSize);
if (rect != null)
{
var result = PackedRTree.StreamSearch(count, nodeSize, rect, (ulong treeOffset, ulong size) => {
stream.Seek(offset + (long)treeOffset, SeekOrigin.Begin);
return(stream);
}).ToList();
foreach (var item in result)
{
stream.Seek(offset + (long)size + (long)item.Offset, SeekOrigin.Begin);
var featureLength = reader.ReadInt32();
var feature = FeatureConversions.FromByteBuffer(new ByteBuffer(reader.ReadBytes(featureLength)), geometryType, 2, columns);
yield return(feature);
}
yield break;
}
stream.Seek(8 + 4 + headerSize + (long)size, SeekOrigin.Begin);
}
while (stream.Position < stream.Length)
{
var featureLength = reader.ReadInt32();
var feature = FeatureConversions.FromByteBuffer(new ByteBuffer(reader.ReadBytes(featureLength)), geometryType, 2, columns);
yield return(feature);
}
}
