GeometryDecoder.java

/**
 * Container for link between two Osm nodes
 *
 * @author ab
 */
package btools.mapaccess;

import btools.util.ByteDataReader;


public final class GeometryDecoder
{
  private ByteDataReader r = new ByteDataReader( null );
  private OsmTransferNode[] cachedNodes;
  private int nCachedNodes = 128;

  public GeometryDecoder()
  {
    // create some caches
    cachedNodes = new OsmTransferNode[nCachedNodes];
    for( int i=0; i<nCachedNodes; i++ )
    {
      cachedNodes[i] = new OsmTransferNode();
    }
  }



  public OsmTransferNode decodeGeometry( byte[] geometry, OsmNode sourceNode, OsmNode targetNode, boolean reverseLink )
  {
      OsmTransferNode firstTransferNode = null;
      OsmTransferNode lastTransferNode = null;
      OsmNode startnode =  reverseLink ? targetNode : sourceNode;
      r.reset( geometry );
      int olon = startnode.ilon;
      int olat = startnode.ilat;
      int oselev = startnode.selev;
      int idx = 0;
      while ( r.hasMoreData() )
      {
        OsmTransferNode trans = idx < nCachedNodes ? cachedNodes[idx++] : new OsmTransferNode();
        trans.ilon = olon + r.readVarLengthSigned();
        trans.ilat = olat + r.readVarLengthSigned();
        trans.selev = (short)(oselev + r.readVarLengthSigned());
        olon = trans.ilon;
        olat = trans.ilat;
        oselev = trans.selev;
        if ( reverseLink ) // reverse chaining
        {
          trans.next = firstTransferNode;
          firstTransferNode = trans;
        }
        else
        {
          trans.next = null;
          if ( lastTransferNode == null )
          {
            firstTransferNode = trans;
          }
          else
          {
            lastTransferNode.next = trans;
          }
          lastTransferNode = trans;
        }
      }
      return firstTransferNode;
  }
}