/usr/include/CGAL/halfedgeDS_cut_component.h is in libcgal-dev 4.5-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// Utrecht University (The Netherlands),
// ETH Zurich (Switzerland),
// INRIA Sophia-Antipolis (France),
// Max-Planck-Institute Saarbruecken (Germany),
// and Tel-Aviv University (Israel). All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 3 of the License,
// or (at your option) any later version.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL$
// $Id$
//
//
// Author(s) : Lutz Kettner <kettner@mpi-sb.mpg.de>
// Cuts out a piece of a halfedge data structure defined by a predicate.
#ifndef CGAL_HALFEDGEDS_CUT_COMPONENT_H
#define CGAL_HALFEDGEDS_CUT_COMPONENT_H 1
#include <CGAL/basic.h>
#include <CGAL/HalfedgeDS_decorator.h>
namespace CGAL {
template < class HDS, class Predicate >
typename HDS::Halfedge_handle
halfedgeDS_cut_component( HDS& hds,
typename HDS::Halfedge_handle h,
Predicate pred,
typename HDS::Halfedge_handle& cut_piece)
// Cuts out a piece of a halfedge data structure for which the predicate
// `pred' is true for the vertices.
// The edge-vertex graph of the piece has to be a connected component.
// The remaining piece gets a new boundary. Returns a border halfedge of
// the new boundary on the remaining piece. Assigns a halfedge of the
// cut outpiece to `cut_piece'.
// The geometry for the vertices
// on the boundary and the hole have to be taken care of after this
// function call. The cut-out piece can be deleted with the member
// function erase_connected_component of the decorator class. It can
// technically happen that only an isolated vertex would remain in the
// cut out piece, in which case a dummy halfedge pair and vertex will be
// created to keep this vertex representable in the halfedge data structure.
// Precondition: pred( h->vertex()) && ! pred( h->opposite()->vertex()).
{
typedef typename HDS::Vertex_handle Vertex_handle;
typedef typename HDS::Halfedge_handle Halfedge_handle;
typedef typename HDS::Face_handle Face_handle;
typedef typename HDS::Vertex Vertex;
typedef typename HDS::Halfedge Halfedge;
typedef typename HDS::Face Face;
CGAL::HalfedgeDS_decorator<HDS> D(hds);
CGAL_precondition( D.is_valid(false,3));
CGAL_precondition( pred( h->vertex()));
CGAL_precondition( ! pred( h->opposite()->vertex()));
Halfedge_handle start = h;
Halfedge_handle hnew;
Halfedge_handle hlast;
while (true) {
// search re-entry point
Halfedge_handle g = h;
while ( pred( g->next()->vertex())) {
g = g->next();
// create border edges around cap
D.set_face( g, Face_handle());
}
if ( hnew == Halfedge_handle()) {
// first edge, special case
CGAL_assertion( g->next() != h && g->next()->opposite() != h);
Halfedge_handle gnext = g->next()->opposite();
D.remove_tip( g);
Vertex_handle v = D.vertices_push_back( Vertex());
D.close_tip( gnext, v);
hnew = hds.edges_push_back( Halfedge(), Halfedge());
hlast = hnew->opposite();
D.insert_tip( hlast, gnext);
D.set_face( hnew, D.get_face( gnext));
D.set_face_halfedge( hnew);
h = g;
D.set_vertex_halfedge( h);
} else { // general case and last case
Halfedge_handle gnext = g->next()->opposite();
if ( gnext == start && gnext == g) {
// last edge, special case of isolated vertex.
// Create dummy edge and dummy vertex and attach it to g
g = hds.edges_push_back( Halfedge(), Halfedge());
D.insert_tip( g, gnext);
D.close_tip(g->opposite(), D.vertices_push_back(Vertex()));
D.set_vertex_halfedge( g);
D.set_vertex_halfedge( g->opposite());
}
D.remove_tip( g);
Vertex_handle v = D.vertices_push_back( Vertex());
D.close_tip( hnew, v);
D.insert_tip( gnext, hnew);
hnew = hds.edges_push_back( Halfedge(), Halfedge());
D.insert_tip( hnew->opposite(), gnext);
D.set_face( hnew, D.get_face( gnext));
D.set_face_halfedge( hnew);
h = g;
D.set_vertex_halfedge( h);
if ( gnext == start) {
// last edge, special
D.insert_tip( hnew, hlast);
break;
}
}
} // while(true)
Face_handle fnew = D.faces_push_back( Face());
D.set_face_in_face_loop( hlast, fnew);
D.set_face_halfedge( hlast);
cut_piece = h;
CGAL_postcondition( D.is_valid(false,3));
return hlast;
}
template < class HDS, class Predicate >
typename HDS::Halfedge_handle
halfedgeDS_cut_component( HDS& hds,
typename HDS::Halfedge_handle h,
Predicate pred)
// Same function as above, but deletes the cut out piece immediately.
{
typedef typename HDS::Halfedge_handle Halfedge_handle;
CGAL::HalfedgeDS_decorator<HDS> D(hds);
CGAL_precondition( D.is_valid(false,3));
CGAL_precondition( pred( h->vertex()));
CGAL_precondition( ! pred( h->opposite()->vertex()));
Halfedge_handle cut_piece;
Halfedge_handle hnew = halfedgeDS_cut_component( hds, h, pred, cut_piece);
D.erase_connected_component( cut_piece);
CGAL_postcondition( D.is_valid(false,3));
return hnew;
}
} //namespace CGAL
#endif // CGAL_HALFEDGEDS_CUT_COMPONENT_H //
// EOF //
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