loop.cpp

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/**
 *\file         loop.cpp
 *
 *\brief        
 *
 *\author       Xianming Chen\n
 *              Computer Science Department\n
 *              University of Utah
 *
 *\date         16 Aug 2006\n
 *              Copyright (c) 2006, University of Utah
 */


#include "euler.h"


namespace euler
{

  loop_t :: loop_t(face_t* f)  : f(f), e(0), pre(0), nxt(0) 
  { 
    append_to_loop_list();
  }
  loop_t :: loop_t(face_t* f, vertex_t *v)  : f(f), e(0), pre(0), nxt(0) 
  {
    append_to_loop_list();
    new edge_t(v, this);
    new edge_t(v, this->e);
  }

  loop_t :: ~loop_t()
  {
    if(! e) return;
    
    edge_t *e0 = e;
    do
    {
      edge_t *temp = e;
      e = e->nxt;
      delete temp;
    }
    while(e != e0);
  }




  void loop_t :: append_to_loop_list()
  {
    if(f->l) 
    {
      loop_t* lp = f->l; 
      for(; lp->nxt; lp = lp->nxt);
      lp->nxt = this;
      pre = lp;
    }
    else
      f->l = this;
  }
  

  void loop_t :: del_single_vertex_edge_pair()
  {
    edge_t *e1=0, *e2=0, *cur = e;
    do
    {
      if(! cur->o)
        if(! cur->nxt->o)
        {
          e1 = cur, e2 = cur->nxt;
          break;
        }
    }
    while( (cur=cur->nxt) != e );
    
    if(!e1 || !e2) return;

    assert(e1->v == e2->v);
    
    if(e->nxt->nxt->nxt != e)
    {
      if(e == e1 || e == e2)
        e = e2->nxt;

      e2->nxt->pre = e1->pre;
      e1->pre->nxt = e2->nxt;

      delete e1; delete e2;
    }
  }

  int loop_t :: total_vertices() const
  {
    int total = 0;
    edge_t *cur = e;
    do
    {
      total++;
    }
    while( (cur=cur->nxt) != e );
    return total;
  }
  


}//end namespace euler

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